Nanophotonics X

We discuss extensions to the standard polarization formalism for situations in which all three Cartesian components of the electric field are significant. Standard concepts for paraxial formalism such as the degree of polarization, the Stokes parameters, and the Poincaré sphere have generalizations that are neither unique nor trivial. It is shown that this formalism is particularly useful for the description of wobbling fluorophores in single molecule orientation and localization microscopy (SMOLM).

Pushed to their limit, tip-enhanced photoluminescence and electroluminescence can be used to generate sub-molecularly resolved fluorescence maps of individual molecules. Combined with spectral selection and time-correlated measurements, these hyper-resolved fluorescence microscopies allowed us to scrutinize the vibronic and charged states of individual molecules [1,2], to track the motion of hydrogen atoms within free-based phthalocyanine molecules [3,4], and to follow resonance energy transfers between individual pigments [5]. These results constitute an important step towards photonic measurements with atoms-scale resolution. References [1] B. Doppagne et al., Phys. Rev. Lett. 118, 127401 (2017) [2] B. Doppagne et al. Science 361, 251 (2018) [3] B. Doppagne et al. Nature Nanotechnol.15, 207 (2020). [4] A. Roslawska et al. arXiv:2305.13157. [5] S. Cao et al. Nature Chem. 12, 766 (2021)

In this paper, we report the microscopic excitation and imaging of dielectric Mie resonators. The interaction of tightly focused vector beams with dielectric nanoparticles leads to exotic phenomena including multipolar excitation by displacement resonances, directional scattering, as well as superresolution imaging

Photonic jet was originally imagined in optics when a laser beam interacted with dielectric nanoparticles. Under specific physical and geometric conditions of the nanoparticles and the surrounding media, the light beam exhibits intriguing properties, including a high intensity and an extremely short Full Width at Half Maximum (FWHM). These characteristics pave the way for various applications based on imaging and detection with high accuracy. In our recent research, we have successfully demonstrated these phenomena at microwave frequencies (referred to as electromagnetic jet) by implementing several microwave systems, including antennas and waveguides equipped with dielectric tips of various geometries. In addition to detection and imaging applications, we present the possibility of also using the jet for local material characterization applications.

Here, we take advantage of spectrally separated scattering and absorption resonance bands in hyperbolic meta-antennas (HMA) to enhance the hot electron generation and prolong the relaxation dynamics of hot carriers. In this regard, for the realization of HMA, multilayered metal-dielectric structures based on gold/silica stacking layers are designed and fabricated to separate well-defined scattering and absorption bands. In contrast, conventional plasmonic (gold) nanodisk antennas (NDA) of thickness equivalent to that of total metal layers of an HMA are also realized as reference samples to distinguish the effect of multilayer HMA. First, we demonstrate the extended plasmon-modulated photoluminescence spectrum in HMA towards longer wavelengths due to its scattering spectrum in comparison to the corresponding NDA. Then, we demonstrate that the tunable absorption band of HMA controls and modifies the lifetime of the plasmon-induced hot electrons with enhanced excitation efficiency in the near-infrared region and broadens the utilization of the visible/NIR spectrum in comparison to NDA.

Plasmonic phenomena induce a highly concentrated electric field in small areas, manipulating the dynamic of microscopic objects. We report on a plasmonic structure that modulates the electric field by generating the propulsive motion of the nanoparticles. The system consists of two gold scalene trapezoids forming a planar V-groove. The designed geometrical configuration is suitable for an array configuration (circular or linear arrangement) that amplifies the output velocities of nanoparticles. The optical forces induced by the system enable the displacement of macroscopic objects with interesting applications in the biomedical and aerospace fields.

In this work, we compare the bulk and localized sensing results of one dimensional (1-D) and two dimensional (2-D) arrays of plasmonic nanostructures of aluminum. Aluminium (Al) metal is the material of choice for plasmonic sensing in ultra-violet (UV) regime since it has a strong plasmonic response in UV regime. We carried out finite difference time domain (FDTD) simulations to simulate these plasmonic nanostructure arrays and to study their bulk and localized sensing behavior. We determined the bulk and localized sensing performance characteristics by calculating the sensitivity and figure of merit, and optimized these performance characteristics by varying various geometrical parameters of the nanostructures. We also determined the effect of the oxide layer on the bulk and localized sensing performance of these UV plasmonic sensors.

I will explore various facets of photonic quantum systems and their application in photonic quantum technologies. Firstly, I will focus into quantum foundations and by discuss quantum interference, a key element in photonic quantum technologies. I will highlight how the distinguishability and mixedness of quantum states influence the interference of multiple single photons – and demonstrate novel schemes for generating multipartite entangled quantum states. I will then address photonic quantum computing, specifically focusing on the building blocks of photonic quantum computers. This includes the generation of resource states essential for photonic quantum computing. I will then shift to photonic quantum networks, covering both their hardware aspects and showcasing quantum-network applications that extend beyond bi-partite quantum communication. Lastly, I will outline how photonic integration facilitates the scalability of these systems and discuss the associated challenges.

Joining the rich photophysics of organic light-emitting materials with the exquisite sensitivity of optical resonances to geometry and refractive index enables a plethora of devices with unusual and exciting properties. Examples from my team include biointegrated microlasers for real time sensing of cellular activity and long-term cell tracking, as well as the development of photonic implants with extreme form factors and wireless power supply that support thousands of individually addressable organic LEDs and thus allow optogenetic targeting of neurons deep in the brain with unprecedented spatial control. Very recently, by driving the interaction between excited states in organic materials and resonances in thin optical cavities into the strong coupling regime, we unlocked new tuning parameters which may play a crucial role in the next generation of TVs and computer displays to achieve even more saturated colour while retaining angle-independent emission characteristics.

In monolayer transition metal dichalcogenides (TMDs), the interplay between space-inversion and time-reversal (TR) symmetry defines the spin-valley degree of freedom: direct transitions at the ±K valleys are energetically degenerate but non-equivalent. Thus, engineering of TR symmetry naturally leads to the field of valleytronics, a new type of information technology that allows to manipulate data at the speed of ultrashort light pulses. However, all the methods that have been developed to date for the detection of a valley polarization (VP) are based on linear optics and suffer from severe limitations. In this talk, I will discuss a new method for the detection of broken TR symmetry and VP in TMDs based on nonlinear optics. I will show that the VP can be measured from a rotation in the polarization angle of the second harmonic (SH) signal emitted from the ±K valleys of a TMD monolayer. In addition, I will show signatures of valley polarization-electric dipole interference and demonstrate that this is a direct consequence of a phase-mismatch between the intrinsic (broken space-inversion symmetry) and valley (broken TR symmetry) terms of the second order nonlinear susceptibility.

One of the major challenges in nanophotonics is the direct measurement of the interaction of a nanostructure with a single fluorescent emitter at the nanometer level. Several approaches developed to this aim can be found in the literature. Recently, single molecule localization imaging, traditionally used for the study of biological samples, entered the nanophotonics realm opening new horizons. We report on the development of single-molecule fluorescence lifetime imaging microscopy (sm-FLIM), an innovative approach enabling the simultaneous measurement of the lifetime and the intensity of single-molecules densely labeling a nanostructured sample, with a field of view of 10 µm2 , a spatial resolution of ~14 nm and a temporal resolution of ~ 50 ps. smFLIM enabled us to image, at the single molecule level, the local density of optical states (LDOS, which is related to the inverse of the fluorescence lifetime) of dielectric nanoantennas and periodic arrays of hollow truncated plasmonic nanocones.

The different electron scattering in Al-doped ZnO (AZO) under intraband excitation was investigated through transient transmittance and reflectance. The electron-phonon scattering was probed to play a vital role in the hot carrier relaxation process while the electron-electron scattering also exhibits strong influence at high electron temperature.

INVITED Polaritons in two-dimensional layered crystals offer an effective solution to confine, enhance and manipulate terahertz (THz) frequency electromagnetic waves at the nanoscale. In this talk I’ll review recent results in the detection of dirac plasmon polaritons at THz frequencies, in hBN-encapsulated black-phosphorus field effect transistors through THz near-field photocurrent nanoscopy and in large area topological insulators through detectorless near-field digital holography.

We report the first-ever observation of optomagnetically-driven rotation of a magnetic particle, optically levitated inside a chiral hollow-core photonic crystal fibre (HC-PCF). Rotation of the optically biaxial particle causes a change in the transmitted power and ellipticity of a linearly polarised probe beam at 632.8 nm. HC-PCF offers a versatile platform for investigating the optomechanical response of levitated magnetic particles.

Fluoranthene and Pyrene (PAHs) airborne particles are well known for their mutagenic and carcinogenic properties. Manipulation of such nanoparticles below 100 nm makes it challenging due to their low polarizability and dielectric properties. Current optical nano-tweezer designs such as trench, slot and hybrid plasmonic waveguides (HPWG) provides a strong gradient force for trapping, but they often have ≤ 50 nm gaps and have very low fabrication tolerances. In this work, we show the modeling of optical forces and sensitivity of different waveguide structures to sense large numbers of particles to monitor the air quality index (AQI). To increase the trapping gaps and sensitivity in HPWG, we have designed them to use radiation modes of the dielectric waveguides. We call this phenomenon a “mode-lift” [3]. Here we present the numerical and experimental results of industrially compatible integrated photonic sensors such as strip, slot, subwavelength grating (SWG) and HPWG used for measuring AQI.

Moving from diffractive optics to metalenses offers innovative tools for shaping light, facilitating their incorporation into compact optical setups. This paves the way for creating novel metaoptics specifically engineered to govern structured light beams with customizable vectorial configurations. This approach enables the attainment of diverse optical designs, in particular dual-functional metalenses capable of producing various types of scalar and vector beams that carry orbital angular momentum (OAM) based on user requirements.

Multipole expansions enable rapid numerical modeling of optical scatterer arrays, but choosing expansion centers is ambiguous. We derive optimal centers where multipolar spectra become unique, separately minimizing electric and magnetic quadrupole norms. This significantly reduces computations, benefiting differentiable solvers critical for machine learning photonics design. Analysis of dispersive mutual center positions provides insight into scattering and optical forces. Connections to optomechanics, and quantum/topological photonics are also hinted through links between the number of optimal magnetic centers and the topological metrics of resonant modes.

In recent years, significant interest has emerged in the inverse design1 of artificial layered heterostructures for photonic applications2. Specifically, the unique optical properties of near-zero permittivity (ENZ) metamaterials have enabled the exploration of novel physical effects and mechanisms. In this presentation, I will delve into how thin film photonics harnesses the potential of Fano resonances3-4 and extreme optomechanics5. By layering metal-dielectric thin films, we can create a distinct type of optical coating that exhibits photonic Fano resonance, referred to as a Fanoresonant optical coating (FROC). We extend the concept of coupled mechanical oscillators to thinfilm nanocavities, shedding light on semi-transparent FROCs that can both transmit and reflect the same color, akin to a beam splitter filter. This remarkable property is beyond the capabilities of conventional optical coatings. In the latter part of my presentation, I will discuss recent theoretical and experimental efforts aimed at exploring optomechanics based on epsilon-near-zero materials5.

Minin et al. demonstrated that dielectric cuboids can generate 'curved photonic nanojets' (photonic hooks) that function similarly to Airy beams, enabling the manipulation of particles along curved paths . Asymmetry in particles, like using cuboids or Janus particles, or masking the illumination path, creates these photonic hooks. Potential applications encompass optical trapping, particle manipulation, and imaging. Nevertheless, current designs are unwieldy for integration into microfluidic platforms. This discussion presents a planar photonic chip design that generates subwavelength-width photonic hooks. Illumination of 532 nm TE polarised plane wave on three Si3N4 micro-pillars (2λ high) including one λ-wide and two λ/3-wide produces intense photonic hooks several orders of λ above the micro-pillars, with a 0.7 λ FWHM. The larger pillar is separated by 2λ from the smaller pillars, which are λ/3 apart. We further investigate how pillar dimensions and spacing impact photonic hook properties and calculate the optical forces generated.

In microfluidic environments, particle transport is typically governed by slow diffusion near interfaces. However, by introducing localized fluid flow, it becomes feasible to actively transport suspended nano-objects within confined spaces. To achieve precise and dynamic control over fluid flow at the microscale, one promising approach is to leverage photothermal effects through the illumination of metallic or all-dielectric nanostructures. In this context, we explore the potential of manipulating the flow direction by adjusting the absorption characteristics of these metallic or dielectric nanostructures. By strategically designing the nanostructures and tailoring their absorption properties, we can exert precise control over the temperature distribution, thereby influencing the direction of fluid flow. This control over the flow direction opens up new possibilities for achieving desired transport capabilities within microfluidic systems.

Metallic nanoantennas have been studied as efficient coherent phonon generators and detectors, harnessing their characteristic optical absorption and polarization dependence of the optical modes. The ability to control the excitation of phononic modes depends on the properties of the multiple optical resonances of the system. Lately, it has been made possible to optimally excite and detect phonon modes via plasmon resonances at the same optical frequency using chiral nanostructures and circularly polarized light. However, torsional modes remain elusive in nanophononic studies. In this work we present a simple system composed of two coupled bars, where torsional mechanical modes can be excited using light with null angular momentum. The twisting of the phononic mode is provided by the peculiar symmetry of the mechanical eigenmode due to the interaction of the bars via either the substrate or a central connector. We will present a complete theoretical analysis of the phononic and plasmonic modes, their surface deformation field and electromagnetic field profiles.

Recent advances in optical trapping have opened new opportunities for manipulating micro and nanoparticles, establishing optical tweezers as a powerful tool for single-cell analysis. In this study, we assessed the capability of optical tweezers to distinguish bound and unbound states of streptavidin-functionalized 5 μm PMMA particles targeting biotinylated bovine serum albumin. The bound states are characterized by an added molecular layer to the particles, resulting in a 7 nm size increase. An automatic OT system was used for the acquisition of the forward scattered signals. Using signal pre-processing and subsequent machine learning algorithms, our findings demonstrate the potential of using optical tweezers to detect nanoscale changes in the size of the microparticles, as a proof of concept for studies with shape-changing bio affinity tools.

Optical trapping and sensing platforms based on plasmonics were developed due to the desire to both trap and manipulate ever smaller particles using noninvasive optical techniques. Through careful engineering of the plasmonic structures, a Fano resonance can yield a surprisingly large improvement to the trapping efficiency for nanoparticles. Using a split ring array, we have demonstrated trapping of particles as small as 10 nm and have exploited the SIBA effect to improve the trap stiffness for gold nanoparticles. We have extended the technique to sense and determine the phase of E-coli bacteria and have explored thermal effects which can contribute to the trapping processes. Here, we discuss characterization of the devices themselves, to engineer them for specific applications such as enhanced photoluminescence from nano-emitters, particularly nanographenes.

Implementation of metasurface scanning for directional beam steering and metasurface arrays on imaging sensors are used to achieved 3D light Detection And Ranging (LiDAR) with impressive imaging performances. Our works show that metasurfaces have relevant industrial applications in 3D sensing, way beyond the basic usage of metalenses for imaging or point-cloud projection.

Nanophotonic devices for structural color generation based on plasmonics are usually built using the archetypal noble low loss metals Au and Ag, which are scarce and expensive. In this work, we show how underexplored p-block elements such as Bi or Sb in spite of being lossy, are promising alternative plasmonic materials that yield low-cost, sustainable and high purity colours. First, we demonstrate how Bi can be successfully nanostructured in the form of both gap-plasmon metasurfaces and metal/insulator/metal Fabry-Perot cavity colors, outperforming the colour purity achievable with traditional low loss metals. Second, using thin cavity structures, we explore their color performance on industrially important substrates such as silicon or steel directly as the back reflector. The results show high purity and environmentally robust vivid colors, suitable for cheap, outdoor, and daylight-friendly macroscopic coloring.

Acoustic interface states have been evidenced in superlattices with frequencies at tens to hundreds of GHz, by concatenating two periodic lattices with inverted spatial mode symmetries around the bandgap [1]. In this work, we present high-order topological nanophononic interface states in multilayered structures [2]. We achieve and control the band inversion by modifying the unit cells of the two superlattices. We then extend the principle of band inversion to create an interface state at higher order bandgaps. We showcase designs for versatile topological devices where interface states are simultaneously created across a wide frequency range. Additionally, we designed hybrid structures formed with two concatenated superlattices with different order bandgaps centered around the same frequency, which also support interface states. The demonstrated systems can be exploited investigate schemes that are difficult or impossible to study in electronics or optics, due to their non-linear dispersion relations. References [1] M. Esmann et al., Optica 6, 854 (2019). [2] A. Rodriguez et al, Physical Review B, 108, 205301 (2023).

Hybrid CuS/Au nanostructures enhance second- and third- harmonic generation (SHG, THG) due to coupling of localized surface-plasmon resonances (LSPRs) when the broad plasmon band of CuS nanoparticles (NPs) is excited by two-photon absorption. However, the mechanism of interactions between the plasmonic nanoparticles is still unclear. Here, we deposited insulating, spacer layers of alumina between Au and CuS NPs to explore the distance-dependence of SHG and THG intensities. An inverse sixth-power dependence of harmonic generation seen in both experimental and theoretical (finite-difference, time-domain calculations) results suggests that plasmon-induced resonant energy transfer (PIRET) accounts for plasmon-plasmon coupling in CuS-Au bilayer nanoparticle films. Using an optical parametric amplifier, we tuned the pump wavelength away from the CuS LSPR to show that the dominant upconversion pathway changed from harmonic generation to multiphoton photoluminescence (MPPL), implying that the two-photon resonance excited in CuS is critical to the enhanced harmonic generation. This suggests that PIRET can be the basis of ultrafast, thin-film nanostructures for frequency conversion.

Metal nanoclusters (NCs) have emerged as prospective luminescent materials which can be beneficial for numerous applications. The most intriguing properties of NCs are long photoluminescence (PL) lifetime with broadband PL emission, however, low PL quantum yield (PLQY) and unclear excitonic dynamics mechanism strongly hinder their practical utilization. Gold-doped silver nanoclusters were synthesized and were covalently bonded in a solid matrix, polyvinylpyrrolidone (PVP). The fabricated gold-doped silver nanoclusters embedded in PVP matrix (AuAgNCs@PVP) have bright red emission with microseconds PL lifetime. By probing the nanosecond time resolution, it was revealed that two distinct decay profiles exist in AuAgNCs@PVP, showing the occurrence of thermally-activated delayed fluorescence (TADF). We also found that after the photoexcitation, thermal equilibrium between singlet and triplet states were quickly reached due to fast intersystem and reverse intersystem crossing (ISC/RISC) process and small singlet triplet energy splitting. Hence, we proposed the mechanism behind broadband PL emission with long PL lifetime was due to thermally-equilibrated delayed fluorescence (TEDF).

Nanoparticle on mirror (NPoM) plasmonic cavity can be utilized to enhance the spontaneous decay rate of a quantum emitter to a great extent. Here, we calculated the Purcell factor of a quantum emitter placed in such a cavity using COMSOL Multiphysics software. We first simulated the extinction cross-section of a nanorod placed on top of a metal film separated by a small gap. Then, we calculated the Purcell factor for a varying gap. We observed that the Purcell factor is greatly enhanced when the gap between the nanorod and the metal film is sufficiently low (<4 nm).

This contribution discusses the role of hexagonal boron nitride (hBN) as a host for photon emitters. In this study we employ gallium ion implantation to create emitters within hBN. Gallium ions are found to be optimal for generating many emitters, when both the ion energy and fluence are carefully controlled. Post-irradiation thermal annealing induces defect transmutation, providing spectral tunability to the emitters. Together with focused ion beam (FIB) implantation, allowing for nanoscale defect positioning, it is possible to precisely pattern multiple photon emitters at various optical frequencies on one platform. Overall, the research highlights hBN potential in advancing quantum technologies.

We report the study of the FRET (Förster Resonance Energy Transfer) effect between AgInS2 QDs as donor and fluorophore F (cyanine 5) as acceptor, with the QD-F inter-distance d tuned by DNA strands. A fluorophore linked to single DNA was first hybridized with its complementary thiolated DNA sequence. This hybridized double-strand is then used to functionalize the QD. We have characterized the optical properties of these nanohybrid assemblies by carrying out fluorescence and decay time measurements. We found a characteristic Förster distance R0 = 6 nm for this system with an experimental FRET efficiency of 48 % for a distance d= R0 = 6 nm, and 16 % for d=2R0 = 12 nm in agreement with the theory. To explore the potential of such assembly for sensing applications using FRET and DNA hybridization, we have studied another approach: the QD was first functionalized by a thiolated DNA single strand, and then a fluorophore linked to complementary DNA sequence were added to realize the DNA hybridization. For this second approach, a strong FRET is observed whatever the targeted QD-F distance (efficiency >70%). We will discuss the reasons for this non-expected effect.

We image the micro-photoluminescence of single self-assembled chains of CdSe nanoplatelets. Some portions of a chain show collective fluorescence intermittency, with around 30 platelets blinking at the same time. This effect is explained and modelled as Förster-resonant energy tranfer (FRET) funneling all the excitons from a chain portion to a single blinking quencher.

We will demonstrate two methodologies for the retrieval of wavefront and polarization characteristics within optical fields. The first method offers a digital analog to Stokes polarimetry, requiring only four measurements, as opposed to the conventional six. Here we make use of a Polarization Grating (PG) together with a Digital Micro-mirror Device (DMD) to introduce a phase retardance between orthogonal polarization states to reconstruct both phase and polarization. The second approach leverages the concept of the transport-of-intensity, which capitalizes on the relationship between observed energy propagation in optical fields and their wavefront properties. To demonstrate the effectiveness of these techniques, we illustrate their application in spatially resolving exotic polarization structures, including metasurfaces, liquid crystal devices, and chiral materials.

We present a comprehensive study of the elementary dipolar contributions to the absorption and scattering cross sections in chiral, twisted, vertically stacked plasmonic plates that have been proposed as acoustoplasmonic transducers. Using a very basic model system we show scattering and absorption cross sections presenting very large qualitative differences for left-circular and right-circular polarizations. We make use of an expansion in vector-spherical-harmonics multipoles to analyze the different contributions to the cross sections depending on the helicity of the incoming wave. In the analysis of the scattering cross section, we demonstrate that interactions not only modify the spectral dependence of the dipoles representing the elements in the nanostructure, but they affect the cross section itself elucidating the dependence on the helicity of the incoming light beam.

We demonstrate the coherent manipulation of the spatial and temporal properties of ultrashort pulsed laser beams to generate wave packets that trace helical trajectories in space-time. This is achieved by introducing a non-separable correlation between the beam’s frequency (related to its temporal structure) and its orbital angular momentum (that defines its spatial topology). The demonstration relies on a diffractive axicon grating to separate the frequencies of a pulsed beam into colinear radial rings which are then independently modulated with an azimuthal phase using a digital spatial light modulator. The all-digital setup allows to tailor the topological-spectral correlations, affording control over a range of beam properties, while more complex correlations realize exotic space-time wave packets with extended beam dynamics. These unique beams open new horizons in ultrafast light-matter interactions, microscopy and multiplexing.

Material anisotropy and chirality produce polarization-dependent light-matter interactions. Absorption leads to linear and circular dichroism, whereas elastic forward scattering produces linear and circular birefringence. Here we highlight an extraordinary form of dichroism and birefringence whereby ordered media display locally different absorption and scattering of linearly polarized light that depends upon the sign of the topological charge $\ell$ of a focused vortex beam. The result represents a method of probing the nano-optics of advanced materials and the topological properties of structured light.

Fluorine-doped indium oxide (IO) nanocubes separated by nanometric gaps constitute a versatile system hosting high-quality mid-infrared plasmons with potential application in optoelectronics and light harvesting. In this theory-experiment combined work, we predict large tunability of these hybridized plasmon modes by controlling the gap size and the dimensionality of the gap region. We confirm this prediction through electron energy-loss spectroscopy (EELS) measurements performed in a scanning transmission electron microscope (STEM). Our theorical-experimental results elucidate the influence of gap geometry on the coupled plasmons and field concentration in doped IO nanostructures, and further suggest exciting applications in plasmonic sensing and surface-enhanced spectroscopies.

In this work, we use monocrystalline LaPO4:Eu nanorods as polarized luminescent probes. By distinguishing between emission peaks originating from magnetic and electric dipole transitions, we can derive the three-dimensional orientation of the nanorods through measurements of their polarized luminescence [1]. This spectroscopy-based orientation analysis can furthermore be used to characterize microfluidic media, as the collective orientation of nanorods is directly related to flow conditions they are subjected to [2]. Using a confocal microscope, we can locally determine their collective orientation which provides a direct measure of the shear stress. We demonstrate this method to map the shear stress profile in different microfluidic channel geometries and monitor the shear stress in an energy harvesting device . [1] Kim, J. et al. Nat Commun 12, 1943 (2021). [2] Kim, J. et al. Nature Nanotech 12, 914–919 (2017).

In this work, we prepare plexcitonic nanoparticles composed by plasmonic nanoparticles, Au@Ag@mSiO2 nanorattles, and J-aggregates of TDBC cyanine dye to be used as ultra-efficient SERS-tags. The methodology used here allowed us to improve the colloidal stability of the plexcitonic nanoparticles. The optical properties have been characterised by UV-vis-NIR and Surface-Enhanced Raman Scattering (SERS) spectroscopies. Besides, finite-difference time-domain (FDTD) calculations revealed that the electromagnetic field is strongly confined into the J-aggregate deposited over the surface of the plasmonic nanoparticle at wavelengths near the upper plexciton. However, for the lower plexciton mode, the electromagnetic field decays through the J-aggregate/water interface. In summary, the plexcitonic nanoparticles showed high SERS efficiency for 532 nm and 633 nm laser lines, even reaching single-nanoparticle detection. The results obtained showed us the significance of strong coupling effect which might lead new possibilities for ultrasensitive biosensing and bioimaging.

Quantum emitters in hexagonal boron nitride (hBN) crystals are optimal candidates for the observation of single photon emission, but achieving control over their features is a challenging task. In this work, we present the deterministic generation of emitters with selected position and spectral features with a method that combines ion implantation and annealing of the sample. With this method, we even achieved control over the density of emitters. Such control is a fundamental step towards the engineering of emitter ensembles that can be readily embedded in Van der Waals heterostructures and advanced quantum systems.

Highly anisotropic crystals have recently attracted considerable attention due to their ability to support polaritons with unique properties, such as hyperbolic dispersion, negative phase velocity, or extreme confinement. In particular, the biaxial van der Waals semiconductor α-phase molybdenum trioxide (α-MoO3) has received much attention [1] due to its ability to support in-plane hyperbolic phonon polaritons (PhPs) —infrared (IR) light coupled to lattice vibrations in polar materials— with ultra-low losses, offering an unprecedented platform for controlling the flow of energy at the nanoscale. In this talk, we will show experimental demonstrations of the unique behavior of PhPs in these crystals, including the visualization of anomalous cases of the fundamental optical phenomena of refraction [2] and reflection [3], and the exotic phenomenon of canalization, in which PhPs propagate along a single direction with ultralow losses [4]. References [1] W. Ma et al., Nature, 562, 557 (2018). [2] J. Duan et al., Nature Communications, 12, 1, 1-8 (2021). [3] G. Álvarez-Pérez et al., Science Advances 8, 29, (2022) [4] J. Duan et al., Nature Materials, 22, 867-872 (2023).

Photo-induced Force Microscopy (PiFM) offers a promising alternative to traditional Scanning Near-Field Optical Microscopy for subwavelength imaging. PiFM's key advantage is its fully mechanical detection through the Atomic Force Microscope (AFM) cantilever, simplifying the setup by eliminating the need for optical detectors and complex interferometric techniques. However, PiFM typically requires laser modulation at the AFM cantilever's intrinsic frequency, which can be challenging in the visible and near-infrared ranges, often involving acousto-optic modulators (AOMs) that introduce a wavelength-dependent laser steering. Our innovative setup eliminates the need for realignment, making PiFM a valuable tool for near-field spectroscopy in the visible and near-infrared spectral ranges.

We will provide an overview of IR s-SNOM for studying nano-optics and local chemistry of various 2D natural phyllosilicates, as a promising class of large bandgap lamellar insulators for optoelectronics and nanophotonics applications.

This presentation will reveal the rules on selecting efficient plasmonic nanoheaters for biomedical proposes. Here, a size dependence of plasmonic nanoparticle optical heating will be disclosed. The continuous laser heating of gold nanoparticles is evaluated exploring theoretical and experimental approach. This study demonstrates the use of optimized plasmonic gold nanparticles as photothermal agent for photoacoustic imaging technic, for the inactivation of yeast and for in-vivo hyperthermia treatment of the Sarcoma-180. Our results pave the way for the rational use of plasmonic nanoheaters in photothermal applications.

Nanoscale resolved imaging and spectroscopy utilizing scattering-type Scanning Near-field Optical Microscopy (s-SNOM) or tapping AFM-IR (local detection of photothermal expansion) bypass the ubiquitous diffraction limit of light and achieve a spatial resolution less than 20 nm in the infrared (IR) spectral range. Measurements have successfully demonstrated a wide range of analytical capabilities such as nanoscale chemical mapping and material identification, conductivity profiling and electric field mapping. The employed laser source critically determines the range of materials and phenomena which can be studied, motivating to continuously explore options to expand the accessible range, especially towards longer IR wavelengths. Here, we introduce a new tunable OPO laser source optimized for IR nanoscopy applications which covers a spectral range of 2-18µm. To illustrate the capabilities of this laser source, we demonstrate correlative s-SNOM and tapping AFM-IR+ based imaging, point spectroscopy and hyperspectral imaging. Application examples for investigating phonon polaritons in hBN and MoO3 and determining the nanoscale chemical composition of a thin film polymer blend.

Optical cavities with nonlinear elements and delayed self-coupling are widely explored candidates for photonic reservoir computing (RC). For time series prediction applications that appear in many real-world problems, energy efficiency, robustness and performance are key indicators. With this contribution I want to clarify the role of internal dynamic coupling and timescales on the performance of a photonic RC system and discuss routes for optimization. By numerically comparing various delay-based RC systems e.g., quantum-dot lasers, spin-VCSEL (vertically emitting semiconductor lasers), and semiconductor amplifiers regarding their performance on different time series prediction tasks, to messages are emphasized: First, a concise understanding of the nonlinear dynamic response (bifurcation structure) of the chosen dynamical system is necessary in order to use its full potential for RC and prevent operation with unsuitable parameters. Second, the input scheme (optical injection, current modulation etc.) crucially changes the outcome as it changes the direction of the perturbation and therewith the nonlinearity. The input can be further utilized to externally add a memory timescale that is needed for the chosen task and thus offers an easy tunability of RC systems.

Programmable photonic circuits manipulate the flow of light on a chip by electrically controlling a set of tunable analog gates connected by optical waveguides. Light is distributed and spatially rerouted to implement various linear functions by interfering signals along different paths. A general-purpose photonic processor can be built by integrating this flexible hardware in a technology stack comprising an electronic monitoring and controlling layer and a software layer for resource control and programming. This processor can leverage the unique properties of photonics in terms of ultra-high bandwidth, high-speed operation, and low power consumption while operating in a complementary and synergistic way with electronic processors. This talk will review the recent advances in the field and it will also delve into the potential application fields for this technology including, communications, 6G systems, interconnections, switching for data centers and computing.

Nanophotonics opens up novel opportunities for frequency comb generation and frequency-comb based sensing. Beyond integration and compactness, it provides new powerful concepts of instruments for interferometry, three-dimensional imaging, molecular physics and spectroscopy. With selected examples, I will provide a summary of advances in the vibrant emerging field of integrated optics for frequency-comb applications.

In this study, we present a high-performance, robust, and compact grating-based SPR sensor enabled by a tunable laser working at normal incidence. This configuration eliminates the spectral analysis and moving parts, thereby enhancing the robustness of the instrumentation. The setup is 10x25x10 cu. cm in in size, excluding the tunable laser. Both computationally and experimentally, we demonstrated the SPR dip splitting at normal incidence, which was lacking in previously reported grating-based SPR sensor studies. The sensor was tested with glucose solutions, achieving a sensitivity of 1101.6 nm/RIU and a resolution on order of 10^-5 RIU. The figure of merit of the sensor was 229.5 surpassing other reported grating-based SPR sensors by one order of magnitude.

Here, we apply a novel technique involving Joule-assisted modulation to enhance the sensitivity of the well-established surface plasmon resonance (SPR) method. Typically, SPR curves are generated from an angularly resolved scan of the reflected light beam from a metal thin film – dielectric interface. Due to the sensitivity of surface plasmon polaritons (SPPs), and confinement to the vicinity of the interface, they are an important utility in a variety of applications. In this work, a modified setup allows insight into the metal surface characteristics not seen through classical attenuated total reflection (ATR) measurements. Here, a constriction in the metal acts as a microscale bridge which is heated, via the Joule effect, and whose temperature follows the cycle of an alternating current. Employing a lock-in amplifier, referenced to the applied sine wave, enables detection of the reflected light now modulated by the changing optical constants. This dynamic technique is sensitive to the metal composition, surface chemistry, and morphology above the active plasmonic element, and has opened the door to enhance already highly sensitive SPR devices currently on the market.

Pump-probe spectroscopy is a well-established technique used to monitor the dynamics occurring in any state of matter, in timescales ranging from attoseconds to seconds and beyond. When performed at synchrotrons the technique offers probe with high repetition rate, wide scanning capabilities in terms of energy, spatial resolution at the nanometre scale, and elemental specificity. Recently, recognizing the impact and importance of such experiments across its science spectrum, Diamond with the strong support from the UK academic community, invested and deployed a novel laser source, PORTO, which can be used in various beamlines for pump-probe experiments. PORTO is a portable femtosecond laser system which has been used so far, for optical-pump and X-ray-probe absorption (XAS) and diffraction (XRD) experiments. Here we present its main characteristics and capabilities as well as its application in the areas of plasmonic photocatalysis and coordination chemistry, along with recent results about the ultrafast dynamics of hot electron ejection from plasmonic nanoparticles to semiconductor materials used in the field of plasmonic N2 photofixation.

Single photon emitters within hosts with high refractive indices suffer from low collection efficiencies due to total internal reflection at the host interface. This can be alleviated through shaping the local refractive index environment, specifically through forming open cavities and allowing matching between the emission mode in the host and travelling mode in air. We design micropillars around single photon emitters within aluminium nitride via electromagnetic simulations, and show that the collection efficiency can be increased by an order of magnitude compared to the base case. We fabricate the designs through standard clean room procedures and confirm collection enhancement through confocal microscopy.

Plasmonic nanoheaters, have attracted great attention in nanomedicine, due to their ability to efficiently generate and control heat delivery [1-2] at the nanoscale. There is a wide offer [3] of nanostructures that provide with strong photothermal responses and heat delivery, however most of them deliver heat in a symmetric way or require a certain orientation with respect to the excitation source to perform adequately. Here, we will first present an overview of some novel designs, fully plasmonic or hybrid dielectric/plasmonic, capable of offering not only enhanced photothermal response but also directional heat delivery. The thermal enhancing mechanism rely on the excitation of either dipolar or anapolar modes, depending on the design [4]. In the rest of the talk, we will show some of our recent findings on the thermal performance of DNA origami-based structures, offering theoretical insights into their potential for photothermal therapy applications. 1. J. González-Colsa et al. Sci. Rep 2022, 12, 14222. 2. J. González-Colsa et al. J. Phys. Chem. C 2023, 127, 19152. 3. G. Baffou et al. Nat. Mater. 2020, 9, 19, 946. 4. J. González-Colsa et al. J. Phys. Chem. Lett. 2022, 13, 6230.

Controlling Surface Plasmon Polariton (SPP) formation via temperature changes is very relevant for active plasmonic devices, sensors, and imaging systems. Understanding how heating affects plasmonic materials' optical properties in real conditions is crucial. Previous studies often use large temperature increments, overlooking precise optical constants-temperature relationships in non-ideal setups. This research addresses these gaps with a systematic approach: employing a temperature-controlled Surface Plasmon Resonance setup for precise data acquisition, coupled with computational analysis to elucidate optical property changes. Finite Element Method simulations via COMSOL Multiphysics further verify temperature's influence on electric field localisation. These simulations reveal temperature-induced differences in electromagnetic field distribution across systems.

The applications of photonic jet are proposed massively since it was coined in 2004, including for microscopy. Our first research proposing the application was photonic jet submicron etching using a nanosecond Nd:YAG laser with 1064 nm wavelength. Since 2018, we shifted to photonic jet microscopy – that is more feasible to conduct in our home facility. We used an optical fiber with a camera at the end (endoscope camera). Considering this optical fiber as a laser waveguide, we use the endoscope camera to observe a micro meter size object. The results are quite amazing. We show that we can apply photonic jet microscopy using an endoscopy camera and a glass microsphere.

Janus nanoparticles, incorporating plasmonic materials, have become important in thermoplasmonics. Controlled by pulsed excitation lasers, these nanostructures transfer thermal energy through material-fluid interfaces, regulated by interfacial thermal conductance. Here, we will present our most recent results [1] in revealing the influence of interfacial thermal conductance on the thermal relaxation of metal-polymer Janus nanoparticles that exhibit directional heat dissipation under pulsed illumination. In particular, we will discuss how neglecting the temperature dependence of thermophysical properties leads to an overestimation of the nanoparticle's temperature. We demonstrate the potential of gold/polymer semishell nanostructures as effective nanoheaters for photothermal therapies. Our findings can motivate the exploration of innovative strategies for efficient nanoheating platforms in temperature-controlled devices. [1] Javier González-Colsa, Fernando Bresme, and Pablo Albella. Impact of the Interfacial Thermal Conductance on the Thermoplasmonic Response of Metal/Polymer Hybrid Nanoparticles under Nanosecond Pulsed Illumination. J. Phys. Chem. C 2023, 127, 38, 19152–19158.

Linear quadrupole ion traps are established as a versatile platform for an environment-isolated manipulation of ions or charged micro-sized particles placed in an optically easy accessible spot. The preparation of ion species by sympathetic cooling at room-temperature demands up to several minutes, while encountering rf-heating and scattering losses. We have simulated the trapping process for a better understanding of the underlying dynamics and to test different trapping optimization approaches, for example exotic driving waveforms. Statistical analysis over a range of initial conditions and trap parameter showed a non-negligible influence of the driving waveform with up to 20 % reduced cooling time in a rectangular driven trap compared to a harmonic driven Paul-trap. The simulation reveals general observations in rf-heating, cooling speed, steady state energies at Coulomb-crystallization, and shifted stability regions compared to the harmonic trap driving. Based on these results a further systematic investigation with alternative drivings appears to be promising for improving the trapping stability and preparation times.

We demonstrated a novel depth sensing system that utilizes metasurfaces and photonic crystal surface-emitting lasers (PCSELs), realizing structured light generation and facial recognition in monocular depth sensing. Our single-shot system projects approximately 45,700 infrared spots from a 297^2 μm^2 metasurface area, which is 233 times smaller than the commercial DOE-based dot projector used in the Face ID on iPhone. The proposed system provides a measured field-of-view (FOV) of 158°. The system is lens-free and power consumption due to the utilization of PCSEL, reducing 5-10 times of power compared to VCSEL-array based dot projectors.

In this work, we study lasing in plasmonic nanoparticle arrays with complex structures. Complex structures can be formed by unit cells that contain more than one particle or by creating supercells i.e. giant unit cells, which contain tens of particles. Here, we study lasing in supercell arrays which are based on a square array geometry. The supercell is created by leaving certain lattice sites empty, creating an aperiodic pattern. This supercell is repeated to form an array. We calculate the band structures of the arrays by combining the structure factors of the lattice geometries with an empty lattice approximation. We show that by leaving certain lattice sites empty, some of the destructive interference is removed, leading to additional dispersive branches. This provides new band edges that support lasing. We experimentally demonstrate lasing in such supercell arrays which show interesting lasing emission patterns and multimode lasing.

Hexagonal SiGe alloys offer a group IV direct bandgap for integrated photonics, addressing the limitations of traditional silicon-based electronics. We have synthesized coaxial nanowire shells comprising direct bandgap hex-Ge/SiGe and hex-SiGe/SiGe quantum wells (QWs) around a wurtzite GaAs core. Time-resolved photoluminescence measurements demonstrate a 1 nanosecond radiative lifetime, proving direct bandgap emission. Photoluminescence spectra show the QW emission in between the emission of the well and the barrier material, indicating type-I band alignment. Measurements as a function of QW thickness demonstrate clear quantum confinement with emission up to room temperature for thick QWs. By changing the QW-thickness and the well composition, the emission could be tuned between 2000-3400 nm. The experimentally observed direct bandgap SiGe QWs with type-I band alignment are expected to be pivotal for the development of novel low-dimensional devices based on hex-Ge and hex SiGe.

Efficient integration of quantum emitters (QEs) with beam shaping and polarization encoding functionalities has always been on the agenda but heretofore remained elusive. Here, we proposed a general approach for designing chip-integrated single-photon sources with flexible control of photon polarization states and orbital angular momenta (OAM), including the possibility for multichannel single-photon generation. The developed approach is based on meticulous design of QE-coupled anisotropic metasurfaces for outcoupling QE-excited diverging surface plasmon polaritons (SPPs) into single-photon beams with desired properties. We have realized independent manipulation of the single-photon spin angular momentum (SAM) and OAM states by using anisotropic metasurfaces. Furthermore, we have demonstrated the generation of high-purity linearly polarized (LP) single-photon beams with arbitrary different OAMs and further extend to realize multiplexing of single-photon emission channels with orthogonal LPs carrying different topological charges. Our findings provide a promising approach for chip-scale control of quantum emission with versatile functionalities.

We have demonstrated a string of novel nonlinear chiroptical effects, in Rayleigh and Mie scattering. Here, the latest progress will be reported, which includes observation of the effects in new materials. We will also present data on nonlinear chiroptical Raman scattering.

In this study, we showcase the innovative application of orbital angular momentum (OAM) beams for precise manipulation of 2D material structures, emphasizing spatial and temporal control. Focusing on graphene and WS2, we illustrate the efficacy of OAM beams in manipulating the materials electrical properties. Additionally, we present a device—an optically controlled graphene Field-Effect Transistor (FET)—as a prime example of the practical implementation of this technique, highlighting its potential in advancing the field of optoelectronics and material science.

Generation of structured light in optical fiber science and technology is severely limited by mode mixing or by the lack of optical elements that can be integrated onto fiber end-faces for wavefront engineering. I will present a metafiber platform capable of creating arbitrarily structured light on the hybrid-order Poincaré sphere. 3D polymeric metasurfaces, with unleashed height degree of freedom, were 3D laser nanoprinted and interfaced with polarization-maintaining single-mode fibers. Multiple metafibres have been developed to transform the fiber output into different structured-light fields, including cylindrical vector beams, circularly polarized vortex beams, and arbitrary vector field.

We just entered a new era of materials characterization, where atomic sensitivity can be achieved by plasmon-enhanced optical spectroscopy. During this talk you’ll hear about a new characterization method where nanoparticle-mediated electrical contacts can “squeeze” light in the device active material, providing an innovative non-destructive technique able to characterise various device materials changes in operando. We will discuss how we probed few hundreds oxygen vacancies drift in thin (~5 nm) dielectric films during device switching just by the aid of visible light, an approach that helped to identify the breakdown mechanisms upon cycling in memristive device and ultrathin ferroelectric memory devices (FeRAMs). Ypu will hear about the first characterization of nanoscale MoS2-based electrical switches at room temperature and in air, where we proved volatile threshold resistive switching due to the intercalation of metallic atoms (nanofilaments 1–2 Au atoms thick) from electrodes directly between Mo and S atoms.

Photonic nanojets typically require a spherical object onto which a laser beam is illuminated. The presence of the spherical object creates a near field nanojet where light is emitted in the vicinity of the sphere. We explore the nanojet emanating from various diameters of the spheres and find that there are two different regimes which can be present. In the first regime, the sphere is small compared to the wavelength of the incident light when the transverse dimension of the nanojet is smaller than the diffraction limit while the axial dimension is diffraction limited, as has been recently shown. In addition, we find another regime where the sphere diameter is much larger than wavelength, when the axial dimension of the nanojet is now smaller than the diffraction limit keeping the transverse dimension the same as diffraction limit. This yield very high numerical apertures. We also show that we can optically confine particles with a axial corner frequency which is a factor of 3 larger than regular optical trapping with 100x objective due to the subdiffractive axial nanojet.

The Born series is in principle an insightful method for solving forward electromagnetic scattering problems, but in practice the series almost always diverges. We present a vectorial perturbation method based on the Born series for scattering by a diffraction grating. We show the general theoretical formalism, as well as a semi-analytical implementation for a diffraction grating. To deal with cases in the strong-scattering regime, where the Born series diverges, we use Padé approximation to still retrieve an accurate result. The presented method has the inherent benefit of showing the underlying physical mechanisms that lead to the solution, helping to understand how a scattered signal is generated. This makes the method potentially interesting for applications in optical metrology, among others.

In this paper, we present an innovative top-down approach for fabricating billions of InGaN/GaN-based dot-light-emitting diodes (LEDs) that eliminate the need for a sacrificial layer. Our method combines electrochemical etching (ECE) and sonochemical separation to isolate the dot-LEDs. A detailed investigation into electrochemical parameters reveals their impact on the nanopore size, separation efficiency, and the dot-LEDs’ emission properties. Higher voltages result in more extensive ECE of the n-GaN portion. Furthermore, lower vapor pressures, along with higher viscosities and surface tensions, enhance the sonochemical separation efficiency of dot-LEDs during the ECE process. The blue electroluminescent (EL) devices fabricated using these dot-LEDs achieved an external quantum efficiency (EQE) of 7.34% at a forward voltage of 4.2 V, with remarkable luminance efficacy. Although the current generation of blue Au-coated dot-LEDs does not surpass the EQE of existing displays, it marks a significant step in the burgeoning field of dot-LED display technology.

A three-dimensional MAPbI3 quantum dot (QD) with geometries including spherical, cubic, and conical has been embedded in the CsPbBr3 matrix. Bound energy wavefunction gives rise to miniband, which results in the formation of IB. If there is more than one miniband then there is a possibility of having more than one IB. The optimization of QD size results in more IBs in the forbidden region. One band time-independent Schrödinger equation using the effective mass approximation with step potential barrier is solved to compute the electronic states. Envelope function approximation with BenDaniel-Duke boundary condition is used in combination with the Schrödinger equation for the calculation of eigen energies and eigen energies are solved for the quasi-bound states using an eigenvalue study. The transfer matrix method is used to study the quantum tunneling of MAPbI3 QD through neighbor barriers of CsPbI3. Electronic states are computed using the Schrödinger equation with effective mass approximation by considering quantum dot and wetting layer assembly. Results have shown that varying the quantum dot size affects the energy pinning of QD.

This study employs numerical discretization and the effective-mass approximation to investigate exciton states in asymmetric biconical quantum dots, focusing on the influence of electric fields on photoluminescence (PL). Biconical quantum dots offer enhanced control over charge carrier confinement, making them promising for applications in fields like bioimaging and quantum computing. The research calculates excitonic properties in GaAs bicones, demonstrating their potential as tunable light sources. In conclusion, this research provides a solid theoretical foundation for manipulating biconical quantum dot properties and highlights their practical significance in optoelectronic device development.

In this study, we investigated electronic properties of a dumbbell-shaped quantum dot (QD) made from gallium arsenide. For this purpose, we employ the finite element method. Our investigation begins by calculating the wave functions and energies of the ground state and the first nine excited states. This allows us to understand how the quantum dot's shape impacts its electronic structure. Based on the obtained results for the wave functions and energies of one electron, we calculated the oscillator strengths for different quantum transitions. We discover that the most pronounced absorption occurs during transitions between the ground state and the second, third, eighth, and ninth excited states. Additionally, we analyzed the absorption processes between these energy levels and revealed the dependence of the absorption coefficient for the intraband transitions dumbbell-shaped QD on the energy of the incident light.

This work is dedicated to laser engineering of spherical resonant Mie-excitonic nanoparticles from layered materials, particularly transition metal dichalcogenides (TMDC). The proposed approach leverages femtosecond laser ablation and fragmentation in liquids for the fabrication of water-dispersed ultra-stable spherical TMDC nanoparticles (NPs) of variable size (5 – 250 nm). Such nanoparticles demonstrate exciting optical and electronic properties inherited from the TMDC crystals, due to preserved crystalline structure, which offers a unique combination of pronounced excitonic re-sponse and high refractive index value, making possible a strong concentration of electromagnetic field in nanoparticles.

The Goos-Hänchen shift (GHS) can be measured typically by fixing the wavelength of incident light and changing the angle of incidence to analyze the optical modulation characteristics of the film material or its relevant parameters. In this paper, the membrane structure of one-dimensional photonic crystals (1DPC) was analyzed by varying the wavelength of incident light combined with GHS measurements. The theoretical analysis and experimental results show that the spectrum-GHS analysis method can show the band gap of 1DPC well and enhance the GHS, so as to improve the sensitivity of the prism-type sensors with 1DPC film sensitive layer.

Silver nanowires (AgNW) assembled through "Grazing Incidence Spraying" (GIS) method offer precise control over light polarization. These anisotropic materials can be combined with the layer-by-layer (LbL) technique to create intricate multilayer films. Understanding their optical properties involves investigating interactions on both microscopic and macroscopic scales. A homemade white light interferometric microscopy was developed to generate high-resolution spectral maps, and new local spectroscopy methods have been designed for pixel-by-pixel or area measurements. Additionally, a super-resolution local spectroscopy technique achieves a lateral resolution of 100 nm without markers and allows multimodal data acquisition. The setup has been enhanced to include TE and TM polarization measurements.

The fast manufacturing of centimeter-scale color printing and color filter arrays has been demonstrated by combining the concept of pixelated F–P cavities and the laser grayscale lithography technique. A centimeter scale F–P type color printing device with a spatial resolution of 5 μm × 5 μm and the 1/3-in. color filter arrays with resolutions higher than 1200 ppi were successfully fabricated. The proposed strategy can be used for colorful painting, flat panel displays, and so on.

Coupled semiconductor quantum dots and plasmonic structures are currently a topic interest for the generation of single photons for quantum applications. We have addressed the challenge of precise QD placement near plasmonic structures using a plasmon-induced two-photon polymerization method. Au bipyramids offer a single hotspot on the substrate surface, with localization of the electric field at the pointed tip, resulting in sharp plasmon resonances and strongly enhanced field intensity. By employing a two-photon polymerization method, QDs were successfully localized near Au BPs, and have revealed signatures of strong coupling, thus validating the method's potential for photonics applications.

This project explores optical near-field characterizations of dielectric thin films, such as SiO2 and Nb2O5, using a scattering Scanning Nearfield Optical Microscope (s-SNOM). The s-SNOM involves light scattering from a nanometer sharp tip, where the resolution is no longer wavelength-dependent. Our goal is to use dielectric thin films of different optical thicknesses to quantitatively investigate the optical near-field interactions. This work addresses the challenge of working with dielectric samples in the visible range. SiO2 and Nb2O5 layers were deposited on Si substrates by reactive magnetron sputtering, and theoretical models were used for comparison, providing insights into accurately measuring optically transparent components with s-SNOM.

Photosynthetic organisms use different types of nanophotonic-based strategies in their light-harvesting process to adapt to changing light environments. Recently, it was found that the epidermal cells of some brown algae, (e.g species C. tamariscifolia) show adaptative intracellular opal-like photonic crystals (PC) responsible for variable strong reflectance of individual cells at specific wavelengths. Mimicking these properties may allow for self-adapting strategies towards smart photonic nanomaterials. Here we show that is possible to use hierarchical self-assembly of colloidal polymer nanoparticles combined with pigments, architecting a similar structure to the epidermal cells in C.tamariscifolia. We believe that the biomimetic hierarchical structure could be suitable first as a means for bright colour production and ultimately as a path to better understand the role of the photonic organelle in the algae. Moreover, our developments could be suitable for biomimetic light-harvesting technologies.

Only work-related stress was estimated to cost US companies more than $300 billion a year in healthcare costs, absences and decreased performance. Early diagnosis of stress conditions and therefore improved recovery and reduced costs could potentially be achieved with continuous monitoring of stress biomarkers using wearable devices. Compared to the conventional electrochemical and optical sensing methods used in current wearable devices, plasmonic sensing could offer higher sensitivity, better stability and faster data collection. Our developed plasmonic sensor chip represents a nanograting structured polymer on a silicon substrate, covered with gold. The sensing method is based on detecting a surface plasmon resonance wavelength shift due to refractive index change caused by presence of analytes in the vicinity of the plasmonic grating. The sensitivity of the chip was tested with two different stress-related biomarkers: cortisol and creatinine. With the tested range from 0 to 265 mM, in the current version of the system, without a receptor layer, the detection limits for cortisol and creatinine were 10.65 and 7.09 mM, respectively.

Vanadium dioxide (VO2) undergoes a reversible transition from insulator to metal phase at a critical temperature of 68°, making it a promising candidate for various applications, including smart windows, sensors, and switching devices. In this context, we present an innovative core-shell structure, specifically VO2@Si, to increase the thermal stability of VO2 while adding mechanical protection, deposited on a thin layer of silver to alter the optical properties of VO2. Our research delves into the principal physics underlying this spectral selectivity, highlighting the interplay between the VO2 phase transition and the core-shell design.

This paper presents a comprehensive exploration of Surface-Enhanced Raman Spectroscopy (SERS) substrate design, leveraging Finite-Difference Time-Domain (FDTD) simulations for systematic parameter sweeping. Our investigation goes beyond enhancing SERS performance, addressing the crucial aspect of manufacturability with two-photon polymerization (2PP). By examining parameters such as height, pitch, and diameter, we aim to identify structures that not only exhibit high enhancement factors but also possess higher tolerances suitable for practical fabrication. Novel models are developed to visualize SERS hotspots based on nominal shape and AFM data, providing valuable insights for both substrate performance and manufacturability. This dual-focused strategy, integrating FDTD modeling with 2PP fabrication, offers an understanding for advancing SERS substrate design in both sensitivity and practicality.

In this study, an exploration of excitonic states within a cylindrical GaN/In x Ga 1-x N quantum dot is conducted taking into account piezoelectric effects. The axial confinement is modeled using the modified Poschl-Teller potential, while for the radial direction a parabolic potential is used. The investigation encompasses the computation of exciton energy and binding energy, considering the geometric properties of the cylinder and varying indium concentrations. Furthermore, examination of the effects of these parameters on absorption processes within quantum dots is undertaken. Significantly, the findings elucidate the impact of indium concentration on the spatial distribution of electron (hole) probability along the axial direction within cylindrical quantum dots.

Efficient manipulation of the valley degree of freedom in transition metal dichalcogenide (TMD) monolayers at the nanoscale becomes very desirable for future developments in valleytronics. Resonant optical nanostructures are considered as potential tools in this endeavor; however, it is still unclear how they affect polarization properties of valley-specific monolayer emission. Here, we present a systematic experimental and numerical study that is aimed to bridge this gap. As a simple model, we consider a hybrid system where valley-polarized photoluminescence or second harmonic from MoS2- monolayer is coupled with a plasmonic nanosphere. Through this study, we are not only aimed to refine the exciting simulation approaches for valleytronic devices, but also contribute to the deeper understanding of the rich physics of light-matter interactions at the nanoscale.

Spatiotemporal optical vortices (STOVs) are a type of optical pulse carrying orbital angular momentum. Here, we present analytical expressions for STOVs carrying transverse orbital angular momentum that are as round as possible. We obtain these expressions by applying specific mathematical differential operators to travelling light “blobs” presenting a Poisson frequency spectrum and modelled using the complex focus point method. Both the scalar case and the electromagnetic case are presented.

We propose a highly efficient surface plasmon resonance (SPR)-based sensing device to detect various anaemic conditions in human blood. A thin aluminum (Al) metal-coated glass prism is used to excite surface plasmons. A high-dielectric constant material, TiO2, is used over Al-metal to enhance the sensitivity, and a layer of fluorinated graphene (FG) is used as a bio-recognition element to study biomolecular interactions. To demonstrate sensing application, an Al (30 nm)-based engineered plasmonic device with an optimized value of TiO2 (2nm) and functionalized with an FG layer is utilized to detect various hemoglobin (Hb) concentrations in human blood at a wavelength of 1550 nm. A value of sensitivity of 123 °/RIU and FOM 439 RIU-1 is observed for the proposed Al-TiO2-FG-based SPR sensor. The proposed sensing device can be used as a biosensor to detect anemia by accurately evaluating the level of Hb concentration, making it the best candidate for biomedical applications.

The manipulation of acoustic phonons at ultrahigh frequencies is crucial for utilizing them as information carriers. Characterization of phonon transport is a fundamental step towards manipulating phonon dynamics. Recent works have shown that surface acoustic waves with gigahertz frequencies can propagate over micrometer distances in various structures such as nanowires and nanoantennas. Here, we aim to investigate phonon transport at around 20 GHz by designing a GaAs/AlAs optophononic waveguide. The Fabry-Perot cavity ensures vertical confinement of phonons and the interface of air and semiconductor reflects phonons laterally, guiding them along the waveguide. In this work, by means of coherent phonon generation and detection experiment in a pump-probe setup, where pump and probe beams are spatially separated, we analyze the signal originated from phonons generated in the pump position reaching the remote probe location. We observed a delayed signal at 20 GHz, indicating phonon transport at room temperature.

We report a narrow-band spatial filter inverse designs for broadband spectra achieved via global optimization methods for Guided Mode Resonance (GMR) filters. In this work, the numerical analysis of such a filter is performed with the Rigorous Coupled Wave Analysis method. Lastly, the theoretical predictions were validated by spectral measurements of fabricated surface relief gratings that function in the GMR regime.

A key component of integrated photonics-based Lidar are the optical radiators used as optical antennas arranged in OPAs. We propose a novel design of grating couplers to be used as the building blocks of the optical antennas of Lidar systems, designed in the Si3N4-TriPleX platform, based on asymmetric double-stripe waveguide geometry for operation around 1550 nm. The proposed gratings have non-uniform geometry, varying waveguide width and filling factor, targeting constant emission angle, while optimizing for a uniform emission profile. The designs allow to achieve low theta angle divergence as well as maximum wavelength steering. The reported design showcases theta angle 3dB divergence of 1deg, phi angle 3dB divergence of 20deg and wavelength steering of 10deg/100nm. The proposed components show low fabrication complexity and are compatible with standard fabrication processes. A comparison between uniform and non-uniform grating designs is also presented, investigating also their performance in an OPA configuration.

Brillouin scattering, the inelastic scattering of light by acoustic phonons, have received a lot of attention due to the emergence of cavity optomechanics. In particular, Brillouin spectroscopy schemes are developed to study confined acoustic phonons at ultrahigh frequencies in nanostructures. However, standard Brillouin spectroscopy techniques developed to measure high frequency phonons are optimized for a fixed wavelength, which makes them not compatible with tunable cavities. We introduce a scheme to manipulate the polarisation selection rules of the Brillouin scattering using optophononic elliptical micropillars, which allows the access of frequencies down to few tens of GHz. This scheme leads to differences in polarisation between the Brillouin signal and the reflected laser, allowing its filtering. In this work, the polarisation states are controlled with the incident-laser’s energy and polarisation, as well as the micropillar’s ellipticity. We also explore the optimal filtering conditions to improve the polarisation-based Brillouin spectroscopy technique.

Fundamental studies of the interaction of chiral light with chiral matter are important, especially for the development of methods that allow selective optical detection of chiral organic molecules. One approach to achieve this goal is to develop a Fabry-Perot resonator that supports eigenmodes with desired electromagnetic handedness which interact differently with the left and right molecular enantiomers. In this study, we theoretically investigate chiral Fabry-Perot resonators with mirrors formed by one-dimensional photonic crystal slabs. We show that the electromagnetic field of the eigenmodes of such resonator can reach the maximum chirality and the intensity distribution is homogeneous without zeros. The one-dimensional photonic crystal mirrors of such a Fabry-Perot resonator have a much simpler geometry than existing solutions, and the rotational degree of freedom allows for fine tuning.

Photonic band gap crystals are being pursued for their great potential to govern the spontaneous emission of excited quantum emitters. Here, we study the radiative decay of excited PbS quantum dot nanocrystals inside 3D photonic band gap crystals made from silicon in the near-infrared. At frequencies just above the band gap, we observe 14x enhanced intensity from quantum dots inside the crystal compared to dots outside, indicative of strongly enhanced emission. Moreover, using time-resolved single photon counting, we observe fast non-exponential decay, which is consistent with probing an ensemble of quantum dots at varying depths in the nanopores, each experiencing a position-dependent enhanced local density of states.

Surface-enhanced Raman scattering (SERS) emerges as powerful technique, offering the unique advantage of capturing the molecular "fingerprint". However, a recurrent concern revolves around the reproducibility of SERS results, highlighting a gap between published high-quality outcomes and limited practical applications. This study introduces a novel SERS platform fabricated using ultra-violet nanoimprint lithography (UV-NIL) and deep reactive ion etching (DRIE) to produce large-area, ordered nanostructured arrays. Using UV-NIL imprinted patterns in resist, we were able to overcome the main limitations present in most common SERS platforms, such as nonuniformity, nonreproducibility, low throughput, and high cost. Three approaches for fabricating SERS substrates based on the same NIL template are presented: the NIL imprint, DRIE: Bosch and Cryogenic etched patterns in silicon, all coated with thin gold layer. The enhancement capabilities of the fabricated SERS substrates are compared by measuring Rhodamine 6G.

Photocathodes are key elements in high-brightness electron sources and ubiquitous in the operation of large-scale accelerators. In this work, we propose the use of ultrafast laser nanostructuring techniques on copper photocathodes as a way to enhance the quantum efficiency of metallic photocathodes and enable their use in next-generation electron photoinjectors. When the surface is nanoengineered with patterns and particles much smaller than the optical wavelength, it can lead to the excitation of localized surface plasmons that produce hot electrons, ultimately contributing to the overall charge produced. To quantify the performance of laser nanopatterned photocathodes, we measured their quantum efficiency in a typical electron gun setup. Our experimental results suggest that plasmon-induced hot electrons lead to a significant increase in quantum efficiency, showing an overall charge enhancement factor of at least 4.5 and up to 25. We demonstrate laser nanopatterned plasmonic photocathodes outperform standard metallic photocathodes, and can be directly produced in-situ at the electron gun level in vacuum environments and without any disruptive intervention.

This study investigates the fabrication of high-quality diffractive optical elements (DOEs) by direct laser ablation using femtosecond UV laser pulses (240 fs, 100 kHz, 257 nm) from a solid-state Yb:KGW laser system. The resulting microstructures exhibit low roughness and precise depth control. The ultrashort pulse duration minimizes heat transfer, particularly advantageous for high band-gap materials. The utilization of higher harmonics (4th–5th harmonic of Yb:KGW laser system) in the UV range enables linear absorption, reducing heat-affected zones and providing the necessary precision in depth control for effective light phase manipulation in DOEs. This simplified, mask-less approach using femtosecond laser systems showcases the potential for cost-effective and high-quality DOE fabrication, offering an alternative to complex, high-cost methods.

By constructing a residual convolutional neural network to form an autoencoder, a two-way mapping relationship between the structural parameters of the designed metasurface absorber and the absorption spectrum was constructed. The forward prediction network can simulate the FDTD method to quickly and accurately predict the absorption spectrum for given absorber structural parameters. Inverse engineering networks enable the design of ideal encoding structures for user-specified absorption spectra. Compared with traditional methods, the deep learning design method proposed in this study has significant advantages in accuracy and efficiency, greatly reducing computing resource consumption. This method can be used for the metasurface designs of other functions. This is of great significance for the rapid development of nanooptics theory.

Plasmonic excitation, driven by collective electron oscillations in metallic nanostructures, are vital in nanophotonics for manipulating light at the nanoscale. This study focuses on metal nanogaps of 20 nm width fabricated via photolithography and atomic layer deposition, exhibiting tunable transmission resonances across visible to near-infrared wavelengths. Raman spectroscopy of Poly p-phenylene vinylene (PPV) on these metal nanogaps reveals altered Raman linewidths without significant changes in Raman frequencies, elucidating the intricate interplay between plasmonics and molecular interactions. These findings are pivotal for advancing our understanding of plasmonic effects at the molecular level, offering insights for innovative optoelectronic device design and sensing applications.

Bragg-Grating-Waveguide (BGW) delay lines are commonly used in transmission mode, owing to the significant elevation in group index observed at the edge of the stopband. However, achieving delays often necessitates structures with a larger footprint, such as cascaded or spiral designs, which consume a substantial amount of chip estate. Recent approaches to optimize chip space involve round-trip configurations with reflectors, but these can restrict bandwidth and cause mode conversion. Our study introduces an efficient solution: a meta-reflector for TE0 mode, enabling double delays via a single path, while also employing a step taper in TM0 mode to couple the TM signal into a strip waveguide, within a 1.9 × 2.6μm^2 area. Simulations show that in TE mode, there is a peak attenuation of -0.18 dB within the 1530–1590nm wavelength spectrum, and in TM mode, the loss reaches -4.73 dB across the 1500–1600nm band. In the computation of losses, the customary impact of the Bragg grating waveguide was disregarded, with attention concentrated exclusively on the design of the reflector.

We experimentally study and numerically analyze arrays of more than 400 coupled spherical resonators, with optical Q exceeding 10^7. We fabricate a 2D hexagonal lattice of resonators and couple light to one of the resonators. Using fluorescent materials in the spheres' surroundings permitted spatial and spectral mapping of the cavity ensemble's resonances. This reveals that light reaches distant resonators in various ways, including while passing through dark gaps, resonator groups, or resonator lines. Our almost infinite periodic array of resonators might impact a new type of photonic ensembles, having high-Q (>10^7) resonators as unit cells for sensing via their unique spatio-spectral signature and its sensitivity to changes over large areas.

Integrated optical phased arrays (OPAs) are important for various applications such as LIDAR, microscopy, wireless communication, and holography. Traditional one-dimensional N-element OPAs with individual phase shifters for varied steering angles often have emitter spacings that exceed half a wavelength, leading to grating lobes. Moreover, using true-time-delay lines with varied numbers of periods for different delays may cause amplitude inconsistencies and further side lobe elevation. The proposed partially apodized (PA) one-dimensional grating waveguide design controls amplitude while conserving the time delay for targeted steering angles, using distributions such as Uniform, Tschebyscheff, and Binomial to minimize grating and side lobes. We fabricated an eight-element-array with insertion losses of -3 dB (uniform) and -4.1 dB (PA) across the 1530-1580 nm wavelength band.

Numerical optimization for the inverse design of nanophotonic structures is a tool which is providing increasingly convincing results -- even though the wave nature of problems in photonics makes them particularly complex. In the meantime, the field of global optimization is rapidly evolving but is prone to reproducibility problems, making it harder to identify the right algorithms to use. Here we benchmark different global optimization algorithms on a diversity of nanophotonic tests cases. We present general guidelines to get the most out of Nevergrad, a state-of-the-art optimization platform. We detail which observables – such as convergence or consistency curves – are relevant for judging the reliability of an optimization and the quality of the generated solution. We provide benchmark examples on a broad range of topics, including 1D, 2D, 3D problems, with a continuous or a discrete parameter description, to illustrate the versatility of the Nevergrad platform.

We propose ultra-compact, highly stable interferometer based on single-layer dielectric metasurface for common path off-axis digital holography. Our ultracompact metasurface based interferometric system enables non-destructive, real-time, label-free imaging of transparent specimens and can reveal information about their fundamental physical, chemical, and morphological propertiesThe metasurface interferometric imaging system could provide birefringence properties of anisotropic test samples from quantitative phase analysis.

The current lack of transmissive photonic components in the extreme ultraviolet (XUV) spectral range poses a challenge for guidance and confinement at micro/nano-scale. In this study, we propose a novel theoretical approach for achieving guidance of XUV radiation by leveraging the electromagnetic linear response of Titanium-Aluminum-Titanium heterostructures within this spectral range. Our findings indicate that, due to the near-zero-index properties of aluminum and titanium, effective coupling of XUV radiation with plasma oscillations occurs in these heterostructures, enabling the excitation of diverse plasmon polariton modes. Our predictions, based on the semi-analytical solution of fully vectorial Maxwell’s equations, reveal that the aluminum thickness can efficiently modulate the dispersion profile of plasmon polariton modes, allowing for nanometer-scale confinement and micrometer-scale propagation length. These results hold promise for the development of future devices enabling advanced control and manipulation of XUV radiation.

We explore the evolving landscape of planar optics, driven by a growing demand for lenses with reduced thickness and enhanced super-resolution capabilities. Traditional methods face limitations in forward design, stemming from low discrete levels, periodic arrangements, and electromagnetic coupling between structures. To address these challenges, we present a lens design employing gradient topology optimization within the inverse design paradigm. Utilizing randomly arranged topology optimization under various critical conditions, our innovative approach yields supercritical lenses surpassing the highest Fourier frequencies. The objective is to attain subwavelength planar lenses with a 100 nm structural thickness. Considering practical manufacturing constraints, convolution is introduced during optimization, limiting the structure's minimum width and simulating real-world imperfections. Expanding functionality, we optimize a complex lens design for multi-band operation through a unified structure and correct chromatic aberrations using advanced methods. Furthermore, our analysis extends to spherical and off-axis aberrations, offering valuable insights into intricate lens design.

Grating coupled surface plasmon resonance (GCSPR) devices with wavelength, angle or intensity modulation are used in many fields including sensing and switching. Here, we report the comprehensive analysis of metal-dielectric gratings with broad opto-geometric parameter range, for the angular interrogation of surface plasmonic excitation. We show that angular spectral features of the surface plasmons can be precisely controlled with the grating geometry, incident angle and excitation wavelength. The multi-parameter optimization of sinusoidal and rectangular grating structures yields the design coordinates for sharp resonance features in the angular reflection response of surface plasmons.

A topologically optimized photonic cavity with an integrated lateral p-i-n structure-based silicon (Si) photodetector has been fabricated. The silicon-based cavity allows for the integration of photodetectors (PDs) in CMOS technology, bypassing challenges associated with adding other materials. The goal of the topological optimization is to maximize the rate of two-photon absorption in silicon while maintaining small dimensions. The fabricated device was characterized, obtaining a resonant wavelength at 1543 nm with a Q-factor of 6315 and a responsivity of 0.36 mA/W at an optical power of 1.8 mW while maintaining a low dark current of 45pA.

2D materials are compatible with many material platforms as they adhere to other materials strictly by van der Waals interactions. This, together with the variety of band gaps found among transition metal dichalcogenides (TMDCs), makes them uniquely interesting to study for on-chip light sources, as the photonic integrated circuit (PIC) industry is developing into several material platforms depending on the application (gold, silicon, silicon nitride, indium phosphide, etc). 2D materials could thus potentially provide a universal on-chip light source (and detector) scheme for all PIC platforms in the future. In the presentation, I will show recent results on how exfoliated monolayer TMDC flakes can be integrated with plasmonic slot-waveguides and plasmonic dipole antenna couplers to inject their photoluminescence into plasmonic waveguides for use as a future on-chip light source.

We present a retroreflective optical grating designed to work as a sensor which can be read out remotely using a tunable laser. The goal is a simple device for gathering high spatial resolution environmental measurements without requiring electronics or manual intervention at every sampling location, and which does not require elaborate set up or alignment. The design is made using an inverse design method and by combining ideas from the fields of diffractive optics, metasurfaces and grating couplers.

The search for nano-scaled light sources and detectors with an emission/absorption precisely controlled through the design of their morphology and structure is fundamental to elaborate new synthesis and fabrication solutions for optoelectronics. In this context, a core-shell heterostructure with promising application in telecommunication is taken as an example to demonstrate the technical capabilities available at the hard X-ray nanoprobe beamline ID16B of the European synchrotron (ESRF) to characterize optically active nano-materials. The proposed case study is an InGaAs/InP multi-quantum well (MQW) structure grown with a perfectly hexagonal shape onto InP nanowires (NWs)[1]. Nano-characterization via a combination of X-ray fluorescence (XRF), X-ray near edge spectroscopy (XANES) and X-ray excited optical luminescence (XEOL) techniques, was carried out to locally probe the elemental homogeneity at the deep submicrometric scale and to investigate on the local optical properties and their correlations with the phase structure and defects. [1] Zhang, F. et al., Adv. Funct. Mater. 32, 2103057 (2022).

This study centers on the comparative analysis of three artificial neural network (ANN) models designed to predict the optical changes in low-E glass coatings following heat treatment. Focused on enhancing the manufacturing process of coated glass, which undergoes significant alterations in both aesthetic and thermal properties due to tempering, our research aims to streamline and improve prediction accuracy beyond traditional methods. By evaluating the performance of these three ANN models using data from prior experiments, we identify the most effective approach for forecasting post-tempering optical properties. This comparative study not only advances our understanding of predictive modeling in glass coating technology but also provides valuable insights for the automotive and architectural industries, promising to revolutionize the design process, reduce costs, and spur further innovation in coated glass products.

We propose a plasmonic near-field active switch based on the Cayley fractal as the building block, such that two Cayley fractal elements are placed in a dimer-configuration on top of a thin film of VO2 on a plasmonic substrate. This switch is capable of offering a high intensity switching ratio. Finite Difference Time Domain (FDTD) modelling is carried out to analyze the intensity switching ratio spectra as a function of the fractal order. The effect of geometrical parameters such as the length of the cayley fractal, thickness of the VO2 layer is also analyzed to explore wavelength tunability of the proposed switch.

Nitrogen vacancy (NV) centres in nanodiamonds (NDs) are excellent fluorophores. They find applications in bio-sensing, bio-imaging and as single photon emitters. The photoluminescence (PL) spectra of NV centres span over the visible-near IR region (500-900 nm). The spectra consist of temperature-dependent sharp characteristic peaks of neutral and negatively charged NV centres corresponding to zero phonon line (ZPL) transition. When these NV centres are coupled with microcavities, sharp ripple-like resonant modes known as whispering gallery modes (WGMs) are observed in the emission spectra. The time-resolved fluorescence of NV centres are found to be dependent on excitation and emission energies. The fluorescence decay of NV centres reveals the contribution of different charge states. In addition, jet-like structures (photonic nanojet, PNJs) are observed due to the non-resonant interaction of light and NV centre-coupled microcavity. The PNJs have been used to enhance the weak Raman scattering signal.

Generally obtained with microsphere or dielectric micro-objects, photonic jets or nanojets are narrow and intense beams that can be focused beyond the diffraction limit. They are obtained at the mesoscale, that is at a distance that can be compared to the microsphere size. Since few years, they are now also available out from optical fibers. Initially, with a microsphere at the distal end of a hollow core fiber or with lensed multimode fiber fabricated by thermoforming. More recently, photonic jets have also been demonstrated with single mode fibers functionalized by a high curvature micro-lens deposited just on their core. A specific fabrication method has been developed and patented for this application. We will show how this method can be used to generate four independent photonic jets out from four cores of a multi-core fiber, making of this technique a very promising one for many applications.

The study of ultrahigh-frequency acoustic phonons is a promising pathway for important technological advancements. Acoustic resonators operating in the gigahertz range usually require atomically flat interfaces to avoid phonon scattering and dephasing, leading to costly fabrication processes, and are bound to fixed frequency operations. Mesoporous materials, with pores at the nanoscale, are good candidates to surmount such constraints. Resonators based on mesoporous SiO2 and TiO2 have been demonstrated to present acoustic resonances in the 5-100 GHz range. The infiltration of liquids and vapors into the pores modifies the effective material optical and elastic parameters. Here, we study acoustic resonators based on mesoporous materials at different ambient relative humidity conditions. We demonstrate that the water infiltration into the pores modifies the acoustic response in the GHz range. Such functionality would enable the development of inexpensive responsive acoustic devices in the gigahertz range, ideal for ultrafast data processing.

In this experimental study, we delve into the potential implementation of logic operations using the interference of propagating spin waves within a device comprising intersecting yttrium iron garnet waveguides with submicrometer width. Notably, we extend our exploration to incorporate phase-change materials as memory elements atop these waveguides. Our results underscore critical considerations in the design of magnonic nanodevices operating with short-wavelength spin waves, offering valuable insights for optimizing their performance in practical applications.

Hyperuniform disordered photonic structures offer a novel setting for the study of electromagnetic wave propagation in disordered media. They have been shown to have large and complete photonic band gaps in two-dimensions, which have proved useful for arbitrarily shaped waveguides, enhanced solar absorption, and high-Q optical cavities. Investigation of one-dimensional stealthy hyperuniform disordered (SHD) photonic structures in the literature remains sparse. Consequently, we have generated SHD point patterns using a potential minimisation technique. From these patterns we generated and simulated SHD photonic structures using a plane-wave expansion method. Photonic band gap behaviour was observed when constraints were placed on the underlying SHD pattern. Further, we present preliminary study of the localisation of electromagnetic waves in the SHD structures using an inverse participation ratio measure, and a level spacing statistics approach.

The origin of the long lifetime of self-trapped exciton emission in low-dimensional copper halides is currently the subject of extensive debate. In this study, we address this issue in a prototypical zero-dimensional cooper halide, Cs2(C18)2Cu2I4-DMSO, through temperature-dependent magneto-optical studies.Our results exclude spin-forbidden dark states and indirect phonon-assisted recombination as the origin of the long PL lifetime. Instead, we propose that the minimal Franck-Condon factor of the radiative transition from excited states to the ground state is the decisive factor. Our findings offer profound insights into the electronic processes in low-dimensional copper halides and have the potential to advance the application of these distinctive materials in optoelectronic devices.

The paper aims to reveal the relationship between the geometrical features and linear and nonlinear optical properties of InAs quantum dots (QDs). This problem is justified by the extreme variety offered by the recent advances in growth techniques tailored to attainment of QDs and nanostructures with virtually any shape. To that end the Finite Element Method in conjunction with the Effective Mass Approximation and Envelope Function Approximation was employed allowing the solution of the one particle eigenproblems in domains with any complex geometries. The paper explores nanoplatelets, spherical QDs, nanocones, nanorods, nanotadpoles and nanostars. It has been found that there is a clear correlation between the complexity and symmetry of the QDs and their linear and nonlinear absorption spectra for transitions between the electronic ground state and first three excited states.

Efficient and high-speed photodetection in the NIR is essential in several applications such as LiDAR and imaging. Silicon is an established choice as the base material for absorbing and converting photons to charge carriers. However, its high absorption length in the NIR imposes a trade-off between the absorption efficiency and detection bandwidth. Here, the rigorous coupled-wave analysis method together with the particle swarm optimisation algorithm has been employed to optimise photonic crystal slab architectures with hexagonal symmetry to achieve efficient coupling of incoming pulses of light to the guided modes of the silicon photodetector. Our optimal design yields an ultra-efficient compact photodetector with more than 80% average absorption in the wavelength range 700 – 900 nm. Furthermore, considering scatterers of arbitrarily shaped polygonal cross-section, augments significantly the landscape in the optimisation parameter space and results in further enhancement of the absorption efficiency. Our results show that introducing different length scales in the texturing leads to efficient broadband absorption in the compact device.

Silicon wafers for photoelectrochemical (PEC) water splitting are highly reflective and prone to corrosion. Nanoporous structures were created using a simple etching method that does not require complex multilayer heterojunctions to reduce reflectance. This approach significantly reduced reflectance to less than 1%, improving light absorption. However, this method also introduced many defects and made the surface hydrophobic. These issues can slow down carrier transport, cause more recombination, destabilize the reaction zone, and disrupt the PEC reaction. To solve this problem, a TiO2 thin film was coated on the surface to correct the surface defect and make the surface hydrophilic. TiO2 is beneficial because it is chemically stable and absorbs ultraviolet rays that silicon cannot. However, if the TiO2 layer is suboptimal, it can hinder carrier movement and reduce light reaching the silicon. This study investigates how the addition of a nanoporous structure and ~3 nm TiO2 film changes the PEC process. Provides insight through a variety of chemical analyzes and band diagram interpretation.

Gradient-based topology optimization via the adjoint method has been successfully used in nanophotonics to uncover shapes with superior performances compared to what would be possible with traditional design methods. Here, we have extended this technique to optimize nanostructures to engineer their induced multipole moments. As an example, we demonstrate the method's application to realize the first Kerker effect in a silicon nanoparticle. The optimization results show a complex shape with highly suppressed backscattering due to the excitation of in-phase electric and magnetic dipoles with the same amplitude. This promising approach can pave the way for the inverse design of photonic structures based on a set of desired multipole moments, which can exhibit a variety of complex photonic phenomena.

Here, we show that the wings of Jersey Tiger (Euplagia quadripunctaria) moths exhibit fluorescence, a phenomenon observed for the first time in this species. Both the white and red scales of these moths display fluorescence. While UV lamp illumination prompts similar emissions from both white and red scales, 405 nm laser illumination reveals distinct fluorescence spectra. Despite no apparent structural differences observed under SEM between the white, black, and red scales, fluorescence emanates from the entire nanostructured architecture of the scales, indicating a chemical presence throughout. Chemical disparities between the scales are detected via FTIR, though identifying the specific pigment proves elusive. Further investigation is necessary to ascertain the pigments responsible for fluorescence. Additionally, this study prompts exploration of fluorescence patterns in other moth species.

We experimentally demonstrate a new type of level crossing where resonances accompany each other along broad spectral bands. Beyond extending the known types of level crossing (simple, avoided, and diabolic), our accompanying levels might transform current supercontinuum-generation technology to be continuous in frequency and time [cw].

3D laser nanoprinting based on multi-photon absorption (or multi-step absorption) has become an established commercially available and widespread technology. Here, we focus on recent progress concerning increasing print speed, improving the accessible spatial resolution beyond the diffraction limit, increasing the palette of available materials, and reducing instrument cost.

Biological discovery is a driving force of biomedical progress. With rapidly advancing technology to collect and analyze information from cells and tissues, we generate biomedical knowledge at rates never before attainable to science. Nevertheless, conversion of this knowledge to patient benefits remains a slow process. To accelerate the process of reaching solutions for healthcare, it would be important to complement this culture of discovery with a culture of problem-solving in healthcare. The talk focuses on recent progress with optical and optoacoustic technologies, as well as computational methods, which open new paths for solutions in biology and medicine. Particular attention is given on the use of these technologies for early detection and monitoring of disease evolution. The talk further shows new classes of imaging systems and sensors for assessing biochemical and pathophysiological parameters of systemic diseases, complement knowledge from –omic analytics and drive integrated solutions for improving healthcare.

Surface-enhanced Raman Spectroscopy (SERS) is a powerful optical sensing technique widely used in fields like medicine, microbiology, and environmental analysis. Planar SERS substrates are preferred for their ease of integration into lab-on-chip systems and superior reproducibility. Substrate performance is assessed using metrics like enhancement factor, sensitivity, and reproducibility. Many experimental and post-processing factors can influence these metrics and their interpretations, with one of the most critical being the illumination area—essentially, the number of hotspots generating the signal. We investigated with Raman mapping the impact of the illumination area on 5 SERS substrates showing that a larger illumination area improves reproducibility on random structures, while it sacrifices resolution. Furthermore, a larger illumination area leads to more stable signals, particularly in irregular nanostructures, yielding higher sensitivity. In conclusion, choosing a SERS substrate should consider the trade-off between uniformity for resolution and larger illumination area for signal reproducibility.

I will present our recent experimental results with optical resonators made of various phases of matter, including plasma microcavities and liquid ones. In plasma microresonators, we demonstrate an ultrahigh Q optical microresonator with plasma inside. This plasma cavity might impact new types of plasma-based optical interconnects and electrically pumped ultracoherent-microlasers In liquid-based resonators, we demonstrate a Fabry–Pérot resonator, where one of its mirrors is based on total internal reflection from a liquid phase boundary. As such, they can optically interrogate capillary waves and resonances at the liquid-air interface. Such FP cavities can serve as a new way to bridge between capillary waves in liquids and electromagnetic waves in optics while benefitting mutual resonance enhancement (capillary and optical) This is the first time that such resonators have been demonstrated.

Gallium is a well-suited material for the fabrication of flexible photonic devices due to its fluidic and metallic properties. Localized Plasmonic resonance rely on the fabrication of metallic structures at the nanoscale with an extremely small gap between them, thus employing lithography or self-assembly techniques that involve multiple reagents and process steps. In this work, we demonstrate a single-step and scalable fabrication of non-coalescent Ga Nanospheres on a biocompatible elastomeric substrate, Polydimethylsiloxane (PDMS), by exploiting the capillary interactions between liquid Ga and the uncured oligomers of PDMS. This approach enables the fabrication of multiple structural colors and mechanochromic sensors in a single deposition, owing to the active role played by PDMS in determining Ga nanostructures.

Plasmonic Electronically Addressable super-Resolution (PEAR) aims to improve on limitations faced by currently established super-resolution methods. PEAR uses an active plasmonic element, modulated by passing an electric current through the nanostructure in a silver thin film. The modulated electric current causes changes in the electrical near field at the modulation frequency. Fluorescent material interacting with this modulated electric near field will transfer the local information into the far-field which can be collected using standard optics. By scanning a fluorescent sample over the active plasmonic element in a raster fashion, a map of the localised information is compiled to form an image of the sample’s surface. The ability to tie the resolution to the physical size of the active plasmonic element makes the PEAR imaging method unique among other imaging technology at the forefront of super-resolution imaging.

In this work, we have carried out the design, fabrication, and characterization of highly sensitive plasmonic hydrogen sensors. These plasmonic hydrogen sensors are based on an array of gold nanostructures coated with a thin layer of palladium (Pd) layer. We experimentally measured the sensitivity of the hydrogen sensors either by employing spectral interrogation, i.e. by measuring the shift in the plasmon resonance wavelengths upon exposure to hydrogen gas, or by employing intensity interrogation, i.e. by measuring the change in intensity of reflectance upon exposure to hydrogen gas. The specificity of these plasmonic hydrogen sensors to other gases was also evaluated and the sensors were found to be highly sensitive to hydrogen gas. The plasmonic sensors developed by us were found to be highly sensitive and could be fabricated at a low cost using a large-area fabrication process.

Currently, strong light-matter interaction is a focal point of interest. Investigating hybrid states' properties, we present a novel computational method using COMSOL Multiphysics to get the surface plasmon polariton propagation length on metal-dielectric interfaces. Demonstrating wavelength dependence, our study explores how these lengths change in the strong coupling regime, particularly when coated with absorber material, forming hybrid states. This significantly alters propagation length, influencing the decay of polariton with combined properties of SPPs and the absorber material.

We have demonstrated that the defective photonic crystal exhibits exceptional optical properties when its defect layer is doped with three-level atoms. We have incorporated scattering matrix formalism and observed that the crystal indeed behaves as a non-PT-symmetric one. As a result, we have observed asymmetric reflection and absorption, for two opposite directions of the probe field, resonance to either of two defect modes, while the transmission remains reciprocal. Further, this critical coupling condition can be coherently controlled in the proposed non-PT- symmetric photonic crystal.

Light transport through disordered media exhibits various behaviors depending on the disorder strength. Insight is gained on how light interacts with the medium by investigating the statistical properties of the scattering matrix. Historical results were obtained by considering non-resonant scattering systems. In this work, we present innovative numerical results using a microscopic description of systems entirely made out of point-like resonant scatterers. We access light transmission and energy storage in these systems. Their resonant behavior engenders strong frequency-dependent response to incident wavefronts which allows switching between transport regimes while fixing the scatterers density. We show that light can travel ballistically, diffusively or be localized, by only tuning the incident field frequency. The velocity of energy is affected by the resonant behavior of the scatterers, becoming dependant on the disorder strength. Our results suggest benefits in using fully resonant systems for applications aiming at maximal energy deposition within strongly scattering media.

We report a new phenomenon: the Fano resonances, related with the bound states of the wave function in the potential well, modify significantly when the corresponding eigenfrequency approach the edge of the continuum. This modification is related with the delocalisation of the bound states, i.e. transition from bound states to the extended states (leaky modes). The Fano resonances at the vicinity of transition obtain unusual property, that their peaks become extremely sharp. We demonstrated such unusual resonances in thin, nano-modulated dielectric films, We will discuss the possible realisation of the effect in passive systems (the thin film on the dielectric substrate) as well as in active (the film on amplifying material).

The miniaturisation of semiconductor lasers to the nanoscale is difficult because of increasing losses as the laser cavity size approaches the wavelength of light, with some recent efforts focusing on high-refractive index dielectric materials and plasmonics to try and overcome this challenge. With this in mind, we immobilize CdSe1-xSx/ZnS colloidal quantum dot (CQD) supraparticle (SuP) microlasers onto gold nanoparticle (AuNP) coated glass substrates. We study the interaction of the absorption, the non-resonant luminescence, and the whispering gallery modes (WGMs) of SuPs with the localised surface plasmon resonances (LSPRs) of a AuNP substrate. This interaction produces an increase in LSPR peak intensity of 10%. The luminescence and the WGM-to-non-resonant-luminescence ratio are both significantly increased (x2) under continuous wave excitation at the LSPR wavelength. Individual SuP lasers on AuNP-coated and bare glass substrate are found to have thresholds 47% when greater when they are pulsed optically pumped on AuNPs outside the LSPR at 355 nm. These findings suggest this platform as a candidate for further development towards device miniaturisation.

Plasmonic-molecular systems are gaining interest as a platform to studying strong light-matter coupling effects, owing to small mode volumes of plasmonic modes and relatively small systems sizes (hundreds of atoms) enabling tackling them by the ab initio methods. In our work we use real-time TD-DFT method to study what modifications of the systems occur under strong coupling conditions, including plasmon redshift and molecular absorption quenching. We observe mixed transitions, i.e. ocurring when the initial and excited states are located in different subparts of the system, as well as the drastic modifications of the molecular oscillator when modeling the systems with the coupled oscillators model. We show how atomistic scale effects influence the coupling and how to tailor the polaritonic states to obtain desired features in the system.

We introduce a flexible approach for fabricating 3D nanopores with diverse materials and shapes on a SiN membrane, offering versatility for various nanoscale applications. The method provides considerable design freedom for 3D profiles by manipulating the exposure dose of a photoresist using focused ion beam (FIB). A crucial aspect involves substituting the developed resist with a dielectric oxide deposited through atomic layer deposition. Employing this technique, we successfully generated 3D nanopores with arbitrary shapes, constructed from SiO2, Al2O3, TiO2, and HfO2, while maintaining precise control over pore diameter, reaching dimensions as small as a few nanometers. Comprehensive characterization through electrical analysis, scanning electron microscopy (SEM), cross-sectional imaging, and energy-dispersive X-ray spectroscopy (EDS) was conducted. We explored convex, straight, and concave nanopore configurations, investigating their distinct electrical and optical response and potential for a wide range of applications.

Van der Waals (vdW) materials are at the core of modern optoelectronics and nanophotonics. However, relatively limited research attention is devoted to their giant optical anisotropy. Here, we demonstrate that the use of giant anisotropy leads to the next-generation integrated circuits and optical elements, determining the exact values of anisotropic dielectric permittivity tensor for the variety of vdW materials in the broad spectral range (250–1700 nm) using cross-validation of far- and near-field techniques, accompanied by first-principle calculations. Our results show high refractive index, transparency over the whole studied spectral range and giant optical anisotropy for all investigated vdW materials. Furthermore, we suggest applications of vdW materials for chiral optics and integrated photonics.

Anisotropic materials play a pivotal role in contemporary nanophotonics applications, such as polaritonic physics, subdiffractional guiding, and strong light-matter coupling. However, anisotropic materials have static optical axes, which prevent their complete manipulation of light in anisotropic devices. Here, we found that natural van der Waals crystals rhenium disulfide and diselenide demonstrate wavelength-dispersive optical axes owing to noncollinear excitons. It results in unusual far-field and near-field responses with the opportunity to control light propagation with even a slight wavelength shift. Moreover, we developed a technology for engineering systems with wavelength-dispersive optical axes via carbon and transition metal dichalcogenide nanotubes. It allows us to design almost any rotation of optical axes. Thus, the discovered phenomenon of wavelength-dispersive optical axes offers a novel route for light manipulation without nanostructuring.

Experimentally, strong localization of electromagnetic waves in three dimensions has never been achieved, despite extensive studies. Moving away from the paradigm of disordered systems, we perform microwave transport experiments in planar aperiodic Vogel spiral arrays of cylinders with high dielectric permittivity. By characterizing the electromagnetic modal structure in real space, we observe combinations of long-lived modes with Gaussian, exponential, and power law spatial decay. This distinctive modal structure, not present in conventional photonic materials with periodic or disordered structures, is the cause of significant electromagnetic wave localization that persists even in a three-dimensional environment.

Vectorial optical fields have recently attracted significant attention due to their importance in sensing, imaging, light-matter interactions and controlling photonic responses of nanoparticles and nanostructures. In this respect, the interaction of polarised fields with chiral nano-objects is of particular interest because controlling directionality of scattering via chirality of light or nanostructures would open up new applications in nanophotonics and photochemistry. Here, a novel concept of rotating chiral dipoles is introduced to obtain the relationship between the directionality and the handedness of scattering fields and realize unidirectional chiral scattering. Through the engineering of multipole excitation in plasmonic helicoid nanoparticles, we systematically introduce and demonstrate, both numerically and experimentally, the rotating chiral dipole for highly-directional forward scattering of circularly-polarized light. This concept of rotating chiral dipoles may be important for designing scattering from nanostructures and optical nano-antennas.

Traditional optical microscopy methods with microscope objectives limit interaction angles with biological samples. Microlasers, particularly based on Whispering Gallery Mode (WGM) resonators, offer potent sensing capabilities but face excitation constraints. We present an innovative platform that overcomes these challenges using optically trapped micromirrors on flexible polymeric membranes to enable arbitrary excitation angles for WGM microlasers. This approach allows precise environmental sensing and versatile light delivery and collection within microfluidic chambers. Beyond advancing refractive index sensing, optically trapped micromirrors find applications in advanced imaging and light sheet microscopy, promising conditioned light delivery anywhere in the sample plane when combined with metasurfaces.

Simple acoustoplasmonic resonators, such as nanobars and crosses, are efficient light-hypersound transducers. The excitation of hypersonic modes in these structures strongly depends on the spatial profile of the acoustic and plasmonic eigenmodes and the optical properties of the system's resonances. Lately, it has been made possible to selectively excite and detect phonon modes via plasmon resonances at the same frequency using chiral nanostructures and circularly polarized light. In this work we present a system that is composed of a metallic propeller-like structure, based in a three lobed perforated clover whose top face is twisted with respect to its bottom one. The presence of the twisting angle gives rise to the excitation of non-conventional phononic modes. We will present a complete theoretical analysis of the phononic and plasmonic modes, their surface deformation field and electromagnetic field profiles.

In the present work, we experimentally demonstrate a suspended tunable subwavelength nanobeam cavity based on our recently proposed advanced dielectric bow-tie design combining ultra-low mode volume and high Q-factor. The nanobeam cavity is efficiently coupled to waveguide ports, allowing full integration with the existing silicon photonic platform and mitigation of the detuning between the optical mode and quantum emitter, which inevitably appears in a coupled system of an emitter and cavity due to fabrication disorder. The tunability of the nanobeam cavity is achieved through nanoelectromechanical actuation using electrostatic comb-drive actuators. The proposed bow-tie nanobeam cavity supports a fundamental optical mode confined in solid in the telecom C-band with a normalized mode volume below 0.12 and Q-factor of 3500. By applying the voltage to the comb-drive actuators, we experimentally observe the dynamic reconfigurability of the cavity resonance wavelength within 11 nm. Our findings can open a new prospect for efficient and tunable nanodevices for enhanced light-matter interactions.

Solar energy conversion to green energy production via solar water splitting, imitates photoinduced charge transfer into water or an electrolyte using a photoelectrode. Bandgap limitation affects common semiconductors used as photoelectrodes. From that perspective, interband and nonradiative decay of plasmon resonance facilitates a plasmonic phenomenon with a more comprehensive spectrum performance. This work systematically studies photoelectrochemical current generation using plasmonic gold nanoparticles(GNPs) organized in a one-dimensional lattice. Such arrangement of plasmonic GNPs produced photonic effects such as guided mode resonance and grating-coupled surface plasmon resonance, which contributed to superior photoelectrochemical current production than metal bar grating, and random gold nanoparticles. Additionally, a semiconductor layer was deposited over the grating of plasmonic particles to enhance plasmonic charge collection and current generation and extended the UV-limited semiconductor's PEC spectral response bolstered by multiphotonic-plasmonic resonance phenomena. Our research offers a derived approach to enable light harvesting mechanisms for the production of gre

This study explores the antimicrobial activity of gamma-aminobutyric acid (GABA) silver nanoparticles. GABAAgNPs were synthesized by the photoreduction process and characterized by spectroscopies in the UV-Vis and infrared (FTIR), X-ray diffraction, transmission electron microscopy, and zeta potential. The antimicrobial potential of GABAAgNPs was evaluated in a MIC test and by photodynamic effect under irradiation with excitation with LED at 460 +/- 10 nm (2 min), 590 nm +/- 10 nm (2 min), and 660 nm +/- 10 nm (2, 5 and 10 min). The results showed that GABAAg induced porphyrin production in E. coli, leading to the inhibition of microorganisms improved by the photodynamic effect.

This work presents the conjugation of tumor-specific targeting ligands, folic acid, onto the surface of Conjugated Polymer Nanoparticles (CPNs) based on a common solar cell material (PTB7), which exhibits low nonspecific cell adhesion. The goal is to create near-infrared (NIR)-active theranostic probes capable of specifically targeting cancer cells. By adjusting the proportion of folic acid during the synthesis process, the targeting efficiency and singlet oxygen generation efficiency of the nanoparticles can be finely tuned.

We investigate the emergence and development of collective resonant effects in finite-size arrays of silicon nanoparticles. We focus our research on two different scenarios of collective resonances: the lattice resonant Kerker effect and the quasi-bound state in the continuum. In the coupled dipole approximation, the implementation of such resonances is explored depending on the number of particles in the arrays and the conditions of external excitation. The results of the work are important for the prediction and experimental observation of collective resonances in real finite-size structures.

Integrated photonic devices are at the basis of all-optical chips, essential ingredients for quantum information technology applications. In such devices, one of the key features relies on the control of the emission properties of integrated solid-state quantum emitters, most importantly, the spontaneous emission dynamics. In this way, one is able to control, for instance, the single-photon emission repetition rate and improve the coherence of the emitted quantum light, by reducing the spontaneous emission lifetime. We demonstrate the potential of nano-photonic devices characterized by a bio-inspired deterministic aperiodic structure, based on spiral geometries, as an on-chip platform for cavity quantum electrodynamics experiments. Aperiodic order, in particular, following spiral configurations, is present in natural systems where, for instance, the arrangements of leaves and seeds in plants follow Fibonacci series. The study of bio-inspired systems has attracted considerable interest in classical photonics and we here implement such an approach to quantum photonics.

The amplification and phase modulation of a surface electromagnetic wave propagating along a helical trajectory in a cylindrical semiconductor waveguide under the condition of phase matching with a longitudinal space-charge wave are considered. The evolution of a phase-modulated wave after passing through a semiconductor waveguide is studied and the conditions leading to the transformation of an initially stationary wave into a sequence of optical pulses with a terahertz repetition rate are determined.

The possibility of strong modification of the reflection spectrum in the photonic bandgap range of a one-dimensional photonic crystal using a dilute two-dimensional array (monolayer) of metal nanoparticles is demonstrated. It is shown that the reflection of electromagnetic wave can be completely suppressed by nanoparticles located in the surface dielectric layer. The dependence of the absorption and reflection spectra of hybrid photonic structure on the array parameters and on the shape of nanoparticles is studied. The obtained results can be used to create filters, polarizers and absorbers for predetermined frequencies in the visible and near-IR domains.

Optical vortex (OV) beams, known for their spiral phase and orbital angular momentum (OAM), have diverse practical applications. Their utility is constrained by the topological charge's impact on beam characteristics. Integrating perfect vortex beams with metasurfaces provides nanoscale solutions. Previous studies struggle to control beam shape. This study used numerical simulations to generate broadband polygonal perfect vortex beams, retaining OAM and radius. A zinc sulfide nanoantenna was optimized for visible spectrum operation. Shapes like ovals and hexagons enabled asymmetric intensity profiles for flexible nanoparticle traps. This research has implications in optical trapping, manipulation, and communication.

In this study, we propose a zinc sulfide-based, all-dielectric super dispersive, circular polarization (CP) discriminator metalens. The dispersion-controlled metalens is an integral component of compact spectrometers, with focal spots residing on the same plane and undergoing minimal broadening across the visible spectrum (i.e., 475nm-650nm). Moreover, the proposed device fulfills an additional role as a CP filter, permitting one state to focus on the intended position while simultaneously defocusing the other. In practice, the incorporation of a novel spin-decoupling approach, in conjunction with wavelength and phase multiplexing through a single-phase mask, equips the proposed device to provide not only optimal spectral performance but also exhibit helicity-resolved capabilities, establishing it as a state-of-the-art meta-spectrometer.

Whispering-gallery mode (WGM) microlasers were obtained using the impregnation technique of polystyrene microspheres in an aqueous solution of plasmonic nanoparticles and Rhodamine 6G. Emission spectra of Rhodamine-doped microspheres with diameters of 1 μm and 5-7 µm demonstrated spikes corresponding to WGM, with a low Q-factor for 1-μm and a higher Q-factor for 5-7-µm spheres. Plasmonic nanoparticles do not affect emission lines, only slightly reducing the lasing threshold.

Plasmonic nanostructures of gold and silver with a high degree of anisotropy are of great importance in the field of nanotechnology and nanophotonics. These nanostructures have unique optical properties that can be adapted for various applications. Noble metal nanoparticles exhibit strong optical absorption in the visible range of the spectrum due to the excitation of localized surface plasmon resonance and when the shape of the particle deviates from the sphere, the absorption spectra depend on the orientation of the particle relative to the polarization of the incident light. In our study, we obtained chiral structures in the form of golden hemispheres on the surface that absorb light with different polarization and intensity and the possibility of creating linear dichroism in metal nanoparticles without using complex and expensive methods was demonstrated.