Metamaterials, Metadevices, and Metasystems 2024

Quasi-2D perovskites have gained significant attention in the field of optics and photonics recently due to their intriguing optical properties. Endowed with optical properties typically found in both 2D and 3D systems, they offer a premier platform for tunable optical devices. Here we studied the prospects of Quasi-2D perovskites for lasing by first delving into excitonic and free carrier ultrafast dynamics, exploring into random lasing from naturally formed cavities in planar films and investigating lasing from structurally-tuned nanowires. Our results give insights on the fundamental radiative processes in these novel materials and build a foundation for future experiments and applications.

Two-dimensional materials have emerged as platforms for tailored and enhanced light-matter interactions. In this study, we utilize cathodoluminescence (CL) spectroscopy to investigate the optical response of two different two-dimensional materials: liquid-exfoliated thin films of WSe2 flakes, and atomic defect centers in hexagonal boron nitride. The former hosts self-hybridized exciton polaritons, while the latter exhibits strong luminescence and serves as single-photon emitters. Employing an electron-driven photon source and sequential interaction of electron beams with the EDPHS and the sample, we demonstrate a novel method for exploring the dephasing dynamics of exciton polaritons, as well as phonon-mediated population decay and decoherence mechanisms in hBN defect centers at sub 5 femtosecond temporal resolution and nanometer spatial resolution.

Monolayers with closely packed molecules of amphiphilic Eu(TTA)3(DPT) deposited on plasmonic metal demonstrate bright luminescence in contrast with diluted systems and theoretical predictions of full quenching. In order to better understand the role of intermolecular interactions and surface plasmons, we study the spontaneous emission in Eu(TTA)3(DPT) ultra-thin films in dielectric and plasmonic environments. The emission kinetics in systems with closely packed emitters strongly differs from that in diluted emitters. The kinetics and spectra are very sensitive to the environment. Using multilayered structures, we are able to enhance the magnetic to electric dipole transition branching ratio by more than order of magnitude.

The ability to distinguish between different states of a given cell, as well as between different types of cells, is crucial for a variety of fundamental and clinical life sciences applications. Those include: monitoring biochemical processes, detection of the drug effects, and real-time non-pertubative imaging of living cells. I will describe an experimental technique developed in our lab – Metasurface-Enhanced Infrared Reflection Spectroscopy (MEIRS) – used to produce chemical images of evolving live cells with diffraction-limited spatial resolution. Different types of metasurfaces used in this study will be described, including flat two-dimensional, three-dimensional meta-on-dielectric, and multi-resonant plasmonic metasurfaces

I will discuss the design and implementation of space plates and space optics, which are space plates with position-dependent responses. I will show how new variants in gradient-based topology optimization can yield space plates with enhanced compression factors, sizes, and efficiencies compared to conventional designs. I will also show how space plates and space optics can be co-designed with refractive optical systems to yield imaging systems with new capabilities and form factors. These concepts showcase the emergent capabilities of multi-scalar optical systems that combine the synergistic properties of macroscopic and subwavelength-scale structured media.

Optical imaging techniques are the most commonly used methods in biology and medical research. Nano-photonics, the emerging optical techniques, with unique optical capabilities to manipulate the basic characteristics of light have recnetly received a significant amount of interest in the field of optical microscopy and endoscopy. This talk will introduce the latest studies on the biomedical use of structured light, as well as metasurfaces. In addition, structured light plays vital roles to enhance resolution. The following are the topics that will be covered: optical microscopy, light sheet microscopy, optical endoscopy, and deep learning. This talk will also discuss the technological challenges presently encountered with metasurface from the point of view of preclinical and clinical systems.

The ability to locally control incident light's polarization state is one of the primary distinguishing factors between metasurfaces and past generations of diffractive optical elements. Polarimetry, the measurement of light’s polarization state, can benefit from the metasurfaces which sort light based on its polarization into several channels enabling polarimetry with a minimum of optical components. Here, we present a wide field-of-view polarimetric imager integrated on a single glass substrate. The device captures polarimetric images over a 40 degree field-of-view in a 10 nm bandwidth in the near-IR around 870 nm and consists of polarization-sensitive metasurface diffraction grating (for polarimetry) and a metalens-aperture stop system (for imaging). Imaging polarimetry with this camera is demonstrated and practical considerations surrounding this approach are discussed.

We aim to address one of the fundamental limitations of machine learning (ML): its reliance on extensive training datasets by incorporating physics-based intuition and Maxwell-equation-based constraints into ML process. We show that physics-guided networks require significantly smaller datasets, enable learning outside the original training data, and provide improved prediction accuracy and physics consistency. The proposed approaches are illustrated on examples of photonic composites, from photonic crystals to hyperbolic metamaterials.

We report an experimental validation of a machine learning-based design method that significantly accelerates the development of all-dielectric complex-shaped meta-atoms supporting specified Mie-type resonances at the desired wavelength, circumventing the conventional time-consuming approaches. We used machine learning to design isolated meta-atoms with specific electric and magnetic responses, verified them within the quasi-normal mode expansion framework, and explored the effects of the substrate and periodic arrangements of such meta-atoms. Since the implemented method allowed for the swift transition from design to fabrication, the optimized meta-atoms were fabricated, and their corresponding scattering spectra were measured using white light spectroscopy, demonstrating an excellent agreement with the theoretical predictions.

The field of nanophotonics is based on the ability to confine light to sub-diffractional dimensions. In the infrared, this requires compression of the wavelength to length scales well below that of the free-space values. Two predominant forms of polaritons, the plasmon and phonon polariton, which are derived from light coupled with free carriers or polar optic phonons, respectively, are broadly applied in the mid- to long-wave infrared. Within anisotropic materials, these optical modes can be induced to propagate with different wavevectors along different axes, or even be restricted to propagate only along a single direction. Here, we discuss the influence of crystalline anisotropy in dictating the polaritonic dispersion, including highly directional hyperbolic shear polaritons in low-symmetry monoclinic and triclinic crystals, as well as the ability to control the wavelength and propagation direction of these modes using free-carrier injection and twist-optic concepts. Further, we highlight how such phonon polaritons can be employed as ultrafast and efficient carriers of thermal energy, providing alternative dissipation pathways for heat.

This study investigates the thermal optical coefficient (TOC) of Si, SiNx, SiO2, and TiO2, establishing a comprehensive database across temperatures (20°C-80°C) and wavelengths (400nm-1800nm). This dataset informs the design of anti-thermal optical devices. For instance, utilizing TOC disparities at 1550nm, we developed an anti-thermal quarter-wave plate optical mirror with Si and TiO2. This innovative approach harnesses material-specific thermal responses, showcasing potential applications in designing reliable optical platforms. Our research contributes not only to understanding TOC variations but also provides a practical foundation for advancing anti-thermal optical technologies.

Type-II superlattice (T2SL)-based detectors as a new platform for mid-IR detectors, aiming to bring the performance of state-of-the-art HgCdTe based designs to room-temperature operation. T2SLs provide a way to highly reduce detector thickness when a thin T2SL layer is implemented in a multilayer core combined with a dielectric metasurface that uses guided mode resonance (GMR) to couple the incoming light into the detector. However, supporting a GMR requires the detector to have significantly expanded spatial area, potentially preventing the creation of truly compact finite detectors. In this work we propose a possible solution to this problem. The proposed design of a detector relies on the reflective metasurface to couple incident light (λ_0) into a guided mode that overlaps T2SL absorber layer. Our analysis demonstrates that the width of the detector must be at least ~20λ_0-wide to achieve ~60% external quantum efficiency (EQE), with narrower detectors exhibiting decreased performance. To counteract this, we propose a design that combines the benefits of GRM and Fabry-Perot cavity enhancement, resulting in 2λ_0-wide, subwavelength-thick detector that in theory achieves ~51% EQE.

This talk will consider the future of metal halide perovskite (MHP) photovoltaic (PV) technologies as photovoltaic deployment reaches the terawatt scale. The requirements for significantly increasing PV deployment beyond current rates and what the implications are for technologies attempting to meet this challenge will be addressed. In particular how issues of CO2 impacts and sustainability inform near and longer-term research development and deployment goals for MHP enabled PV will be discussed. To facilitate this, an overview of current state of the art results for MHP based single junction, and multi-junctions in all-perovskite or hybrid configurations with other PV technologies will be presented. This will also include examination of performance of MHP-PVs along both efficiency and reliability axes for not only cells but also modules placed in context of the success of technologies that are currently widely deployed.

The recent advent of robust, refractory (having a high melting point and chemical stability at temperatures above 2000°C) photonic materials such as plasmonic ceramics, specifically, transition metal nitrides (TMNs), MXenes and transparent conducting oxides (TCOs) is currently driving the development of durable, compact, chip-compatible devices for sustainable energy, harsh-environment sensing, defense and intelligence, information technology, aerospace, chemical and oil & gas industries. These materials offer high-temperature and chemical stability, great tailorability of their optical properties, strong plasmonic behavior, optical nonlinearities, and high photothermal conversion efficiencies. This lecture will discuss advanced machine-learning-assisted photonic designs, materials optimization, and fabrication approaches for the development of efficient thermophotovoltaic (TPV) systems, lightsail spacecrafts, and high-T sensors utilizing TMN metasurfaces. We also explore the potential of TMNs (titanium nitride, zirconium nitride) and TCOs for switchable photonics, high-harmonic-based XUV generation, refractory metasurfaces for energy conversion, high-power applications, photodynamic therapy and photochemistry/photocatalysis. The development of environmentally-friendly, large-scale fabrication techniques will be discussed, and the emphasis will be put on novel machine-learning-driven design frameworks that leverage the emerging quantum solvers for meta-device optimization and bridge the areas of materials engineering, photonic design, and quantum technologies.

Artificial intelligence (AI) techniques have boosted the capability of optical imaging, sensing, and communication. Concurrently, photonics facilitate the tangible realization of deep neural networks, offering potential benefits in terms of latency, throughput, and energy efficiency. In this talk, I will discuss our efforts in AI photonics with two examples. The first involves employing a convolutional neural network for achieving single-shot full-field measurement of optical signals. The second example pertains to implementing a deep neural network with a multiple-scattering system featuring structural nonlinearity, thereby enabling nonlinear computations using linear optics.

With the proliferation of networked sensors and artificial intelligence, there is an increasing need for edge computing where data is processed at the sensor level to reduce bandwidth and latency while still preserving energy efficiency. In this talk, I will discuss how meta-optics can be used to implement computation for optical edge sensors, serving to off-load computationally expensive convolutional operations from the digital platform, reducing both latency and power consumption. I will discuss how meta-optics can augment, or replace, conventional imaging optics in achieving parallel optical processing across multiple independent channels for identifying, and classifying, both spatial and spectral features of objects.

Keynote: We witness the growing excitement and breadth of research on Time Crystals. I argue that nanophotonics can play a pivotal role in bringing this sophisticated, yet esoteric subject to the domain of “timetronics” – an information and data technology relying on the unique functionalities of Time Crystals.

Recently, the emerging field of time-varying photonics has called for a broader theoretical framework to include the effects of temporal variations on light-matter interactions. A notable development in this context is the photonic temporal crystal, whose optical properties are modulated in a time-periodic manner. A distinctive feature of these crystals is their non-Hermitian band structures, which lead to momentum gaps with non-Hermitian degeneracies, or exceptional points, at their edges. In this talk, I will discuss how the spontaneous emission rate is net positive at the momentum gap frequency. This observation highlights the importance of the non-orthogonality of photonic Floquet eigenstates and brings the Petermann factor into focus in the context of photonic temporal crystals.

Conducting polymers (CP) have enabled many actively tunable applications. However, due to the difficulty in synthesis and limited understanding of its dynamic optical properties, CP-based electrochromic applications Here, we aim to introduce solution processable conducting polymer with electrochemically tunable IR electrochromic CP. We synthesized solution-processable polyaniline doped with camphor sulfonic acid (PANI-CSA) and characterized its large IR permittivity contrast from intrinsically reflective metal to lossy dielectric through spectroscopic ellipsometry. By incorporating PANI-CSA with asymmetric Fabry-Pérot cavity and gap surface plasmon resonator, we utilize the large IR electrochromic contrast in the metasurface design. Finally, we will discuss and compare the several CPs and design properties that affect the overall performance and efficiency in IR electrochromic metasurfaces.

Structured light is important in various fields including metrology, optical trapping, communications, and nonlinear optics. Here, we introduce a method to manipulate cylindrical vector beams using a strongly anisotropic epsilon-near-zero metamaterial. The longitudinal and transverse fields of a vector beam interacts differently with the metamaterial due to its anisotropy with an efficiency which depends on the numerical aperture of the objective, the initial state of polarisation and the quality of the metamaterial. These anisotropic interactions lead to reshaping the vector beam and its polarisation as demonstrated experimentally and theoretically. The approach facilitates wave front shaping and spatial polarization engineering, promising applications in microscopy, information encoding, and biochemical sensing.

The field of metasurfaces has opened tremendous new opportunities in many areas of optics, photonics, and electromagnetics. In this talk, I will discuss our recent research efforts on two emerging classes of metasurfaces that leverage new degrees of freedom, namely, “time” and “wavevector,” with a focus on their theoretical aspects and the new opportunities they enable.

We present an approach to non-perturbative optical modulation based on virtual interband transition excitation. It can induce the a large change of the refractive index, that is inherently ultra-fast and dissipation-free.

Time interfaces, which arise when an abrupt change in the properties of the host material occurs uniformly in space, have opened interesting opportunities for extreme wave manipulation, e.g., amplified emission and lasing in photonic time crystals (PTCs). Yet, altering the material properties is conventionally limited to active systems, which suffer from instabilities or saturation. In this talk, we introduce a passive path to achieving time interfaces in a switched transmission-line metamaterial. We first discuss the experimental evidence of distinct temporal boundary conditions at such passive time interfaces. Combing these unusual temporal discontinuities periodically, we then introduce passive PTCs. Unlike conventional PTCs where waves are exponentially amplified inside the momentum gaps, we demonstrate that PTCs can be achieved without parametric amplification, featuring stable momentum bandgaps. The passive PTC not only behaves as an anti-laser in time but also features momentum-filtering responses. This feature may establish a building block to realize functional time-metamaterials, with opportunities for extreme spacetime wave control, e.g., real-time waveform shaping.

This research explores a novel approach to manipulating waves using dynamic modulation in artificial materials across space and time. We employ PT symmetry to demonstrate the interactions between gain and loss in dynamic systems, predicting unique wave behaviors during phase transitions from energy bandgaps to momentum bandgaps. By generating PT-symmetric spatiotemporal photonic crystals (STPCs) through the application of sinusoidal perturbations in space and time, we analytically derive the eigenstates and scattering matrix of the STPC slab. The spatial periodicity, connected to the PT symmetry transition, influences both the STPC bandgap and mitigates parametric gain. At the PT transition, the STPC bandgap closes, exhibiting linear dispersion and phase-dependent bidirectional invisibility or backward radiation. In the broken symmetry phase, lasing states emerge when the total modulation length surpasses a lasing threshold. This study offers new insights into wave behaviors in photonic crystals under simultaneous spatial and temporal modulations and can find potential applications in tunable cloak-amplifiers.

The speed of transfer of mass may not be greater than the speed of light, however, the apparent motion of objects may be superluminal. Space-time modulations of a surface that exhibit superluminal motion have been the topic of myriad theoretical investigations that promise nanoscale control over electromagnetic waves via the Doppler effect and Fresnel drag. Herein, we use the ultrafast photoexcitation of a 40 nm film of Indium Tin Oxide to generate superluminally travelling modulations, which act as diffractive apertures in both the spatial and temporal domains. By designing continuous and discrete forms of motion we realise a tuneable platform for generation of complex momentum-frequency beam profiles and exploring exotic phenomena like hawking radiation.

In this study we explore strong coupling of polariton modes within patterned 2D Van der Waals materials and optical cavities, a frontier promising transformative advances in nanoscale light-matter interactions. Utilizing a quasistatic eigenmodes expansion approach, we develop a theoretical framework that bridges quantum and classical analyses, enabling precise manipulation and prediction of polariton behavior. This study not only elucidates the impact of pattern shape and material properties on these interactions but also establishes a crucial connection between the quantum and classical realms. Our findings pave the way for novel techniques in engineering optical phenomena, offering significant insights into the intricate dynamics of polaritons in 2D material systems, with potential implications for next-generation photonic and quantum technologies.

We developed a theory for Förster resonance energy transfer (FRET) between donor and acceptor molecules in the presence of an inhomogeneous absorbing environment such as metallic structures characterized by a complex dielectric function. We show that energy transfer to the environment that accompanies FRET results in a reduction of the effective Förster radius characterizing FRET efficiency between the molecules. For large concentration of molecules situated near a metal surface, this leads to a suppression of fluorescence concentration quenching for small average molecule separations from the metal and to a reduction of the effective fluorescence decay rate relative to that in the absence of metal. Our numerical calculations of effective fluorescence decay rate for molecules embedded in a dielectric slab on top of a metal surface reveal a characteristic minimum at intermediate slab thicknesses for high molecule concentrations, consistent with the experiment.

We will report on our investigations of laser-induced dewetting (in the cw and fs regimes) on thin metallic films deposited on substrates with different nonlocal optical environments. We observed that the morphology of dewetted plasmonic nanostructures is affected by incident pulse duration, and by the nonlocal optical environment. In addition, we will report on a broader effort on understanding mechanisms of short-pulse-induced damage on several materials and structures such as metallic/refractory thin films and metasurface components. We will also present on laser beam shape engineering efforts for damage mitigation in fused silica optics, for applications in extreme environments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. 24-FS-015. LLNL-ABS-861157.

We demonstrate a novel method for effectively coupling light with surface-plasmon polaritons using specially designed dipolar scatterers strategically positioned at an optimal distance from the surface. In our experiments, we constructed gold disks with a silica spacer from a flat gold surface and adjusted the spacer thickness to match a specific scatterer geometry that resonates at a predetermined optical frequency. This setup achieved a peak coupling efficiency of light to plasmon that is comparable to the square of the light's wavelength, at an ideal distance facilitated by the balance between strong particle-surface interactions and minimal surface-induced particle-dipole damping, both of which are enhanced at closer distances. Our findings, which are consistent with both analytical theory and electromagnetic simulations, propose the use of strategically placed scatterers as an innovative solution to the longstanding issue of efficient coupling in and out of nanophotonic systems.

Systems with both plasmonic and magnetic properties can present interest for various applications, including optical control of magnetization and magnetically controlled plasmonics. We have fabricated and studied permalloy metasurfaces and gold-permalloy bilayer structures with various profile modulation. These structures demonstrate plasmonic resonances, in-plane uniaxial magnetic anisotropy and spin wave resonances determined by the profile modulation. Significant photoinduced voltages are observed in response to pulsed laser light illumination, maximized at the plasmon resonance conditions. The voltages depend on magnetic field with characteristic hysteresis. The switching fields are found to be in good correlation with the magnetic anisotropy fields determined by the ferromagnetic resonance method, indicating the direct relationship between the photoinduced electric effects and sample magnetization. Varying illumination intensities, we also show possibility to control magnetization with light. The possible mechanisms of the effects are discussed.

Artificial neural networks (ANNs) are known to be a versatile tool for device optimization. This work proposes a method to optimize a polarization converter composed of T-shaped periodic resonators, inclined at 45 deg using an ANN. The result is compared with previous work conducted using CST simulation, demonstrating broadband and wide-angle reflective linear polarization conversion. Employing an ANN resulted to improved performance metrics, leading to increased fractional bandwidth of 7.6% for normal incident and 9.8% for 45° incident angle. The neural network achieved a mean square error (MSE) as low as 5.78 × 10−5, indicating high accuracy. This approach demonstrates the efficiency of ANNs in designing metasurfaces for a wide range of applications.

The realization of high Q EIT metasurface generally relies on the high degree of structural asymmetry by positional displacement of optically resonant structures. Here we demonstrate a high quality EIT metasurface without any displacement of constituent resonator elements.

We present microwave planar antenna designed for exciting electromagnetic waves to spin waves at frequency range from GHz up to THz. We investigated broadband characteristics of photon–magnon coupling between and permalloy (Py) film and inverse split-ring resonator (ISRR). A microwave planar antenna design consists of a single inverse split-ring resonator which is located on the opposite side of a dielectric substrate with respect to the microstrip feeding line. We obtained and analyzed transmission and reflection spectra using numerical simulations, as well as spatial distributions of the amplitudes of the magnetic component of the MW field excited by conducting narrow strip of ISRR under different strengths of externally applied, static magnetic field.

The measurement of the concentration of nitrates in different solutions is of interest in industrial and biomedical applications. Due to this, it is proposed to work with resonant structures manufactured with microstrip technology which were designed as dielectric permittivity sensors. These devices depend on changes in the dielectric properties of the medium, so they can detect variations in the concentration of nitrates. Depending on the dielectric properties of the sample, the electrical response will be such that changes in the response can be related to variations in the percentage content of nitrates in the measured solutions. The increase in the dissolution of calcium, magnesium and potassium nitrates in water shows a clear and notable change in the resonance frequency with which it is possible to identify the percentage level of dissolution in the samples.

In this work, we present ParallelGDS, a framework for ultra-fast and memory-efficient layout generation of large-scale metadevices. It outperforms existing methods by factors of 10 to 100 times in speed and reduces memory requirements significantly. This framework is adaptable to various computing resources and promises to revolutionize metadevice technology, enabling efficient and accessible applications with large metasurfaces.

In recent AR/VR display field, demands for substituting traditional lens into more compact form such as meta-lens has been increased. However, conventional methods for optimizing meta-atoms having many objective functions, such as simultaneously achieving uniform, highly-efficient, and polarization-independency in broadband spectrum is quite difficult and time-consuming due to its low level of design freedom. Here, by applying inverse design algorithm based on gradient-descent method into meta-atom design, we achieved such broadband, polarization-independent metasurface. Moreover, to verify high transmission efficiency and broadband phase delay characteristics of the proposed meta-atom, a numerical simulation for meta-lens is also demonstrated. We expect our inverse design method can play key role in showing metasurface-applied devices.

This study investigates the simultaneous modulation of dual multispectral and polarization states using a singular metasurface. Given the information-rich nature of spectral content and polarization in light, their integrated manipulation has significant implications in various domains ranging from telecommunications to biomedical imaging. Our main goal is to develop multispectral states capable of accommodating different polarization configurations, including simultaneous linear and circular polarization. Particular attention is paid to exploiting the compact form factor and optical efficiency inherent in miniaturized planar surfaces.

To achieve ultra-high resolution in OLED display, the meta-mirror which equalizes the optical length of the Fabry-Pérot resonance of each color pixel has been proposed. However, the crosstalk between each subpixels decrease the color purity of OLED panel. Simply increasing the lateral distance between meta-mirror will significantly increase overall pixel pitch, and reflectance from flat mirror region is too high therefore additional black matrix layer might be required. To overcome these problems, we applied the resonant plamonic nanoslit designed with extraordinary optical transmission (EOT) phenomenon as a black matrix of meta-mirror applied micro-OLED subpixel.

Recently, AR/VR technologies have gained attention, facing challenges such as size and motion sickness. Developing high-resolution, compact components is crucial. Micro-OLED, with its fast switching speed and high contrast, is promising but requires complex adjustments for the Fabry-Perot effect. Metasurfaces offer a solution by manipulating light through phase delay rather than cavity length adjustment. Coating an insulator on the metal substrate can work as plasmonic absorbers to reduce angle-dependent light reflection, enhancing component stability. Metasurface designed for phase compensation along angular variation maintains proper functionality of the Fabry-Perot resonance even if the source emitted with the oblique angle.

In the areas of photovoltaics, electronics and nanophotonics, work functions play important roles. Our research of wave functions has been conducted in three different settings. In our first experiment, we studied work functions in nanomaterials of different thicknesses using dye doped polymers R6G:PMMA. In the second study, we investigated how light illumination affected work functions of BiTh at the monomer/polymer transition. Finally, we studied electron emission of the nanophotonic materials above.

We investigated the dispersion properties of Rhodamine laser dyes using the Kretschmann geometry. Our study revealed multi-branch "staircase" dispersion curves and the emergence of a new dispersion "fork" branch. These findings provide a deeper understanding of the complex dispersion behaviors in laser dyes, theoretically enhancing the design and performance of optical devices. Our results contribute to the field by highlighting critical interactions and phenomena that can influence the development of advanced photonic applications. Further research may explore the practical implications of these discoveries in various technological contexts.

We present 3D printed microoptics as a tool for quantum technologies. Specifically, when coupling single photons from quantum emitters into single mode fibers and when coupling single photons from single mode fibers into superconducting single nanowire detectors, 3D printed microoptics enables emission collection, mode conversion, and efficient coupling from one device into the other. We demonstrate different solutions which include 3D printed optics directly onto single mode fibers, as well as onto no-core fibers spliced onto single mode fibers. We also present solutions for the emission collection and recollimation of different quantum emitters such as semiconductor quantum dots or defect centers [1]. Furthermore, we demonstrate how 3D printed optics can be utilized to focus the photons of a single mode fiber down to an extremely small active area of a superconducting single nanowire detector, which can enhance its detection speed due to reduced capaticance and kinetic inductance [2]. Finally, we also demonstrate how 3D printed optics on single mode fibers enables coupling of light to single trapped atoms inside of a vacuum chamber [3]. [1] M. Sartison, K. Weber, S. Thiele, L. Bremer, S. Fischbach, T. Herzog, S. Kolatschek, M. Jetter, S. Reitzenstein, A. Herkommer, P. Michler, S. Portalupi and H. Giessen, “3D printed micro-optics for quantum technology: Optimised coupling of single quantum dot emission into a single-mode fibre”, Light Adv. Manuf. 2, 6 (2021). [2] S. Mennle, P. Karl, M. Ubl, P. Ruchka, K. Weber, M. Hentschel, P. Flad and H. Giessen, “Towards fiber-coupled plasmonic perfect absorber superconducting nanowire photodetectors for the near- and mid-infrared”, Opt. Continuum 2, 1901 (2023). [3] P. Ruchka, S. Hammer, M. Rockenhäuser, R. Albrecht, J. Drozella, S. Thiele, H. Giessen and T. Langen, „Microscopic 3D printed optical tweezers for atomic quantum technology”, Quantum Sci. Technol. 7, 045011 (2022).

This work shows the realization of highly efficient real-time ultraviolet photodetectors using the high band gap semiconductor amorphous indium-gallium-zinc-oxide. Spatially resolved measurements are enabled by the configuration of an active-matrix sensor array. The necessary switching transistors are simultaneously produced to the as photosensor acting single gate thin-film transistors. The presented phototransistors are characterized at room temperature with a continuous-wave laser at 226 nm. The characterization includes the detection efficiency (responsivity R) and the response time tR. Applications of on glass ultraviolet photosensor arrays are indicated by the waist determination of a laser beam.

We demonstrate Ge-on-Si avalanche photodiodes based on a separate absorption, charge, and multiplication structure using a novel double mesa structure. This double mesa structure effectively confines the electric field inside the diode, as confirmed through simulation data. This leads to a reduced contribution of charge carriers from interface states at the etched sidewalls to the dark current. The diodes exhibit a dark current reduction by a factor of 7 compared to a standard single mesa structure, while the optical properties remain unchanged. At a wavelength of 1310 nm, a maximum optical responsivity of 10.1 A/W, corresponding to a gain of 46, is achieved. Temperature-dependent dark current measurements showed an increase of the underlying activation energy from 0.13 eV to 0.28 eV. This results to a dark current of 0.14 nA at a temperature of 170 K and a bias voltage of 95 % of the breakdown voltage, which is approximately 100 times smaller than that of the single mesa APDs at 12.7 nA.

We demonstrate an in situ, non-invasive measurement method for characterizing waveguide losses to ensure stable manufacturing and quality control of integrated waveguides. This method is based on the presumption that the scattered light of a waveguide is proportional to the propagating light inside the waveguide. Consequently, we can estimate the waveguide losses by measuring the scattered light across the waveguide. We compare this newly demonstrated measurement method with state-of-the-art measurement methods. To validate our measurement method’s working principle, we fabricated multiple amorphous silicon waveguides and characterized them using both the presented and cut-back methods. Both methods yielded comparable results, indicating losses around 1 dB/cm.

For the second quantum revolution, technologies such as quantum computing and quantum communications promise substantial impact. Quantum repeaters are an essential part of quantum communications, as they allow data transfer beyond current physical limits of several hundred kilometers for quantum communications in optical fibers. In our work, we utilize 3D printing based on 2-photon polymerization to produce micro-optics and micromechanics for coupling light between quantum emitters, quantum detectors, and optical fibers, providing a crucial building block for a quantum repeater. We present several designs of coupling structures and discuss the tolerances required to achieve high coupling efficiencies. We explore various 3D-printed coupling structures, namely fiber-coupled quantum dot emitters as well as superconducting nanowire detectors. The first measurements indicate coupling efficiencies in the range of 25%. We also study the stability of such structures for operation down to 4K in cryostats. In the future, multiples of such coupling structures can be 3D-printed on a single semiconductor platform, allowing efficient coupling of multiple emitters or detectors on a chip.

Transitioning to all-inorganic cesium perovskites is an alternative route to tackle the long-term stability challenges in perovskite solar cells (PSCs). CsPbBr3 perovskites offer robust stability and do not suffer from polymorphism relative to its counterpart, CsPbI3. With a Shockley-Queisser single-junction limit of ~ 16 % and a wide bandgap of ~ 2.3 eV, it is attractive for semi-transparent, building-integrated photovoltaics and multijunction applications. Here, an all-vacuum-processed all-inorganic PSC is demonstrated to achieve a phase-pure, compact film of the desired thickness, paving the way for exploring the CsPbBr3 active layer in other optoelectronic devices such as LEDs.

This paper reports on SiGeSn/GeSn multi-quantumwell microdisk lasers. The fabrication of the devices includes a selective underetching step, which enhances the guiding of the whispering gallery modes inside the cavity. Lasing occurs under different electrical pumping conditions with a very low threshold current and for long, quasi-continuous wave pulses compared to previously reported GeSn-based microdisk lasers. Furthermore, the lasing threshold current is reduced by a factor of ten compared to similar double-heterostructure devices.

Applications such as quantum computing or quantum sensing, have the potential to revolutionize many industries and pave the way for a new era of groundbreaking capabilities across various important fields such as medicine and material-science. To scale these applications up to the point where they can address real-world industry relevant problems, the development of high-efficiency photon extraction and coupling interfaces is crucial. In this work, we explore the use of micro-optical beam shaping interfaces to facilitate the extraction of light from points emitters which are fundamental unit blocks for many of these quantum technology applications.

Silicon photonics for telecommunication applications has garnered much attention recently. The optical transparency and the large refractive index contrast of silicon in the telecommunication wavelengths allow the implementation of high-density photonic integrated circuits. The drawback of silicon photonics is that there is no native efficient light source. Integration of III-V material, which offers outstanding optical emission properties, on silicon provides a potential solution. One of the approaches for large-scale integration is through heterogeneous integration of a III-V membrane using adhesive bonding. Here, we will report on the integration of telecom C-band emitting InAs QDs on a silicon platform through such bonding.

Spin defects in diamond are a promising candidate for quantum information processing applications. One of those is the tin vacancy (SnV) defect in diamond. It shows an individually addressable spin, bright emission into the zero phonon line (Debye-Waller factor of 0.6) and a large ground state splitting, enabling it to work at relatively high temperatures of 2 K. So far, it has been challenging to create stable SnV centers and incorporate them into nanophotonic devices. In this work, we report on the successful generation of bulk SnVs and integration into nanophotonic structures. The implanted SnV show stable PL and PLE spectra in bulk and nanostructure.

In this talk I will explore the hidden potential of electrochemically actuated metasurfaces. Electrochemical actuation is unique in that it provides for control over both the volume expansion of a scatterer as well as the free electron density for permittivity control. I will explore this freedom in dynamic tuning of titanium dioxide and silicon-based metasurfaces, materials already popularized in the field of photonics for their high index and low loss throughout the visible spectrum. Using these materials, we leverage electrochemical intercalation of lithium to initiate phase changes in a continuously tunable, reversible, and bi-stable manner, using bias voltages that are an order of magnitude less than similar devices.

Sub-wavelength structuring of semiconductors has recently provided a powerful tool to engineer the dispersion of the light. Such structures, commonly known as meta-optics can achieve a non-trivial relation between the energy and momentum of photons. One particular possibility is to create a dispersion-free flat band, which allows a resonator to maintain the same resonance frequency for different incidence angles. In this work, we utilize a flat band meta-optic to create a photodiode which has a critically coupled absorption for a wide angular range (±18°). By implementing a lens-based concentrator, the size of the photodiode can remain small while collecting large amounts of light, which results in high resolution, low energy consumption, and fast operation speed of the photodiode.

Metamaterial perfect absorbers (MPAs) are subwavelength structures offering powerful light/matter interaction characteristics: high spectral resolution, tunable absorption, polarization insensitivity, and angle independence. Numerical and analytical simulations show over 98% absorption in the mid-infrared (MID-IR) with a narrow FWHM of 4%. This technology could pave the way for cost-effective and compact hyperspectral MID-IR filters, making the "spectral fingerprint region" more accessible for atmospheric sensing

We present an optical method to de-trap THz radiation from semiconductor substrate, smoothing FP transmission oscillations, and decoupling MM resonance from FP oscillations such that the quality-factor of the LC resonance is improved and maintained throughout the THz spectra and is rendered independent of the spectral-shift, consequently increasing its dielectric sensitivity and demonstrating MM resonance spectra free from substrate effects.

Laser-based 3-D nanoprinting exemplified by two photon polymerization (TPP) has emerged as a practical route for additive manufacturing of sub-wavelength scale structures with broad applications in photonic packaging, nanofluidics, NEMS, drug delivery, tissue engineering, and beyond. Conventional TPP relies on compound refractive lenses for light focusing. In this talk, we present a novel alternative approach leveraging optical metalenses as the light manipulation element for versatile TPP fabrication. Using an inverse design algorithm, we show that the point spread function (PSF) of the metalens can be custom tailored to realize a variety of TPP writing modes, enabling fabrication of unconventional geometries difficult to process with traditional TPP. We demonstrated integration of metalenses with both commercial and home-built TPP systems, and experimentally implemented TPP to writing of 3-D polymer microstructures.

In this work, we design neural network architectures, including fully connected neural networks (FC) and convolutional neural networks (CNN), to solve forward design problems. We show that FCs and CNNs can predict the acoustic response based on the positions of cylindrical scatterers. These networks develop regressor models for approximating the absolute acoustic pressure at a focal point. A comparative study between the two networks is conducted against exact results from multiple scattering theory. We implement the FC and CNN models to simulate acoustic multiple scattering from cylindrical structures. While CNNs are computationally intensive, they perform better by leveraging spatial correlations between scatterers. This study tests the model's applicability to our problem. Numerical examples of pressure amplitude prediction at the focal point using random planar configurations of cylindrical rigid scatterers in water are presented. Results from deep learning models are compared to semi-analytical solutions from multiple scattering theory, with computations performed on MATLAB.

Atomically thin materials enable the manipulation of light at the nanoscale, leveraging a diversity of polaritonic modes, from plasmons in thin metals and doped graphene to excitons in transition metal dichalcogenides and phonons in ionic insulators. We will discuss recent results on the fabrication and characterization of ultrathin noble metal plasmonic nanostructures, ultrafast carrier dynamics in those films, and advances toward complete coupling from plasmons in those structures to propagating light.

Meta-lenses, distinguished by their compact size and adaptable manipulation, have attracted considerable interest. Yet, challenges persist for conventional tunable meta-lenses, including complexity, high costs, and limited responses, constraining their performance and applications. In our research, we introduce innovative tunable water and 3D printing meta-lenses tailored for millimeter waves. This technology empowers the delivery of the focusing spot to arbitrary positions in two-dimensional or three-dimensional space. Notably, it allows the precise transmission of a highly concentrated signal to a specific location, with the added capability of adjusting the transmission direction freely. This breakthrough enables the development of secure, flexible, and highly directive 6G communication systems. Our proposed approach overcomes existing limitations and holds promise for diverse applications in wireless power transfer, zoom imaging, and remote sensing.

This work focuses on engineering the band structures of multilayer metallo-dielectric structures using the dispersion relation approach and the transfer matrix method, particularly in the visible and near-IR range. We first illustrate the differences between the dispersion relation of multilayer metallo-dielectric (MD) structures and that of dielectric stacks. The distinctive properties of metallo-dielectric structures can be utilized as advantages in the design of bandpass filters with sharp cutoffs. We also demonstrate the potential for flexible control over the transmittance passband using dielectric gaps between two identical 3-layer MDM structures. This control can be extended to the adjustment of center wavelength, bandwidth, and profile symmetry, offering the prospect of developing low-cost bandpass filters with fewer layers and having smaller bandwidths with sharper cutoffs.

Our goal is to reduce the lead (Pb) content through partial replacement with tin (Sn) and enhance stability by encapsulating the PQDs with (3-Aminopropyl)triethoxysilane (APTES). The inorganic CsPbBr3 green light PQDs were prepared using the thermal injection method with varying Pb-Sn ratios. It was observed that the relative quantum yield (QY) was extremely high, reaching up to 198%, with a Pb-Sn ratio of 4:1. The emission wavelength of non-doped samples shifts over time, approximately 3 nm in two months, reducing to around 1 nm when the Pb-Sn ratio was 1:1. Furthermore, for both Pb-Sn ratios of 1:1 and 4:1, the QY also increases after aging for 2 months, reaching up to 1.7 times. PQDs encapsulated with APTES exhibit a stable full width at half maximum (FWHM), and the QY also increases after aging for 2 month, up to 1.4 times, for both of Pb-Sn ratios of 1:0 and 4:1.

This talk introduces an on-chip realization of the discrete fractional Fourier transform (DFrFT), proposed and experimentally implemented in the microwave domain utilizing a passive metamaterial coupled lines network (MCLN). This renders a lensless device capable of performing the DFrFT in real-time. The MCLN comprises N microstrip transmission lines coupled to their nearest neighbors through an array of interdigital capacitors composed of interlaced microstrip fingers. In the latter, the dimension and number of fingers allow for controlled and enhanced coupling terms that render the required DFrFT couplings highly accurate. The MCLN is exploited to design a new compact planar electromagnetic lensless solution that enables a beam steering operation through the focal plane array concept. The latter is performed by independently exciting the input ports of the MCLN through a switch tree, while the output ports are connected to an antenna array to realize a focal plane array system. Contrary to other approaches, this device does not require any external phase element, reducing the overall power consumption.

Meta-optic commercialization and manufacturing readiness is an important topic as optics designers begin evaluating meta-surfaces into optics modules. Moxtek has established a volume production line for visible and NIR wavelength meta-optics with a manufacturing readiness level 8. This provides a unique environment to evaluate the uniformity and capabilities of meta-optic manufacturing techniques. With a statistically significant dataset, mild variations in design concept and lens characteristics can be easily highlighted. We will present baseline MTF and efficiency data related to a variety of metalens characteristics. The goal is to highlight unique meta-optic characteristics that impact performance in volume production. Moxtek has manufactured and characterized metalenses in a wide range of wavelengths, lens diameter, and focal lengths.

In this talk, I will discuss our recent progress on metasurfaces based on engineered nonlocalities, stemming from long-range resonant interactions and lattice phenomena locally perturbed through tailored symmetries. Engineered nonlocality in metasurfaces offers enhanced spectral control, both temporally and spatially, ideal for image processing, and enhanced light-matter interactions. We achieve these features by combining quasi-bound states in the continuum with geometric phase variations in engineered metasurfaces, tailoring at will the supported eigenwaves. The resulting metasurfaces support sharp responses selective to the impinging wave properties, effectively realizing ultrathin transparent films that highly reflect light only when illuminated by selected polarization, frequency and wavefront spatial distribution of choice. The demonstrated wavefront selectivity of nonlocal metasurfaces opens exciting opportunities for augmented reality, secure communications, thermal emission management, optical modulators and enhanced light-matter interactions for nonlinear and quantum optics. In particular, in the talk we demonstrate our recent experimental demonstrations on highly efficie

Controlling the quality (Q) factor and far-field polarization response of a metasurface is critical for many applications in classical and quantum optics with new applications driving the creation of increasingly sophisticated devices with multi-dimensional control. In particular, one emerging need is the ability to create and control nearly degenerate pairs of high-Q modes while robustly shaping the frequency splitting, Q-factors, and polarization responses across two bands simultaneously. Here, we solve this challenge with a design paradigm for pairwise control of symmetry-guaranteed pairs of symmetry-protected bound states in the continuum and their corresponding polarization singularities. We experimentally demonstrate dual band control over mode splitting, Q-factors, and polarization responses in dielectric metasurfaces. Building upon this demonstration, we will conclude by expanding the design methodology to enable narrowband wavefront shaping without deeply sub-wavelength features.

The high computational demand of deep neural networks for computer vision must be alleviated by hardware-based strategies to facilitate applications in resource constrained systems. A potential solutions is to offload computations onto a front-end analog optical preprocessor, which could perform low-level feature encoding operations instantaneously as images are captured. To that end, this study showcases incoherent, broadband, low-noise optical edge encoding for thermal imaging of real-world scenes, which is achieved using a hybrid system of a 24-mm, inversely-designed metasurface and a refractive lens. Using an inverse design approach, the metasurface is optimized for Laplacian-based edge detection across the 7.5 – 13.5 µm LWIR imaging band. This work could be expanded to enable optically-encoded feature maps for accelerating convolutional neural networks for image segmentation and classification.

Here, we introduce a novel demonstration of utilizing scalable nitride-based resonant plasmonic metasurfaces, with a work function of 4.7 eV, to dramatically augment the light-matter interaction in wafer-scale monolayer single-crystal MoS2 photodetectors. Our pioneering approach has achieved not only excellent responsivity but also an impressive detectivity of 2.58 × 1012 Jones via the plasmon-enhanced photogating effect. A salient feature of this work is the introduction of a novel concept: the giant photocurrent enhancement propelled by the local-electromagnetic-field enhanced photogating effect. This leads to a substantial 190-fold photocurrent boost compared to conventional MoS2 photodetectors.

Chirality, essential for distinguishing molecular enantiomers, impacts various scientific fields. Circular dichroism (CD) spectroscopy, which measures differential absorption of circularly polarized light, is limited by weak chiral-optical interactions, yielding minimal signals. Superchiral metasurfaces, enhancing optical chirality, offer improved CD signal and interaction with chiral molecules, necessitating advanced development for accurate analysis. This study presents a novel two-stage design methodology for optimizing superchiral metasurfaces, employing a neural network-based optimizer and adjoint topology optimization for enhanced optical chirality density. The results provide a platform for sensitive CD spectroscopy, facilitating fast optimization of metasurface unit cells for better chiral molecule analysis.

In this talk we will present our recent results related to metasurfaces. This includes new CMOS compatible platforms for structural colors, overcoming chromatic aberrations in metalenses, the fusion of atomic physics and metasurfaces, and metasurface real time control.

We report resonance gradient metasurfaces, which show nearly continuous tunability of the high-Q resonance over a broadband wavelength range. The spectral tuning of the high-Q resonance is realized by gradually scaling the unit cell’s geometrical parameters along one coordinate of the metasurface. By using the gradient metasurface and a tunable infrared laser, a resonantly enhanced tunable generation of optical harmonics over a broad spectral range is realized (Adv. Mater. 2024, 36, e2307494). Additionally, broadband biosensing and control of vibrational light-matter coupling by using the gradient metasurface were demonstrated. This research establishes the groundwork for innovative light-generating devices and biosensors.

We present nonlocal chiral metasurfaces with a relatively high-Q factor for the direct detection of Stokes parameters. To realize it, we leverage the optimized interaction between nonlocal and local resonances in a constituent nanostructured meta-unit. By revealing the working principles of such interaction, we experimentally demonstrate effective nonlocal resonance-based high-Q polarimetric detection, which affords the direct tracking of azimuthal and ellipticity paths at the Poincaré sphere. Such metasurfaces are demonstrated by designing nanostructured meta-units with minimal geometric perturbation from the circular nanopost and keeping the filling ratio of meta-units to be constant for all targeted Stokes metasurfaces. We further prove that such design approach ensures consistent sized nanofabrication and facilitates effective operation across different samples at specific wavelengths and polarizations in experimental setups.

Developing new science often requires developing new tools. Regarding structured light, one of the most discussed tools in recent years is metalenses. Their inherent capability to manipulate phase, polarization, and intensity allows complex optical operations to be implemented with simple and compact optical architectures. In this talk, we will uncover the design and fabrication process that goes from the concept to the metadevice for the generation, manipulation, and sorting of highly-structured vectorial beams. In particular, we propose the design, fabrication, and characterization of new dielectric dual-functional silicon metaoptics that generate orbital angular momentum beams with on-demand different vectorial behaviors by acting only on the input polarization. The subwavelength metastructures, so-called meta-atoms, are designed in different shapes and sizes and organized into one or several layers, to provide the combined control of amplitude and of the geometric and dynamic phases. Bi-layer and multi-layer metalenses have been fabricated to obtain ultra-compact devices such as (de)muxers, OAM multiplicators, and dividers, considering applications to life science and ICT.

We report on the active control of transmissive polarization switching of near infrared light in two dimensions (2D) using liquid crystal (LC) infiltrated Ti3O5 nanostructures with > 50% efficiency in experiment. Our device consists of a periodic array of elliptical Ti3O5 pillars submerged in a thin (~ 2 um) LC layer and supports overlapping electric and magnetic dipoles under linearly polarized incidence. Using a biased photoactive top contact, we manipulate light in 2D by patterning a 435 nm pump laser on its surface to locally modulate LCs in illuminated areas. This work can find applications in solid-state programmable beam shaping and steering.

With significant advances in mid-wave infrared (MWIR) photonics, reducing unwanted reflections is critical for MWIR devices. Recently, multi-resonant metasurfaces have emerged as a potentially attractive platform for broadband antireflection (AR) across the solar spectrum. Unfortunately, such metasurfaces provide only a restricted AR efficiency in a broader MWIR range. Here, we show that broadband AR can be enabled by leveraging the generalized Kerker effect on a judiciously designed elliptical Si metasurface. It is argued that the generalized Kerker effect can be maximized by suppressing the near-field coupling between Mie resonators and controlling the symmetry of resonators. With this understanding, we can achieve broadband AR with more freedom by engineering symmetry rather than physical dimensions. We demonstrate the value of our optimized metasurface by showing 1.9% averaged reflectance in the 2.5−6 μm spectral range. This work opens up new design strategies for antireflective nanophotonic structures applicable to high-performance MWIR devices.

Large-area and transparent all-dielectric metasurfaces supporting photonic bound states in the continuum (BICs) offer several inherent advantages for highly sensitive biosensing applications. A BIC represents a unique mode within the energy spectrum of free-space waves that remains uncoupled with free-space radiation, resulting in a divergent radiative Q-factor and a topological singularity in reciprocal space. In this study, the synergistic combination of photonic crystal slabs (PhCS) supporting bound states in the continuum (BIC) with aptamers and molecularly imprinted polymers (MIPs) offers a groundbreaking approach to achieving ultrahigh sensitivity in detecting mycotoxins in wine and cytokines in artificial saliva. Mycotoxins, toxins produced by certain fungi, pose significant health risks when present in food and beverages like wine. Our research endeavors represent a significant step forward in the field of biosensing, offering a pathway toward the development of versatile, efficient, and reliable sensing platforms with broad applications across scientific, industrial, and societal domains.

Considerable demand exists for smart, low-cost and portable gas sensors. Although IR spectroscopy-based sensors work well for this application, their deployment is limited by their size and cost. We demonstrate a smart, low-cost, multi-gas sensing system comprising a mid-infrared microspectrometer and a machine learning algorithm. The microspectrometer is a metasurface filter array integrated with an IR camera. A machine learning algorithm is trained to analyze the data from the microspectrometer and predict the gases present. The system detects greenhouse gases carbon dioxide and methane at concentrations ranging from 10 - 100% with 100% accuracy. It also detects hazardous gases at low concentration levels with an accuracy of 98.4%. We detect ammonia at a concentration of 100 ppm. We detect methyl-ethyl-ketone at the permissible exposure limit (200 ppm). This work demonstrates the viability of using machine learning with IR spectrocopy to deliver a smart and low-cost multi-gas sensing platform.

We present breathalyzer-based prompt screening technology that can detect and screen multiple respiratory diseases using the exhaled breath of a patient, collected on an LC resonant metasurface, demonstrating a spectral red-shift (ΔF). We categorized ΔF for multiple respiratory diseases, which do not overlap. This was physically possible by removing the constraint of detection limit in metamaterials, along with significant sensitivity enhancement physics.

In this study, we introduce a novel optical sensor utilizing bound states in the continuum (BIC) to achieve unprecedented sensitivity in quantifying exosome secretion from individual cells. Our approach overcomes the limitations of current single-cell analysis methods by enabling dynamic, real-time monitoring of cell secretion and protein analysis at the single-cell level. Utilizing an asymmetric all-dielectric nanostructure, our sensor exhibits a high figure of merit of 677 and a sensitivity of 440 nm/RIU. This advancement promises significant contributions to biomedical applications, offering a powerful tool for understanding cellular processes and interactions at a granular level. Our findings represent a pivotal step toward the development of highly sensitive optical sensors for different biomedical applications.

This study demonstrates a stent sensor made of nitinol, a nickel—titanium alloy used in the medical field for its pseudo-elasticity and strong corrosion resistance, poly(vinylidene fluoride) (PVDF) and polydimethylsiloxane (PDMS), which can measure several physiological parameters while placing it in the arteries. This nitinol health monitor sensor (NHMS) device thus integrates the TENG with a specific medical application. The NHMS possesses memory shape nitinol elec-trodes that preserve the device structure, while using PDMS and PVDF triboelectric effect to measure heart rate, blood pressure and breathing patterns. Three constant pressures were meas-ured in this study. At a constant pressure of stage 1 (5 psi), stage 2 (11 psi) and stage 3 (13 psi), the NHMS produces an average alternating current (AC) of 0.31 V, 0.49 V and 0.71 V, respectively. Several beats per minute (bpm) were measured and clear readings were obtained from 30 bpm to 180 bpm. Additionally, this device was able to charge a commercial capacitor, which shows its performance as a self-powered sensor, thus holding great potential in medical application.

Refractory materials, known for their exceptional thermal stability and robustness in extreme high-temperature conditions, have gained attention in recent years. These materials, including high-melting-point metals, such as titanium, tungsten, chromium, molybdenum, and tantalum, are ideal for applications demanding high-temperature resistance and durability. Here, we present the design of polyatomic refractory metastructures capable of achieving perfect absorptivity as well as near-unity emissivity. We design arrays of clustered refractory-metal nanodisks (tungsten and titanium) coupled to a same-metal backplane with dielectric spacers between the nanodisks and the backplane. Similarly, the spacer is made of refractory materials, silicon nitride and titania, respectively. By tuning the thickness of this spacer, our polyatomic metastructures achieve near-perfect absorptivity and near-unity emissivity across visible and near-infrared spectral ranges. This work highlights the potential of refractory materials for high-performance absorbers and thermal emitters that are capable of withstanding extreme temperatures without compromising performance.

When an intense laser interacts with a gas of atoms, high-order harmonics are generated. In the time domain, this radiation forms a train of extremely short light pulses, of the order of 100 attoseconds. Attosecond pulses allow the study of the dynamics of electrons in atoms and molecules, using pump-probe techniques. This presentation will highlight some of the key steps of the field of attosecond science.

I will present some novel AI techniques for photonics and physics in general. In particular, AI techniques which enable discovering new material properties, as well as new materials will be discussed. I will also discuss using photonics to implement certain novel computation schemes at the intersection between classical and quantum physics.

Increasingly, we need to find and count channels for waves. In nanophotonics, knowing how many optical channels can usefully enter or leave a small structure is critical for understanding what the structure can do and how to design it efficiently. Though conventional diffraction theory gives useful answers for large objects, for nanostructure on wavelength scales, there has been no clear picture. We show how understand such channels based on a concept of tunneling escape of waves from small volumes. We also show how to find the best coupled channels automatically through arbitrary optics, based on self-configuring photonic integrated circuit processors, which function as real-time optical analog processing systems.

Using representation theory, one can prove that current implementations of symmetry-protected bound states in the continuum (BICs) in photonic crystal slabs can only yield BICs at the center of the Brillouin zone and below the Bragg diffraction limit, which fundamentally restricts their use to single- or few-frequency applications. Instead, this limitation must be overcome by altering the system’s radiative environment. In this talk, I will show how to create lines of BICs by altering the radiative environment surrounding a photonic slab, as well as degenerate pairs of symmetry-protected BICs with independent control over their Q factors and frequency splitting.

Photonic funnels, conical waveguides with hyperbolic metamaterial (HMM) cores, efficiently focus mid-IR light to spatial areas much smaller than the free space wavelength. These devices were originally conceived as having a perfect electric conductor (PEC) coating to confine light as it propagates to their subwavelength tip, however, recent numerical analysis demonstrates that funnels without a conductive cladding exhibit peak intensities over 1,000 times greater than their clad counterparts while maintaining a confinement scale determined by their tip radius. The funnel's conical surface provides an oblique interface between the highly anisotropic HMM and an isotropic medium. This oblique interface enables anomalous reflections which reshape and redirect the incident beam towards the funnel tip. In this work we analyze how the gold cladding suppresses the field enhancement and demonstrate the importance of the anomalous reflection to the funnel's performance.

Our study examines how light's angular momentum affects magnetic all-optical switching (AOS), which involves reversing magnetization using ultrafast laser pulses on a magnetic structure. The magnetic system consists of a ferromagnetic thin sheet of Co/Pt, which is stimulated by Femtosecond vortex beams of light can carry spin, orbital angular momentum, or both.

The study presents a novel framework for generating random metamaterials using graph algorithms, offering connectivity and adaptability across diverse base shapes. Our approach enables precise manipulation of macroscale and microscale elements, facilitating tailored designs for specific applications and enhancing data representation. Our designs exhibit controllable properties such as stiffness, density, and acoustic impedance, promising wide-ranging applications in metamaterial research. We showcase computational results illustrating the method's efficacy across various geometries, laying the groundwork for advancements in materials science and innovative solutions in diverse fields.

Large language models (LLMs) such as ChatGPT are trained on massive quantities of text parsed from the internet and have shown a remarkable ability to respond to complex prompts in a manner indistinguishable from humans. We present a fine-tuned LLM that can predict electromagnetic spectra over frequencies given a text prompt which only specifies the metasurface geometry. Results are compared to conventional machine learning approaches including feed-forward neural networks, random forest, linear regression, and K-nearest neighbor. We demonstrate the LLM’s ability to solve inverse problems by providing the geometry necessary to achieve a desired spectrum. Furthermore, our fine-tuned LLM excels at “physics” understanding, explaining how certain resonances are directly related to geometry. LLMs possess some advantages over humans that may give them benefits for research, including the ability to process enormous amounts of data, finding hidden patterns in data, and operating in higher dimensional spaces. We propose that fine-tuning LLMs on large datasets specific to a field allows them to grasp the nuances of that domain, making them valuable tools for research and analysis.

Strain engineering of the two-dimensional semiconductor gallium selenide has recently revealed exciting nanophotonic effects such as localized bandgap tuning, exciton funneling, and the creation of site-specific single photon emitters. We investigate the reversible local strain engineering of suspended gallium selenide flakes by using a novel micromechanical spring with nanoscale probes for inducing symmetry-controlled localized strain. By performing strain engineering measurements on suspended gallium selenide flakes as opposed to using patterned substrates, unintended strain originating from the surrounding environment is avoided. Our results show that gallium selenide undergoes a reversible bandgap redshift of >6 meV. The presented research establishes a new platform for streamlining the quantitative understanding of material properties as a function of complex local strain in two-dimensional materials for quantum photonics applications.

In this work, and inspired by the multimode fiber refractive index sensors, we propose and design a refractive index sensor in a silicon-on-insulator (SOI) semiconductor structure using a complex multimode resonator. The resonator is optimized with an adjoint-based inverse design topology optimization technique using the commercial software Lumerical. We model the structure in a two-dimensional platform and the device's effective refractive index is calculated based on a suitable figure of merit. The sensor is tailored to operate within the telecommunication band, making it suitable for applications such as wearable devices for patient monitoring or detection of pathogens or toxins in environmental monitoring. The biosensor's design is optimized for maximum sensitivity to changes in the surrounding refractive index within the 1450 nm to 1650 nm wavelength range. It is also compatible with standard fabrication processes and the minimum manufacturable feature size, which is crucial for practical implementation.

Space and time-varying electromagnetic structures give access to regimes of operation that do not occur in their time-invariant counterparts due to modal orthogonality. Here we present the theory of intermodal energy transfer in time-varying plasmonic structures. Using a perturbative approach, we obtain closed-form solutions describing the intermodal energy transfer between modes. We further show that the modal amplitudes reach a steady state, and determine the optimal modulation conditions that maximize the amplitude of the high-order mode. Finally, we identify a coherent control strategy to enhance the conversion efficiency to higher order modes.

We present a dynamic metasurface driven by polarization-twisting beams to demonstrate the rotational Doppler effect. Polarization-twisting pulses, composed of left and right circularly polarized pulses with shifted center frequencies, generate a rapidly rotating linearly polarized field. We employed nanocylinders made of amorphous silicon as the building blocks of the metasurface. The rotating field alters the permittivity of the nanocylinders due to the nonlinear Kerr effect, thereby enabling the metasurface to function effectively as a fast-rotating waveplate. When a probe beam passes through this metasurface, both its frequency and spin state are altered due to the rotational Doppler effect. This phenomenon could be potentially used for developing magnetic field-free optical isolators.

Over the past decade, metalenses have been investigated to overcome the limit of classical refractive lenses. They offer thin, lightweight, and mass-producibility through photolithography fabrication process. However, chromatic aberration remains a challenge for high-quality images. We present a comparative study of wavefront aberration between commercial plano-convex lenses (PCXs) and nanofabricated dielectric metalenses for an infrared wavelength of 1,550 nm. We developed an off-axis interferometry system to analyze a point-spread function (PSF) at the focal plane from phase-resolved interference patterns. The phase characteristics of PSF were extracted and computed as a sum of Zernike polynomials. Through this analysis, metalenses demonstrate diffraction-limit characteristics and are competitive to PCXs in most metrics regarding a well-defined monochromatic wavelength.

Optical Rectification (OR), where photon frequencies subtract to give a zero-frequency direct current (d.c.), is an interesting nonlinear optical effect. Rectifying antenna-coupled diodes have produced the highest-efficiency microwave power conversion > 80%. Most IR detectors are expensive unsustainable semiconductors with a band gap, built n specialized clean rooms with trained staff, dangerous chemicals. Recently OR, not band gap limited, did not require an insulator or semiconductor; plasmonic metals are sufficient. We have observed a near-IR OR longitudinal current along the surface of a resonant 1-D metasurface (no photon drag), and coupling of incident photon helicity to plasmon transverse spin (“spin-momentum locking”). Future OR may be tuned. Here, we report experimental observations of OR voltages from off-center laser beam illumination and a transverse OR current (an ‘OR Hall Effect’), present in the same simple plasmonic gold film patterned into a 1-D grating; left-right patterning breaks symmetry. The strong stripe optical nonlinearity and field enhancement cross-couple higher order polarization terms generating a transverse OR current. We discuss applications.

The eigenstates of the quasi-static electric potential field in a host medium with inclusions are used to represent the local physical electric field produced either by given values of that field at the system envelope or by a given local charge density in the system. The novelty is that not all the eigenstates are used, but only those of the isolated inclusions. Those of the host are not used. The local electric permittivity is assumed to have a uniform value in each constituent, but to differ in the different constituents.