Quantum Sensing and Nano Electronics and Photonics XXI

Matter-wave sensors drive versatile interferometers for on-field operations and fundamental exploration, emphasizing enhanced navigation through quantum-classical integration, promising optimized performance and miniaturization. These advancements fuel competitive research in precision metrology, marking a transformative era in scientific exploration and technological innovation.

We report a novel graphene-based biosensor for label-free detection of immunoglobulin M (IgM) with a sensitivity of 100 zeptomolar (10−19^{-19}−19 M). The sensor uses a bio-functionalized gold interface with anti-IgM antibodies, capacitively coupled to a graphene electrode via a water-soaked paper strip. Binding events alter the surface potential, changing the graphene's carrier concentration and Fermi level. These changes are detected through shifts in graphene phonon frequencies using Raman spectroscopy, which align with surface potential shifts measured by Kelvin probe atomic force microscopy (AFM). This design enables precise biomarker quantification and improves flexibility and optimization over traditional sensors. The two-terminal electric scheme simplifies architecture, reduces noise, and increases reliability. Additionally, the electrolyte-soaked paper strip supports a stable environment, ideal for self-contained microfluidic platforms, paving the way for advanced portable diagnostic tools.

The implementation of free-space optical communication and sensing systems operating in the mid infrared represents a critical advancement for next-generation high-speed communication networks, offering a robust solution for environments where traditional radio frequency (RF) and near-IR systems face significant limitations. Here we report on our recent advancements in free-space optical communication and sensing using MIR QCL sources. Two setups will be discussed, one using a QCL comb aimed at optical communication in the 4- μm atmospheric transparency window, and one LIDAR based on single-mode cw QCL aimed at both air quality analysis and range finding. Moreover, experimental results demonstrating few-photon coherent detection will be shown.

In this presentation, I will show the recent application of two-dimensional (2D) Transition Metal Dichalcogenides (TMDs) to terahertz (THz) photonics and spintronics. I will concentrate on the layer controlled bandstructure of these TMD materials, which can be controlled and engineered for a wide range of physical phenomena – from semiconducting, semimetal, giant nonlinearities to spin-to-charge conversion properties – simply by controlling the number of atomic layers and the interlayer interaction. This opens up novel prospects for THz physics and applications. In particular, I will present our recent work on the utilization of Group-10 2D TMDs, such as PtSe2, in the realms of nonlinear THz valleytronics [1], THz spintronics [2] and the semiconductor-semimetal transition [3], demonstrating how their layered controlled electronic and photonic properties introduces novel functionalities to these domains. [1] M. Hemmat et al, InfoMat. 2023;e12468. doi:10.1002/inf2.124 [2] K. Abdukayumov et al, Adv. Mater. 2024, 2304243 [3] M. Martin et al, submitted (2024)

Metasurface with giant nonlinear response ($\chi^{(2)} >10^5$pm/V) for terahertz difference-frequency generation is experimentally realized. Terahertz generation using commercial continuous-wave lasers is demonstrated with infrared-to-terahertz conversion efficiency exceeding that of photomixers in the 3-6 THz range, at least two orders of magnitude higher than that of photomixers in this frequency range.

Color centers in nanodiamonds offer light-matter coupling rates in the near-THz range, and can be integrated with any photonic platform. They constitute promising building blocks for high-bandwidth quantum photonics, potentially at non-cryogenic temperatures. However, the properties of the color centers are heterogenous. To interface these emitters with the on-chip photonic circuitry one must pre-select and deterministically manipulate them with nanoscale precision. We will present a study of fundamental plasmon-enhanced emission rate limits in quantum emitters and a suite of recently developed techniques for realizing deterministically assembled plasmon-enhanced single-photon sources. These techniques include rapid automatic focusing, optical nanoparticle sizing, neural network-driven quantum optical measurements, probe-assisted nanoantenna assembly and the optical control of plasmonic cavity mode volume.

Optically-active solid-state qubits based on silicon vacancy (VSi) centres in silicon carbide (SiC) are a promising emerging platform for use in quantum technologies due to their long-lived electronic spin states and strong spin-photon interaction. SiC possesses a high optical refractive index, strongly limiting light collected from quantum emitters due to reflections at the crystal interface. Solid immersion lenses (SILs) fabricated through grayscale hard-mask lithography provide a scalable and controllable solution, with a factor of 4.4±1.0 brightness enhancement demonstrated for VSi centres. However, these emitters were generated with no spatial selectivity, so that most were not optimally located for light extraction. Here, we present results utilising femtosecond laser writing to generate single VSi centres near the centre of SIL structures. We discuss the improvement in positional accuracy, yield of single photon emitters with respect to writing energy, and preliminary results indicating the effects of laser writing on the surrounding crystal lattice.

Due to properties such as tight confinement of light, small form factor and high non-linearity, silicon-on-insulator (SOI) based integrated photonics has proven to be an effective platform for realizing photonic quantum technologies such as computing, communications and sensing. An important resource for these technologies is the single photon source and the ability to efficiently generate high quality photons is of great interest. By harnessing photon-pair generation via spontaneous four-wave mixing (SFWM), micro-ring resonator photonic structures can behave as heralded single photon sources, where one photon of a generated pair is detected to flag the presence of the other. This work investigates how the brightness and heralding efficiency of micro-ring resonators can be optimized by tuning the coupling of light into the resonator. It is experimentally demonstrated that operating within an over coupled regime provides the optimum heralding rate and efficiency.

SPAD detectors used in space based quantum communications systems and lidars degrade in a space radiation environment where the Dark Count Rate (DCR) can increase by orders of magnitude over the life of a typical mission. We subjected commercial SPAD chips with integrated quench circuitry to ionizing and nonionizing radiation up to the equivalent expected in a typical 10 year on-orbit mission. A significant degradation in DCR was observed. The SPADs were then annealed at temperatures up to 350 degrees Celsius and for times up to 90 minutes. Experimental results will be presented to show an optimal anneal time and temperature to be 30 minutes at 325 degrees Celsius.

Previous works on single photon time-bin qubits for use in quantum communications were limited to the nano-timescale regime due to constraints in the temporal resolution of detector systems caused by detector dead time. We seek to circumvent these limitations by utilizing up-conversion detection. This allows for the usage of single photons in the femtosecond regime to encode quantum information, enabling a drastic increase in bandwidth in quantum communication processes.

Combination of ultra-stable quantum cascade lasers and an ultra-sensitive spectroscopic technique, named SCAR, has allowed to achieve the record parts-per -quadrillion sensitivity for radiocarbon dioxide (14CO2). Recent developments for cantilever-enhanced photoacoustic spectroscopy suggest there is still room for significant enhancements. These three aspects will be discussed during the presentation.

Engineered quantum states of atoms can have exotic properties that can be tailored to produce extremely sensitive sensors. I will describe two types of such states. In the first type, all atoms are placed in a quantum state where the electron and nuclear spin in each atom are aligned or anti-aligned. When these atoms are dressed with a laser highly detuned from an optical transition, the resulting system produces a highly dispersive gain. When placed inside a cavity, this system produces the superluminal laser, with a group velocity larger than the vacuum speed of light by a factor as large as a million. Such a laser is extremely sensitive to variations in the cavity length. Applications of the superluminal laser include ultrasensitive gyroscopes, accelerometers and search for dark matter. In the second type, a maximally entangled Schroedinger cat state of cold atoms is produced via the process of spin squeezing. In addition to applications in precision time keeping and rotating sensing, this state can be used to seek violation of the equivalence principle via dual species atom interferometry, at a level that is five orders of magnitude better than the current limit.

The mid-infrared (MIR) spectral range provides significant advantages for applications such as spectroscopy and high-speed free-space communication, primarily due to its low atmospheric attenuation. However, existing MIR systems that utilize quantum cascade lasers and interband cascade lasers tend to be bulky and power-intensive, limiting their practicality. To overcome this, integrated platforms are essential. This work showcases recent advancements in MIR transmission, achieving Gbit/s data rates across various systems while highlighting thin-film lithium niobate on sapphire as a promising integration material. Its low absorption and high nonlinearity render it ideal for compact, efficient systems, enabling future applications in portable spectroscopy, lidar, and telecommunications.

Laser cavities based on bound states in the continuum (BICs) utilize high refractive index periodic structures in low index dielectric surroundings for vertical confinement, traditionally incompatible with standard semiconductor technology. We demonstrate the first unidirectional lasing from a vertically nonsymmetric true BIC cavity using a conventional GaAs-based half-VCSEL with a shallow etched SiO2 grating. We introduce the fundamentals of BIC-cavity design and discuss experimentally characterized lasing properties, showcasing robustness against grating parameter changes. This facilitates broad spectral tuning and opens the door for electrically driven configurations in conventional semiconductor technology.

Monolithic High Contrast Gratings (MHCGs) represent a significant advancement in optoelectronics, particularly in source and diagnostic applications. These structures, capable of achieving nearly 100% optical reflectance, can be fabricated from various semiconductor and dielectric materials, facilitating their integration into a wide range of optoelectronic devices [1]. A key advantage of MHCGs is their ultra-thin profile, up to 20 times thinner than traditional distributed Bragg reflectors, making them ideal for compact and high-efficiency optical systems [1]. Additionally, MHCGs can function as highly efficient transparent electrodes, with record-setting transmittance values [2]. In this work, we present the development of both MHCG for transmission and reflectance applications, highlighting the impact of various fabrication procedures. We used different materials depending on the intended application, including semiconductors, dielectrics, and polymers. The presentation will cover fabrication methods, material properties, and the resulting optical functionalities, offering insights into the practical applications of MHCGs for advanced optoelectronic systems.

Attoseconds: When intense light interacts with a gas of atoms (or a transparent solid), electron wave packets are released. Attosecond pulse formation exploits the correlated electrons and holes, forcing the electron to return. Without the plasma connection, two of the most important strong-field process that accompany attosecond pulse formation—hot electron formation (inverse Bremsstrahlung) and non-sequential double ionization (collisional ionization)—seemed mysterious. These plasma-like processes lead to laser induced electron diffraction and orbital tomography. THz generation: Terahertz pulse formation by ionization has a similar linage. Using PIC codes to describe azimuthally polarized l=4 mm and 2 mm light interacting with a 150 µm thick jet of helium, we calculate THz pulses reaching 8.5 Tesla. But 10 Tesla is not a limit. 30 THz azimuthally polarized beams can be amplified in high-pressure CO2 reaching isolated magnetic fields of 1-gigagauss.

In recent years, topological phenomena in photonic systems have attracted much attention, with their striking features arising from robust states in the energy gaps of spatially periodic media. However, light waves are entities that extend in space as well as time, such that one may ask whether topological effects can also occur in the temporal domain, or even space-time. Intuitively, systems that are periodic in time may be gapped in momentum, leading to topological states localized at time interfaces. However, time - in contrast to space - exhibits a unique unidirectionality often referred to as the “arrow of time”. Inspired by these features, I will present our most recent experiments on topological states residing at temporal interfaces. Moreover, I will discuss the formation of spacetime-topological events and demonstrate unique features such as their limited collapse under disorder and causality-suppressed coupling.

Quantum technologies promise a change of paradigm for many fields of application, for example in communication systems, in high-performance computing and simulation of quantum systems, as well as in sensor technology. However, the experimental realization of suitable system still poses considerable challenges. Current efforts in photonic quantum science target the implementation of practical devices and scalable systems, where the realization of quantum devices and controlled quantum network structures is key for envisioned future technologies. Here we present our progress on the engineering of integrated photonic systems, which can overcome current limitations for the realization of scalable photonic systems. Specifically, our research currently focuses on three different but complementary topics: integrated devices based on lithium niobate circuits, engineering and harnessing the temporal-spectral structure of quantum states of light, and photonic quantum computation.

We review several interferometric experimental realizations dedicated to the qualification of key properties of optical materials by i) exploiting photonic quantum entanglement and ii) mimicking photonic entanglement using cascaded nonlinear optical processes. Both methods rely on extracting the relative phase difference within the interferometer. In this context, we present state-of-the-art measurements of refractive index variations and chromatic dispersion, showcasing their superior precision compared to classical measurements, all achieved by leveraging the non-classical properties of the quantum states of light used to probe the interferometer.

We provide a brief overview on the recent progress toward the synthesizing of 4”-dimater wafers of h-BN quasi-bulk crystals (epitaxial layers with 100s microns in thickness) by hydride vapor phase epitaxy (HVPE) and the attainment of h-BN thermal neutron detectors with a record high efficiency of 60%, achieved exclusively by our group. These recent developments serve as a solid stepstone for further advancing the crystal growth technology to produce electronic grade h-BN for use as an active host as well as a substrate material for applications ranging from deep UV photonics, power electronics, neutron detectors, and quantum information technology.

A new technique for realization of lateral heterostructures with an arbitrary shape and material composition in two-dimensional transition metal dichalcogenides (TMDs) is presented. The possibility of achieving sub-micron feature sizes, unprecedented flexibility in shape and material composition, and forming lateral heterostructures with dimensions well below 50 nm in mono-layer films provide a unique opportunity for forming heterostructures for quantum applications in atomically thin materials.

Hybrid interlayer exciton in bilayer MoS2 form, when the hole is tunneling between both layers. This can be seen as a combination of the A intra-, and B inter-layer excitons. These excitons exhibit a dipole moment out of plane and one in plane. The in-plane moment allows the exciton to couple to light such as in a cavity to form exciton polaritons. The out of plane dipole moment allows stronger interactions with the exciton. This can be used to couple to different layers in the system and interact with charge carries located in those layers. Combining both effects allows us to create structures where we us the properties of light via the exciton-polaritons to imprint on another layer. In this work we focused on the hybrid interlayer excitons and how they behave if their density is changed. As the interaction with another layer can be enhanced by orientating the out of plane dipole moments, we also studied the behavior while an external electric field acts on the sample.

We will give an overview of the efforts at Honeywell to use photonic integrated circuits to enable quantum sensors. Honeywell has developed a state-of-the-art silicon nitride photonics platform to enable atomic clocks, Rydberg electromagnetic field sensors, and other quantum sensing technologies. We will discuss the advantages and remaining challenges for using photonic integrated circuits to advance quantum sensors to the point where they can be adopted in mainstream applications.

We introduce a general approach for quantifying the performance of a sensing system based on spectral transduction, i.e. the change of the reflected/transmitted spectrum. Based on the fundamental Cramér-Rao lower bound, it allows identifying transducer-readout combinations which achieve high sensing performance with low hardware complexity as alternative to common high-resolution readout equipment.

Rare earth ions in solids provide a versatile platform for quantum optical information control. Our research focuses on light storage at telecom wavelengths in Erbium-doped crystals, aiming to develop efficient quantum optical memories for applications in quantum communication and computation. Additionally, we design solid-state devices relying on collective atom-atom interactions to enhance light-matter interactions, based on rare-earth photonic devices.

Lattices in synthetic dimensions offer the potential for novel system configurations and interactions, increased dimensionality and non-local nonlinearities. When the synthetic lattice is an equally spaced frequency ladder, the manipulation of the lattice dynamics is transferred to the control over the frequency comb formation and its stabilization. The process of generation typically involves the proliferation of frequency modes followed by a stabilization process. Specifically, in multimode lasers, the stabilization process is governed by the gain recovery time. Historically, this stabilization was associated with slow and selective dissipation mechanisms. Recent advancements in semiconductor lasers have shown that fast gain recovery times diversify the dynamics of light. In this talk, I will discuss the effects of ultrafast gain recovery times on the dynamics of light in a discrete frequency space, and show that fast dissipative processes enforce coherent dynamics of light, enabling the full exploration of the frequency space. This platform paves the way for innovative quantum-inspired devices, among which is the recently discovered quantum walk comb.

In this talk we summarize our recent theoretical developments leading to the design, simulation and experimental verification of different types of THz and Mid Infrared (TERA-MIR) sensors and photonic function devices. Giant control of THz nonlinearities in superlattices is predicted and compared with experiments. The resultant superlattice devices are used for the detection of nitriles, showing potential for metabolomics medical diagnostics. Next, MIR QCLs and photoacoustic sensors deliver precise detection of ammonia traces in water. To conclude, we show a direct comparison of our technological solutions for light polarization control devices, such as polarizers, polarization splitters, and polarization splitters/rotators against other devices in the literature and show some of our recent MIR designs.

Free space optics in the 10 µm wavelength range is an interesting option for transmitting data wiht high bit rate. Using unipolar devices embedded into metal-insulator-metal metamaterials we have demonstrated short range link with bit rate close to 70 Gbit sec-1.

We observe the emission of mid-infrared radiation in h-BN-encapsulated graphene devices under high bias and demonstrate that it results from the electroluminescence of hyperbolic phonon-polaritons.

We demonstrate free-space amplitude modulators for mid-infrared radiation (around 9.6 um) operating at room temperature up to at least 20 GHz, with a -3dB cutoff frequency of approximately 10 GHz. The devices operate in the 9.4-9.8 um and 8.5-8.9 um wavelength range, with relatively low input RF powers in the 0 – 9 dBm range. The modulator response is linear in this RF input range, and it is linear up to laser power of the order 15/20 mW. Binary data modulation signals applied to display eye diagrams as a figure of merit confirm the performances of these ultra-fast modulators.

In this paper polarization and hybrid entangled source of light which were built using a fully on-chip battery-powered source of entangled photons will be discussed. These devices use monolithically integrated Bragg reflection waveguide laser diode (BRL) enabling high fidelity, record flux, compact photon pairs to be generated via a type-II intracavity phase-matching process.

We report on arrays of superconducting nanowire single photon detectors to enable a wide range of applications in quantum optics. Our device allows for the acquisition of spectra with high efficiency, high time resolution and low noise over a wide spectral range. By time-stamping every photon detection event, we also enable the extraction of photon correlation and cross correlations from a measurement as well as lifetimes. This new instrument has applications in quantum optics, in microscopy, lidar and can replace streak cameras with a better signal to noise ratio.

Single photon emitters represent a critical component for enabling several quantum technologies such as quantum communication, quantum photonic computing, sensing, and imaging. One example of quantum imaging that leverages the non-classical nature of light radiated by quantum emitters is the so-called antibunching super-resolution microscopy. We present a machine learning (ML)-assisted approach for the realization of rapid antibunching super-resolution imaging and demonstrate 12 times speed-up compared to conventional, fitting-based autocorrelation measurements. The developed framework paves the way to the practical realization of scalable quantum on-chip devices hosting various types of quantum emitters as well as quantum material metrology. Additionally, for security applications, we develop a robust, ML-assisted on-chip device testing method that can be used to ensure the integrity of a chip avoiding risks of tampering and failure. Both ML approaches could pave the way to the realization of large-scale, secure quantum on-chip devices.

We present a novel approach using the Microwave Kinetic Inductance Detector (MKID) combined with a Digital Micromirror Device (DMD) for Computational Ghost Imaging (CGI). This technique leverages MKIDs' high sensitivity and energy-resolving capability to detect single-photon events, while the DMD dynamically encodes spatial patterns. High spatial resolution, wavelength-resolved images are reconstructed across the spectral range from 0.2 to 1.8 micrometers. Although large MKID arrays are not yet readily available, our results show CGI significantly increases image pixels while retaining MKIDs' advantages. MKIDs with multiple pixel arrays can subsequently be used to capture dynamic images at microsecond time scales.

We report a low light infrared raster-scanning nonlinear imaging system that utilises a single-mode fiberized zinc-indiffused MgO:PPLN waveguide for upconversion via sum-frequency generation, permitting detection with an 850nm superconducting nanowire single-photon detector. The system operates with 1950nm illumination or pulsed 1571nm illumination, to generate upconverted images and time-of-flight upconverted images, respectively, at 870nm.

While neuromorphic imaging demonstrated a plethora of exciting cutting-edge capabilities, benchmarks and comparative performance metrics against traditional imaging modalities are scarce. Simple questions, such as “At what distance can an event camera detect a drone?” cannot be answered without full design, prototyping, and data collection cycles. The unique asynchronous and sparse signal streaming from event cameras, together with the innate dependency on scene dynamics, requires unique metrics suited for target motion and closed-loop systems. We define metrics and criterions aimed for community accepted “general” performance metrics and suggest a simple modular model to estimate performance for event-based imaging systems design in dynamic environment. Promoting rapid and industry-oriented design processes, this model may eventually constitute what is a “good” event sensor, setting new standards for manufacturers of sensors, cameras, and systems.

The gravitational potential of the high-intensity laser is very weak. It would be interesting if it can be detected. We consider the extremely intense laser to be enclosed by an atom interferometer. We compute the strength of the gravitational force and study the feasibility of measuring the weak force using the atom interferometer. The intense laser field from the laser pulse can induce a phase change in the interferometer composed of Bose–Einstein condensates. The sensitivity limit of the microring interferometer with Bose–Einstein condensates can be enhanced by using spin-squeezing effect. We study the effect of spin-orbit interaction in the condensates and determine the sensitivity.

Dynamic control of a material’s optical properties lays the groundwork for reconfigurable flat optical devices, tunable devices that can learn from optical inputs, and energy-efficient chip-scale communications and computation platforms that promise to reduce the energy consumption of the modern telecommunications infrastructure. One appealing method to achieve this relies on electro-optics, which provides a direct connection between driving electronics and optical properties of materials. Integrating electro-optic materials into micro and nanostructures heralds a new generation of devices with light-matter-microwave interactions much stronger than bulk devices, creating a platform for unprecedented photonic devices. This presentation will highlight integrated photonic devices based on Lithium Niobate on Insulator, including femtosecond optical pulse generation driven by dispersion engineering and microwave modulation. I will conclude the presentation with some work establishing the fundamental processing-performance relationships that give rise to low frequency instability in the device platform, enabling a new generation of compact, ultra-stable photonic switches.

This research explores the dynamical properties of the anomalous Hall effect (AHE) in topological antiferromagnet Mn3Sn using terahertz (THz) time-domain polarimetry. The anomalous Hall conductivity spectrum from dc limit to a few THz is observed, and further this study reveals that the AHE is suppressed by 40% immediately after optical pulse irradiation, indicating that the AHE in ultrafast time scale is ascribed to the intrinsic Berry-curvature mechanism. We will also discuss further intriguing change in the Hall conductivity spectrum for extremely nonequilibrium condition. These findings highlight the potential of Mn3Sn for high-speed spintronic devices and provide new insights into the nonequilibrium dynamics of the AHE.

Photodetectors based on colloidal quantum dots (QD)/graphene nanohybrids are quantum sensors due to strong Photodetectors based on colloidal quantum dots (QD)/graphene nanohybrids are quantum sensors due to strong quantum confinement in QD and graphene. The optoelectronic properties of QD/graphene nanohybrids are affected by the quantum physics that predicts a high photoconductive gain and hence photoresponsivity (R*) depending on the pixel length (L) as R*L-2. Experimental confirmation of the effect of the pixel geometric parameters on the optoelectronic properties of the QD/graphene photodetector is therefore important to elucidate the underlying quantum physics but presents a challenge in atomic-scale control of the device microstrcuture to allow the geometric effect to be extracted precisely. Motivated by this, an array of QDs/graphene nanohybrid photodetectors were designed with variable QD/graphene pixel length L and width W in the range of 10-150 µm for a study of R*, noise, and D*. Intriguingly, R* exhibits a monotonic decreasing trend of 1/L2 while being independent of W, confirming experimentally the theoretical prediction.

Ferritin has quantum dot properties and is related to neural electron transport. Ferritin is a spherical structure with an 8 nm inner core and an outer 12 nm sphere. Ferritin is a self-assembled nanocage that consists of 24 subunits under different pH environments, and the subunit will disassemble and assemble. We designed Au nanoclusters (NCs) coupled with Au particle systems to control the quantum electronic properties of these protein plasmonic structures. Plasmon-enhanced photoluminescence and electroluminescence are observed from the apoferritin-based quantum biological neurophotonic system. The electron transport pathway can be regulated by the optical excitation wavelength, intensity, and density of the Au NCs. These novel quantum biological properties also have the potential to be used as optogenetic fields for optical manipulation of neural activity in the future.

We report progress toward a miniaturized chemical threat detector, based on infrared spectroscopy, for applications requiring miniaturized SWAP. We recently demonstrated the selective detection of dimethyl methylphosphonate vapor (DMMP, a nerve agent simulant) by monitoring the optical loss induced in an interband cascade laser (ICL) with exposed top sensing window coated by a custom sorbent to reversibly sorb hydrogen-bond basic molecules. DMMP levels down to ~20 ppb were measured by monitoring the lasing threshold. In earlier work an off-chip InSb detector measured output from the ICL’s end facet. However, in this update we employ a fully-integrated on chip device that monitors the L-I characteristics. With increasing concentration of DMMP, the ICL threshold current variation derived from the L-I characteristics alone was comparable to that determined by an external InSb detector. After returning to a clean airflow, the device signal returned to its original baseline.

Imagine dragging a plate across the surface of a tranquil water pool. Quite excitingly, you would form a pair of swirling vortex and antivortex, propagating steadily across the surface. In optics, vortices materialize as phase twists of the electromagnetic field. While traditionally optical vortices arise from interactions between light and matter, we have recently reached a new extreme regime of optical nonlinearity where quantum vortices form due to effective, strong interactions between the photons themselves. These interactions are realized in a ‘quantum nonlinear optical medium’ based on ultracold Rydberg atoms. Analogous to the water pushed by the plate, the excess phase accumulating due to the photon-photon interaction gives rise to pairs of vortices within the photonic wavefunction. The ‘conditional’ phase flip localized between these vortices can be used for deterministic quantum logic operations. Counter-propagating photons, in a configuration suitable for quantum gates, exhibit even stronger and longer-range interactions.

We explored the relation of electronic and optical properties to ultrafast strain in topological Weyl antiferromagnet Mn3Sn thin films using near-infrared femtosecond laser pulses. The oscillation of coherent longitudinal acoustic phonon was clearly identified in pump-probe spectroscopy, exhibiting a remarkably large amplitude exceeding 1% in the differential transmission. Our quantitative analysis considering pulse-induced heat-driven coherent acoustic phonon successfully reproduced the result. We proposed a simple analysis procedure to estimate the photoelastic coefficient as a complex number, revealing that the near-infrared real-part photoelastic coefficient in Mn3Sn is several times larger than that in typical materials. We discuss the origin of the large response and the potential to manipulate magnetism by ultrafast strain field.

Traditional detectors and imaging arrays have achieved remarkable success, and modern solid-state imaging is significantly influencing various aspects of our social, economic, and scientific endeavors. However, the advancement of silicon-based imaging is limited by constraints pertaining to materials and devices. In comparison to natural imaging systems, such as the human eye, current artificial systems exhibit inferior performance in terms of power consumption, sensitivity, and adaptability. Recent breakthroughs have unveiled new material and devices for bio-inspired imaging systems. During this presentation, I will provide an overview of these innovative developments and discuss our research on "bio-inspired retinas," which consist of highly sensitive photodetectors and in-sensor computation techniques that consume extremely low amounts of energy. Furthermore, I will showcase our recent progress in integrating new 2D materials onto silicon CMOS chips through heterogeneous integration and explore potential future directions for the development of high-performance and energy-efficient 2D and 3D imaging systems.

Ultrafast pump-probe microscopy-spectroscopy have been utilized as a promising new ultrafast approach. Transient absorption microscopy enables to visualization and localization of the photochemical and photophysical processes in complex systems. Ultrafast diffuse reflectance spectroscopy is of great value for in-situ time-resolved analysis of complex photophysical processes in opaque or highly absorbing materials and devices. We have developed an ultrafast time-resolved pump-probe diffuse reflectance spectrometer with a sub-200 femtoseconds time resolution. We also integrated DR-TAS with pump-probe transient absorption microscopy (fs-DR-TAM) and showed that the technique allows the in-situ localization of and visualization of charge carrier kinetics within the sample. Environmentally friendly and low-cost solution-processed materials with tunable bandgaps are desired for photonics, energy conversion, optoelectronic, bioelectronic, and biomedical applications. Latest advancements with our ultrafast microscopy and quantitative ultrafast image analysis methods for visualization of time-resolved photophysical processes in sustainable materials will be discussed.

We present recent advancements in intracellular temperature sensing using both, proteins and nanodiamond-based quantum sensors. The application of these temperature sensors in in vitro cellular assays can help gauge the parameters required for efficient but low damage introducing hyperthermia cancer therapies. We will report both on in vitro intracellular temperature measurements performed during magnetic - as well as during photo-thermal therapy of in vitro cancer models. The combination of both fluorescence molecules and nanodiamond based temperature sensors, which are highly photostable and robust across wider temperature ranges relevant to hyperthermia applications, helps understand the intracellular and extracellular temperature evolution during hyperthermia treatments. We identify a temperature readout technique for nanodiamonds which render them a highly promising tool for intracellular temperature assessment.

We present a novel hybrid platform idea for detecting medical biomarkers. As examples, we will focus on glucose and the SARS-CoV-2 S protein. The main components are optical biosensors, characterized by high sensitivity, rapid response, low cost, and capability for non-invasive detection. The sensors operate by utilizing variations in reflection or transmission resulting from modifications in Fano resonance conditions. The development of the platform involves a multi-step process.The detection mechanism relies on the biosensor's optical response. The presence of analytes induces a spectral shift of the Fano resonance, caused by the modification of the biolayer thickness (in case of virus or cancer detection) or changes in the refractive index contrast between the structure and the environment (in case of glucose detection). By leveraging the unique properties of Fano resonance and utilizing engineered subwavelength quasi-periodic structures with specially adjusted optical coatings, the sensor properties can be tailored for detecting selected biomarkers. At the same time, we observed an electrochemical response on the gold electrode.

Our work investigates the generation of nonclassical light by cascade lasers in the mid-infrared (MIR) 3-5-μm spectral region. Using a MIR-balanced detector sensitive to the intensity noise below the classical level, we showed shot-noise-limited operation of cascade lasers in the 1-100 MHz range. The same setup has been exploited to measure four-wave-mixing-induced correlations between modes in harmonic combs emitted by these devices. Moreover, we recently tested the electron-to-photon noise transfer function in cascade lasers, paving the way to the control of their emissions down to the quantum level. These novel insights should make possible laser sensing at unprecedented sensitivity levels.

We present an inverse-designed active wavelength division multiplexing (WDM) device tailored for THz frequencies, fully integrated with a THz QCL to enable amplification and spectral selection of the laser output. Power at the output channels is extracted via surface-emitting patch-array antennas. The optimized WDM design splits the qcl output in three channels, covering the spectral range from 2.2 THz to 3.2 THz. The predicted transmission is around 90% with crosstalk below -12 dB for each output channel. The fabricated device shows an increase of roughly 30% in the output power collected from the antennas when biasing the WDM section to achieve gain compared to when unbiased and purely passive. QCL's emission spectra exhibit features at frequencies above the design bandwidth of the WDM and are strongly suppressed by the demultiplexer. The spectra collected from the antennas are noticeably different although showing a higher crosstalk than anticipated from the optimization.

Interband cascade lasers (ICL) are promising sources for particular applications in photonic integrated circuits. In particular free-space optical communications and LIDAR systems are two practical fields where their use, and especially their controlled behaviour when prone to optical feedback is of great importance. In this work we experimentally observed the transition from the short to the long delay regime of optical feedback on Fabry-Perot mid-infrared ICLs. We observed, in the first case, the emission of regular pulse package, which with increased delay progressively transitioned to low frequency fluctuations. This work is to our knowledge a first experimental demonstration of regular pulse packages in the short feedback delay regime of ICL and paves the way to the development of mid infrared LIDAR based on ICLs.

Quantum Walk Combs form in unidirectional circular lasers with fast saturable gain under resonant phase modulation. The modulation initiates coherent side-mode generation, exhibiting ballistic expansion—a quantum walk signature—until dispersion balances the modulation-induced coupling. The fast gain non-linearity allows stabilization on high-order eigenmodes of the coupled system, resulting in flat-topped high-bandwidth spectra. In this work, we investigate Quantum Walk Combs from Quantum Cascade Lasers under the effect of dynamic disorder, introduced by phase-modulating the resonant radio-frequency drive with Gaussian noise. Doing so, we uncover mobility transitions from the ballistic case with a Bessel-like envelope to diffusive states with Gaussian spectra, finally reaching exponentially localized states with arrested transport depending on the level of disorder. Time-resolved spectral evolution measurements and numerical simulations provide further insight into these dynamics.

LWIR-based free-space optical (FSO) communications are foreseen competitors for current atmospheric communication links established in the telecom C-band, but their deployment relies on mature and commercially-available building blocks which are still missing in the LWIR domain. Here we report the preliminary performances of a first generation of Quantum Cascade Detectors (QCDs) operating at 9 µm wavelength at room temperature in ridge configuration. A maximum peak responsivity of ~140 mA/W at around 9.5µm and a maximum -3dB bandwidth of ~1.5 GHz have been measured, which currently represents the state-of-the-art for waveguide QCDs operating in the LWIR. These preliminary performances indicate high potential of such components and pave the way for their future integration in an integrated photonic platform for high-speed LWIR FSO datacom.

This research introduces an innovative approach to infrared (IR) sensing through the evolutionary-based inverse design of 2D materials multilayer structures. We develop a multi-modal nano-pixel sensing system for high-efficiency IR detection across a broad wavelength range. The methodology includes selecting effective 2D materials, optimizing multilayer structures for dynamic wavelength adjustment, and integrating advanced back-end processing algorithms. Our design features a spectral pixel array with 12 optimized structures, achieving high absorption efficiency and adhering to SWaP+C (size, weight, power, and cost) constraints. Advanced machine learning algorithms, including the Snap Random Forest Regressor, enhance detection accuracy, achieving an RMSE of 3.750e-4 and refining wave resolution to 10-15 nm. This approach significantly improves IR detection by optimizing wavelength sensitivity, selectivity, response time, and quantum efficiency.

Single crystalline quality LiNbO3 films were grown on the sapphire by means of the direct liquid injection CVD. Particular effort was done to achieve films with controlled and homogeneous Li2O composition (± 0.05 mol%) over 4 inch wafers and to grow stoichiometric films. CVD growth also assured highly homogeneous film thickness on the wafer scale. In order to bring epitaxial films towards the integrated photonic applications requiring the integration of LiNbO3 films offering strong electro-optic effect with semiconductor platforms, the layer transfer process is under developments. This includes epitaxial growth of LiNbO3 on LiNbO" substrates with sacrificial layer and then bonding on freely chosen structure and liberation of LiNbO3 from the growth template by chemical etching.

Considerable efforts have been recently devoted to combining ultracold atoms and nanophotonic devices to obtain not only better scalability and figures of merit than in free-space implementations, but also new paradigms for atom-photon interactions. Dielectric waveguides offer a promising platform for such integration because they enable tight transverse confinement of the propagating light, strong photon-atom coupling in single-pass configurations and potentially long-range atom-atom interactions mediated by the guided photons. In the talk, I will present our efforts in this emerging neutral-atom waveguide-QED field of research using different types of waveguides.

Integrated terahertz circuits offer means to route and store terahertz signals on-chip, and provide means to not only increase their amplitude e.g. inside resonators, but also to engineer their phase and group velocity through geometry. However, efficiently coupling terahertz signals in and out of these circuits, and their generation and detection require the development of an entire toolbox that is compatible with their small footprint that is appealing for miniaturization and field control. In our work, we make use of integrated photonic circuits to drive, modulate and read-out terahertz field. This talk will discuss the latest developments in this burgeoning field.

Neural network (NN) concepts revolutionize computing by solving challenges previously thought to be reserved to the abstract intelligence of humans. However, the astonishing and substantial conceptual breakthroughs are so far not mirrored by advances in hardware specialized in physically implementing NNs. As always with computing, scalability is the key metric. I will present our work on the fully autonomous photonic NN based on a high-dimensional semiconductor laser. Using optical injection we realize the scalable photonic NN fully in parallel within the complex laser's high dimensional state space while reducing the role of auxiliary support by a classical digital computer to a minimum. We achieve this by employing exclusively black-box, evolutionary optimization algorithms to train all weights of the NN. The nextwork comprises of more than 5000 neurons with an inference rate of 8e9 results a second, and we achieve >95% realtime accurazy in the MNIST test without any pre or post processing. The large dimensionality is enabled by using lasers with non-classical cavity designs.

In this study, photoluminescence (PL) spectroscopy is used to probe the detailed dynamics of the 2D to 3D growth transition during InAs/GaAs stacked submonolayer (SML) deposition by molecular beam epitaxy. The changes in the PL spectra reveal the sequential phases of the SML growth transition, where the stacked SML growth starts with a predominantly 2D growth mode, followed by a 2D-3D coexistence, and finally concluded by a full conversion to 3D growth. The results elucidate the dynamics of 2D to 3D growth transition during stacked SML deposition, and provide essential understanding for future applications.

Photon Number Resolution (PNR) is the capability to determine the accurate number of photons detected by a photon detector such as Superconducting Nanowire Single-Photon Detectors (SNSPDs) in a single event. The ability to accurately resolve photon numbers is crucial for a wide range of advanced applications in photonics and quantum information science. While pulse separation to many detectors is a generic approach (pseudo-PNR), SNSPDs can be combined with advanced Time Correlated Single Photon Counting (TCSPC) electronics to obtain PNR with high sensitivity. Accurate PNR measurements require meticulous optimization of the signal chain, powerful software tools, advanced triggering capabilities, and precise calibration techniques. This work focuses on improving PNR capabilities by optimizing the entire data acquisition system, including the initial signal detection via state-of-the-art Quantum Opus SNSPDs and the accompanying data analysis architecture via picosecond-resolution Swabian Instruments’ Time Taggers. Improving photon number distinguishability paves the way for advanced quantum photonics research.

Trace-gas sensing at parts-per-trillion level, or below, has become a hot research topic impacting daily-life applications such as human health, environmental monitoring, and security control. The scientific effort together with the technological progress have enabled the possibility to reach ultra-high sensitivities also with compact and robust photoacoustic-based setups, exploiting their intrinsic high degree of flexibility with the sensitivity enhancement provided by mid-IR semiconductor laser sources and high-finesse optical cavities. In this framework, we present a study of an advanced configuration for photo-acoustic trace-gas sensors, aiming at optimizing all the key components to enable a ppt minimum detection level. Alongside the exploitation of a mid-infrared continuous-wave Quantum cascade laser as the excitation source, a Fabry-Perot optical resonator has been implemented for an efficient intra-cavity power enhancement. For the acoustic-to-voltage transduction an unconventional and highly performing “racket-shaped” silicon-based Micro-Electro-Mechanical System is exploited, whose oscillations are measured via a balanced-Michelson interferometric readout.

Efficient light-emitting devices are pivotal missing elements in commercially available advanced silicon photonics platform. Conversely, III-V compound semiconductors offer an ideal solution for engineering efficient light emitters. Thereby, the monolithic integration of III-V nanostructures on silicon holds promise for unlocking significant advancements in integrated photonics technology . However, overcoming the issue of significant differences in thermal expansion, polarity, and lattice mismatch is crucial to achieve defect-free epitaxy on silicon. Our work focuses on the monolithic integration of nano-meter scale III-V light emitters into silicon photonic circuitry using the selective area epitaxy technique on the silicon-on-insulator platform with high spatial precision. This work aims to realize a hybrid III-V/Si nanolaser device with photonic crystal nanobeam cavity. The III-V nano-heterostructures are monolithically grown only in the cavity formed in silicon-based circuitry where the field is maximal. This method presents a pathway towards achieving fully integrated, densely packed, and scalable photonic integrated circuitry.

The effect of growth rate variations of 3ML SK quantum DWELL heterostructures on their optical and strain behaviour. Three different samples A, B and C with growth rate 0.1 ML/s, 0.075 ML/s and 0.05 ML/s with growth time 30s, 40s and 60s, respectively have been considered. The observed emission PL wavelength were approximately 1045 nm (A), 1054 nm (B) and 1071 nm (C) respectively. Also, the PL intensity of sample C is high as compared to that of other samples. The strain inside sample C shows significant improvement. Hence, sample C can be utilised for MWIR optoelectronic applications.

Through spin injection from a defect-enabled GaNAs spin filter [1] to adjacent InAs quantum-dots (QDs), we recently demonstrated generation of electron spin polarization exceed 90% at room temperature – the highest value ever reported in a semiconductor [2]. Here, we showcase spin nonlinearity in such opto-spintronic nanostructures, by closely examining the higher-harmonic generation, which converts the modulation of excitation polarization into the second-, third-, and fourth-order harmonic oscillations of the QD exciton density and spin polarization that can be directly measured by photoluminescence intensity and polarization. The demonstrated spin nonlinearity can readily operate at a frequency exceeding 1 GHz in the studied GaNAs/InAs nanostructure at room temperature, with the potential of approaching THz [3]. This may help to extend the functionality of current semiconductor-based electronic and photonic technologies and could pave the way for nonlinear spintronic and spin-photonic device applications based on nonmagnetic semiconductor nanostructures.

We present a 1024x1024 RGB SPAD camera with gating capabilities for FLIM microscopy, high-speed, and low-light applications. It features microlenses and RGGB-pattern filters, achieving a 90% fill factor and RGB images at 1024x1024 resolution. The asynchronous read-out system allows flexible use, with a transmission speed of 1.2 Gbits/s per lane, enabling 100,000 1-bit frames per second at full resolution. The customizable read-out system supports various resolutions and can achieve over 1 million frames per second for reduced resolutions. The global gating mechanism, with a minimal gate width of 1.5ns, ensures precise synchronization for diverse applications.

Free-space optical communications (FSOC) operating at long-wave infrared (LWIR) wavelengths are of particular interest due to a reduced sensitivity to atmospheric perturbations. However, their deployment requires the development of active and passive photonic components, and in particular of external modulators. To address this requirement, we developed an external modulator in a waveguide geometry based on the intersubband Stark effect in asymmetrical coupled quantum wells. Our device showed promising performances for phase and amplitude modulation as well as high speed operation capabilities. This demonstration paves the way to its future integration on a LWIR integrated photonic platform for LWIR FSOC applications.

We demonstrated the applicability of remote spectroscopic sensing using frequency entanglement via a real-world fiber network. An entangled photon pair was generated in the telecom band by spontaneous parametric down-conversion in a PPMgSLT crystal pumped by a mode-locked laser. One photon of the pair was transmitted over a 2.6 km real-world fiber network using a fiber sensor. Using the quantum frequency correlation, the spectral information of the fiber sensor was remotely deduced from the spectrum of the counter part of the photon, which did not directly interact with the sensor. This demonstrated the applicability of remote spectroscopic sensing using frequency entanglement via a real-world fiber network. This research will lead to practical quantum remote spectroscopy, eliminating the need for sophisticated spectroscopy equipment at the remote site.

In the current report, a wide bandgap metal-oxide and 2-dimensional (2D) semi-metallic heterojunction based optoelectronic device is fabricated on a Si platform by employing Chemical vapour deposition (CVD) and pulse laser deposition (PLD) techniques. The thin film of Ga2O3 is deposited on a high-resistive Si (100) by optimized deposition conditions. Further, a single layer of CVD graphene of size 5 mm x 5 mm is transferred onto the Ga2O3 thin film. After transfer the graphene is also functionalized with hydroxyl (-OH) groups to enhance the photoresponse of the graphene/Ga2O3 heterojunction. Finally, the graphene/Ga2O3 and graphene-OH/Ga2O3 2D-oxide heterojunctions have been studied by measuring dark and photo-current at various wavelengths and such heterojunctions exhibit photoresponse at the UV region.

The current study explores the effect of varying InAs QD monolayer coverages on the structural and optical properties of InAs dot-in-a-well (DWELL) heterostructures. Three samples (S1, S2, and S3) with InAs QD coverages of 3 ML, 3.2 ML, and 3.4 ML are grown, where S1 is capped with a 6 nm In0.15Ga0.85As layer, samples S2 and S3 are additionally doped with Si for 2 seconds before capping. Temperature-dependent PL measurements reveal varying activation energies, with S2 displaying superior thermal stability and carrier confinement. Power-dependent (PD) PL spectra analysis indicated no emission wavelength shift at different power levels. A red shift in emission wavelength is observed at 20 K as monolayer coverage decreases. High-resolution X-ray diffraction (HRXRD) measurements show the enhancement in strain for higher monolayer coverage QDs.

Fluorine-doped indium oxide (IO) nanocubes, separated by nanoscale gaps, present a highly adaptable system for hosting high-quality mid-infrared plasmons, with significant potential for optoelectronics and light-harvesting applications. In this comprehensive study that integrates both theoretical and experimental approaches, we demonstrate that these hybridized plasmon modes exhibit substantial tunability by adjusting the gap size and the dimensionality of the gap region. This prediction is validated through electron energy-loss spectroscopy (EELS) conducted with a scanning transmission electron microscope (STEM). Our findings reveal how gap geometry profoundly impacts the behavior of coupled plasmons and the concentration of electromagnetic fields in doped IO nanostructures. These insights open up new possibilities for applications in plasmonic sensing and surface-enhanced spectroscopies, highlighting the versatility and potential of this nanostructured system.

We will detail several CMOS SPAD photodetectors for use in a range of high-energy and nuclear physics applications, implemented at EPFL’s AQUA Lab in collaboration with external partners. The requirements are often quite different, e.g. high timing precision and detection at low event rates in time-of-flight positron emission tomography (ToF-PET), possibly requiring 3D-stacked implementations, very high data rates, spatial granularity, and photon-starved operation in ring imaging Cherenkov counters at colliders (RICH), or the coupling of sensors to scintillating fibers as active neutrino targets with a dedicated hybrid architecture. High photon detection efficiency in the visible is often required, along with tiling capability to achieve large surfaces. Operation in hostile environments is often needed as well, such as low or even cryogenic temperatures and/or high radiation levels.

Quantum-cascade vertical-cavity surface-emitting lasers (QCVCSELs) could combine the single longitudinal mode operation, low threshold currents, circular output beam, and on-wafer testing associated with VCSEL configuration and the unprecedented flexibility of QCs in terms of wavelength emission tuning in the infrared spectral range. The key component of QC VCSEL is the monolithic high-contrast grating (MHCG) inducing light polarization, which is required for stimulated emission in quantum wells. In this paper we present results of InP based MHCGs fabrication by means of electron beam lithography and plasma etching process. Critical technological aspects of MHCG fabrication will be discussed. The experimental results will be supplemented by measured and simulated spectral characteristics of MHCGs.

Intersubband devices, such as quantum cascade lasers (QCLs), are promising for mid-infrared to terahertz applications due to their customizable intersubband structures. However, practical performance often deviates from theoretical gain and absorption predictions, necessitating experimental analysis. We present a delay-resolved device design to evaluate QCL gain performance across different biases and temperatures. Our findings indicate that gain profiles match theoretical predictions at low-temperature biases below the threshold, with gain and dispersion clamping after lasing. Gain performance significantly degrades above 130 K. These results provide precise evaluations and valuable insights for optimizing high-temperature performance in QCLs and developing QCL-based frequency combs.

Spin-orbit coupling (SOC) in photonics has garnered significant attention due to its potential in manipulating light-matter interactions for advanced photonic applications. Here we discuss SOC driven by third harmonic generation (THG) in χ(3) isotropic nonlinear media. Our findings are driven by the fact that THG is symmetry forbidden for circularly polarized pump beams in isotropic nonlinear media. Using this robust zero generation condition, we thus demonstrate experimentally frequency agnostic SOC for circularly polarized gaussian pump beams in amorphous silicon thin films. All our experimental findings are supported by theoretical analysis and numerical simulations. As a prototype example, we propose to exploit our results for enhancing image contrast and detecting edges with high precision without engineering the surface, thus removing the need of complex fabrication techniques. In summary, our investigation highlights the pivotal role of material symmetries for utilizing nonlinear optical processes in photonic device applications

This work demonstrates the fusion of high-power, mutually incoherent pulse-trains via nonlinear mixing between the modes of a time-multiplexed synthetic mesh lattice. We employ the optical thermodynamic framework for highly multimoded systems to predict the amplitude and phase information in the resulting pulse train and show its coherence.

This work demonstrates the extension of the transparent electrodes based on monolithic high-contrast grating integrated with deep sub-wavelength scale metal stripes (mMHCG) to near-infrared applications. This research advances the technology by achieving mMHCGs with periods as small as 100 nm. Experimental validation shows optical transmission of 85 % largely exceeding the one of plain semiconductor-air interface and sheet resistance of 1,4 Ω/sq similar as for the bulk gold, highlighting the robustness and versatility of mMHCGs in the near-infrared range. These findings enable the development of efficient transparent conductive electrodes for applications that require wide transparent electrodes on semiconductor surfaces, allowing for simultaneous light transmission and high current densities. This advancement is particularly significant for applications such as LEDs, vertical-cavity surface-emitting lasers (VCSELs), and photodetectors.

In 1924, Einstein received a short manuscript in the mail from the Indian physicist S. N. Bose. He quickly translated Bose's manuscript to German and submitted it to Zeitschrift fur Physik. Within a few weeks, Einstein presented his own findings (using a generalization of Bose's counting method) to a session of the Prussian Academy of Sciences. Whereas Bose had suggested a new counting method for the quanta of the electromagnetic field (one that yielded Planck's black-body radiation formula), Einstein applied Bose's method to an ideal monoatomic gas. Shortly afterward, Einstein presented to the Academy a follow-up paper in which he described the Bose-Einstein condensation for the first time. In this presentation, I describe some of the fascinating issues that Einstein struggled with as he attempted to unify the quantum statistical properties of matter with those of the electromagnetic field.

Controlling light transport in a multimode environment is a topic of considerable interest in the field of optics. Here, we realized, for the first time, a nonlinear conservative system where light from a wide range of channels funnels into a universal localized spot, regardless of the initial input distribution, with high efficiency. In our work, a nonlinear waveguide is implemented in a time-synthetic photonic mesh lattice with a judiciously crafted “refractive index” distribution that supports localized lower-order modes in the central region of the lattice. Due to a balanced exchange between the potential and kinetic energy components, a high-power pulse can drop its optical temperature to near-zero values and expand while simultaneously funneling itself to the fundamental mode. After being funneled, light will remain thermally locked to its maximum entropy state, minimizing its microcanonical fluctuations.

A novel symbolic-numerical co-simulation approach is employed to derive a minimal set of expectation values for bosonic mode operator equations, which are then solved numerically. The Hamiltonian in this model incorporates free field propagation, nonlinear wave-mixing, coherent gain, and incoherent loss mechanisms. Although nonclassical light features have been observed in passive microcavity resonators, the coherent gain and waveguide losses in a quantum cascade laser (QCL) counteract the generation of entanglement between comb modes, despite the QCL's significant Kerr-like nonlinearity. Utilizing the developed symbolic-numerical co-simulation framework, we investigate higher-order quantum correlations among QCL frequency comb modes, potentially revealing nonclassical features in the emitted optical field.

Coherent radiation sources at terahertz (THz) frequencies are becoming increasingly valuable due to the growing scientific and industrial interest in integrated photonic platforms at this spectral range. Advanced applications in spectroscopy or quantum technologies might be unlocked by using quantum cascade lasers (QCLs), which emit frequency combs at milliwatt power levels from chip-sized laser cavities. This presentation discusses recent work of tailoring THz QCL emission by controlled cavity engineering. In detail, we present current modeling results for novel device geometries and compare them to experimental findings.

Among high-performing trece-gas sensing technology, photoacoustic spectroscopy (PAS) has proven to be a very promising and widely used technique, mostly because of its unique advantages. Among them it is worth mentioning the zero-background detection, the high versatility in the choice of the excitation source, and the possibility of interrogating gaseous samples in very reduced volumes. The key component of a PAS sensor is the spectrophone, which is responsible for the transduction of the acoustic wave into a measurable signal and whose properties determine the performance of the sensor. In the search of novel and highly-performing spectrophones, a novel configuration combining a custom-made "racket-shaped" silicon-based Micro-Electro-Mechanical system (MEMS) cantilever with an easy-to-build acoustic resonator, made by a dual-tube configuration, is presented. The new configuration was tested for trace-gas sensing in a simple single-pass configuration, demonstrating a final detection sensitivity of 0.34ppb at 10 second of averaging time for N2O trace-molecule detection.

Photonic crystal is an effective way to extract light for surface emission from terahertz quantum cascade laser (THz QCL). However, single mode emission, high power output with controlled beam quality remains a challenge owing to the severe modal competition among the different optical modes. In this talk, I will first briefly introduction our rencent work on THz topological lattice design for stable single mode operation with high output power up to 150 mW. Then I will present our latest work on high brightness surface-emitting THz QCL. We proposed and demonstrated a metallic THz photonic crystal resonator with a phase-engineered design for single mode surface emission over a broad area. The quantum cascade surface-emitting laser is capable of delivering an output peak power over 185 mW with a narrow beam divergence of 4.4°×4.4° at 3.88 THz. A high beam brightness of 1.6×107 W sr−1m−2 with near-diffraction-limited M2 factors of 1.4 in both vertical and lateral directions is achieved from a large device area of 1.6×1.6 mm2 without using any optical lenses.

We present a mobile drone-assisted dual comb remote sensor based on mid-infrared quantum cascade laser frequency combs for simultaneous sensing of multiple atmospheric trace gases. As a proof-of-concept demonstration, a measurement campaign targeting Freon R134a, a refrigerant with strong global warming potential, will be discussed.

A systematic study of the avalanche multiplication of a series of GaAsBi/GaAs MQW p-i-n structures shows that having increasingly thin GaAs barriers effectively increases the average Bi content of the MQW region. This has the effect of reducing the hole ionization coefficient significantly while leaving the electron ionization coefficient relatively unchanged. Such MQW structures may be a way to incorporate Bi into an avalanching structure without degrading the material quality, and thereby give rise to low excess noise avalanche photodiodes.

One of the main challenges for medium infrared (MIR) high-operating temperature (HOT) photovoltaic detectors is obtaining high junction resistance, which is required not only to reduce the thermal noise of the detector itself but also to enable proper integration with a preamplifier. Long-wavelength infrared (LWIR) photodiodes suffer additionally from poor quantum efficiency due to short diffusion length and low absorption coefficient in narrow gap semiconductors. These problems are addressed by multistage detectors which comprise many photovoltaic cells connected in series. VIGO Photonics has developed three such cascade devices differing in stages' arrangement and connection: two horizontal cascade detectors (based on mercury cadmium telluride for LWIR and III-V compounds for MWIR), and a vertical cascade detector with InAs/InAsSb type-II superlattice absorbers (for both MWIR or LWIR). These devices are successfully applied in gas sensing, industrial process monitoring, etc. We would like to present their performance, discuss differences and applications.

The demand for high-speed, broadband mid-infrared detectors is increasing due to their importance in communications, sensing, and security. Current solutions trade off speed (thermal detectors) or broadband capabilities (photonic detectors) and typically require low-temperature operation for optimal performance. In this talk, we will present our advancements in the development of uncooled CMOS-compatible plasmon-based detection systems, emphasizing their capability for broadband light detection ranging from visible to longwave infrared. Our devices are based on monolithic Al-Ge-Al or Al-Si-Al heterostructures developed on GeOI and SOI wafers. The fabrication process utilizes a thermally induced exchange reaction to achieve high-quality crystalline interfaces. Broadband detection is facilitated by an electrostatic gate, enabling Schottky barrier modulation. Key phenomena such as photoconductivity, and ultra-fast detection speeds of up to 50 GHz will be discussed. Additionally, they show great potential for large-scale integration, use in focal plane arrays, and high scalability, using only conventional fabrication techniques.

Control and manipulation of quantum states by light are increasingly important for both fundamental research and applications. This can be achieved, among other techniques, through the strong coupling between light and semiconductor quantum wells, typically observed at THz frequencies in integrated lithographic optical cavities. Here, we explore the possibility of achieving ultrastrong coupling at room temperature between conduction sub-band states in Si(1−x)Ge(x) heterostructures and THz cavity photons fabricated with a potentially silicon-CMOS-compliant process. We developed Si(1−x)Ge(x) parabolic quantum wells with a temperature-independent transition at 3.1 THz and hybrid metal-plasmonic THz patch-antenna microcavities resonating between 2 and 5 THz depending on the antenna length. In this first demonstration, we achieved anticrossing around 3 THz with spectroscopically measured Rabi frequency of 0.7 THz leading to an ultrastrong coupling regime where the ratio between Rabi and resonant frequency surpasses 0.2.