arXiv subjects

Uriel Levy

Publications and source records attributed to Uriel Levy.

At least 19 recordsLinked to original sources

arXiv2026

Magnetic field free nonreciprocity in tapered atomic cladded nano waveguide

Optical nonreciprocity is a fundamental requirement for modern optical communications and quantum information processing, where it is essential to protect sensitive sources from destabilizing feedback and preserving quantum coherence. Conventional nonreciprocal devices are based on the Faraday effect; however, their dependence on bulky permanent magnets poses a significant barrier to chip-scale integration and scalability. Moreover, the application of a magnetic field is undesired in many quantum atomic systems. In this work, we demonstrate magnet-free optical nonreciprocity on a fully integrated platform utilizing a Nanophotonic Alkali Silicon Waveguide (NASWAG) interfaced with hot rubidium vapor. By employing velocity-selective optical pumping (VSOP), we break time reversal symmetry by taking advantage of the Doppler effect-generated by the thermally moving atoms, a phenomenon traditionally viewed as a limitation in atomic spectroscopy. We show that the use of suspended tapered waveguides significantly mitigates transit-time broadening, thereby enabling the observation of a robust nonreciprocal response. We further characterize the dependence of the isolation contrast on pump power, finding that the experimental measurements and numerical simulations correspond and provide mutual support for the underlying physical model. With proper optimization, the demonstrated effect may be used in the future for applications such as magnetic free optical isolators.

physics.optics↗

arXiv2026

Continuous Wave Second Harmonic Generation from an Etchless Lithium Niobate Resonant Metasurface

Nonlinear metasurfaces provide a route to compact frequency conversion by replacing phase matching and long interaction lengths with resonantly enhanced light matter interaction in subwavelength structures. Extending this capability to continuous wave (CW) operation is particularly important for applications requiring narrow linewidth, stable frequency, and stationary optical fields, but remains extremely challenging. Here, we demonstrate CW second-harmonic generation on a transmission mode, etchless thin film lithium niobate platform enabled by a patterned silicon rich nitride metasurface. This hybrid design combines guided mode resonance coupling, low optical loss, and CMOS compatible processing while keeping most of the optical mode confined in the unpatterned lithium niobate, yielding a measured quality factor of ~2300. Clearly resolved SHG is achieved under sub-kW/cm^2 CW pumping, with a normalized conversion efficiency of 0.156 % cm^2/GW in the low power regime. Interestingly, our work reveals that CW resonant SHG in metasurfaces can exhibit pronounced transient dynamics, including power dependent resonance evolution, overshoot, and nonideal scaling. These findings establish etchless LN SRN metasurfaces as a promising platform for compact CW nonlinear photonics, and show that resonance dynamics are central to the operation and evaluation of CW driven nonlinear metasurfaces.

physics.optics↗

arXiv2026

Transmission-Mode Silicon-Rich Nitride Mie-Void Metasurfaces in the Visible

Mie-void metasurfaces have so far been developed mainly in reflection, where subwavelength voids embedded in high-index media support localized resonances and spectrally selective optical responses. Yet, many optical systems could benefit from integrating such optical elements operating in transmission mode. Motivated by this great need, we hereby introduce Mie-void metasurfaces operating in transmission. To allow for their operation in the visible range, our Mie-voids are implemented using the silicon-rich nitride (SRN) platform. We show that this transition from reflection to transmission is not a simple change in geometry: placing the voids in a finite film on a substrate introduces slab-guided and Fabry-Perot-like contributions that hybridize with the underlying Mie-void response. Rigorous coupled-wave analysis shows that the dominant spectral transformation occurs when the semi-infinite host is replaced by a finite SRN film, while the substrate acts mainly as a secondary perturbation. Thickness-dependent dispersion maps reveal an avoided crossing between interacting modes, supporting the interpretation of a hybrid transmission regime and identifying film thickness as a clean parameter for tracking the evolution of the coupled modal structure. Experimentally, we realize transmission-mode structural colors by varying the void depth and observe good agreement between measured and simulated spectra and chromaticity coordinates. By spatially programming the void depth, we further demonstrate transmitted-light patterns and image encoding within a single metasurface architecture. These results establish transmission-mode Mie-void metasurfaces as a viable inverse-dielectric platform operating in transmission, with plethora of potential important applications such as transmissive spectral filtering, optical encoding, and display-oriented photonic elements, to name a few.

physics.optics↗

arXiv2026

Single-Step Grayscale Lithography of Multi-Depth Mie Void Metasurfaces

The height of dielectric metasurfaces is largely considered a constant in the fabrication process due to the top-down fabrication approach, resulting in a binary structure. Yet, for the recently introduced Mie voids metasurfaces, controlling the thickness of the voids locally is crucial for achieving significant spectral tuning. In this work we demonstrate Mie voids metasurfaces with local precise depth control using electron beam grayscale lithography. We underexpose PMMA with varying doses, which in turn translates to multiple depth levels in the developed resist. Transferring the pattern to a silicon substrate we generate Mie voids, trapping the light in the void which generates colors in reflection. By controlling the depth of the void at the nanoscale, we tune the resonance over the whole visible range and with high precision, resulting in a large gamut of colors, which is demonstrated with spectral measurements, images of uniform patterns and spatially varying patterns showcasing different geometrical designs and a detailed artistic image. The demonstrated approach can be used for the implementation of various types of dielectric metasurfaces, providing an additional important degree of freedom for their realization, with potential applications in structured light and structural colors, imaging, robotics, polarization control, sensing, virtual reality and more.

physics.optics↗

arXiv2026

Prompt-to-prescription: towards generative design of diffraction-limited refractive optics

The design of high-performance optical systems remains a specialized domain gated by the limited availability of expert engineers, creating a bottleneck that stalls innovation despite the growing demand for imaging hardware. While deep learning has improved parameter optimization, it has yet to address the fundamental challenge of conceptualizing valid optical architectures from functional requirements. Here, we present an end-to-end generative framework that couples the semantic reasoning of Large Language Models (LLMs) with a differentiable ray-tracing engine to democratize the synthesis of diffraction-limited optical prescriptions. By treating optical design as a semantic-to-physical translation task, the system autonomously interprets prompts ranging from high-level end-user requests to rigorous technical specifications. We demonstrate the framework's versatility across three distinct regimes: (1) finite-conjugate industrial metrology systems, where the model autonomously enforces application-specific constraints such as telecentricity to achieve diffraction-limited performance; (2) a suite of infrared objectives (NIR, SWIR, and LWIR), demonstrating the framework's ability to synthesize valid topologies and optical prescriptions for non-visible spectral bands, and (3) complex aspheric mobile lenses, where the system successfully navigates the high-dimensional optimization landscape to produce high-resolution designs suitable for modern sensors. Validated against industry-standard simulation tools, these results establish a new paradigm for automated optical engineering, bridging the gap between semantic intent and physical realization.

physics.optics↗

arXiv2025

Roadmap on Nonlocality in Photonic Materials and Metamaterials

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally made in optical material modeling. On one end, the growing interest in plasmonic, polaritonic and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials--metamaterials and metasurfaces--can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In the case of metasurfaces, in particular, nonlocality engineering has become a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward--toward new scientific discoveries and technological advancements.

cond-mat.mes-hall↗

arXiv2025

Nature Inspired Design Methodology for a Wide Field of View Achromatic Metalens

Metalenses have become ubiquitous in academic research and have begun to make their transition to industry. However, chromatic aberration still greatly limits the applications of metalenses. Achieving a wide field-of-view (FOV) is another challenge that has been dealt with successfully by using a removed stop, but when combined with broadband spectrum, lateral chromatic aberration severely limits performance. In this paper we tackle this grand challenge and present a comprehensive design methodology for a simultaneously wide-FOV and achromatic metalens which is inspired by the human visual system. As a design example, we present a metalens operating in the near infrared (NIR), with 10% relative spectral bandwidth (807-893nm), focal length of 5mm, F/5, and FOV of +/-20 degrees. In particular, we show how to optimize the stop position, and correct the lateral chromatic aberration, both of which have not been reported in the past. In addition, we evaluate the performance of the metalens using accurate performance metrics, and demonstrate the improvement compared to a chromatic metalens. Our approach paves the way for the design of wide FOV metalenses that can operate over a relatively large bandwidth, effectively contributing to the widespread implementation of metalens science and technology.

physics.optics↗

arXiv2024

Tunable transmissive metasurface based on thin-film lithium niobate

Active metasurfaces hold great promise for spatial light modulation, and electro-optic tuning using lithium niobate is particularly attractive due to its high transparency and well-established thin-film platform. In this work, we present a free-space transmissive light modulator based on a seemingly un-patterned thin-film lithium niobate-on-insulator platform, integrated with a transparent conductive oxide meta-grating fabricated through a single lithography process. Guided mode resonance in the near-infrared region is induced with high mode confinement within lithium niobate layer, which directly in contact with the electrodes. A notable resonance shift of 0.38 nm is observed for the fundamental mode under +-10 V bias, while a maximum modulation amplitude of 4.6% is achieved for another higher-order mode. Incident angle is further exploited as another tuning parameter to split and sensitively shift the resonances. These results demonstrate the potential of this design for applications in compact, scalable, and tunable spatial light modulation devices.

physics.app-ph↗

arXiv2024

Faraday-Ramsey rotation measurement in a thin cell as an analogy to an atomic beam

Atomic beams are powerful tools for measuring spin coherence in hot vapors but require bulky setups, limiting device miniaturization. We demonstrate that micron-thin vapor cells can mimic atomic beam behavior by exploiting geometry-dependent velocity filtering. In a 5 {\mu}m rubidium cell, coherence is preserved for atoms moving parallel to the cell walls, enabling observation of the Faraday-Ramsey effect without buffer gas or anti-relaxation coatings. Using a spatially displaced pump-probe scheme and magnetic field scanning, we achieve clear Ramsey fringes and validate our model experimentally. This technique offers a compact alternative to atomic beam systems, supporting scalable sensors and frequency standards.

quant-ph↗

arXiv2023

Achromatic imaging systems with flat lenses enabled by deep learning

Motivated by their great potential to reduce the size, cost and weight, flat lenses, a category that includes diffractive lenses and metalenses, are rapidly emerging as key components with the potential to replace the traditional refractive optical elements in modern optical systems. Yet, the inherently strong chromatic aberration of these flat lenses is significantly impairing their performance in systems based on polychromatic illumination or passive ambient light illumination, stalling their widespread implementation. Hereby, we provide a promising solution and demonstrate high quality imaging based on flat lenses over the entire visible spectrum. Our approach is based on creating a novel dataset of color outdoor images taken with our flat lens and using this dataset to train a deep-learning model for chromatic aberrations correction. Based on this approach we show unprecedented imaging results not only in terms of qualitative measures but also in the quantitative terms of the PSNR and SSIM scores of the reconstructed images. The results pave the way for the implementation of flat lenses in advanced polychromatic imaging systems.

physics.optics↗

arXiv2022

Inversionless gain in a lossy medium

We study gain without inversion due to coherence effects in a Doppler-broadened degenerate three-level system of a rubidium-hydrogen mixture in a miniaturized micron scale custom vapor cell. The cell miniaturization gives rise to collisions of atoms with the walls of the cell. This, combined with the high collision rate with the hydrogen buffer gas allows us to observe gain in the absorption spectra. Furthermore, we analyze the role of cell miniaturization in the evolution of the gain profile. In addition to fundamental interest, the observation of gain without inversion in our miniaturized cells paves the way for applications such as miniaturized lasers without inversion.

quant-ph↗

arXiv2022

Magnetic-field-independent spin-exchange relaxation-free magnetometer

SERF magnetometers based on dense ensembles of alkali-metal spins are precision quantum sensors that hold the record of measured and projected sensitivity to magnetic fields, in the $\mu\textrm{G}-\textrm{mG}$ range. At geomagnetic fields however, these sensors quickly lose their magnetic sensitivity due to spin decoherence by random spin-exchange collisions. Here we discover that atoms with nuclear spin $I=1/2$ can operate in the Spin-Exchange Relaxation Free (SERF) regime even at high magnetic field. We counter-intuitively show that frequent collisions between a dense and optically-inaccessible $(I=1/2)$ gas with another optically-accessible spin gas ($I>1/2$) improve the fundamental magnetic sensitivity of the latter. We analyze the performance of a dual-specie potassium and atomic hydrogen magnetometer, and project a fundamental sensitivity of about $10\,\mathrm{aT}\sqrt{\mathrm{cm}^3/\mathrm{Hz}}$ at geomagnetic fields for feasible experimental conditions.

quant-ph↗

arXiv2022

Suppressing the Decoherence of Alkali-Metal Spins at Low Magnetic Fields

Interactions of electron spins with rotational degrees of freedom during collisions or with external fields are fundamental processes that limit the coherence time of spin gases. We experimentally study the decoherence of hot cesium spins dominated by spin rotation-interaction during binary collisions with N$_2$ molecules or by absorption of near-resonant light. We report an order of magnitude suppression of the spin decoherence rate by either of those processes at low magnetic fields. This work extends the use of magnetic fields as a control knob, not only to suppress decoherence from random spin-conserving processes in the Spin-Exchange Relaxation Free (SERF) regime but also to suppress processes that relax electron spins rather than conserve them.

quant-ph↗

arXiv2022

One-dimensional quasi bound states in the continuum in the ω~k space for nonlinear optical applications

The phenomenon of bound state in the continuum (BIC) with infinite quality factor and lifetime has emerged in recent years in photonics as a new tool of manipulating light-matter interactions. However, most of the investigated structures only support BIC resonances at very few discrete points in the w~k space. Even when the BIC is switched to a quasi-BIC(QBIC) resonance through perturbation, its frequency will still be located within a narrow spectral band close to that of the original BIC, restricting their applications in many fields where random or multiple input frequencies beyond the narrow band are required. In this work, we demonstrate that a new set of QBIC resonances can be supported by making use of a special binary grating consisting of two alternatingly aligned ridge arrays with the same period and zero-approaching ridge width difference on a slab waveguide. These QBIC resonances are distributed continuously over a broad band along a line in the w~k space and can thus be considered as one-dimensional QBICs. With the Q factors generally affected by the ridge difference, it is now possible to choose arbitrarily any frequencies on the dispersion line to achieve significantly enhanced light-matter interactions, facilitating many applications where multiple input wavelengths are required, e.g. sum or difference frequency generations in nonlinear optics.

physics.optics↗

arXiv2021

MoSe2/WS2 heterojunction photodiode integrated with a silicon nitride waveguide for visible light detection with high responsivity

We demonstrate experimentally the realization and the characterization of a chip scale integrated photodetector for the visible and the near infrared spectral regime based on the integration of a MoSe2/WS2 heterojunction on top of a silicon nitride waveguide. This configuration achieves high responsivity of ~1 A/W at the wavelength of 780 nm (indicating an internal gain mechanism), while suppressing the dark current to the level of ~50 pA, much lower as compared to a reference sample of just MoSe2 without WS2. We have measured the power spectral density of the dark current to be as low as ~1x10^-12 A/Hz^0.5 , from which we extract the noise equivalent power (NEP) to be ~1x10^-12 W/Hz^0.5. To demonstrate the usefulness of the device, we use it for the characterization of the transfer function of a microring resonator that is integrated on the same chip as the photodetector. The ability to integrate local photodetectors on chip and to operate such devices with high performance at the visible and the near-infrared regime is expected to play a critical role in future integrated devices in the field of optical communications, quantum photonics, biochemical sensing and more.

physics.optics↗

arXiv2021

Dynamic Control of Plasmonic Colors by Voltage Actuation MEMS Cantilevers for Optical Display Applications

Conventional optical displays using ITO (indium tin oxide) and LC (liquid crystal) materials present a lot of challenges in terms of long-term sustainability. We show here how it is possible to generate a cost effective and CMOS compatible fast and full range electrically controlled RGB color display by combining transmission based plasmonic metasurfaces with MEMS (Microelectromechanical systems) technology, using only two common materials: Aluminum and silicon oxide. White light is filtered into red, green, and blue components by plasmonic metasurfaces made of aluminum nanohole arrays, and the transmission through each color filter is modulated by MEMS miniaturized cantilevers fabricated with aluminum and silicon oxide on top of the color filters. We show that the relative transmission of a color subpixel can be freely modulated from 35% to 100%. Our pixels can also operate well above 800Hz, enabling future ultrafast displays. Our work provides a road to future circular economic goals by exploiting advances in structural colors and MEMS technologies to innovate optical displays.

physics.app-ph↗

arXiv2021

WS2 Monolayers Coupled to Hyperbolic Metamaterial Nanoantennas: Broad Implications for Light-Matter-Interaction Applications

Due to their atomic layer thickness, direct bandgap, mechanical robustness and other superior properties, transition metal dichalcogenides (TMDCs) monolayers are considered as an attractive alternative to graphene for diverse optoelectronic applications. Yet, due to the very nature of atomic layer thickness, the interaction of light with TMDCs is limited, hindering overall efficiency for optical applications. Therefore, in order for TMDCs to become a true candidate as the material of choice for optoelectronics, there is a need for a mechanism which significantly enhances the interaction of light with TMDCs. In this paper, we demonstrate about 30-fold enhancement of the overall photoluminescence emission intensity from a WS2 monolayer, by its coupling to a hyperbolic metamaterial nanoantenna array. This enhancement corresponds to nearly 300-fold enhancement per individual nanoantenna. This overall enhancement is achieved by the combination of enhancing the excitation (absorption) efficiency, alongside with enhancing the radiative decay rate. Our result paves the way for the use of TMDCs in diverse optoelectronic applications, ranging from light sources and photodetectors to saturated absorbers and nonlinear media.

physics.optics↗

arXiv2021

A True Assessment of Flat Lenses for Broadband Imaging Applications

A plethora of metalenses and diffractive lenses (flat lenses) have been demonstrated over the years. Recently, attempts have been made to stretch their performance envelope, particularly in the direction of wide-band achromatic performance. While achromatic behavior has been demonstrated, an actual improvement in imaging performance relative to conventional (non-chromatically corrected) flat lenses has not. The reasons for this are use of inappropriate performance metrics, lack of comparison to a baseline conventional design, and lack of a performance metric that combines signal-to-noise ratio and resolution. In this work we present a metric that will allow comparison of different types of flat lenses, even if their first order optical parameters are not the same. We apply this metric to several published achromatic flat lens designs and compare them to the equivalent conventional flat lens, which we consider as the lower bound for achromatic flat lens performance. Use of this metric paves the way for future developments in the field of achromatic flat lenses, which will display proven progress.

physics.optics↗