arXiv subjects

Huigao Duan

Publications and source records attributed to Huigao Duan.

17 recordsLinked to original sources

arXiv2026

Volumetric Optical Scattering Neural Networks

Optical neural networks rely on planar photonic circuits or spatially separated diffractive planes, limiting volumetric integration and requiring precise alignment. Here we propose a volumetric optical scattering neural network (OSNN) comprising densely packed refractive-index neurons with weak contrast $Δn = 0.006$. Direction-dependent first-order Born scattering provides local coupling, while ordered propagation accumulates these weak updates into global task-specific transformations. Fabrication-aware training and two-photon nanolithography produced a sub-$4 \times 10^{-4}$ mm$^3$ device containing 376,320 neurons at $1.0 \times 10^9$/mm$^3$ in a continuously written, intrinsically registered volume. Experimentally, a classifier performed class-selective energy routing with 95.8% blind-test accuracy on MNIST. The calculated passive optical transit time is below 1 ps. A separately optimized imager provided fourfold full-field spatial-sampling compression, resolved 1-$μ$m features and enabled cross-domain transfer. An OSNN co-designed for multiple tasks encoded single-cell fluorescence-derived images into measured output maps, which were pooled into a 16-dimensional representation supporting organelle classification, morphology reconstruction, doublet detection and morphology regression, with all reported metrics exceeding 0.92. Volumetric weak scattering thus establishes an ultracompact, intrinsically registered optical computing architecture, opening a new route to scalable machine vision and biomedical analysis.

physics.optics↗

arXiv2026

Sublime Transfer Printing of Three-Dimensional Nanostructure Ensembles

High-resolution three-dimensional (3D) nanostructures for visible-light photon manipulation provide unique and bespoke capabilities in optics and photonics. However subwavelength nanofabrication and reliable ensemble manipulation of the 3D prints onto arbitrary substrates remain challenging. Here, we introduce sublime transfer strategy tailored for transfer printing ensembles of delicate 3D printed nanostructures. This strategy enables conformal, damage-free integration of arrays of 3D structures on diverse substrates. Naphthalene acts as a transient stamp to encapsulate the structures during transfer and placement. We rely on the low sublimation temperature of naphthalene to release the structures reliably with nearly zero stress, preventing mechanical damage and positional misalignment. This approach is broadly applicable to integrate diverse nanostructures and photonic devices onto various substrates, and enabling inorganic architectures through ensemble uniform post-processing, including 2.5D photonic crystals on flexible PDMS, diffractive optical elements on curved lenses, spiral phase plates on CMOS chips, multilayer achromatic metalens on optical fiber facet, as well as 3D glass photonic crystals and optical topological resonators on anti-stiction quartz.

physics.optics↗

arXiv2025

Ultracompact Wide-FOV Near-infrared Camera with Wafer-level Manufactured Meta-Aspheric Lens

Overcoming the trade-off between wide field of view (FOV) and compactness remains a central challenge for integrating near-infrared (NIR) imaging into smartphones and AR glasses. Existing refractive NIR optics cannot simultaneously achieve ultra-wide angles above 100° and ultrathin total track length (TTL) below 5 mm, limiting their use in portable devices. Here, we present a wafer-level-manufactured meta-aspheric lens (MAL) that achieves a 101.5° FOV, 3.39 mm TTL, and F/1.64 aperture within a compact volume of 0.02 cubic centimeters. Unlike previous hybrid lenses with separate refractive and diffractive components, our MAL features a fully integrated structure, which enables a compact form factor. This integration also simplifies fabrication, allowing high-throughput production via micrometer-level precision alignment and bonding on a single wafer, with only one dicing step and no need for additional mechanical fixtures. Furthermore, the design process explicitly considers manufacturability and accurately models metalens dispersion, ensuring that experimental performance matches simulated results. We validate our MAL through both direct and computational imaging experiments. Despite its small form factor, our scalable MAL demonstrates strong NIR imaging performance in blood vessel imaging, eye tracking, and computational pixel super-resolution tasks. This scalable MAL technology establishes a new benchmark for high-performance, miniaturized NIR imaging and opens the door to next-generation smartphone and AR optical systems.

physics.optics↗

arXiv2024

Achromatic single-layer hologram

Phase retrieval is a fundamental technique of advanced optical technologies, enabling precise control over wavefront properties. A persistent challenge in diffractive optical element (DOE) design is that a single hologram typically operates within a single wavelength or color channel, limiting it to monochromatic image generation. This limitation in channel capacity significantly restricts the applicability of DOE in optical applications. In this study, we propose a design strategy for full-color, single-layer hologram based on a variable-scale diffraction model. By imposing strict constraints in Fourier domain and reducing depth of focus (DOF), we achieve the simultaneous encryption and storage of red, green, and blue channel information within a single achromatic hologram. This strategy facilitates color separation in large-depth 3D holography and enables achromatic full-color image displays. We demonstrated full-color holographic video playback at a full refresh rate of 60 Hz, achieving a temporal resolution three times greater than that of existing methods. Furthermore, we successfully fabricated achromatic, twin-image-free, full-color binary pure-phase DOEs at low cost. This achromatic strategy addresses the demands across various fields in optics, including high-refresh-rate full-color displays, high-density optical information storage, advanced optical security, high-reusability holographic metasurface optical element, and high-performance achromatic metalenses.

physics.optics↗

arXiv2024

Synthetic gain for electron-beam spectroscopy

Electron-beam microscopy and spectroscopy featuring atomic-scale spatial resolution have become essential tools used daily in almost all branches of nanoscale science and technology. As a natural supercontinuum source of light, free electrons couple with phonons, plasmons, electron-hole pairs, inter- and intra-band transitions, and inner-shell ionization. The multiple excitations, intertwined with the intricate nature of nanostructured samples, present significant challenges in isolating specific spectral characteristics amidst complex experimental backgrounds. Here we introduce the approach of synthetic complex frequency waves to mitigate these challenges in free-electron--light interaction. The complex frequency waves, created through causality-informed coherent superposition of real-frequency waves induced by free electrons, offer virtual gain to offset material losses. This amplifies and enhances spectral features, as confirmed by our electron energy loss and cathodoluminescence measurements on multi-layer membranes, suspended nanoparticles, and film-coupled nanostructures. Strikingly, we reveal that our approach can retrieve resonance excitation completely buried underneath the zero-loss peak, substantially enhance the quality of hyperspectral imaging, and resolve entangled multiple-photon-electron events in their quantum interaction. Our findings indicate the versatile utility of complex frequency waves in various electron-beam spectroscopy and their promising diagnostic capabilities in free-electron quantum optics.

physics.optics↗

arXiv2024

Metasurface-Integrated Polarization-Insensitive LCoS for Projection Displays

Liquid crystal on silicon (LCoS) panels, renowned for their high resolution and fill-factor, are integral to modern projection displays. However, their inherent polarization sensitivity constrains the upper limit of light utilization, increases system complexity and restricts broader applicability. Here, we demonstrate a dual-layer metasurface-integrated LCoS prototype that achieves polarization-insensitive, addressable amplitude modulation in the visible. Polarization sensitivity is eliminated in the reflective architecture through polarization conversion in the underlying metasurface and polarization-sensitive phase modulation of the liquid crystals (LC). This is further enhanced by the electrically tunable subwavelength grating formed by the upper metasurface and LC, resulting in a high-contrast, polarization-insensitive optical switch. We showcase a 64-pixel 2D addressable prototype capable of generating diverse projection patterns with high contrast. Compatible with existing LCoS processes, our metasurface device reduces system size and enhances energy efficiency, offering applications in projectors and AR/VR displays, with the potential to redefine projection chip technology.

physics.optics↗

arXiv2024

Neural Network-Assisted End-to-End Design for Dispersive Full-Parameter Control of Meta-Optics

Flexible control light field across multiple parameters is the cornerstone of versatile and miniaturized optical devices. Metasurfaces, comprising subwavelength scatterers, offer a potent platform for executing such precise manipulations. However, the inherent mutual constraints between parameters of metasurfaces make it challenging for traditional approaches to achieve full-parameter control across multiple wavelengths. Here, we propose a universal end-to-end inverse design framework to directly optimize the geometric parameter layout of meta-optics based on the target functionality of full-parameter control across multiple wavelengths. This framework employs a differentiable forward simulator integrating a neural network-based dispersive full-parameter Jones matrix and Fourier propagation to facilitate gradient-based optimization. Its superiority over sequential forward designs in dual-polarization channel color holography with higher quality and tri-polarization three-dimensional color holography with higher multiplexed capacity is showcased. To highlight the universality, we further present polarized spectral multi-information processing with six arbitrary polarizations and three wavelengths. This versatile, differentiable, system-level design framework is poised to expedite the advancement of meta-optics in integrated multi-information display, imaging, and communication, extending to multi-modal sensing applications.

physics.optics↗

arXiv2024

Phase space framework enables a variable-scale diffraction model for coherent imaging and display

The fast algorithms in Fourier optics have invigorated multifunctional device design and advanced imaging technologies. However, the necessity for fast computations has led to limitations in the widely used conventional Fourier methods, manifesting as fixed size image plane at a certain diffraction distance. These limitations pose challenges in intricate scaling transformations, 3D reconstructions and full-color displays. Currently, there is a lack of effective solutions, often resorting to pre-processing that compromise fidelity. In this paper, leveraging a higher-dimensional phase space method, we present a universal framework allowing for customized diffraction calculation methods. Within this framework, we establish a variable-scale diffraction computation model which allows the adjustment of the size of the image plane and can be operated by fast algorithms. We validate the model's robust variable-scale capabilities and its aberration automatic correction capability for full-color holography, achieving high fidelity. The large-magnification tomography experiment demonstrates that this model provides a superior solution for holographic 3D reconstruction. In addition, this model is applied to achieve full-color metasurface holography with near-zero crosstalk, showcasing its versatile applicability at nanoscale. Our model presents significant prospects for applications in the optics community, such as beam shaping, computer-generated holograms (CGHs), augmented reality (AR), metasurface optical elements (MOEs) and advanced holographic head-up display (HUD) systems.

physics.app-ph↗

arXiv2024

Achromatic Full Stokes Polarimetry Metasurface for Full-color Polarization Imaging in the Visible

Metasurfaces composed of anisotropic subwavelength structures provide an ultrathin platform for a compact, real-time polarimeter. However, applications in polychromatic scenes are restricted by the limited operating bandwidths and degraded imaging quality due to the loss of spectral information. Here, we demonstrated full-color polarization imaging based on an achromatic polarimeter consisting of four polarization-dependent metalenses. Boosted by an intelligent design scheme, arbitrary phase compensation and multi-objective matching are effectively compatible with a limited database. Broadband achromaticity for wavelengths ranging from 450 nm to 650 nm, with a relative bandwidth of nearly 0.435, is achieved for the full Stokes imaging. The experimental polarization reconstructed errors for operating wavelengths of 450 nm, 550 nm, and 650 nm are 7.5%, 5.9%, and 3.8%, respectively. The full-color and full-polarization imaging capability of the device is also verified with a customized object. The proposed scheme paves the way for further developing polarization imaging toward practical applications.

physics.optics↗

arXiv2022

Tunable Polarization-Multiplexed Achromatic Dielectric Metalens

Tunable metasurfaces provide a compact and efficient strategy for optical components that require active wavefront shaping. Varifocal metalens is one of the most important applications. However, the existing tunable metalens rarely serves broadband wavelengths restricting their applications in broadband imaging and color display due to chromatic aberration. Herein, we demonstrate an electrically tunable polarization-multiplexed varifocal achromatic dielectric metalens integrated with twisted nematic liquid crystals (TNLCs) in the visible region. The phase profiles at different wavelengths under two orthogonal polarization channels are customized by the particle swarm optimization algorithm and optimally matched with the metaunits database to achieve polarization-multiplexed dispersion manipulation including achromatic performance. By combining the broadband linear polarization conversion ability of TNLC, the tunability of varifocal achromatic metalens is realized by applying different voltages. Further, the electrically tunable customized dispersion-manipulated metalens and switchable color metaholograms are demonstrated. The proposed devices will accelerate the application of metasurfaces in broadband zoom imaging, AR/VR displays, and spectral detection.

physics.optics↗

arXiv2021

Ultra-Broadband Dispersion-Manipulated Dielectric Metalenses by Nonlinear Dispersive Phase Compensation

Dispersion decomposes compound light into monochromatic components at different spatial locations, which needs to be eliminated in imaging but utilized in spectral detection. Metasurfaces provide a unique path to modulate the dispersion only by adjusting the structural parameters without changing the material as required for refractive elements. However, the common linear phase compensation does not conform to the dispersion characteristics of the meta-unit limiting dispersion modulation in broader wavelength bands, which is desired for ultra-broadband or multiband imaging. Here, we propose a nonlinear dispersive phase compensation method to design polarization-insensitive achromatic metalenses from 400 nm to 1000 nm constructed with single-layer high aspect ratio nanostructures. This band matches the response spectrum of a typical CMOS sensor for both visible and near-infrared imaging applications without additional lens replacement. Moreover, the capability of the method in achieving arbitrary dispersion modulation is demonstrated for applications such as chromatography imaging and spectral detection.

physics.optics↗

arXiv2021

Observation of optical gyromagnetic properties in a magneto-plasmonic metamaterial

Metamaterials with artificial optical properties have attracted significant research interest. In particular, artificial magnetic resonances in non-unity permeability tensor at optical frequencies in metamaterials have been reported. However, only non-unity diagonal elements of the permeability tensor have been demonstrated to date. A gyromagnetic permeability tensor with non-zero off-diagonal elements has not been observed at the optical frequencies. Here we report the observation of gyromagnetic properties in the near-infrared wavelength range in a magneto-plasmonic metamaterial. The non-zero off-diagonal permeability tensor element causes the transverse magneto-optical Kerr effect (TMOKE) under s-polarized incidence that otherwise vanishes if the permeability tensor is not gyromagnetic. By retrieving the permeability tensor elements from reflection, transmission, and TMOKE spectra, we show that the effective off-diagonal permeability tensor elements reach the 10-3 level at the resonance wavelength (~900 nm) of the split-ring resonators that is at least two orders of magnitude higher than that of magneto-optical materials at the same wavelength. The artificial gyromagnetic permeability is attributed to the change in the local electric field direction modulated by the split-ring resonators. Our study demonstrates the possibility of engineering the permeability and permittivity tensors in metamaterials at arbitrary frequencies, thereby promising a variety of applications of next-generation nonreciprocal photonic devices, magneto-plasmonic sensors, and active metamaterials.

physics.optics↗

arXiv2021

Circular displacement current induced anomalous magneto-optical effects in high index Mie resonators

Dielectric Mie nanoresonators showing strong light-matter interaction at the nanoscale may enable new functionality in photonic devices. Recently, strong magneto-optical effects have been observed in magneto-optical nanophotonic devices due to the electromagnetic field localization. However, most reports so far have been focused on the enhancement of conventional magneto-optical effects. Here, we report the observation of circular displacement current induced anomalous magneto-optical effects in high-index-contrast Si/Ce:YIG/YIG/SiO2 Mie resonators. In particular, giant modulation of light intensity in transverse magnetic configuration up to 6.4 % under s-polarized incidence appears, which is non-existent in planar magneto-optical thin films. Apart from that, we observe a large rotation of transmitted light polarization in the longitudinal magnetic configuration under near normal incidence conditions, which is two orders of magnitude higher than for a planar magneto-optical thin film. These phenomena are essentially originated from the unique circular displacement current when exciting the magnetic resonance modes in the Mie resonators, which changes the incident electric field direction locally. Our work indicates an uncharted territory of light polarization control based on the complex modal profiles in all-dielectric magneto-optical Mie resonators and metasurfaces, which opens the door for versatile control of light propagation by magnetization for a variety of applications in vectoral magnetic field and biosensing, free space non-reciprocal photonic devices, magneto-optical imaging and optomagnetic memories.

physics.optics↗

arXiv2021

Metasurface-Enabled On-Chip Multiplexed Diffractive Neural Networks in the Visible

Replacing electrons with photons is a compelling route towards light-speed, highly parallel, and low-power artificial intelligence computing. Recently, all-optical diffractive neural deep neural networks have been demonstrated. However, the existing architectures often comprise bulky components and, most critically, they cannot mimic the human brain for multitasking. Here, we demonstrate a multi-skilled diffractive neural network based on a metasurface device, which can perform on-chip multi-channel sensing and multitasking at the speed of light in the visible. The metasurface is integrated with a complementary metal oxide semiconductor imaging sensor. Polarization multiplexing scheme of the subwavelength nanostructures are applied to construct a multi-channel classifier framework for simultaneous recognition of digital and fashionable items. The areal density of the artificial neurons can reach up to 6.25x106/mm2 multiplied by the number of channels. Our platform provides an integrated solution with all-optical on-chip sensing and computing for applications in machine vision, autonomous driving, and precision medicine.

eess.SP↗

arXiv2021

Magnesium-Based Metasurfaces for Dual-Function Switching between Dynamic Holography and Dynamic Color Display

Metasurface-based color display and holography have greatly advanced the state of the art display technologies. To further enrich the metasurface functionalities, recently a lot of research endeavors have been made to combine these two display functions within a single device. However, so far such metasurfaces have remained static and lack tunability once the devices are fabricated. In this work, we demonstrate a dynamic dual-function metasurface device at visible frequencies. It allows for switching between dynamic holography and dynamic color display, taking advantage of the reversible phase transition of magnesium through hydrogenation and dehydrogenation. Spatially arranged stepwise nanocavity pixels are employed to accurately control the amplitude and phase of light, enabling the generation of high-quality color prints and holograms. Our work represents a paradigm toward compact and multifunctional optical elements for future display technologies.

physics.optics↗

arXiv2020

Electrically Tunable Multifunctional All-Dielectric Metasurfaces Integrated with Liquid Crystals in the Visible

As two-dimensional metamaterials, metasurfaces open up new avenues for designing static planar optics. However, the dynamic modulation of metasurfaces in the optical band is required for practical applications. The existing dynamic devices rarely utilized the polarization manipulation capability of metasurfaces. Here, we demonstrate an electrically tunable multifunctional metasurface in the visible range by integrating birefringent liquid crystals (LCs) with all-dielectric metasurfaces based on a novel packaging scheme. By combining the helicity-dependent geometric phase of the metasurface and the polarization control ability of LC molecules, continuous intensity tuning and switching of two helicity channels are realized. Electrically tunable single-channel switchable metaholograms, multicolor multiplexed metaholograms, and dynamic varifocal metalenses are designed to verify the concept. The exploration of polarization control in dynamic tuning can pave the way for dynamic metasurface devices in various applications, such as space light modulators, light detection and ranging systems, and holographic displays.

physics.optics↗

arXiv2018

Dynamic Color Displays Using Stepwise Cavity Resonators

High-resolution multicolor printing based on pixelated optical nanostructures is of great importance for promoting advances in color display science. So far, most of the work in this field has been focused on achieving static colors, limiting many potential applications. This inevitably calls for the development of dynamic color displays with advanced and innovative functionalities. In this Letter, we demonstrate a novel dynamic color printing scheme using magnesium-based pixelated Fabry-Perot cavities by grey-scale nanolithography. With controlled hydrogenation and dehydrogenation, magnesium undergoes unique metal and dielectric transitions, enabling distinct blank and color states from the pixelated Fabry-Perot resonators. Following such a scheme, we first demonstrate dynamic Ishihara plates, in which the encrypted images can only be read out using hydrogen as information decoding key. We also demonstrate a new type of dynamic color generation, which enables fascinating transformations between black/white printing and color printing with fine tonal tuning. Our work will find wide-ranging applications in full-color printing and displays, colorimetric sensing, information encryption and anti-counterfeiting.

physics.app-ph↗