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Research Articles|192 Article(s)
Research Articles
High-resolution and wide-field microscopic imaging with a monolithic meta-doublet under annular illumination
Jiacheng Sun, Wenjing Shen, Junyi Wang, Rongtao Yu... and Tao Li|Show fewer author(s)
Metalenses have exhibited significant promise across various applications due to their ultrathin, lightweight, and flat architecture, which allows for integration with microelectronic devices. However, their overall imaging capabilities, particularly in microscopy, are hindered by substantial off-axis aberrations that limit both the field of view (FOV) and resolution. To address these issues, we introduce a meta-microscope that utilizes a metalens doublet incorporated with annular illumination, enabling wide FOV and high-resolution imaging in a compact design. The metalens-doublet effectively mitigates off-axis aberrations, whereas annular illumination boosts resolution. To validate this design, we constructed and tested the meta-microscope system, attaining a record resolution of 310 nm (for metalens image) with a 150 μm FOV at 470 nm wavelength. Moreover, by utilizing the integration of metasurface, we implemented a compact prototype achieving an impressive 1-mm FOV with a resolution of 620 nm. Our experimental results demonstrate high-quality microscopic bio-images that are comparable to those obtained from traditional microscopes within a compact prototype, highlighting its potential applications in portable and convenient settings, such as biomedical imaging, mobile monitoring, and outdoor research. Metalenses have exhibited significant promise across various applications due to their ultrathin, lightweight, and flat architecture, which allows for integration with microelectronic devices. However, their overall imaging capabilities, particularly in microscopy, are hindered by substantial off-axis aberrations that limit both the field of view (FOV) and resolution. To address these issues, we introduce a meta-microscope that utilizes a metalens doublet incorporated with annular illumination, enabling wide FOV and high-resolution imaging in a compact design. The metalens-doublet effectively mitigates off-axis aberrations, whereas annular illumination boosts resolution. To validate this design, we constructed and tested the meta-microscope system, attaining a record resolution of 310 nm (for metalens image) with a 150 μm FOV at 470 nm wavelength. Moreover, by utilizing the integration of metasurface, we implemented a compact prototype achieving an impressive 1-mm FOV with a resolution of 620 nm. Our experimental results demonstrate high-quality microscopic bio-images that are comparable to those obtained from traditional microscopes within a compact prototype, highlighting its potential applications in portable and convenient settings, such as biomedical imaging, mobile monitoring, and outdoor research.
Advanced Photonics
- Publication Date: May. 27, 2025
- Vol. 7, Issue 4, 046006 (2025)
Observation of doubly degenerate topological flatbands of edge states in strained graphene
Yongsheng Liang, Jingyan Zhan, Shiqi Xia, Daohong Song, and Zhigang Chen
Flatbands are of significant interest due to their potential for strong energy confinement and their ability to facilitate strongly correlated physics such as unconventional superconductivity and fractional quantum Hall states. When topology is incorporated into flatband systems, it further enhances flatband mode robustness against perturbations. We present the first realization of doubly degenerate topological flatbands of edge states in chiral-symmetric strained graphene. The flatband degeneracy stems from the merging of Dirac points, achieved by tuning the coupling ratios in a honeycomb lattice with newly discovered twig boundary conditions. The topology of these modes is characterized by the nontrivial winding number, which ensures their robustness against disorder. Experimentally, two types of topological edge states are observed in a strained photonic graphene lattice, consistent with numerical simulations. Moreover, the degeneracy of the topological flatbands doubles the density of states for zero-energy modes, facilitating the formation of compact edge states and providing greater control over edge states and light confinement. Our findings underscore the interplay among lattice geometry, symmetry, and topology in shaping doubly degenerate topological flatbands. This work opens new possibilities for advancements in correlated effects, nonlinear optical phenomena, and efficient energy transfer in materials science, photonic crystals, and quantum devices. Flatbands are of significant interest due to their potential for strong energy confinement and their ability to facilitate strongly correlated physics such as unconventional superconductivity and fractional quantum Hall states. When topology is incorporated into flatband systems, it further enhances flatband mode robustness against perturbations. We present the first realization of doubly degenerate topological flatbands of edge states in chiral-symmetric strained graphene. The flatband degeneracy stems from the merging of Dirac points, achieved by tuning the coupling ratios in a honeycomb lattice with newly discovered twig boundary conditions. The topology of these modes is characterized by the nontrivial winding number, which ensures their robustness against disorder. Experimentally, two types of topological edge states are observed in a strained photonic graphene lattice, consistent with numerical simulations. Moreover, the degeneracy of the topological flatbands doubles the density of states for zero-energy modes, facilitating the formation of compact edge states and providing greater control over edge states and light confinement. Our findings underscore the interplay among lattice geometry, symmetry, and topology in shaping doubly degenerate topological flatbands. This work opens new possibilities for advancements in correlated effects, nonlinear optical phenomena, and efficient energy transfer in materials science, photonic crystals, and quantum devices.
Advanced Photonics
- Publication Date: May. 23, 2025
- Vol. 7, Issue 4, 046005 (2025)
High-speed readout for direct light orbital angular momentum photodetector via photoelastic modulation
Dehong Yang, Chang Xu, Jiawei Lai, Zipu Fan... and Dong Sun|Show fewer author(s)
Recent progress in direct photodetection of light orbital angular momentum (OAM) based on the orbital photogalvanic effect (OPGE) provides an effective way for on-chip direct electric readout of orbital angular momentum, as well as large-scale integration focal-plane array devices. However, the recognition of OAM order from photocurrent response requires the extraction of circular polarization-dependent response. To date, the operation speed of such a detector is currently at the minute level and is limited by slow mechanical polarization modulation and low OAM recognition capability. We demonstrate that the operation speed can be greatly improved via an electrical polarization modulation strategy with a photoelastic modulator (PEM) accompanied by a phase-locked readout approach with a lock-in amplifier. We demonstrate an operation speed of up to kilohertz level with this new technology in the mid-infrared region (4 μm) on an OAM detector using multilayer graphene as photosensitive material. In principle, with a new modulation and readout scheme, we can potentially increase the operation speed to megahertz with a PEM that operates at a state-of-the-art speed. Our work paves the way toward high-speed operation of direct OAM detection devices based on the OPGE effect and pushes such technology to a more practical stage for focal plane array applications. Recent progress in direct photodetection of light orbital angular momentum (OAM) based on the orbital photogalvanic effect (OPGE) provides an effective way for on-chip direct electric readout of orbital angular momentum, as well as large-scale integration focal-plane array devices. However, the recognition of OAM order from photocurrent response requires the extraction of circular polarization-dependent response. To date, the operation speed of such a detector is currently at the minute level and is limited by slow mechanical polarization modulation and low OAM recognition capability. We demonstrate that the operation speed can be greatly improved via an electrical polarization modulation strategy with a photoelastic modulator (PEM) accompanied by a phase-locked readout approach with a lock-in amplifier. We demonstrate an operation speed of up to kilohertz level with this new technology in the mid-infrared region (4 μm) on an OAM detector using multilayer graphene as photosensitive material. In principle, with a new modulation and readout scheme, we can potentially increase the operation speed to megahertz with a PEM that operates at a state-of-the-art speed. Our work paves the way toward high-speed operation of direct OAM detection devices based on the OPGE effect and pushes such technology to a more practical stage for focal plane array applications.
Advanced Photonics
- Publication Date: May. 23, 2025
- Vol. 7, Issue 4, 046004 (2025)
Highly integrated all-optical nonlinear deep neural network for multi-thread processing
Jialong Zhang, Bo Wu, Shiji Zhang, Junwei Cheng... and Xinliang Zhang|Show fewer author(s)
Optical neural networks have emerged as feasible alternatives to their electronic counterparts, offering significant benefits such as low power consumption, low latency, and high parallelism. However, the realization of ultra-compact nonlinear deep neural networks and multi-thread processing remain crucial challenges for optical computing. We present a monolithically integrated all-optical nonlinear diffractive deep neural network (AON-D2NN) chip for the first time. The all-optical nonlinear activation function is implemented using germanium microstructures, which provide low loss and are compatible with the standard silicon photonics fabrication process. Assisted by the germanium activation function, the classification accuracy is improved by 9.1% for four-classification tasks. In addition, the chip’s reconfigurability enables multi-task learning in situ via an innovative cross-training algorithm, yielding two task-specific inference results with accuracies of 95% and 96%, respectively. Furthermore, leveraging the wavelength-dependent response of the chip, the multi-thread nonlinear optical neural network is implemented for the first time, capable of handling two different tasks in parallel. The proposed AON-D2NN contains three hidden layers with a footprint of only 0.73 mm2. It can achieve ultra-low latency (172 ps), paving the path for realizing high-performance optical neural networks. Optical neural networks have emerged as feasible alternatives to their electronic counterparts, offering significant benefits such as low power consumption, low latency, and high parallelism. However, the realization of ultra-compact nonlinear deep neural networks and multi-thread processing remain crucial challenges for optical computing. We present a monolithically integrated all-optical nonlinear diffractive deep neural network (AON-D2NN) chip for the first time. The all-optical nonlinear activation function is implemented using germanium microstructures, which provide low loss and are compatible with the standard silicon photonics fabrication process. Assisted by the germanium activation function, the classification accuracy is improved by 9.1% for four-classification tasks. In addition, the chip’s reconfigurability enables multi-task learning in situ via an innovative cross-training algorithm, yielding two task-specific inference results with accuracies of 95% and 96%, respectively. Furthermore, leveraging the wavelength-dependent response of the chip, the multi-thread nonlinear optical neural network is implemented for the first time, capable of handling two different tasks in parallel. The proposed AON-D2NN contains three hidden layers with a footprint of only 0.73 mm2. It can achieve ultra-low latency (172 ps), paving the path for realizing high-performance optical neural networks.
Advanced Photonics
- Publication Date: May. 15, 2025
- Vol. 7, Issue 4, 046003 (2025)
On-chip twisted hollow-core light cages: enhancing planar photonics with 3D nanoprinting
Johannes Bürger, Jisoo Kim, Thomas Weiss, Stefan A. Maier, and Markus A. Schmidt
Twisted optical fibers are a promising platform for manipulating circularly polarized light and orbital angular momentum beams for applications such as nonlinear frequency conversion, optical communication, or chiral sensing. However, integration into chip-scale technology is challenging because twisted fibers are incompatible with planar photonics and the achieved twist rates are limited. Here, we address these challenges by introducing the concept of 3D-nanoprinted on-chip twisted hollow-core light cages. We show theoretically and experimentally that the geometrical twisting of light cages forces the fundamental core mode of a given handedness to couple with selected higher-order core modes, resulting in strong circular dichroism (CD). These chiral resonances result from the angular momentum harmonics of the fundamental mode, allowing us to predict their spectral locations and the occurrence of circular birefringence. Twisted light cages enable very high twist rates and CD, exceeding those of twisted hollow-core fibers by more than two orders of magnitude (twist period, 90 μm; CD, 0.8 dB / mm). Moreover, the unique cage design provides lateral access to the central core region, enabling future applications in chiral spectroscopy. Therefore, the presented concept opens a path for translating twisted fiber research to on-chip technology, resulting in a new platform for integrated chiral photonics. Twisted optical fibers are a promising platform for manipulating circularly polarized light and orbital angular momentum beams for applications such as nonlinear frequency conversion, optical communication, or chiral sensing. However, integration into chip-scale technology is challenging because twisted fibers are incompatible with planar photonics and the achieved twist rates are limited. Here, we address these challenges by introducing the concept of 3D-nanoprinted on-chip twisted hollow-core light cages. We show theoretically and experimentally that the geometrical twisting of light cages forces the fundamental core mode of a given handedness to couple with selected higher-order core modes, resulting in strong circular dichroism (CD). These chiral resonances result from the angular momentum harmonics of the fundamental mode, allowing us to predict their spectral locations and the occurrence of circular birefringence. Twisted light cages enable very high twist rates and CD, exceeding those of twisted hollow-core fibers by more than two orders of magnitude (twist period, 90 μm; CD, 0.8 dB / mm). Moreover, the unique cage design provides lateral access to the central core region, enabling future applications in chiral spectroscopy. Therefore, the presented concept opens a path for translating twisted fiber research to on-chip technology, resulting in a new platform for integrated chiral photonics.
Advanced Photonics
- Publication Date: May. 07, 2025
- Vol. 7, Issue 4, 046002 (2025)
Spin Hamiltonian in the modulated momenta of light
Juan Feng, Zengya Li, Luqi Yuan, Erez Hasman... and Xianfeng Chen|Show fewer author(s)
Spatial photonic Ising machines (SPIMs) are promising computation devices that can be used to find the ground states of different spin Hamiltonians and solve large-scale optimization problems. The photonic architecture leverages the matrix multiplexing ability of light to accelerate the computing of spin Hamiltonian via free space light transform. However, the intrinsic long-range nature of spatial light only allows for uncontrolled all-to-all spin interaction. We explore the ability to establish arbitrary spin Hamiltonian by modulating the momentum of light. Arbitrary displacement-dependent spin interactions can be computed from different momenta of light, formulating as a generalized Plancherel theorem, which allows us to implement a SPIM with a minimal optical operation (that is, a single Fourier transform) to obtain the Hamiltonian of customized spin interaction. Experimentally, we unveil the exotic magnetic phase diagram of the generalized J1-J2-J3 model, shedding light on the ab initio magnetic states of iron chalcogenides. Moreover, we observe Berezinskii-Kosterlitz-Thouless dynamics by implementing an XY model. We open an avenue to controlling arbitrary spin interaction from the momentum space of light, offering a promising method for on-demand spin model simulation with a simple spatial light platform. Spatial photonic Ising machines (SPIMs) are promising computation devices that can be used to find the ground states of different spin Hamiltonians and solve large-scale optimization problems. The photonic architecture leverages the matrix multiplexing ability of light to accelerate the computing of spin Hamiltonian via free space light transform. However, the intrinsic long-range nature of spatial light only allows for uncontrolled all-to-all spin interaction. We explore the ability to establish arbitrary spin Hamiltonian by modulating the momentum of light. Arbitrary displacement-dependent spin interactions can be computed from different momenta of light, formulating as a generalized Plancherel theorem, which allows us to implement a SPIM with a minimal optical operation (that is, a single Fourier transform) to obtain the Hamiltonian of customized spin interaction. Experimentally, we unveil the exotic magnetic phase diagram of the generalized J1-J2-J3 model, shedding light on the ab initio magnetic states of iron chalcogenides. Moreover, we observe Berezinskii-Kosterlitz-Thouless dynamics by implementing an XY model. We open an avenue to controlling arbitrary spin interaction from the momentum space of light, offering a promising method for on-demand spin model simulation with a simple spatial light platform.
Advanced Photonics
- Publication Date: May. 02, 2025
- Vol. 7, Issue 4, 046001 (2025)
Toward the meta-atom library: experimental validation of machine learning-based Mie-tronics
Hooman Barati Sedeh, Renee C. George, Fangxing Lai, Hao Li... and Natalia M. Litchinitser|Show fewer author(s)
Although predicting light scattering by homogeneous spherical particles is a relatively straightforward problem that can be solved analytically, manipulating and studying the scattering behavior of non-spherical particles is a more challenging and time-consuming task, with a plethora of applications ranging from optical manipulation to wavefront engineering, and nonlinear harmonic generation. Recently, physics-driven machine learning (ML) has proven to be instrumental in addressing this challenge. However, most studies on Mie-tronics that leverage ML for optimization and design have been performed and validated through numerical approaches. Here, we report an experimental validation of an ML-based design method that significantly accelerates the development of all-dielectric complex-shaped meta-atoms supporting specified Mie-type resonances at the desired wavelength, circumventing the conventional time-consuming approaches. We used ML to design isolated meta-atoms with specific electric and magnetic responses, verified them within the quasi-normal mode expansion framework, and explored the effects of the substrate and periodic arrangements of such meta-atoms. Finally, we proposed implementing the designed meta-atoms to generate a third harmonic within the vacuum ultraviolet spectrum. Because the implemented method allowed for the swift transition from design to fabrication, the optimized meta-atoms were fabricated, and their corresponding scattering spectra were measured. Although predicting light scattering by homogeneous spherical particles is a relatively straightforward problem that can be solved analytically, manipulating and studying the scattering behavior of non-spherical particles is a more challenging and time-consuming task, with a plethora of applications ranging from optical manipulation to wavefront engineering, and nonlinear harmonic generation. Recently, physics-driven machine learning (ML) has proven to be instrumental in addressing this challenge. However, most studies on Mie-tronics that leverage ML for optimization and design have been performed and validated through numerical approaches. Here, we report an experimental validation of an ML-based design method that significantly accelerates the development of all-dielectric complex-shaped meta-atoms supporting specified Mie-type resonances at the desired wavelength, circumventing the conventional time-consuming approaches. We used ML to design isolated meta-atoms with specific electric and magnetic responses, verified them within the quasi-normal mode expansion framework, and explored the effects of the substrate and periodic arrangements of such meta-atoms. Finally, we proposed implementing the designed meta-atoms to generate a third harmonic within the vacuum ultraviolet spectrum. Because the implemented method allowed for the swift transition from design to fabrication, the optimized meta-atoms were fabricated, and their corresponding scattering spectra were measured.
Advanced Photonics
- Publication Date: Apr. 25, 2025
- Vol. 7, Issue 3, 036004 (2025)
Breaking the diffraction limit in molecular imaging by structured illumination mid-infrared photothermal microscopy
Pengcheng Fu, Bo Chen, Yongqing Zhang, Liangyi Chen... and Delong Zhang|Show fewer author(s)
Super-resolution microscopy techniques have revolutionized biological imaging by breaking the optical diffraction limit, yet most methods rely on fluorescent labels that provide limited chemical information. Although vibrational imaging based on Raman and infrared (IR) spectroscopy offers intrinsic molecular contrast, achieving both high spatial resolution and high chemical specificity remains challenging due to weak signal levels. We demonstrate structured illumination mid-infrared photothermal microscopy (SIMIP) as an emerging imaging platform that provides chemical bond selectivity and high-speed, widefield detection beyond the diffraction limit. By modulating fluorescence quantum yield through vibrational infrared absorption, SIMIP enables both nanoscale spatial resolution and high-fidelity IR spectral acquisition. The synergy of enhanced resolution and chemical specificity positions SIMIP as a versatile tool for studying complex biological systems and advanced materials, offering new opportunities across biomedicine and materials science. Super-resolution microscopy techniques have revolutionized biological imaging by breaking the optical diffraction limit, yet most methods rely on fluorescent labels that provide limited chemical information. Although vibrational imaging based on Raman and infrared (IR) spectroscopy offers intrinsic molecular contrast, achieving both high spatial resolution and high chemical specificity remains challenging due to weak signal levels. We demonstrate structured illumination mid-infrared photothermal microscopy (SIMIP) as an emerging imaging platform that provides chemical bond selectivity and high-speed, widefield detection beyond the diffraction limit. By modulating fluorescence quantum yield through vibrational infrared absorption, SIMIP enables both nanoscale spatial resolution and high-fidelity IR spectral acquisition. The synergy of enhanced resolution and chemical specificity positions SIMIP as a versatile tool for studying complex biological systems and advanced materials, offering new opportunities across biomedicine and materials science.
Advanced Photonics
- Publication Date: Apr. 13, 2025
- Vol. 7, Issue 3, 036003 (2025)
Real-time measurement of non-Hermitian Landau–Zener tunneling near band crossings
Lange Zhao, Shulin Wang, Chengzhi Qin, Bing Wang... and Peixiang Lu|Show fewer author(s)
Landau–Zener (LZ) tunneling, i.e., the nonadiabatic level transition under strong parameter driving, is a fundamental concept in modern quantum mechanics. With the advent of non-Hermitian physics, research interest has been paid to the LZ tunneling involving level dissipations. However, experimental demonstrations of such an interesting non-Hermitian LZ problem remain yet elusive. By harnessing a synthetic temporal lattice using a fiber-loop circuit, we report on the first real-time measurement of non-Hermitian LZ tunneling in a dissipative two-band lattice model. An innovative approach based on mode interference is developed to measure the transient band occupancies, providing a powerful tool to explore the non-Hermitian LZ tunneling dynamics in non-orthogonal eigenmodes. We find that the loss does not change the final LZ tunneling probability but can highly affect the tunneling process by modifying the typical band occupancies oscillation behaviors. We initiate exploring intriguing LZ physics and measurements beyond the standard Hermitian paradigm, with potential applications in coherent quantum control and quantum technologies. Landau–Zener (LZ) tunneling, i.e., the nonadiabatic level transition under strong parameter driving, is a fundamental concept in modern quantum mechanics. With the advent of non-Hermitian physics, research interest has been paid to the LZ tunneling involving level dissipations. However, experimental demonstrations of such an interesting non-Hermitian LZ problem remain yet elusive. By harnessing a synthetic temporal lattice using a fiber-loop circuit, we report on the first real-time measurement of non-Hermitian LZ tunneling in a dissipative two-band lattice model. An innovative approach based on mode interference is developed to measure the transient band occupancies, providing a powerful tool to explore the non-Hermitian LZ tunneling dynamics in non-orthogonal eigenmodes. We find that the loss does not change the final LZ tunneling probability but can highly affect the tunneling process by modifying the typical band occupancies oscillation behaviors. We initiate exploring intriguing LZ physics and measurements beyond the standard Hermitian paradigm, with potential applications in coherent quantum control and quantum technologies.
Advanced Photonics
- Publication Date: Apr. 11, 2025
- Vol. 7, Issue 3, 036002 (2025)
Exploring uncharted multiband hyperbolic dispersion in conjugated polymers: a first-principles study
Suim Lim, Dong Hee Park, Bin Chan Joo, Yeon Ui Lee, and Kanghoon Yim
Hyperbolic materials are highly anisotropic optical media that provide valuable assistance in emission engineering, nanoscale light focusing, and scattering enhancement. Recently discovered organic hyperbolic materials (OHMs) with exceptional biocompatibility and tunability offer promising prospects as next-generation optical media for nanoscopy, enabling superresolution bioimaging capabilities. Nonetheless, an OHM is still less accessible to many researchers because of its rarity and narrow operating wavelength range. Here, we employ first-principles calculations to expand the number of known OHMs, including conjugated polymers with multiple assembly units. Through the systematic investigation of structural and optical properties of the target copolymers, we discover extraordinary multiband hyperbolic dispersions from candidate OHMs. This approach provides a new perspective on the molecular-scale design of broadband, low-loss OHMs. It aids in identifying potential hyperbolic material candidates applicable to optical engineering and super-resolution bioimaging, offering new insights into nanoscale light–matter interactions. Hyperbolic materials are highly anisotropic optical media that provide valuable assistance in emission engineering, nanoscale light focusing, and scattering enhancement. Recently discovered organic hyperbolic materials (OHMs) with exceptional biocompatibility and tunability offer promising prospects as next-generation optical media for nanoscopy, enabling superresolution bioimaging capabilities. Nonetheless, an OHM is still less accessible to many researchers because of its rarity and narrow operating wavelength range. Here, we employ first-principles calculations to expand the number of known OHMs, including conjugated polymers with multiple assembly units. Through the systematic investigation of structural and optical properties of the target copolymers, we discover extraordinary multiband hyperbolic dispersions from candidate OHMs. This approach provides a new perspective on the molecular-scale design of broadband, low-loss OHMs. It aids in identifying potential hyperbolic material candidates applicable to optical engineering and super-resolution bioimaging, offering new insights into nanoscale light–matter interactions.
Advanced Photonics
- Publication Date: Mar. 13, 2025
- Vol. 7, Issue 3, 036001 (2025)
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