Contents
2025
Volume: 13 Issue 8
37 Article(s)
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Research Articles
Pilot-reference-free continuous-variable quantum key distribution with efficient decoy-state analysis
Anran Jin, Xingjian Zhang, Liang Jiang, Richard V. Penty, and Pei Zeng
Continuous-variable quantum key distribution (CV QKD) using optical coherent detectors is practically favorable due to its low implementation cost, flexibility of wavelength division multiplexing, and compatibility with standard coherent communication technologies. However, the security analysis and parameter estimation of CV QKD are complicated due to the infinite-dimensional latent Hilbert space. Also, the transmission of strong reference pulses undermines the security and complicates the experiments. In this work, we tackle these two problems by presenting a time-bin-encoding CV protocol with a simple phase-error-based security analysis valid under general coherent attacks. With the key encoded into the relative intensity between two optical modes, the need for global references is removed. Furthermore, phase randomization can be introduced to decouple the security analysis of different photon-number components. We can hence tag the photon number for each round, effectively estimate the associated privacy using a carefully designed coherent-detection method, and independently extract encryption keys from each component. Simulations manifest that the protocol using multi-photon components increases the key rate by two orders of magnitude compared to the one using only the single-photon component. Meanwhile, the protocol with four-intensity decoy analysis is sufficient to yield tight parameter estimation with a short-distance key-rate performance comparable to the best Bennett-Brassard-1984 implementation.Continuous-variable quantum key distribution (CV QKD) using optical coherent detectors is practically favorable due to its low implementation cost, flexibility of wavelength division multiplexing, and compatibility with standard coherent communication technologies. However, the security analysis and parameter estimation of CV QKD are complicated due to the infinite-dimensional latent Hilbert space. Also, the transmission of strong reference pulses undermines the security and complicates the experiments. In this work, we tackle these two problems by presenting a time-bin-encoding CV protocol with a simple phase-error-based security analysis valid under general coherent attacks. With the key encoded into the relative intensity between two optical modes, the need for global references is removed. Furthermore, phase randomization can be introduced to decouple the security analysis of different photon-number components. We can hence tag the photon number for each round, effectively estimate the associated privacy using a carefully designed coherent-detection method, and independently extract encryption keys from each component. Simulations manifest that the protocol using multi-photon components increases the key rate by two orders of magnitude compared to the one using only the single-photon component. Meanwhile, the protocol with four-intensity decoy analysis is sufficient to yield tight parameter estimation with a short-distance key-rate performance comparable to the best Bennett-Brassard-1984 implementation..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2013 (2025)
Optical backflow for the manipulations of dipolar nanoparticles
Xiangyang Xie, Peng Shi, Changjun Min, and Xiaocong Yuan
Backflow is a counterintuitive phenomenon that is widely predicted in the fields of quantum physics and optics. In contrast to quantum backflow, which is challenging to be observed, optical backflow is prevailing in structured lights. For instance, the azimuthal backflow has been recently observed experimentally in optics via the superposition of two beams carrying different orbital angular momentum topological charges. In this paper, we investigate the spin-momentum characteristics of the superimposed orbital angular momentum beams to confirm the optical azimuthal backflow, which is closely related to off-axis vortex flow and super-oscillations. Furthermore, we extend our study to axial backflow, characterized by a reversed axial energy flow in tightly focused cylindrical vector vortex beams. Then, we explore the application of optical backflow in the manipulation of dipolar nanoparticles. By optimizing material parameters, we achieve on-demand control of optical forces in both azimuthal and axial backflow scenarios. Our findings provide in-depth insights into the optical backflow phenomena with potential applications in optical manipulations.Backflow is a counterintuitive phenomenon that is widely predicted in the fields of quantum physics and optics. In contrast to quantum backflow, which is challenging to be observed, optical backflow is prevailing in structured lights. For instance, the azimuthal backflow has been recently observed experimentally in optics via the superposition of two beams carrying different orbital angular momentum topological charges. In this paper, we investigate the spin-momentum characteristics of the superimposed orbital angular momentum beams to confirm the optical azimuthal backflow, which is closely related to off-axis vortex flow and super-oscillations. Furthermore, we extend our study to axial backflow, characterized by a reversed axial energy flow in tightly focused cylindrical vector vortex beams. Then, we explore the application of optical backflow in the manipulation of dipolar nanoparticles. By optimizing material parameters, we achieve on-demand control of optical forces in both azimuthal and axial backflow scenarios. Our findings provide in-depth insights into the optical backflow phenomena with potential applications in optical manipulations..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2033 (2025)
Infrared-surface-plasmon-assisted thermal probe nanolithography using a radially polarized vortex and continuous-wave laser
Ruiguang Peng, Yan Meng, Jingda Wen, Shijia Feng, and Qian Zhao
Surface plasmonic polaritons (SPPs) break Abbe’s diffraction limit in the near field and provide a promising solution for high-resolution nanolithography without reducing illuminating wavelength. However, the resolution of the normal plasmonic lithography method based on ultraviolet exposure of a photoresist heavily relies on the size of the elaborate nanostructures, which usually require precise nanofabrication. Meanwhile, a high-cost pulsed laser is required as the light source to further reduce the lithography linewidth. Here, we establish a high-resolution and low-cost scanning probe nanolithography system based on the infrared surface plasmons. An easy-fabrication probe is designed by tailoring four concentric annular slits with a moderate width of 200 nm, which couples the incident radially polarized beam into SPPs, resulting in an ultra-strong spot at the tip apex. Such superfocusing mode is demonstrated to apply to the thermal field through the optical-thermal effect so as to cause the heat accumulation with a more restricted heating area, which is utilized for the thermal probe nanolithography. Experimental results indicate that the subwavelength feature with a linewidth down to 13 nm is realized using an inexpensive 1064 nm wavelength continuous-wave laser. Our scheme shows great potential in fabrication of planar optical elements with small size and high flexibility, and can also find extensive applications in areas such as single-molecule spectra, biological detection, and optical microscopy.Surface plasmonic polaritons (SPPs) break Abbe’s diffraction limit in the near field and provide a promising solution for high-resolution nanolithography without reducing illuminating wavelength. However, the resolution of the normal plasmonic lithography method based on ultraviolet exposure of a photoresist heavily relies on the size of the elaborate nanostructures, which usually require precise nanofabrication. Meanwhile, a high-cost pulsed laser is required as the light source to further reduce the lithography linewidth. Here, we establish a high-resolution and low-cost scanning probe nanolithography system based on the infrared surface plasmons. An easy-fabrication probe is designed by tailoring four concentric annular slits with a moderate width of 200 nm, which couples the incident radially polarized beam into SPPs, resulting in an ultra-strong spot at the tip apex. Such superfocusing mode is demonstrated to apply to the thermal field through the optical-thermal effect so as to cause the heat accumulation with a more restricted heating area, which is utilized for the thermal probe nanolithography. Experimental results indicate that the subwavelength feature with a linewidth down to 13 nm is realized using an inexpensive 1064 nm wavelength continuous-wave laser. Our scheme shows great potential in fabrication of planar optical elements with small size and high flexibility, and can also find extensive applications in areas such as single-molecule spectra, biological detection, and optical microscopy..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2046 (2025)
Maximizing the chirality of bound states in the continuum by inverse design
He Chen, Ning Li, Yunxia Zhao, Huayu Ou... and Lingling Huang|Show fewer author(s)
Planar metasurfaces with both chirality and high quality (Q) factors have important applications in many fields. A chiral metasurface empowered by a bound state in the continuum (BIC) can provide a perfect solution to this problem. However, the metasurface design method based on physical intuition requires a substantial amount of computational resources, and the limited design parameters of meta-atoms restrict metasurfaces from achieving optimal optical performance. Here, we apply an inverse design method based on adjoint topological optimization to automatically alter the refractive index distribution of the metasurface, thereby maximizing the chirality of the BIC metasurface. Through this inverse design approach, chiral BIC metasurfaces with 3D intrinsic chirality at the target wavelength are designed and fabricated. To demonstrate the versatility of the proposed inverse design method, the metasurfaces with specific elliptic polarization states are designed. The inverse design method we propose provides an effective solution for the efficient design of chiral BIC metasurfaces.Planar metasurfaces with both chirality and high quality (Q) factors have important applications in many fields. A chiral metasurface empowered by a bound state in the continuum (BIC) can provide a perfect solution to this problem. However, the metasurface design method based on physical intuition requires a substantial amount of computational resources, and the limited design parameters of meta-atoms restrict metasurfaces from achieving optimal optical performance. Here, we apply an inverse design method based on adjoint topological optimization to automatically alter the refractive index distribution of the metasurface, thereby maximizing the chirality of the BIC metasurface. Through this inverse design approach, chiral BIC metasurfaces with 3D intrinsic chirality at the target wavelength are designed and fabricated. To demonstrate the versatility of the proposed inverse design method, the metasurfaces with specific elliptic polarization states are designed. The inverse design method we propose provides an effective solution for the efficient design of chiral BIC metasurfaces..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2054 (2025)
Measurement of microwave meta-quaternion vortex arrays enabling Luoshu-WeightLock imaging encryption
Sen Feng, Yifeng Wang, Zheng-Da Hu, Jicheng Wang... and Sergei Khakhomov|Show fewer author(s)
Electromagnetic metasurfaces exhibit considerable potential for generating high-purity vortex beams and enabling high-resolution imaging and information encryption. However, traditional GHz devices face challenges, including reduced efficiency due to bulky size and material losses. Herein, we designed a multilayer structure and demonstrated through simulations that this configuration served as an efficient transmissive meta-atom. We designed arrays in multiple sizes and finally determined that the optimal minimal unit was the meta-quaternion vortex array, which was subsequently used as the pixel basis for the target image. A digitally patterned GHz metadevice was fabricated and experimentally characterized with right-handed circularly polarized (RCP) light. The experimental results were in excellent agreement with the simulations. We combined the classical nine-grid encryption method (Luoshu) with metasurfaces and introduced the weighted superposition computation technique (WeightLock) to achieve multilayer encryption of target characters. Our research offered novel strategies for the next-generation 5G/6G communication systems, radar detection, and information encryption fields, demonstrating broad application prospects in intelligent communication and advanced radar technologies.Electromagnetic metasurfaces exhibit considerable potential for generating high-purity vortex beams and enabling high-resolution imaging and information encryption. However, traditional GHz devices face challenges, including reduced efficiency due to bulky size and material losses. Herein, we designed a multilayer structure and demonstrated through simulations that this configuration served as an efficient transmissive meta-atom. We designed arrays in multiple sizes and finally determined that the optimal minimal unit was the meta-quaternion vortex array, which was subsequently used as the pixel basis for the target image. A digitally patterned GHz metadevice was fabricated and experimentally characterized with right-handed circularly polarized (RCP) light. The experimental results were in excellent agreement with the simulations. We combined the classical nine-grid encryption method (Luoshu) with metasurfaces and introduced the weighted superposition computation technique (WeightLock) to achieve multilayer encryption of target characters. Our research offered novel strategies for the next-generation 5G/6G communication systems, radar detection, and information encryption fields, demonstrating broad application prospects in intelligent communication and advanced radar technologies..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2065 (2025)
Manipulating classical triple correlations for optical information processing and metrology
Wanting Hou, Run-Jie He, Zhiyuan Ye, Xue-Jiao Men... and Jun Xiong|Show fewer author(s)
Wave mixing and the intricate optical interactions therein have traditionally been regarded as hallmarks of nonlinear optics. A quintessential example of wave mixing lies in the nonlocal triple correlation between the pump beam and the generated twin photons via spontaneous parametric down-conversion (SPDC). However, the SPDC process typically requires intense laser pumping and suffers from inherently low conversion efficiencies, necessitating single-photon detection. In this work, we establish that analogous triple correlations can be effectively produced using low-power continuous-wave illumination, achieved through a commercially available spatial light modulator (SLM) in a linear optical configuration. Specifically, we show how to spatially manipulate and customize this triple correlation and further investigate the applicability across diverse domains, including pattern recognition, intelligent nonlocal image processing, and sensitivity-enhanced optical metrology. Our findings establish, to our knowledge, a novel framework for classical, linear emulation of quantum and nonlinear optical information processing paradigms rooted in multi-wave mixing.Wave mixing and the intricate optical interactions therein have traditionally been regarded as hallmarks of nonlinear optics. A quintessential example of wave mixing lies in the nonlocal triple correlation between the pump beam and the generated twin photons via spontaneous parametric down-conversion (SPDC). However, the SPDC process typically requires intense laser pumping and suffers from inherently low conversion efficiencies, necessitating single-photon detection. In this work, we establish that analogous triple correlations can be effectively produced using low-power continuous-wave illumination, achieved through a commercially available spatial light modulator (SLM) in a linear optical configuration. Specifically, we show how to spatially manipulate and customize this triple correlation and further investigate the applicability across diverse domains, including pattern recognition, intelligent nonlocal image processing, and sensitivity-enhanced optical metrology. Our findings establish, to our knowledge, a novel framework for classical, linear emulation of quantum and nonlinear optical information processing paradigms rooted in multi-wave mixing..
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2073 (2025)
3D-printed mode-selective micro-scale photonic lantern spatial (de)multiplexer | Editors' Pick
Yoav Dana, Yehudit Garcia, Aleksei Kukin, and Dan M. Marom
We present the design, fabrication, and characterization of a dual polarization, mode-selective photonic lantern (PL) spatial multiplexer supporting three fiber modes (LP01,LP11a,LP11b), measuring only 300 μm in length, for converting between three single-mode input sources and a single three-mode optical fiber. The PL is fabricated directly on the three sources, in this case three cores of a multi-core fiber, using a commercial two-photon polymerization-based 3D nanoprinter. Despite the diminutive size and high index contrast of the polymer core/air cladding waveguides, we observed low insertion loss multiplexing (less than -1.7 dB), low polarization dependent loss (less than -0.25 dB), mode dependent loss of -1.7 dB, low wavelength dependence, and mode group crosstalk of less than -16 dB. We demonstrate mode group multiplexed transmission using our mode-selective multiplexer/demultiplexer pair and a short three-mode fiber link in an on-off keying intensity modulation/direct detection (IM/DD) experiment, recovering two 12.5 Gb/s signals without MIMO processing.We present the design, fabrication, and characterization of a dual polarization, mode-selective photonic lantern (PL) spatial multiplexer supporting three fiber modes (
Photonics Research
- Publication Date: Jul. 21, 2025
- Vol. 13, Issue 8, 2088 (2025)
Comprehensive review of organic/inorganic perovskite-based photodetectors: investigating their evolution and prospects in modern photonics
Muhammad Sulaman, Qianwei Wu, Bingxue Liu, Tianbing Han... and Honglian Guo|Show fewer author(s)
Perovskite-based photodetectors offer a compelling avenue for cutting-edge photonic applications due to their unique blend of optoelectronic characteristics and cost-efficient manufacturing processes. This comprehensive review investigates the advancements and hurdles facing organic and inorganic perovskite-based photodetectors. The introduction sets the stage by underscoring the significance of perovskite photodetectors and outlining the review’s scope. It also provides a primer on perovskite materials and structures, encompassing organic and inorganic variants, their synthesis techniques, and distinct properties. The section on working principles elucidates the fundamental mechanisms governing photovoltaic, photoconductive, phototransistor, and photodiode photodetectors, explaining how these devices capture and convert light into electrical signals. The review explores various device fabrication techniques, offering insights into methods like solution processing, vacuum deposition, and hybrid approaches, each with its merits and challenges. Performance optimization strategies are thoroughly examined, focusing on improving responsivity, detectivity, stability, and reliability, while also reducing noise and optimizing perovskite interfaces. It covers a diverse array of device architectures and configurations, including single-junction, tandem, and multijunction designs, as well as flexible and transparent photodetector configurations. Furthermore, the review discusses the integration and applications of perovskite-based photodetectors across imaging, environmental monitoring, communication, and healthcare, showcasing their versatility in real-world scenarios. Lastly, it addresses the challenges and future prospects of perovskite-based photodetectors, highlighting issues related to stability, toxicity, scalability, and emerging technologies, providing a glimpse into the exciting future of this field.Perovskite-based photodetectors offer a compelling avenue for cutting-edge photonic applications due to their unique blend of optoelectronic characteristics and cost-efficient manufacturing processes. This comprehensive review investigates the advancements and hurdles facing organic and inorganic perovskite-based photodetectors. The introduction sets the stage by underscoring the significance of perovskite photodetectors and outlining the review’s scope. It also provides a primer on perovskite materials and structures, encompassing organic and inorganic variants, their synthesis techniques, and distinct properties. The section on working principles elucidates the fundamental mechanisms governing photovoltaic, photoconductive, phototransistor, and photodiode photodetectors, explaining how these devices capture and convert light into electrical signals. The review explores various device fabrication techniques, offering insights into methods like solution processing, vacuum deposition, and hybrid approaches, each with its merits and challenges. Performance optimization strategies are thoroughly examined, focusing on improving responsivity, detectivity, stability, and reliability, while also reducing noise and optimizing perovskite interfaces. It covers a diverse array of device architectures and configurations, including single-junction, tandem, and multijunction designs, as well as flexible and transparent photodetector configurations. Furthermore, the review discusses the integration and applications of perovskite-based photodetectors across imaging, environmental monitoring, communication, and healthcare, showcasing their versatility in real-world scenarios. Lastly, it addresses the challenges and future prospects of perovskite-based photodetectors, highlighting issues related to stability, toxicity, scalability, and emerging technologies, providing a glimpse into the exciting future of this field..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2096 (2025)
Polarization-multiplexing metasurfaces for tunable wavefront configurations via Moiré engineering
Wenhui Xu, Hui Li, Chenghui Zhao, Jie Li... and Jianquan Yao|Show fewer author(s)
Traditional tunable metasurfaces have evolved through mechanisms relying on external stimuli, such as electrical, thermal, or optical excitation, to dynamically control electromagnetic (EM) wavefronts. While these approaches enable functionalities like focal varying and polarization modulation, they suffer from inherent limitations, including energy inefficiency, structural complexity, and limited adaptability. Here, cascaded all-dielectric Moiré metasurfaces are introduced, which are capable of simultaneous polarization multiplexing and focal-length control for terahertz (THz) beams without external stimuli. Moiré device 1 combines polarization-insensitive (Layer 1) and polarization-sensitive (Layer 2) meta-atoms to independently tailor orthogonal circular polarization channels, including left-handed circular polarization (LCP) and right-handed circular polarization (RCP). Under circularly polarized illumination, it generates focused beams with distinct topological charges (l=0 for LCP→RCP and l=1 for RCP→LCP), while relative layer rotation enables continuous focal-length adjustment from 9.28 mm to 3.22 mm, accompanied by a numerical aperture (NA) increase from 0.54 to 0.88. Moiré device 2 extends this paradigm to orthogonal linear polarization (LP) channels, producing l=1 and l=0 beams under x-LP and y-LP illumination, with a zoom range of 8.42–3.11 mm and NA up to 0.88. Experimental results validate polarization-selective focusing with efficiency exceeding 15% and robust agreement with simulation results, and the calculated absolute percentage errors (APEs) are below 5.9% for focal length and 3% for NA. These values are consistent with the expected theoretical trends, demonstrating that the experimental results align well with the predicted performance. This reconfigurable system introduces additional control dimensions through mechanical adjustments to cascaded metasurfaces, paving the way for adaptive wavefront control and opening new avenues for next-generation optical technologies.Traditional tunable metasurfaces have evolved through mechanisms relying on external stimuli, such as electrical, thermal, or optical excitation, to dynamically control electromagnetic (EM) wavefronts. While these approaches enable functionalities like focal varying and polarization modulation, they suffer from inherent limitations, including energy inefficiency, structural complexity, and limited adaptability. Here, cascaded all-dielectric Moiré metasurfaces are introduced, which are capable of simultaneous polarization multiplexing and focal-length control for terahertz (THz) beams without external stimuli. Moiré device 1 combines polarization-insensitive (Layer 1) and polarization-sensitive (Layer 2) meta-atoms to independently tailor orthogonal circular polarization channels, including left-handed circular polarization (LCP) and right-handed circular polarization (RCP). Under circularly polarized illumination, it generates focused beams with distinct topological charges (
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2130 (2025)
End-to-end all-optical nonlinear activator enabled by a Brillouin fiber amplifier
Caihong Teng, Qihao Sun, Shengkun Chen, Yixuan Huang... and Jiang Wu|Show fewer author(s)
The rapid growth of deep learning applications has sparked a revolution in computing paradigms, with optical neural networks (ONNs) emerging as a promising platform for achieving ultra-high computing power and energy efficiency. Despite great progress in analog optical computing, the lack of scalable optical nonlinearities and losses in photonic devices pose considerable challenges for power levels, energy efficiency, and signal latency. Here, we report an end-to-end all-optical nonlinear activator that utilizes the energy conversion of Brillouin scattering to perform efficient nonlinear processing. The activator exhibits an ultra-low activation threshold (24 nW), a wide transmission bandwidth (over 40 GHz), strong robustness, and high energy transfer efficiency. These advantages provide a feasible solution to overcome the existing bottlenecks in ONNs. As a proof-of-concept, a series of tasks is designed to validate the capability of the proposed activator as an activation unit for ONNs. Simulations show that the experiment-based nonlinear model outperforms classical activation functions in classification (97.64% accuracy for MNIST and 87.84% for Fashion-MNIST) and regression (with a symbol error rate as low as 0%) tasks. This work provides valuable insights into the innovative design of all-optical neural networks.The rapid growth of deep learning applications has sparked a revolution in computing paradigms, with optical neural networks (ONNs) emerging as a promising platform for achieving ultra-high computing power and energy efficiency. Despite great progress in analog optical computing, the lack of scalable optical nonlinearities and losses in photonic devices pose considerable challenges for power levels, energy efficiency, and signal latency. Here, we report an end-to-end all-optical nonlinear activator that utilizes the energy conversion of Brillouin scattering to perform efficient nonlinear processing. The activator exhibits an ultra-low activation threshold (24 nW), a wide transmission bandwidth (over 40 GHz), strong robustness, and high energy transfer efficiency. These advantages provide a feasible solution to overcome the existing bottlenecks in ONNs. As a proof-of-concept, a series of tasks is designed to validate the capability of the proposed activator as an activation unit for ONNs. Simulations show that the experiment-based nonlinear model outperforms classical activation functions in classification (97.64% accuracy for MNIST and 87.84% for Fashion-MNIST) and regression (with a symbol error rate as low as 0%) tasks. This work provides valuable insights into the innovative design of all-optical neural networks..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2145 (2025)
Continuously tunable topological negative refraction via a tailorable Bloch wavevector in momentum space | Editors' Pick
Yidong Zheng, Jianfeng Chen, Zitao Ji, and Zhi-Yuan Li
Topological photonics provides a strategy that makes light transmission immune to structural-defects-induced backward scattering. Leveraging this, topological negative refraction enables robust, reflectionless light deflection, but directly controlling the refraction direction remains challenging. We demonstrate continuously tunable topological negative refraction at the interface between a one-way waveguide state and a free-space beam, overcoming the limitations of fixed refraction angles in conventional systems. The key insight is the ability to adjust the wavevector of the incident one-way waveguide state. Through manipulating the Bloch wavevector of the waveguide states in momentum space, we achieve a transition from negative to positive refraction. The unidirectional nature of these states prevents backscattering from defects, ensuring immunity to imperfections. As a prototypical demonstration, we achieve dynamic steering of refraction beams from -38° to +12° through active magnetic bias control. Our findings provide an exotic pathway for photon manipulation and a promising route toward topological photonics applications.Topological photonics provides a strategy that makes light transmission immune to structural-defects-induced backward scattering. Leveraging this, topological negative refraction enables robust, reflectionless light deflection, but directly controlling the refraction direction remains challenging. We demonstrate continuously tunable topological negative refraction at the interface between a one-way waveguide state and a free-space beam, overcoming the limitations of fixed refraction angles in conventional systems. The key insight is the ability to adjust the wavevector of the incident one-way waveguide state. Through manipulating the Bloch wavevector of the waveguide states in momentum space, we achieve a transition from negative to positive refraction. The unidirectional nature of these states prevents backscattering from defects, ensuring immunity to imperfections. As a prototypical demonstration, we achieve dynamic steering of refraction beams from
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2159 (2025)
Non-line-of-sight imaging via scalable scattering mapping using TOF cameras
Yujie Fang, Junming Wu, Shengming Zhong, Xiaofeng Zhang... and Kejun Wang|Show fewer author(s)
The technique of imaging or tracking objects outside the field of view (FOV) through a reflective relay surface, usually called non-line-of-sight (NLOS) imaging, has been a popular research topic in recent years. Although NLOS imaging can be achieved through methods such as detector design, optical path inverse operation algorithm design, or deep learning, challenges such as high costs, complex algorithms, and poor results remain. This study introduces a simple algorithm-based rapid depth imaging device, namely, the continuous-wave time-of-flight range imaging camera (CW-TOF camera), to address the decoupled imaging challenge of differential scattering characteristics in an object-relay surface by quantifying the differential scattering signatures through statistical analysis of light propagation paths. A scalable scattering mapping (SSM) theory has been proposed to explain the degradation process of clear images. High-quality NLOS object 3D imaging has been achieved through a data-driven approach. To verify the effectiveness of the proposed algorithm, experiments were conducted using an optical platform and real-world scenarios. The objects on the optical platform include plaster sculptures and plastic letters, while relay surfaces consist of polypropylene (PP) plastic boards, acrylic boards, and standard Lambertian diffusers. In real-world scenarios, the object is clothing, with relay surfaces including painted doors and white plaster walls. Imaging data were collected for different combinations of objects and relay surfaces for training and testing, totaling 210,000 depth images. The reconstruction of NLOS images in the laboratory and real-world is excellent according to subjective evaluation; thus, our approach can realize NLOS imaging in harsh natural scenes and advances the practical application of NLOS imaging.The technique of imaging or tracking objects outside the field of view (FOV) through a reflective relay surface, usually called non-line-of-sight (NLOS) imaging, has been a popular research topic in recent years. Although NLOS imaging can be achieved through methods such as detector design, optical path inverse operation algorithm design, or deep learning, challenges such as high costs, complex algorithms, and poor results remain. This study introduces a simple algorithm-based rapid depth imaging device, namely, the continuous-wave time-of-flight range imaging camera (CW-TOF camera), to address the decoupled imaging challenge of differential scattering characteristics in an object-relay surface by quantifying the differential scattering signatures through statistical analysis of light propagation paths. A scalable scattering mapping (SSM) theory has been proposed to explain the degradation process of clear images. High-quality NLOS object 3D imaging has been achieved through a data-driven approach. To verify the effectiveness of the proposed algorithm, experiments were conducted using an optical platform and real-world scenarios. The objects on the optical platform include plaster sculptures and plastic letters, while relay surfaces consist of polypropylene (PP) plastic boards, acrylic boards, and standard Lambertian diffusers. In real-world scenarios, the object is clothing, with relay surfaces including painted doors and white plaster walls. Imaging data were collected for different combinations of objects and relay surfaces for training and testing, totaling 210,000 depth images. The reconstruction of NLOS images in the laboratory and real-world is excellent according to subjective evaluation; thus, our approach can realize NLOS imaging in harsh natural scenes and advances the practical application of NLOS imaging..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2172 (2025)
Enhancement of superchirality induced by matching electromagnetic components of the combined field
Zhishang Wang, Jing Guo, Qian Shou, Wei Hu, and Daquan Lu
We propose an approach for generating the enhanced superchiral needle by matching electromagnetic components of the combined field, which is the superposition of a radially polarized vortex Bessel–Gaussian beam (RPVBGB) and an azimuthally polarized Bessel–Gaussian beam (APBGB). In the tightly focused combined field, the longitudinal magnetic component provided by the APBGB, together with the longitudinal electric component provided by the RPVBGB, induces an additional contribution to the optical chirality and thereby significantly improves the enhancement factor of the superchiral needle. It is revealed that the characteristics of the superchiral needle are mainly influenced by the ring aperture, the phase difference, and the amplitude ratio. Under proper parameters, the enhancement factor can reach from 22.9 to 32.9, and the needle width can reach from 0.0151λ to 0.0043λ and from 0.0182λ to 0.0058λ in the x- and y-directions, respectively. The results would be of interest for the chirality measurement of individual molecules.We propose an approach for generating the enhanced superchiral needle by matching electromagnetic components of the combined field, which is the superposition of a radially polarized vortex Bessel–Gaussian beam (RPVBGB) and an azimuthally polarized Bessel–Gaussian beam (APBGB). In the tightly focused combined field, the longitudinal magnetic component provided by the APBGB, together with the longitudinal electric component provided by the RPVBGB, induces an additional contribution to the optical chirality and thereby significantly improves the enhancement factor of the superchiral needle. It is revealed that the characteristics of the superchiral needle are mainly influenced by the ring aperture, the phase difference, and the amplitude ratio. Under proper parameters, the enhancement factor can reach from 22.9 to 32.9, and the needle width can reach from
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2184 (2025)
Synchronous dynamics of passively synchronized Yb-doped fiber lasers
Fan Wu, Zexin Zhang, Jinrong Tian, Pengxiang Zhang... and Yanrong Song|Show fewer author(s)
A tightly synchronized fiber laser system composed of two mode-locked Yb-doped fiber lasers in a master-slave configuration is built. The synchronization could sustain for more than 6 h, and the maximum tolerance of cavity length mismatch is measured to be about 210 μm. Afterward, a time-stretch dispersive Fourier transform technique is introduced to analyze the synchronization process over multiple cycles. The pulse evolution, center wavelength shift, spectral reshaping, and broadening are all clearly detected. And the synchronization time is experimentally determined on the order of microseconds (hundreds of roundtrips). These results also show the seed pulse acting as a temporal gate for mode locking in some cases. To the best of our knowledge, this is the first time that pulse formation, spectral evolution, center wavelength shift, and synchronization time during the synchronization process are precisely revealed in experiment. These results would help to improve the performances of synchronized laser devices and deeply understand the mechanisms of the synchronization process and other light-light interactions in materials.A tightly synchronized fiber laser system composed of two mode-locked Yb-doped fiber lasers in a master-slave configuration is built. The synchronization could sustain for more than 6 h, and the maximum tolerance of cavity length mismatch is measured to be about 210 μm. Afterward, a time-stretch dispersive Fourier transform technique is introduced to analyze the synchronization process over multiple cycles. The pulse evolution, center wavelength shift, spectral reshaping, and broadening are all clearly detected. And the synchronization time is experimentally determined on the order of microseconds (hundreds of roundtrips). These results also show the seed pulse acting as a temporal gate for mode locking in some cases. To the best of our knowledge, this is the first time that pulse formation, spectral evolution, center wavelength shift, and synchronization time during the synchronization process are precisely revealed in experiment. These results would help to improve the performances of synchronized laser devices and deeply understand the mechanisms of the synchronization process and other light-light interactions in materials..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2192 (2025)
Deep learning assisted real-time and portable refractometer using a
Ziqi Liu, Chang Liu, Tuan Guo, Zhaohui Li, and Zhengyong Liu
In this work, we demonstrate a π-phase-shifted tilted fiber Bragg grating (π-PSTFBG)-based sensor for measuring the refractive index (RI) of NaCl solutions, achieving a real-time and online measurement system by employing a densely connected convolutional neural network (D-CNN) model to demodulate the full spectrum. The proposed π-PSTFBG sensor is prepared by using the advanced fiber grating inscription system based on a two-beam interferometry method, which could introduce deeper features of dip-splitting for all the lossy dips in the spectrum, giving the possibility of fully measuring the change of RI. This enhanced feature gives relatively higher prediction accuracy (R2 of 99.67%) using the well-trained D-CNN model compared with the results achieved by pure TFBG or that with a gold coating. As a further demonstration from a practical view, a prototype integrated with the proposed D-CNN algorithm is developed to conduct RI measurement of NaCl solutions in real time using a π-PSTFBG-based RI sensor. The results show that the proposed real-time demodulation system is capable of measuring RI with an average error of 1.6×10-4 RIU in a short response time of <1 s. The demonstrated spectral demodulation approach powered by deep learning shows great potential in real-time analysis for chemical solutions and point-of-care medical testing based on RI changes, especially for the portable requirements.In this work, we demonstrate a
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2202 (2025)
Observation of coexisting large-area topological pseudospin and valley waveguide states in a planar microstrip heterostructure based on topological LC circuits
Yaoyao Shu, Mina Ren, Xin Qi, Zhiwei Guo... and Yong Sun|Show fewer author(s)
The rapid development of topological photonics has significantly facilitated the development of novel microwave and optical devices with richer electromagnetic properties. A stable and efficient guided wave is a necessary condition for optical information transmission and processing. However, most topological waveguides are confined at a domain wall around the interfaces and usually operate in a single-type topological mode, leading to low-throughput energy transmission over a single frequency band. Here, we propose, design, and experimentally demonstrate a novel planar microstrip heterostructure system based on topological LC circuits that supports a dual-type topological large-area waveguide state, and the system showcases tunable mode widths with different operating bandwidths. Inheriting from the pseudospin and valley topology, the topological large-area waveguides exhibit the pseudospin- and valley-locked properties at different frequency windows and have strong robustness against defects. Moreover, the large-area topological waveguide states of high-energy capacity channel intersections and beam expanders with topological pseudospin and valley mode width degrees of freedom are verified numerically and experimentally. We also show the distinct topological origins of large-area topological waveguide states that provide versatile signal routing paths by their intrinsic coupling properties. Our system provides an efficient scheme to realize the tunable width and the multi-mode bandwidth of topological waveguides, which can further promote the applications of multi-functional high-performance topological photonic integrated circuit systems in on-chip communication and signal processing.The rapid development of topological photonics has significantly facilitated the development of novel microwave and optical devices with richer electromagnetic properties. A stable and efficient guided wave is a necessary condition for optical information transmission and processing. However, most topological waveguides are confined at a domain wall around the interfaces and usually operate in a single-type topological mode, leading to low-throughput energy transmission over a single frequency band. Here, we propose, design, and experimentally demonstrate a novel planar microstrip heterostructure system based on topological LC circuits that supports a dual-type topological large-area waveguide state, and the system showcases tunable mode widths with different operating bandwidths. Inheriting from the pseudospin and valley topology, the topological large-area waveguides exhibit the pseudospin- and valley-locked properties at different frequency windows and have strong robustness against defects. Moreover, the large-area topological waveguide states of high-energy capacity channel intersections and beam expanders with topological pseudospin and valley mode width degrees of freedom are verified numerically and experimentally. We also show the distinct topological origins of large-area topological waveguide states that provide versatile signal routing paths by their intrinsic coupling properties. Our system provides an efficient scheme to realize the tunable width and the multi-mode bandwidth of topological waveguides, which can further promote the applications of multi-functional high-performance topological photonic integrated circuit systems in on-chip communication and signal processing..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2213 (2025)
Fringe projection profilometry via LED array with pre-calibration
Jin Tan, Bo Zhang, Hong-Xu Huang, Wei-Jie Deng, and Ming-Jie Sun
Fringe projection profilometry (FPP) is a method that determines height by analyzing distortional fringes, which is widely used in high-accuracy 3D imaging. Now, one major reason limiting imaging speed in FPP is the projection device; the capture speed of high-speed cameras far exceeds the projection frequency. Among various devices, an LED array can exceed the speed of a high-speed camera. However, non-sinusoidal fringe patterns in the LED array systems can arise from several factors that will reduce the accuracy, such as the spacing between adjacent LEDs, the inconsistency in brightness across different LEDs, and the residual high-order harmonics in binary defocusing projection. It is challenging to resolve by other methods. In this paper, we propose a method that creates a look-up table using system calibration data of phase-height models. Then we utilize the look-up table to compensate for the phase error during the reconstructing process. The foundation of the proposed method relies on the time-invariance of systematic error; any factor that impacts the sinusoidal characteristic would present as an anomaly in the unwrapped phase. Experiments have demonstrated that the root mean square errors (RMSEs) of the results yielded by the proposed method were reduced by over 90% compared to those yielded by the traditional method, reaching 20 μm accuracy. This paper offers an alternative approach for high-speed and high-accuracy 3D imaging with an LED array and presents a workable solution for addressing complex errors from non-sinusoidal fringes.Fringe projection profilometry (FPP) is a method that determines height by analyzing distortional fringes, which is widely used in high-accuracy 3D imaging. Now, one major reason limiting imaging speed in FPP is the projection device; the capture speed of high-speed cameras far exceeds the projection frequency. Among various devices, an LED array can exceed the speed of a high-speed camera. However, non-sinusoidal fringe patterns in the LED array systems can arise from several factors that will reduce the accuracy, such as the spacing between adjacent LEDs, the inconsistency in brightness across different LEDs, and the residual high-order harmonics in binary defocusing projection. It is challenging to resolve by other methods. In this paper, we propose a method that creates a look-up table using system calibration data of phase-height models. Then we utilize the look-up table to compensate for the phase error during the reconstructing process. The foundation of the proposed method relies on the time-invariance of systematic error; any factor that impacts the sinusoidal characteristic would present as an anomaly in the unwrapped phase. Experiments have demonstrated that the root mean square errors (RMSEs) of the results yielded by the proposed method were reduced by over 90% compared to those yielded by the traditional method, reaching 20 μm accuracy. This paper offers an alternative approach for high-speed and high-accuracy 3D imaging with an LED array and presents a workable solution for addressing complex errors from non-sinusoidal fringes..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2224 (2025)
Cascaded Raman lasing in a lithium tetraborate whispering gallery mode resonator | Editors' Pick
Chengcai Tian, Jervee Punzalan, Petra Becker, Ladislav Bohatý... and Florian Sedlmeir|Show fewer author(s)
Lithium tetraborate (LB4) is a lithium borate compound known for its exceptional linear and nonlinear optical properties, including a wide transparency range (0.16–3.5 μm) and high Raman gain. Here, a millimeter-sized LB4 whispering gallery mode (WGM) resonator with a record quality factor of 2.0×109 at 517 nm was fabricated using single-point diamond cutting. Pumped with about 10 mW at 517 nm, it demonstrated four cascaded stimulated Raman scattering (SRS) peaks (537–608 nm), with the first-order SRS achieving a threshold of 0.71 mW and 7.2% slope efficiency. To our knowledge, this marks the first LB4 WGM resonator Raman laser.Lithium tetraborate (LB4) is a lithium borate compound known for its exceptional linear and nonlinear optical properties, including a wide transparency range (0.16–3.5 μm) and high Raman gain. Here, a millimeter-sized LB4 whispering gallery mode (WGM) resonator with a record quality factor of
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2232 (2025)
Grating mediated by three-dimensional director solitons
Chao-Yi Li, Xing-Zhou Tang, Zhi-Jun Huang, Ge Sun... and Yan-Qing Lu|Show fewer author(s)
Within the realm of soft matter, particularly liquid crystals, the ability to leverage material properties to create switchable diffraction gratings holds significant importance in disciplines such as optics and information science. However, designing switchable patterns and compiling information based on output images remain challenging. Here, we introduce an approach to address these limitations by designing switchable gratings mediated by three-dimensional director solitons. We utilize photo-patterning, employing lithography systems with different ultraviolet light, to fabricate the desired patterns. This method allows solitons to nucleate and localize within the regions of the pattern where the anchoring energy is weaker. The periodic structures, alternating between solitons and uniform patterns, exhibit the ability to diffract light beams. By switching the voltage, we can control the generation and localization of solitons within periodic patterns and realize switching between the waveplate and grating. Our experimental findings, complemented by simulation outcomes, validate the feasibility of utilizing three-dimensional solitons in optical applications.Within the realm of soft matter, particularly liquid crystals, the ability to leverage material properties to create switchable diffraction gratings holds significant importance in disciplines such as optics and information science. However, designing switchable patterns and compiling information based on output images remain challenging. Here, we introduce an approach to address these limitations by designing switchable gratings mediated by three-dimensional director solitons. We utilize photo-patterning, employing lithography systems with different ultraviolet light, to fabricate the desired patterns. This method allows solitons to nucleate and localize within the regions of the pattern where the anchoring energy is weaker. The periodic structures, alternating between solitons and uniform patterns, exhibit the ability to diffract light beams. By switching the voltage, we can control the generation and localization of solitons within periodic patterns and realize switching between the waveplate and grating. Our experimental findings, complemented by simulation outcomes, validate the feasibility of utilizing three-dimensional solitons in optical applications..
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2240 (2025)
Damage dynamics and relaxation process of double pulses with nanosecond laser
Qiaofei Pan, Ke Wang, Jiaqi Han, and Bin Ma
The laser-induced damage threshold (LIDT) of optical elements is a critical limitation in advancing next-generation spaceborne laser technologies. Transient mechanisms in multiple-pulse damage dynamics have been recognized, but significant gaps remain in understanding these processes. In this study, we introduce a practice time interval (Δtp)-dependent damage metric. Using a double-pulse double-probe experimental configuration, we systematically examine the double-pulse damage dynamics and relaxation process. The first pulse induces localized modifications that initiate a relaxation process, accumulating material damage caused by the subsequent pulse. Our results show that this relaxation lasts ∼500 ns for surface damage and is on a several millisecond scale for bulk damage. The second pulse induces more pronounced modifications and damage when Δtp is less than 100 ns, dominated by nonlinear phenomena like multiphoton absorption due to temporally overlapping pulses. Conversely, for Δtp>100 ns, thermal accumulation via phonon relaxation predominates. Additionally, the critical energy density for damage correlates positively with LIDT as Δtp increases, reflecting the reduced thermal and mechanical stress influence. These findings highlight the dynamic competition between nonlinear and thermal effects in multiple-pulse laser interactions, providing practical strategies for designing optical components with high damage thresholds and developing high-performance optical systems.The laser-induced damage threshold (LIDT) of optical elements is a critical limitation in advancing next-generation spaceborne laser technologies. Transient mechanisms in multiple-pulse damage dynamics have been recognized, but significant gaps remain in understanding these processes. In this study, we introduce a practice time interval (
Photonics Research
- Publication Date: Jul. 28, 2025
- Vol. 13, Issue 8, 2246 (2025)
Dielectric quarter-waveplate metasurfaces for longitudinally tunable manipulation of high-order Poincaré beams
Teng Ma, Kaixin Zhao, Chuanfu Cheng, Manna Gu... and Chen Cheng|Show fewer author(s)
The dynamic tunability of vector beams (VBs) with metasurfaces plays an important role in the discovery of exotic optical phenomena and development of classic and quantum applications. Using the tunability with longitudinal propagation distance and multifunctional capability of the quarter-waveplate (QWP) meta-atoms, dielectric metasurfaces were designed to generate high-order Poincaré (HOP) beams with tunable elliptical polarization states at arbitrary latitudes. The metasurface contained two interleaved sub-metasurfaces of QWP meta-atoms, each configured with helical, hyperbolic, and primary and secondary axicon-phase profiles to generate a vortex, beam focus, and beam deflection, respectively. Importantly, the axicons were suitably designed by combining the propagation and geometric phases to introduce differences in the z-component wavevectors, and the amplitudes of the co- and cross-polarized vortices were tuned by the longitudinal distance. The method broke through the limitation of previously generating only the linear polarization states on the equator of the HOP sphere, and it also circumvented the traditional tunability using the troublesome waveplate-polarizer combination. This study is of great significance for the miniaturization and integration of optical systems for applications such as optical communications, micromanipulation, and high-precision detection.The dynamic tunability of vector beams (VBs) with metasurfaces plays an important role in the discovery of exotic optical phenomena and development of classic and quantum applications. Using the tunability with longitudinal propagation distance and multifunctional capability of the quarter-waveplate (QWP) meta-atoms, dielectric metasurfaces were designed to generate high-order Poincaré (HOP) beams with tunable elliptical polarization states at arbitrary latitudes. The metasurface contained two interleaved sub-metasurfaces of QWP meta-atoms, each configured with helical, hyperbolic, and primary and secondary axicon-phase profiles to generate a vortex, beam focus, and beam deflection, respectively. Importantly, the axicons were suitably designed by combining the propagation and geometric phases to introduce differences in the
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2257 (2025)
Single-layer metasurface for snapshot high-dynamic-range imaging
Na Zhang, Qixuan Min, Xin Liu, Haiming Yuan... and Guohai Situ|Show fewer author(s)
Imaging systems based on metasurfaces have advantages in terms of integration and flexibility. Here, we present a single-layer metasurface for a snapshot high-dynamic-range (HDR) imaging scheme (SiM-SHDR). The metasurface can integrate functions of multiple components found in traditional HDR imaging systems. Benefiting from the polarization-independent full-space amplitude and phase control mechanism, the single-layer metasurface is capable of capturing multiple high-fidelity images with different levels of intensity in a single shot. After fusing the images, the dynamic range of the pictures can be effectively extended. Using a dual-channel image capture configuration with an intensity ratio of 10:1, the dynamic range can theoretically be enhanced by up to 20 dB. Experimental results in our demonstrated imaging system show the dynamic range improvement can reach 17.5 dB and even more. This metasurface design maintains a similar weight and volume to traditional single-image acquisition systems, making it ideal for lightweight, ultra-compact, and real-time HDR imaging in applications like surveillance, industrial manufacturing, and driving.Imaging systems based on metasurfaces have advantages in terms of integration and flexibility. Here, we present a single-layer metasurface for a snapshot high-dynamic-range (HDR) imaging scheme (SiM-SHDR). The metasurface can integrate functions of multiple components found in traditional HDR imaging systems. Benefiting from the polarization-independent full-space amplitude and phase control mechanism, the single-layer metasurface is capable of capturing multiple high-fidelity images with different levels of intensity in a single shot. After fusing the images, the dynamic range of the pictures can be effectively extended. Using a dual-channel image capture configuration with an intensity ratio of 10:1, the dynamic range can theoretically be enhanced by up to 20 dB. Experimental results in our demonstrated imaging system show the dynamic range improvement can reach 17.5 dB and even more. This metasurface design maintains a similar weight and volume to traditional single-image acquisition systems, making it ideal for lightweight, ultra-compact, and real-time HDR imaging in applications like surveillance, industrial manufacturing, and driving..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2270 (2025)
Precisely tapered fluorotellurite fiber-enabled Raman soliton relay fission for generating a 4–5 μ m mid-infrared high-power laser
Linjing Yang, Chuanfei Yao, Xuan Wang, Yamin Liu... and Pingxue Li|Show fewer author(s)
Ultra-broadband supercontinuum (SC) lasers covering the mid-infrared (MIR) region have significant applications in trace substance detection, national defense, and biomedical fields. Currently, high-power SC spanning 2–5 μm is still dominated by traditional fluoride (InF3) fibers. Although tellurite fibers, with their excellent chemical and thermal stability, have demonstrated significantly higher power scalability compared to other MIR fibers, their spectral broadening capabilities in the 4–5 μm region remain largely unexplored. Here, we demonstrate a >10 W ultra-broadband flat SC spanning the 1.8–5.1 μm spectral range in a fluorotellurite fiber using a cascaded soliton self-frequency shifting technique. The fluorotellurite fiber is precisely tapered to reconstruct dispersion and nonlinearity, which facilitates the evolution of the pre-stage Raman soliton into higher-order solitons, thereby enabling a new round of “rapid relay fission.” At a low pump power of 7.5 W, we also achieved a high-power (0.5 W) Raman soliton (60 fs) at 4.3 μm. These results, for the first time, to our knowledge, demonstrate that tapered fluorotellurite fibers can be used for high-power femtosecond pulse generation beyond 4 μm and high-power SC generation beyond 5 μm, establishing them as an exceptional nonlinear medium for the development of high-power MIR fiber lasers in the 4–5 μm spectral region.Ultra-broadband supercontinuum (SC) lasers covering the mid-infrared (MIR) region have significant applications in trace substance detection, national defense, and biomedical fields. Currently, high-power SC spanning 2–5 μm is still dominated by traditional fluoride (
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2281 (2025)
Optical footprint of ghost and leaky hyperbolic polaritons
Mark Cunningham, Adam L. Lafferty, Mario González-Jiménez, and Rair Macêdo
Manipulating hyperbolic polaritons at infrared frequencies has recently garnered interest as it promises to deliver new functionality for next-generation optical and photonic devices. This study investigates the impact of the crystal’s anisotropy orientation on the attenuated total reflection (ATR) spectra, more specifically, revealing the optical footprint of elliptical, ghost (GHP), and leaky (LHP) hyperbolic polaritons. Our findings reveal that the ATR spectra of GHPs exhibit a distinct hyperbolic behavior that is similar to that recently observed using s-SNOM techniques. Similarly, the ATR spectra of LHPs show its clear lenticular behavior; however, here we are able to discern the effects of large asymmetry due to cross polarization conversion when the crystal anisotropy is tilted away from the surface. Furthermore, we demonstrate that by controlling the anisotropy orientation of hyperbolic media it is possible to significantly alter the optical response of these polaritons. Thus, our results provide a foundation for the design of direction-dependent optical devices.Manipulating hyperbolic polaritons at infrared frequencies has recently garnered interest as it promises to deliver new functionality for next-generation optical and photonic devices. This study investigates the impact of the crystal’s anisotropy orientation on the attenuated total reflection (ATR) spectra, more specifically, revealing the optical footprint of elliptical, ghost (GHP), and leaky (LHP) hyperbolic polaritons. Our findings reveal that the ATR spectra of GHPs exhibit a distinct hyperbolic behavior that is similar to that recently observed using s-SNOM techniques. Similarly, the ATR spectra of LHPs show its clear lenticular behavior; however, here we are able to discern the effects of large asymmetry due to cross polarization conversion when the crystal anisotropy is tilted away from the surface. Furthermore, we demonstrate that by controlling the anisotropy orientation of hyperbolic media it is possible to significantly alter the optical response of these polaritons. Thus, our results provide a foundation for the design of direction-dependent optical devices..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2291 (2025)
THz-fiber waveguide composed of a biocompatible Vaseline core and Teflon holey cladding enabling a centimeter bending radius
Yong Soo Lee, Inhee Maeng, Mingyu Lee, Seokjin Kim... and Kyunghwan Oh|Show fewer author(s)
In this study, we introduce and experimentally validate, to our knowledge, a new type of terahertz (THz) fiber waveguide. The waveguide features a core made from petroleum jelly (commonly known as Vaseline) and a cladding made of holey polytetrafluoroethylene (PTFE), also known as Teflon. Since the core is biocompatible and the cladding is safe for human use, this design has promising applications for biocompatible probes in the THz range. We rigorously analyzed the transmission properties of the waveguide using the finite element method (FEM) and followed up with experimental validation using a THz time-domain spectroscopy (THz-TDS) system. The fiber supports single-mode operation for frequencies below 0.9 THz and demonstrates low-loss transmission of THz waves, even when tightly bent. For instance, with a bending radius as small as 1.61 cm, the fiber exhibited minimal losses of 0.23 dB/cm at 0.2 THz and 0.27 dB/cm at 0.5 THz, surpassing previous technical limitations. Another key advantage is the strong confinement of the THz waves within the petroleum jelly core, which helps maintain low dispersion and ensures stable pulse transmission, even under tight bends. The exceptional stability and flexibility of this biocompatible THz fiber make it highly suitable for sensing and imaging applications in confined, flexible environments, including potential uses within the human body.In this study, we introduce and experimentally validate, to our knowledge, a new type of terahertz (THz) fiber waveguide. The waveguide features a core made from petroleum jelly (commonly known as Vaseline) and a cladding made of holey polytetrafluoroethylene (PTFE), also known as Teflon. Since the core is biocompatible and the cladding is safe for human use, this design has promising applications for biocompatible probes in the THz range. We rigorously analyzed the transmission properties of the waveguide using the finite element method (FEM) and followed up with experimental validation using a THz time-domain spectroscopy (THz-TDS) system. The fiber supports single-mode operation for frequencies below 0.9 THz and demonstrates low-loss transmission of THz waves, even when tightly bent. For instance, with a bending radius as small as 1.61 cm, the fiber exhibited minimal losses of 0.23 dB/cm at 0.2 THz and 0.27 dB/cm at 0.5 THz, surpassing previous technical limitations. Another key advantage is the strong confinement of the THz waves within the petroleum jelly core, which helps maintain low dispersion and ensures stable pulse transmission, even under tight bends. The exceptional stability and flexibility of this biocompatible THz fiber make it highly suitable for sensing and imaging applications in confined, flexible environments, including potential uses within the human body..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2306 (2025)
Wearable nanoplasmonic sensor based on surface-enhanced Raman scattering for multiplexed analysis of sweat | On the Cover
Nan Wang, Youliang Weng, Yi Liu, Yangmin Wu... and Duo Lin|Show fewer author(s)
Wearable sweat sensors that enable non-invasive sampling, efficient and rapid detection, and real-time monitoring capabilities have become an integral and critical component of human health management, with the potential to provide meaningful clinical information related to physiologic diseases in the healthcare field. Here, a flexible nanoplasmonic paper-based sensor based on surface-enhanced Raman scattering (SERS) was developed, in which silver nanoparticles were loaded in the cellulose paper to enhance the Raman signals of targets via the generation of SERS “hotspots.” By incorporating the filter paper channel with a natural core absorbing liquid, the multifunctional chip is formed, which integrates the collection, transmission, and detection of trace sweat. This paper-based chip is soft and stretchable, and fits perfectly onto the human skin surface without causing any damage or irritation. Combined with a hand-held Raman spectrometer, quantitative detection of multiple sweat components can be achieved with the limit of detection of 17 and 1 μmol/L for uric acid and glucose, respectively, and the measurable range is 4–7.5 for pH, enabling wearable and in-situ optical sensing for sweat markers under the condition of human physiology and pathology, within only 5 min for uric acid and glucose detection. This wearable biosensor would provide, to our knowledge, a new way for continuously monitoring the health status by collection and analysis of multiple components in human sweat, contributing to point-of-care testing and personalized medicine applications.Wearable sweat sensors that enable non-invasive sampling, efficient and rapid detection, and real-time monitoring capabilities have become an integral and critical component of human health management, with the potential to provide meaningful clinical information related to physiologic diseases in the healthcare field. Here, a flexible nanoplasmonic paper-based sensor based on surface-enhanced Raman scattering (SERS) was developed, in which silver nanoparticles were loaded in the cellulose paper to enhance the Raman signals of targets via the generation of SERS “hotspots.” By incorporating the filter paper channel with a natural core absorbing liquid, the multifunctional chip is formed, which integrates the collection, transmission, and detection of trace sweat. This paper-based chip is soft and stretchable, and fits perfectly onto the human skin surface without causing any damage or irritation. Combined with a hand-held Raman spectrometer, quantitative detection of multiple sweat components can be achieved with the limit of detection of 17 and 1 μmol/L for uric acid and glucose, respectively, and the measurable range is 4–7.5 for pH, enabling wearable and in-situ optical sensing for sweat markers under the condition of human physiology and pathology, within only 5 min for uric acid and glucose detection. This wearable biosensor would provide, to our knowledge, a new way for continuously monitoring the health status by collection and analysis of multiple components in human sweat, contributing to point-of-care testing and personalized medicine applications..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2316 (2025)
Reconfigurable terahertz beam splitters enabled by inverse-designed meta-devices
Ming-Zhe Chong, Shao-Xin Huang, Zong-Kun Zhang, Peijie Feng... and Ming-Yao Xia|Show fewer author(s)
The beam splitter is one of the most crucial components in optical and electromagnetic systems, and it is also expected to be applied in terahertz (THz) technology. However, most existing beam splitters operate in only a single working mode, restricting their applications. This paper reports a method for the inverse design of a doublet meta-device consisting of two stacked metasurfaces functioning as a reconfigurable THz beam splitter. It is made of photo-curable high-temperature resin using 3D printing technology. By simply adjusting the relative rotation angles between the two metasurfaces to 0°, 90°, 180°, and 270°, the meta-device can produce four distinct focal patterns, thus achieving four different working modes. This scheme avoids introducing complicated active components, offering a simple, low-cost design of a signal divider in future 6G THz communication systems.The beam splitter is one of the most crucial components in optical and electromagnetic systems, and it is also expected to be applied in terahertz (THz) technology. However, most existing beam splitters operate in only a single working mode, restricting their applications. This paper reports a method for the inverse design of a doublet meta-device consisting of two stacked metasurfaces functioning as a reconfigurable THz beam splitter. It is made of photo-curable high-temperature resin using 3D printing technology. By simply adjusting the relative rotation angles between the two metasurfaces to 0°, 90°, 180°, and 270°, the meta-device can produce four distinct focal patterns, thus achieving four different working modes. This scheme avoids introducing complicated active components, offering a simple, low-cost design of a signal divider in future 6G THz communication systems..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2328 (2025)
Integrated ultra-large dynamic vibration sensing with fronthaul analog radio-over-fiber transmission
Jingchuan Wang, Junwei Zhang, Alan Pak Tao Lau, and Chao Lu
The utilization of optical fiber in fronthaul transmission within radio access networks (RANs) offers significant advantages in terms of high quality, stability, and long-reach capabilities. Simultaneously, distributed acoustic sensing (DAS) enables network surveillance and human activity detection through environmental monitoring. However, the implementation of large-scale strain measurement remains a challenge. In this paper, we propose a novel linear frequency modulated (LFM) pilot-aided radio OFDM fronthaul waveform specifically designed for integrated sensing and communication over fiber (ISACoF). The continuous LFM pilots facilitate the demodulation process at the communication side and serve as sensing probes to detect vibrations along the fiber using pulse compression techniques. Furthermore, by leveraging the large bandwidth of OFDM radio signals, the frequency-demodulated DAS enabled by multiple LFM pilots overcomes the limitations of traditional phase-demodulated DAS in scenarios involving large dynamic vibrations. We experimentally demonstrate the transmission of OFDM radio signals through a 10-km fiber and a 4-m free-space channel, assisted by 128 LFM pilots. By utilizing millimeter-wave (MMW) radio signals operating within a frequency range of 27.2 GHz to 29 GHz and a bandwidth of 1.8 GHz, dynamic vibration measurements of up to 6 με are achieved. Additionally, by optimizing the power ratio between OFDM payloads and LFM pilots, we achieve a sensing sensitivity of 0.81 nε/Hz and a demodulated signal-to-noise ratio of over 20 dB for 64-QAM-OFDM. Various modulation formats and vibration waveforms are validated via experiments, thereby confirming the feasibility of implementing the proposed ISACoF system in practical RAN design.The utilization of optical fiber in fronthaul transmission within radio access networks (RANs) offers significant advantages in terms of high quality, stability, and long-reach capabilities. Simultaneously, distributed acoustic sensing (DAS) enables network surveillance and human activity detection through environmental monitoring. However, the implementation of large-scale strain measurement remains a challenge. In this paper, we propose a novel linear frequency modulated (LFM) pilot-aided radio OFDM fronthaul waveform specifically designed for integrated sensing and communication over fiber (ISACoF). The continuous LFM pilots facilitate the demodulation process at the communication side and serve as sensing probes to detect vibrations along the fiber using pulse compression techniques. Furthermore, by leveraging the large bandwidth of OFDM radio signals, the frequency-demodulated DAS enabled by multiple LFM pilots overcomes the limitations of traditional phase-demodulated DAS in scenarios involving large dynamic vibrations. We experimentally demonstrate the transmission of OFDM radio signals through a 10-km fiber and a 4-m free-space channel, assisted by 128 LFM pilots. By utilizing millimeter-wave (MMW) radio signals operating within a frequency range of 27.2 GHz to 29 GHz and a bandwidth of 1.8 GHz, dynamic vibration measurements of up to
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2339 (2025)
Scalable integrated optical switch matrix using ultra-compact thermally tunable dual micro-disk resonators
Lang Zhou, Bin Wang, Yuwen Xu, and Weifeng Zhang
Optical switch matrices are critical components in data centers, telecommunications, and advanced computing systems, facilitating dynamic and flexible routing of optical signals to support the increasing demands of data transmission. As data traffic escalates exponentially, scalability of these matrices becomes paramount. However, the constrained physical space necessitates high integration density, which poses significant challenges related to switching element size and thermal crosstalk, particularly in thermally driven optical switch matrices. In this paper, we propose a scalable optical switch matrix employing ultra-compact thermally tunable micro-disk resonators (MDRs). At each waveguide crossing, dual MDRs are strategically placed to support multiple direction routings, thereby enabling rearrangeable non-blocking connectivity and increasing input/output (I/O) port density. To mitigate thermal crosstalk between adjacent MDRs, specifically engineered routing waveguides are integrated into the matrix. A proof-of-concept silicon photonic 1×8×2λ switch chip is fabricated and evaluated. With the use of the chip, an optical data transmission is experimentally demonstrated. The proposed switch matrix exhibits strong scalability and significantly reduced thermal crosstalk, showcasing its potential for future optical interconnection networks.Optical switch matrices are critical components in data centers, telecommunications, and advanced computing systems, facilitating dynamic and flexible routing of optical signals to support the increasing demands of data transmission. As data traffic escalates exponentially, scalability of these matrices becomes paramount. However, the constrained physical space necessitates high integration density, which poses significant challenges related to switching element size and thermal crosstalk, particularly in thermally driven optical switch matrices. In this paper, we propose a scalable optical switch matrix employing ultra-compact thermally tunable micro-disk resonators (MDRs). At each waveguide crossing, dual MDRs are strategically placed to support multiple direction routings, thereby enabling rearrangeable non-blocking connectivity and increasing input/output (I/O) port density. To mitigate thermal crosstalk between adjacent MDRs, specifically engineered routing waveguides are integrated into the matrix. A proof-of-concept silicon photonic
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2352 (2025)
Fully recoverable fiber lasers under radiation enabled by in-situ blue light photobleaching
Guangbiao Xiang, Hanwei Zhang, Xiaolin Wang, Jiangbin Zhang... and Jinbao Chen|Show fewer author(s)
Fiber lasers are increasingly employed in radiative environments, such as outer space and nuclear facilities. However, their performance is significantly compromised under irradiation due to the accumulation of defects in fiber components. Despite various radiation-hardening strategies, including optimized fiber designs and post-treatment techniques, these approaches have been unable to fully mitigate performance degradation. In this study, we demonstrate near 100% power recovery in a 150 W fiber laser exposed to radiation, achieved through an in-situ photobleaching technique utilizing low-power blue light. This all-fiber photobleaching strategy not only restores laser performance but also provides a robust, compact, and scalable solution for developing high-performance radiation-resistant fiber lasers. The proposed approach holds significant potential for advancing laser applications in challenging radiative environments, such as space exploration, nuclear power plants, and medical radiotherapy.Fiber lasers are increasingly employed in radiative environments, such as outer space and nuclear facilities. However, their performance is significantly compromised under irradiation due to the accumulation of defects in fiber components. Despite various radiation-hardening strategies, including optimized fiber designs and post-treatment techniques, these approaches have been unable to fully mitigate performance degradation. In this study, we demonstrate near 100% power recovery in a 150 W fiber laser exposed to radiation, achieved through an in-situ photobleaching technique utilizing low-power blue light. This all-fiber photobleaching strategy not only restores laser performance but also provides a robust, compact, and scalable solution for developing high-performance radiation-resistant fiber lasers. The proposed approach holds significant potential for advancing laser applications in challenging radiative environments, such as space exploration, nuclear power plants, and medical radiotherapy..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2362 (2025)
Reconfigurable chiral quasi-bound states in the continuum metasurfaces based on an asymmetric interface | Editors' Pick
Xiaofen Zeng, Kejian Chen, Yang Shen, Qian Wang... and Songlin Zhuang|Show fewer author(s)
In this paper, a method to excite chiral quasi-bound states in the continuum (Q-BICs) using an asymmetric interface is proposed for the first time, to our knowledge. The chirality of a metasurface can be controlled by varying the medium of the active layer, achieving a maximum circular dichroism (CD) value of 0.9. Two types of reconfigurable chiral Q-BIC metasurfaces, a single-biased chiral Q-BIC metasurface (SBCBM) and a dual-biased chiral Q-BIC metasurface (DBCBM), are proposed, facilitated by the use of the electronically controlled material polyaniline (PANI). This enables electrically reconfigurable chiral Q-BIC with a maximum CD variability range from -0.9 to +0.9. These results highlight significant potential applications in fields such as reconfigurable devices, optical chiral switching, and environmental monitoring.In this paper, a method to excite chiral quasi-bound states in the continuum (Q-BICs) using an asymmetric interface is proposed for the first time, to our knowledge. The chirality of a metasurface can be controlled by varying the medium of the active layer, achieving a maximum circular dichroism (CD) value of 0.9. Two types of reconfigurable chiral Q-BIC metasurfaces, a single-biased chiral Q-BIC metasurface (SBCBM) and a dual-biased chiral Q-BIC metasurface (DBCBM), are proposed, facilitated by the use of the electronically controlled material polyaniline (PANI). This enables electrically reconfigurable chiral Q-BIC with a maximum CD variability range from
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2371 (2025)
High-efficiency ultraviolet generation in a resonance-free anti-resonant hollow-core fiber
Daiqi Xiong, Yuxi Wang, Ruhai Bai, Zhixun Wang... and Wonkeun Chang|Show fewer author(s)
We report the first demonstration of high-efficiency ultraviolet (UV) pulse generation in a resonance-free anti-resonant hollow-core fiber (AR-HCF). Using the wet-etching technique, we successfully reduced the cladding-tube wall thickness of the AR-HCF to 115 nm, thereby eliminating all cladding-induced structural resonances between the near-infrared pump and the deep UV wavelengths. This structural modification fundamentally suppresses competing conversion to other phase-matching points induced by structural resonances and mitigates the pump spectral broadening limitation, achieving a UV conversion efficiency as high as 12%—twice that of previous demonstrations in gas-filled AR-HCFs. This UV conversion efficiency is comparable to that of meter-scale gas-filled capillaries that require pump pulse energy of hundreds of microjoules while also maintaining the AR-HCF’s inherent advantages of centimeter-scale compactness and low pump energy at the few microjoule level.We report the first demonstration of high-efficiency ultraviolet (UV) pulse generation in a resonance-free anti-resonant hollow-core fiber (AR-HCF). Using the wet-etching technique, we successfully reduced the cladding-tube wall thickness of the AR-HCF to 115 nm, thereby eliminating all cladding-induced structural resonances between the near-infrared pump and the deep UV wavelengths. This structural modification fundamentally suppresses competing conversion to other phase-matching points induced by structural resonances and mitigates the pump spectral broadening limitation, achieving a UV conversion efficiency as high as 12%—twice that of previous demonstrations in gas-filled AR-HCFs. This UV conversion efficiency is comparable to that of meter-scale gas-filled capillaries that require pump pulse energy of hundreds of microjoules while also maintaining the AR-HCF’s inherent advantages of centimeter-scale compactness and low pump energy at the few microjoule level..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2377 (2025)
Compact optical frequency standard using a wafer-level MEMS vapor cell
Qiaohui Yang, Zhenyu Hu, Tianyu Liu, Jie Miao... and Jingbiao Chen|Show fewer author(s)
Atomic clocks represent the most advanced instruments for providing time-frequency standards, with increasing demand for designs that offer high frequency stability while minimizing size. Central to an atomic clock’s function is the atomic vapor cell, which serves as the quantum reference. Compared to traditional cells, wafer-level micro-electro-mechanical systems (MEMS) vapor cells enable cost-effective, scalable production and facilitate integration with silicon-based chips. In this work, we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure. A single wafer is used to fabricate 24 identical atomic vapor cells, each with precise dimensions of 14 mm×14 mm×4.3 mm, ensuring scalability. We demonstrate an optical frequency standard that combines modulation transfer spectroscopy (MTS) with a MEMS vapor cell, featuring a compact design with excellent performance. This frequency standard achieves stability over averaging times of 1–400 s, with short-term stability of 2.6×10-13 at 1 s and 5.1×10-14 at 200 s. The laser linewidth is only 3.9 kHz, marking a substantial improvement over existing thermal standards, and opening potential applications in navigation, radar, and precision measurement. This work provides a crucial step toward the development of chip-scale optical clocks.Atomic clocks represent the most advanced instruments for providing time-frequency standards, with increasing demand for designs that offer high frequency stability while minimizing size. Central to an atomic clock’s function is the atomic vapor cell, which serves as the quantum reference. Compared to traditional cells, wafer-level micro-electro-mechanical systems (MEMS) vapor cells enable cost-effective, scalable production and facilitate integration with silicon-based chips. In this work, we present a wafer-level MEMS vapor cell featuring an innovative silicon-glass-silicon transverse optical path structure. A single wafer is used to fabricate 24 identical atomic vapor cells, each with precise dimensions of
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2384 (2025)
Rapid imaging of chaotic modes in optical microcavities
Zi Wang, Ziyu Li, Ziheng Ji, Shumin Xiao, and Qinghai Song
Identifying optical modes in chaotic cavities is crucial for exploring and understanding the physical mechanisms inside them. Compared with free spectral range estimation, the direct imaging technique has the capability of providing more precise mode information, but it is extremely time-consuming and susceptible to environmental perturbations. Here we report a high-speed imaging technique for visualizing field distributions in chaotic microcavities. When a silicon microdisk is excited by a femtosecond laser, free carriers are locally generated, thereby reducing the refractive index. Under a constant laser power, the spatial distribution of mode inside the silicon microdisk is proportional to its wavelength shift and can be precisely identified by comparing it with numerical simulation. With the assistance of a galvanometer, imaging a mode profile only takes a few hundred milliseconds to a few seconds, orders of magnitude faster than previous reports. The impacts of slight fabrication deviations on spectra have also been identified.Identifying optical modes in chaotic cavities is crucial for exploring and understanding the physical mechanisms inside them. Compared with free spectral range estimation, the direct imaging technique has the capability of providing more precise mode information, but it is extremely time-consuming and susceptible to environmental perturbations. Here we report a high-speed imaging technique for visualizing field distributions in chaotic microcavities. When a silicon microdisk is excited by a femtosecond laser, free carriers are locally generated, thereby reducing the refractive index. Under a constant laser power, the spatial distribution of mode inside the silicon microdisk is proportional to its wavelength shift and can be precisely identified by comparing it with numerical simulation. With the assistance of a galvanometer, imaging a mode profile only takes a few hundred milliseconds to a few seconds, orders of magnitude faster than previous reports. The impacts of slight fabrication deviations on spectra have also been identified..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2393 (2025)
Inherent non-Hermitian Chern insulators with PT-symmetry and synthetic translation dimension
Ke-Xin Sun, Jian-Wen Dong, and Wen-Jie Chen
The introduction of non-Hermiticity provides photonic systems with more design degrees of freedom, along with unique properties, which have aroused widespread interest. On the other hand, the concept of synthetic dimensions has also been introduced into non-Hermitian topological physics. In this work, we theoretically investigate the two-dimensional (2D) band structure of a 1D non-Hermitian photonic crystal (PC) by introducing globally a translation deformation as a synthetic dimension. The resulting two-dimensional photonic crystal is a Chern insulator, which is numerically verified by calculated Chern numbers and edge dispersions. We find that this property stems from the inherent topology of synthetic space (kx,Δx), which does not depend on the crystal’s structural and material parameters. It guarantees robust edge states traversing the gap along the synthetic dimension. To provide deeper insight, we derive the reflection phase of a 1D crystal using the plane wave expansion method and give a clear physical picture of the topological edge states generated by translation deformation. These findings may pave the way for translation-based photonic devices, including topological filters and lasers.The introduction of non-Hermiticity provides photonic systems with more design degrees of freedom, along with unique properties, which have aroused widespread interest. On the other hand, the concept of synthetic dimensions has also been introduced into non-Hermitian topological physics. In this work, we theoretically investigate the two-dimensional (2D) band structure of a 1D non-Hermitian photonic crystal (PC) by introducing globally a translation deformation as a synthetic dimension. The resulting two-dimensional photonic crystal is a Chern insulator, which is numerically verified by calculated Chern numbers and edge dispersions. We find that this property stems from the inherent topology of synthetic space (
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2400 (2025)
On-chip ultra-high-Q optical microresonators approaching the material absorption limit | Spotlight on Optics
Qi Shi, Jianxiong Tian, Shulin Ding, Yunan Wang... and Xiaoshun Jiang|Show fewer author(s)
Chip-based optical microresonators with ultra-high Q-factors are becoming increasingly important to a variety of applications. However, the losses of on-chip microresonators with the highest Q-factor reported in the past are still far from their material absorption limits. Here, we demonstrate an on-chip silica microresonator that has approached the absorption limit of the state-of-the-art material on chip, realizing, to our knowledge, record intrinsic Q-factors exceeding 3 billion at both 1560 nm and 1064 nm. This fact is corroborated by photo-thermal spectroscopy measurements. Especially, compared with the standard optical fibers, its corresponding optical losses are only 38.4 times and 7.7 times higher at the wavelengths of 1560 nm and 1064 nm, respectively. To exhibit the performance of such fabricated microresonator, we achieve a record-low optical parametric oscillation threshold (31.9 μW) for millimeter-sized microresonators and generate a single-soliton microcomb with a record-low pump power of 220.2 μW for all soliton microcombs realized thus far.Chip-based optical microresonators with ultra-high Q-factors are becoming increasingly important to a variety of applications. However, the losses of on-chip microresonators with the highest Q-factor reported in the past are still far from their material absorption limits. Here, we demonstrate an on-chip silica microresonator that has approached the absorption limit of the state-of-the-art material on chip, realizing, to our knowledge, record intrinsic Q-factors exceeding 3 billion at both 1560 nm and 1064 nm. This fact is corroborated by photo-thermal spectroscopy measurements. Especially, compared with the standard optical fibers, its corresponding optical losses are only 38.4 times and 7.7 times higher at the wavelengths of 1560 nm and 1064 nm, respectively. To exhibit the performance of such fabricated microresonator, we achieve a record-low optical parametric oscillation threshold (31.9 μW) for millimeter-sized microresonators and generate a single-soliton microcomb with a record-low pump power of 220.2 μW for all soliton microcombs realized thus far..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2409 (2025)
Self-supervised denoising for enhanced volumetric reconstruction and signal interpretation in two-photon microscopy
Jie Li, Liangpeng Wei, and Xin Zhao
Volumetric imaging is increasingly in demand for its precision in statistically visualizing and analyzing the intricacies of biological phenomena. To visualize the intricate details of these minute structures and facilitate the analysis in biomedical research, high-signal-to-noise ratio (SNR) images are indispensable. However, the inevitable noise presents a significant barrier to imaging qualities. Here, we propose SelfMirror, a self-supervised deep-learning denoising method for volumetric image reconstruction. SelfMirror is developed based on the insight that the variation of biological structure is continuous and smooth; when the sampling interval in volumetric imaging is sufficiently small, the similarity of neighboring slices in terms of the spatial structure becomes apparent. Such similarity can be used to train our proposed network to revive the signals and suppress the noise accurately. The denoising performance of SelfMirror exhibits remarkable robustness and fidelity even in extremely low-SNR conditions. We demonstrate the broad applicability of SelfMirror on multiple imaging modalities, including two-photon microscopy, confocal microscopy, expansion microscopy, computed tomography, and 3D electron microscopy. This versatility extends from single neuron cells to tissues and organs, highlighting SelfMirror’s potential for integration into diverse imaging and analysis pipelines.Volumetric imaging is increasingly in demand for its precision in statistically visualizing and analyzing the intricacies of biological phenomena. To visualize the intricate details of these minute structures and facilitate the analysis in biomedical research, high-signal-to-noise ratio (SNR) images are indispensable. However, the inevitable noise presents a significant barrier to imaging qualities. Here, we propose SelfMirror, a self-supervised deep-learning denoising method for volumetric image reconstruction. SelfMirror is developed based on the insight that the variation of biological structure is continuous and smooth; when the sampling interval in volumetric imaging is sufficiently small, the similarity of neighboring slices in terms of the spatial structure becomes apparent. Such similarity can be used to train our proposed network to revive the signals and suppress the noise accurately. The denoising performance of SelfMirror exhibits remarkable robustness and fidelity even in extremely low-SNR conditions. We demonstrate the broad applicability of SelfMirror on multiple imaging modalities, including two-photon microscopy, confocal microscopy, expansion microscopy, computed tomography, and 3D electron microscopy. This versatility extends from single neuron cells to tissues and organs, highlighting SelfMirror’s potential for integration into diverse imaging and analysis pipelines..
Photonics Research
- Publication Date: Aug. 01, 2025
- Vol. 13, Issue 8, 2418 (2025)
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