Contents
2025
Volume: 13 Issue 7
22 Article(s)
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INNOVATIVE OPTICAL SENSOR SYSTEMS
Parallel sensing of multiple greenhouse gases adopting a mid-infrared dual-comb spectrometer with 300,000 comb-tooth-resolved frequency components
Daping Luo, Lian Zhou, Zefeng Wang, Zejiang Deng... and Wenxue Li|Show fewer author(s)
Mid-infrared (MIR) spectroscopy is instrumental in addressing gas molecule-related environmental and ecological challenges. Especially, massively parallel sensing capability is critical to multi-species molecules analysis, enabling the demands for various MIR gas characterizations. However, real-time, high-accuracy parallel sensing for multiple gases remains a significant challenge due to the limitations in laser bandwidth and sampling speed. Here, we present a broadband MIR dual-comb spectrometer for the simultaneous detection of multiple greenhouse gases. This MIR spectrometer employs a scheme of difference frequency generation (DFG), directly producing a wide spectrum spanning 3.2–4.7 μm with over 300,000 comb-tooth-resolved frequency lines at a 100 MHz resolution. In addition, we demonstrated the parallel detection of four mixed gas molecules (CH4, C2H2, CO, and N2O), in which the absorptions were in excellent agreement with HITRAN database. This broadband MIR dual-comb spectrometer is promising to be integrated with only fiber devices and periodically poled lithium niobate waveguides, providing a high-precision, high-efficiency approach for massively parallel sensing in atmospheric or industrial monitoring.Mid-infrared (MIR) spectroscopy is instrumental in addressing gas molecule-related environmental and ecological challenges. Especially, massively parallel sensing capability is critical to multi-species molecules analysis, enabling the demands for various MIR gas characterizations. However, real-time, high-accuracy parallel sensing for multiple gases remains a significant challenge due to the limitations in laser bandwidth and sampling speed. Here, we present a broadband MIR dual-comb spectrometer for the simultaneous detection of multiple greenhouse gases. This MIR spectrometer employs a scheme of difference frequency generation (DFG), directly producing a wide spectrum spanning 3.2–4.7 μm with over 300,000 comb-tooth-resolved frequency lines at a 100 MHz resolution. In addition, we demonstrated the parallel detection of four mixed gas molecules (
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, A1 (2025)
Research Articles
Holography, Gratings, and Diffraction
Lightweight holographic near-eye display system with self-charging capability using solar energy
Changyu Wang, Yuan Xu, Hong Xu, and Juan Liu
The near-eye display feature in emerging spatial computing systems produces a distinctive visual effect of mixing virtual and real worlds. However, its application for all-day wear is greatly limited by the bulky structure, energy expenditure, and continuous battery heating. Here, we propose a lightweight holographic near-eye display system that takes advantage of solar energy for self-charging. To guarantee the collection of solar energy and near-eye display without crosstalk, we implement holographic optical elements (HOEs) to diffract sunlight and signal light into a common waveguide. Then, small-area solar cells convert the collected solar energy and power the system. Compact power supply components replace heavy batteries, thus contributing to the lightweight design. The simple acquisition and management of solar energy provide the system with sustainable self-charging capability. We believe that the lightweight design and continuous energy input solution will significantly promote the popularity of near-eye display in our daily lives.The near-eye display feature in emerging spatial computing systems produces a distinctive visual effect of mixing virtual and real worlds. However, its application for all-day wear is greatly limited by the bulky structure, energy expenditure, and continuous battery heating. Here, we propose a lightweight holographic near-eye display system that takes advantage of solar energy for self-charging. To guarantee the collection of solar energy and near-eye display without crosstalk, we implement holographic optical elements (HOEs) to diffract sunlight and signal light into a common waveguide. Then, small-area solar cells convert the collected solar energy and power the system. Compact power supply components replace heavy batteries, thus contributing to the lightweight design. The simple acquisition and management of solar energy provide the system with sustainable self-charging capability. We believe that the lightweight design and continuous energy input solution will significantly promote the popularity of near-eye display in our daily lives..
Photonics Research
- Publication Date: Jun. 13, 2025
- Vol. 13, Issue 7, 1792 (2025)
Image Processing and Image Analysis
Super-wide-field-of-view long-wave infrared gaze polarization imaging embedded in a multi-strategy detail feature extraction and fusion network
Dongdong Shi, Jinhang Zhang, Jun Zou, Fuyu Huang... and Gang Li|Show fewer author(s)
Recently, infrared polarization imaging technology has become a research hotspot due to its ability to better resolve the physicochemical properties of objects and significantly enhance the target characteristics. However, the traditional infrared polarization imaging is limited to similar imaging mechanism restrictions, and it is difficult to acquire the polarization information of a wide-area posture in real time. Therefore, we report a combination of hardware and software for super-wide-field-of-view long-wave infrared gaze polarization imaging technology. Utilizing the non-similar imaging theory and adopting the inter-lens coupling holographic line-grid infrared polarization device scheme, we designed the infrared gazing polarized lens with a field-of-view of over 160°. Based on the fusion of infrared intensity images and infrared polarization images, a multi-strategy detail feature extraction and fusion network is constructed. Super-wide-field-of-view (150°×120°), large face array (1040×830), detail-rich infrared fusion images are acquired during the test. We have accomplished the tasks of vehicle target detection and infrared camouflage target recognition efficiently using the fusion images, and verified the superiority of recognizing far-field targets. Our implementation should enable and empower applications in machine vision, intelligent driving, and target detection under complex environments.Recently, infrared polarization imaging technology has become a research hotspot due to its ability to better resolve the physicochemical properties of objects and significantly enhance the target characteristics. However, the traditional infrared polarization imaging is limited to similar imaging mechanism restrictions, and it is difficult to acquire the polarization information of a wide-area posture in real time. Therefore, we report a combination of hardware and software for super-wide-field-of-view long-wave infrared gaze polarization imaging technology. Utilizing the non-similar imaging theory and adopting the inter-lens coupling holographic line-grid infrared polarization device scheme, we designed the infrared gazing polarized lens with a field-of-view of over 160°. Based on the fusion of infrared intensity images and infrared polarization images, a multi-strategy detail feature extraction and fusion network is constructed. Super-wide-field-of-view (
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1902 (2025)
Imaging Systems, Microscopy, and Displays
1725-nm HOPE for segmentation-enabled quantitative photoacoustic microscopy of intrahepatic lipids
Najia Sharmin, Huajun Tang, Chandra Jinata, Ningbo Chen... and Kenneth K. Y. Wong|Show fewer author(s)
Photoacoustic microscopy (PAM) operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues. Despite its potential, the effectiveness of lipid-based PAM has been limited by the performance of existing nanosecond laser sources at this wavelength. In this work, we introduce a 1725-nm hybrid optical parametric oscillator emitter (HOPE) characterized by a narrow bandwidth of 1.4 nm, an optical signal-to-noise ratio (OSNR) of approximately 34 dB, and a high spectral energy density of up to 480 nJ/nm. This advanced laser source significantly enhances the sensitivity of photoacoustic imaging, allowing for the detailed visualization of intrahepatic lipid distributions with an impressive maximal contrast ratio of 23.6:1. Additionally, through segmentation-based analysis of PAM images, we were able to determine steatosis levels that align with clinical assessments, thereby demonstrating the potential of our system for high-contrast, label-free lipid quantification. Our findings suggest that the proposed 1725-nm HOPE source could be a powerful tool for biomedical research and clinical diagnostics, offering a substantial improvement over current technologies in the accurate and non-invasive assessment of lipid accumulation in tissues.Photoacoustic microscopy (PAM) operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues. Despite its potential, the effectiveness of lipid-based PAM has been limited by the performance of existing nanosecond laser sources at this wavelength. In this work, we introduce a 1725-nm hybrid optical parametric oscillator emitter (HOPE) characterized by a narrow bandwidth of 1.4 nm, an optical signal-to-noise ratio (OSNR) of approximately 34 dB, and a high spectral energy density of up to 480 nJ/nm. This advanced laser source significantly enhances the sensitivity of photoacoustic imaging, allowing for the detailed visualization of intrahepatic lipid distributions with an impressive maximal contrast ratio of 23.6:1. Additionally, through segmentation-based analysis of PAM images, we were able to determine steatosis levels that align with clinical assessments, thereby demonstrating the potential of our system for high-contrast, label-free lipid quantification. Our findings suggest that the proposed 1725-nm HOPE source could be a powerful tool for biomedical research and clinical diagnostics, offering a substantial improvement over current technologies in the accurate and non-invasive assessment of lipid accumulation in tissues..
Photonics Research
- Publication Date: Jun. 13, 2025
- Vol. 13, Issue 7, 1810 (2025)
Latent-wavefront Fourier ptychography for stained tissue microscopy
Shuhe Zhang, Jiayun Li, and Liangcai Cao
Fourier ptychographic microscopy (FPM) is a promising technique for achieving high-resolution and large field-of-view imaging, which is particularly suitable for pathological applications, such as imaging hematoxylin and eosin (H&E) stained tissues with high space-bandwidth and reduced artifacts. However, current FPM implementations require either precise system calibration and high-quality raw data, or significant computational loads due to iterative algorithms, which limits the practicality of FPM in routine pathological examinations. In this work, latent wavefront denoting the unobservable exiting wave at the surface of the sensor is introduced. A latent wavefront physical model optimized with variational expectation maximization (VEM) is proposed to tackle the inverse problem of FPM. The VEM-FPM alternates between solving a non-convex optimization problem as the main task for the latent wavefront in the spatial domain and merging together their Fourier spectrum in the Fourier plane as an intermediate product by solving a convex closed-formed Fourier space optimization. The VEM-FPM approach enables a stitching-free, full-field reconstruction for Fourier ptychography over a 5.3 mm×5.3 mm field of view, using a 2.5× objective with a numerical aperture (NA) of 0.08. The synthetic aperture achieves a resolution equivalent to 0.53 NA at 532 nm wavelength. The execution speed of VEM-FPM is twice as fast as that of state-of-the-art feature-domain methods while maintaining comparable reconstruction quality.Fourier ptychographic microscopy (FPM) is a promising technique for achieving high-resolution and large field-of-view imaging, which is particularly suitable for pathological applications, such as imaging hematoxylin and eosin (H&E) stained tissues with high space-bandwidth and reduced artifacts. However, current FPM implementations require either precise system calibration and high-quality raw data, or significant computational loads due to iterative algorithms, which limits the practicality of FPM in routine pathological examinations. In this work, latent wavefront denoting the unobservable exiting wave at the surface of the sensor is introduced. A latent wavefront physical model optimized with variational expectation maximization (VEM) is proposed to tackle the inverse problem of FPM. The VEM-FPM alternates between solving a non-convex optimization problem as the main task for the latent wavefront in the spatial domain and merging together their Fourier spectrum in the Fourier plane as an intermediate product by solving a convex closed-formed Fourier space optimization. The VEM-FPM approach enables a stitching-free, full-field reconstruction for Fourier ptychography over a
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1893 (2025)
Simultaneous multicolor imaging using off-axis spectral encoding in a single camera without sacrificing frame rate
Jiangjiang Zhao, Jing Zhang, Zhangheng Ding, Bolin Lu... and Jing Yuan|Show fewer author(s)
Multicolor imaging has been widely applied across various biological and medical applications, especially essential for probing diverse biological structures. However, existing multicolor imaging methods often sacrifice either simultaneity or speed, posing a challenge for simultaneous imaging of over three fluorophores. Here, we proposed off-axis spectral encoding multicolor microscopy (OSEM) with a single camera that simultaneously captures encoded multicolor signals and reconstructs monochromatic images by decoding. Based on the natural intensity modulation difference of a single illumination spot across off-axis detection positions, we adjusted the multicolor excitation beams with distinct off-axis offsets from the same detection position to achieve spectral encoding. The method achieved multicolor simultaneous imaging in a single camera without extra sacrifice of frame rate. We evaluated OSEM’s imaging performance by imaging multicolor synthetic samples and fluorescent microbeads. We also demonstrated that OSEM reduced imaging time by 5.8 times and achieved 99% accuracy in classifying and counting multicolor fluorescent bacteria, outperforming sequential imaging. We obtained four-color fluorescent optical-sectioning images of a mouse brain slice at a speed of 2.85 mm2/s, demonstrating its effectiveness for high-throughput multicolor imaging of large tissue samples. These results indicate that OSEM offers a reliable and efficient tool for multicolor fluorescent imaging of large biological tissues.Multicolor imaging has been widely applied across various biological and medical applications, especially essential for probing diverse biological structures. However, existing multicolor imaging methods often sacrifice either simultaneity or speed, posing a challenge for simultaneous imaging of over three fluorophores. Here, we proposed off-axis spectral encoding multicolor microscopy (OSEM) with a single camera that simultaneously captures encoded multicolor signals and reconstructs monochromatic images by decoding. Based on the natural intensity modulation difference of a single illumination spot across off-axis detection positions, we adjusted the multicolor excitation beams with distinct off-axis offsets from the same detection position to achieve spectral encoding. The method achieved multicolor simultaneous imaging in a single camera without extra sacrifice of frame rate. We evaluated OSEM’s imaging performance by imaging multicolor synthetic samples and fluorescent microbeads. We also demonstrated that OSEM reduced imaging time by 5.8 times and achieved 99% accuracy in classifying and counting multicolor fluorescent bacteria, outperforming sequential imaging. We obtained four-color fluorescent optical-sectioning images of a mouse brain slice at a speed of
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1925 (2025)
Unsupervised reconstruction with low-rank tensor embedding based on spatial-intensity-temporal constraints for compressed ultrafast photography
Haoyu Zhou, Zhiming Yao, Wenpei Yang, Dongwei Hei... and Yan Song|Show fewer author(s)
Compressed ultrafast photography (CUP) is a computational imaging technique that can simultaneously achieve an imaging speed of 1013 frames per second and a sequence depth of hundreds of frames. It is a powerful tool for observing unrepeatable ultrafast physical processes. However, since the forward model of CUP is a data compression process, the reconstruction process is an ill-posed problem. This causes inconvenience in the practical application of CUP, especially in those scenes with complex temporal behavior, high noise level and compression ratio. In this paper, the CUP system model based on spatial-intensity-temporal constraints is proposed by adding an additional charge-coupled device (CCD) camera to constrain the spatial and intensity behaviors of the dynamic scene and an additional narrow-slit streak camera to constrain the temporal behavior of the dynamic scene. Additionally, the unsupervised deep learning CUP reconstruction algorithm with low-rank tensor embedding is also proposed. The algorithm enhances the low-rankness of the reconstructed image by maintaining the low-rank structure of the dynamic scene and effectively utilizes the implicit prior information of the neural network and the hardware physical model. The proposed joint learning model enables high-quality reconstruction of complex dynamic scenes without training datasets. The simulation and experimental results demonstrate the application prospect of the proposed joint learning model in complex ultrafast physical phenomena imaging.Compressed ultrafast photography (CUP) is a computational imaging technique that can simultaneously achieve an imaging speed of
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1936 (2025)
Multi-angle illumination imaging by using iterative kernel correction
Wanxue Wei, Muyang Zhang, Zhuoqun Yuan, Weike Wang... and Kebin Shi|Show fewer author(s)
Multi-angle illumination is a widely adopted strategy in various super-resolution imaging systems, where improving computational efficiency and signal-to-noise ratio (SNR) remains a critical challenge. In this study, we propose the integration of the iterative kernel correction (IKC) algorithm with a multi-angle (MA) illumination scheme to enhance imaging reconstruction efficiency and SNR. The proposed IKC-MA scheme demonstrates the capability to significantly reduce image acquisition time while achieving high-quality reconstruction within 1 s, without relying on extensive experimental datasets. This ensures broad applicability across diverse imaging scenarios. Experimental results indicate substantial improvements in imaging speed and quality compared to conventional methods, with the IKC-MA model achieving a remarkable reduction in data acquisition time. This approach offers a faster and more generalizable solution for super-resolution microscopic imaging, paving the way for advancements in real-time imaging applications.Multi-angle illumination is a widely adopted strategy in various super-resolution imaging systems, where improving computational efficiency and signal-to-noise ratio (SNR) remains a critical challenge. In this study, we propose the integration of the iterative kernel correction (IKC) algorithm with a multi-angle (MA) illumination scheme to enhance imaging reconstruction efficiency and SNR. The proposed IKC-MA scheme demonstrates the capability to significantly reduce image acquisition time while achieving high-quality reconstruction within 1 s, without relying on extensive experimental datasets. This ensures broad applicability across diverse imaging scenarios. Experimental results indicate substantial improvements in imaging speed and quality compared to conventional methods, with the IKC-MA model achieving a remarkable reduction in data acquisition time. This approach offers a faster and more generalizable solution for super-resolution microscopic imaging, paving the way for advancements in real-time imaging applications..
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1973 (2025)
Instrumentation and Measurements
Fourier domain mode-locked optoelectronic oscillator with an electrically tuned thin-film lithium niobate micro-ring filter | Editors' Pick
Peng Hao, Rui Ma, Zihan Shi, Zijun Huang... and X. Steve Yao|Show fewer author(s)
Linearly chirped microwave waveforms (LCMWs) are indispensable in advanced radar systems. Our study introduces and validates, through extensive experimentation, the innovative application of a thin-film lithium niobate (TFLN) photonic integrated circuit (PIC) to realize a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) for generating high-precision LCMW signals. This integrated chip combines a phase modulator (PM) and an electrically tuned notch micro-ring resonator (MRR), which functions as a rapidly tunable bandpass filter, facilitating the essential phase-to-intensity modulation (PM-IM) conversion for OEO oscillation. By synchronizing the modulation period of the applied driving voltage to the MRR with the OEO loop delay, we achieve Fourier domain mode-locking, producing LCMW signals with an impressive tunable center frequency range of 18.55 GHz to 23.59 GHz, an adjustable sweep bandwidth from 3.85 GHz to 8.5 GHz, and a remarkable chirp rate up to 3.22 GHz/μs. Unlike conventional PM-IM based FDML OEOs, our device obviates the need for expensive tunable lasers or microwave sources, positioning it as a practical solution for generating high-frequency LCMW signals with extended sweep bandwidth and high chirp rates, all within a compact and cost-efficient form factor.Linearly chirped microwave waveforms (LCMWs) are indispensable in advanced radar systems. Our study introduces and validates, through extensive experimentation, the innovative application of a thin-film lithium niobate (TFLN) photonic integrated circuit (PIC) to realize a Fourier domain mode-locked optoelectronic oscillator (FDML OEO) for generating high-precision LCMW signals. This integrated chip combines a phase modulator (PM) and an electrically tuned notch micro-ring resonator (MRR), which functions as a rapidly tunable bandpass filter, facilitating the essential phase-to-intensity modulation (PM-IM) conversion for OEO oscillation. By synchronizing the modulation period of the applied driving voltage to the MRR with the OEO loop delay, we achieve Fourier domain mode-locking, producing LCMW signals with an impressive tunable center frequency range of 18.55 GHz to 23.59 GHz, an adjustable sweep bandwidth from 3.85 GHz to 8.5 GHz, and a remarkable chirp rate up to 3.22 GHz/μs. Unlike conventional PM-IM based FDML OEOs, our device obviates the need for expensive tunable lasers or microwave sources, positioning it as a practical solution for generating high-frequency LCMW signals with extended sweep bandwidth and high chirp rates, all within a compact and cost-efficient form factor..
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1964 (2025)
Integrated Optics
Stable soliton microcomb generation in X-cut lithium tantalate via thermal-assisted photorefractive suppression
Jiachen Cai, Shuai Wan, Bowen Chen, Jin Li... and Xin Ou|Show fewer author(s)
Chip-based soliton frequency microcombs combine compact size, broad bandwidth, and high coherence, presenting a promising solution for integrated optical telecommunications, precision sensing, and spectroscopy. Recent progress in ferroelectric thin films, particularly thin-film lithium niobate (LiNbO3) and thin-film lithium tantalate (LiTaO3), has significantly advanced electro-optic (EO) modulation and soliton microcombs generation, leveraging their strong third-order nonlinearity and high Pockels coefficients. However, achieving soliton frequency combs in X-cut ferroelectric materials remains challenging due to the competing effects of thermo-optic and photorefractive phenomena. These issues hinder the simultaneous realization of soliton generation and high-speed EO modulation. Here, following the thermal-regulated carrier behavior and auxiliary-laser-assisted approach, we propose a convenient mechanism to suppress both photorefractive and thermal dragging effects at once, and implement a facile method for soliton formation and its long-term stabilization in integrated X-cut LiTaO3 microresonators for the first time, to the best of our knowledge. The resulting mode-locked states exhibit robust stability against perturbations, enabling new pathways for fully integrated photonic circuits that combine Kerr nonlinearity with high-speed EO functionality.Chip-based soliton frequency microcombs combine compact size, broad bandwidth, and high coherence, presenting a promising solution for integrated optical telecommunications, precision sensing, and spectroscopy. Recent progress in ferroelectric thin films, particularly thin-film lithium niobate (
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1955 (2025)
Spiral resonator referenced low noise microwave generation via integrated optical frequency division
Long Cheng, Mengdi Zhao, Yang He, Yu Zhang... and Jiang Li|Show fewer author(s)
A low noise oscillator is a crucial component in determining system performance in modern communication, microwave spectroscopy, microwave-based sensing (including radar and remote sensing), and metrology systems. In recent years, ultra-low phase noise photonic microwave oscillators based on optical frequency division have become a paradigm shift for the generation of high performance microwave signals. In this work, we report on-chip low phase noise photonic microwave generation based on spiral resonator referenced lasers and an integrated electro-optical frequency comb. Dual lasers are co-locked to an ultra-high-Q silicon nitride spiral resonator and their relative phase noise is measured below the cavity thermal noise limit, resulting in record low on-chip optical phase noise. A broadband integrated electro-optic frequency comb is utilized to divide down the relative phase noise of the spiral resonator referenced lasers to the microwave domain, resulting in record-low phase noise for chip-based oscillators (-69 dBc/Hz at 10 Hz offset, and -144 dBc/Hz at 10 kHz offset for a 10 GHz carrier scaled from 37.3 GHz output). The exceptional phase noise performance, planar chip design, high technology readiness level, and foundry-ready processing of the current work represent a major advance of integrated photonic microwave oscillators.A low noise oscillator is a crucial component in determining system performance in modern communication, microwave spectroscopy, microwave-based sensing (including radar and remote sensing), and metrology systems. In recent years, ultra-low phase noise photonic microwave oscillators based on optical frequency division have become a paradigm shift for the generation of high performance microwave signals. In this work, we report on-chip low phase noise photonic microwave generation based on spiral resonator referenced lasers and an integrated electro-optical frequency comb. Dual lasers are co-locked to an ultra-high-
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1991 (2025)
Lasers and Laser Optics
Ultra-wideband high-speed wavelength-swept DFB laser array and precision measurement system of nonlinear wavelength variations | Editors' Pick
Yaqiang Fan, Pan Dai, Zhenxing Sun, Yuan Lv... and Xiangfei Chen|Show fewer author(s)
In this study, we developed a robust, ultra-wideband, and high-speed wavelength-swept distributed feedback (DFB) laser array with an 8×3 matrix interleaving structure with no movable or fragile optical components. This wavelength-swept laser (WSL) achieves a continuous (gap-free) wavelength sweeping range of 60 nm and a rapid sweeping speed of 82.7 kHz, marking the widest wavelength sweeping range reported to date for high-speed WSLs based on DFB laser arrays, to our knowledge. To achieve the high-precision mapping from the time domain to the frequency domain, a nonlinear wavelength and frequency variation measurement system based on dual Fabry–Perot (F-P) etalons is designed. The system accurately measures the dynamic relationship of frequency variations over time, enabling precise wavelength interrogation. The proposed WSL was applied to the fiber Bragg grating (FBG) sensor interrogation system. In the high-low temperature and strain experiments, the system performed real-time dynamic interrogation of FBGs for up to 3 h. The experimental results demonstrated good relative accuracy and excellent interrogation performance of the system. In the vibration experiment, the system achieved high-precision interrogation of FBG sensors for high-frequency sinusoidal vibrations up to 8 kHz. Furthermore, the system worked stably under strong vibrations and shocks. Thus, the proposed WSL is applicable to high-speed FBG sensing and optical coherence tomography applications.In this study, we developed a robust, ultra-wideband, and high-speed wavelength-swept distributed feedback (DFB) laser array with an
Photonics Research
- Publication Date: Jun. 19, 2025
- Vol. 13, Issue 7, 1855 (2025)
Compact seven-core fiber spatiotemporal mapping system for spatiotemporal mode-locking buildup dynamics
Yu Ning, Jiangyong He, Jin Li, Yuansheng Ma... and Yange Liu|Show fewer author(s)
Effective detection schemes for spatiotemporal light fields hold significant importance in the study of high-dimensional spatiotemporal nonlinear systems. We propose a compact seven-core fiber spatiotemporal mapping system (SCF-SMS) to investigate the transient dynamics within a spatiotemporal mode-locked (STML) fiber laser. By utilizing this system, we observed intriguing transient phenomena during STML processes, including beating dynamics and spatiotemporal soliton state transition dynamics. In the beating dynamics, two channels corresponding to distinct spatial sampling points exhibited different transient behaviors. Conversely, during the spatiotemporal soliton state transition dynamics, the transition processes of two channels were asynchronous, with observable discrepancies before and after the transitions. Compared with existing spatiotemporal light field acquisition methods, the SCF-SMS enables more compact spatiotemporal mapping within STML fiber lasers. This real-time, synchronous system for spatiotemporal soliton information measurement facilitates an in-depth study of nonlinear dynamical phenomena in STML fiber lasers.Effective detection schemes for spatiotemporal light fields hold significant importance in the study of high-dimensional spatiotemporal nonlinear systems. We propose a compact seven-core fiber spatiotemporal mapping system (SCF-SMS) to investigate the transient dynamics within a spatiotemporal mode-locked (STML) fiber laser. By utilizing this system, we observed intriguing transient phenomena during STML processes, including beating dynamics and spatiotemporal soliton state transition dynamics. In the beating dynamics, two channels corresponding to distinct spatial sampling points exhibited different transient behaviors. Conversely, during the spatiotemporal soliton state transition dynamics, the transition processes of two channels were asynchronous, with observable discrepancies before and after the transitions. Compared with existing spatiotemporal light field acquisition methods, the SCF-SMS enables more compact spatiotemporal mapping within STML fiber lasers. This real-time, synchronous system for spatiotemporal soliton information measurement facilitates an in-depth study of nonlinear dynamical phenomena in STML fiber lasers..
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1947 (2025)
Nonlinear Optics
High-harmonic generation in submicron-thick chirped periodically poled thin-film lithium niobate
Lingzhi Peng, Xiaoni Li, Liqiang Liu, Yuanyuan Liu... and Zhiyuan Li|Show fewer author(s)
Submicron-thick thin-film lithium niobate (TFLN) has emerged as a promising platform for nonlinear integrated photonics. In this work, we demonstrate the efficient simultaneous generation of broadband 2nd–8th harmonics in chirped periodically poled (CPP) TFLN. This is achieved through the synergistic effects of cascaded χ(2) nonlinear up-conversion and χ(3) self-phase modulation, driven by near-infrared femtosecond pulses with a central wavelength of 2100 nm and a pulse energy of 1.2 μJ. Remarkably, the 7th and 8th harmonics extend into the deep ultraviolet (DUV) region, reaching wavelengths as short as 250 nm. The 3rd–8th harmonic spectra seamlessly connect, forming a broadband supercontinuum spanning from the DUV to the visible range (250–800 nm, -25 dB), with an on-chip conversion efficiency of 19% (0.23 μJ). This achievement is attributed to the CPP-TFLN providing multiple broadband reciprocal lattice vector bands, enabling quasi-phase matching for a series of χ(2) nonlinear processes, including second harmonic generation (SHG), cascaded SHG, and third harmonic generation. Furthermore, we demonstrated the significant role of cascaded χ(2) phase-mismatched nonlinear processes in high-harmonic generation (HHG). Our work unveils the intricate and diverse nonlinear optical interactions in TFLN, offering a clear path toward efficient on-chip HHG and compact coherent white-light sources extending into the DUV.Submicron-thick thin-film lithium niobate (TFLN) has emerged as a promising platform for nonlinear integrated photonics. In this work, we demonstrate the efficient simultaneous generation of broadband 2nd–8th harmonics in chirped periodically poled (CPP) TFLN. This is achieved through the synergistic effects of cascaded
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1917 (2025)
Frequency conversion of vortex states by chiral flexural acoustic phonons
Xinglin Zeng, Philip St.J. Russell, and Birgit Stiller
An object or system is said to be chiral if it cannot be superimposed on its mirror reflection. Chirality is ubiquitous in nature, for example, in protein molecules and chiral phonons—acoustic waves carrying angular momentum—which are usually either intrinsically present or magnetically excited in suitable materials. Here, we report the use of intervortex forward Brillouin scattering to optically excite chiral flexural phonons in a twisted photonic crystal fiber, which is itself a chiral material capable of robustly preserving circularly polarized optical vortex states. The phonons induce a spatiotemporal rotating linear birefringence that acts back on the optical vortex modes, coupling them together. We demonstrate intervortex frequency conversion under the mediation of chiral flexural phonons and show that, for the same phonons, backward and forward intervortex conversion occurs at different wavelengths. The results open up, to our knowledge, new perspectives for Brillouin scattering and the chiral flexural phonons offer new opportunities for vortex-related information processing and multi-dimensional vectorial optical sensing.An object or system is said to be chiral if it cannot be superimposed on its mirror reflection. Chirality is ubiquitous in nature, for example, in protein molecules and chiral phonons—acoustic waves carrying angular momentum—which are usually either intrinsically present or magnetically excited in suitable materials. Here, we report the use of intervortex forward Brillouin scattering to optically excite chiral flexural phonons in a twisted photonic crystal fiber, which is itself a chiral material capable of robustly preserving circularly polarized optical vortex states. The phonons induce a spatiotemporal rotating linear birefringence that acts back on the optical vortex modes, coupling them together. We demonstrate intervortex frequency conversion under the mediation of chiral flexural phonons and show that, for the same phonons, backward and forward intervortex conversion occurs at different wavelengths. The results open up, to our knowledge, new perspectives for Brillouin scattering and the chiral flexural phonons offer new opportunities for vortex-related information processing and multi-dimensional vectorial optical sensing..
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1997 (2025)
Optical Devices
Photoelectric response in PMHT/Al2O3 heterostructure artificial synaptic transistors for neuromorphic computation
Yanmei Sun, Yufei Wang, and Qi Yuan
Current synaptic characteristics focus on replicating basic biological operations, but developing devices that combine photoelectric responsiveness and multifunctional simulation remains challenging. An optoelectronic transistor is presented, utilizing a PMHT/Al2O3 heterostructure for photoreception, memory storage, and computation. This artificial synaptic transistor processes optical and electrical signals efficiently, mimicking biological synapses. The work presents four logic functions: “AND”, “OR”, “NOR”, and “NAND”. It demonstrates electrical synaptic plasticity, optical synaptic plasticity, sunburned skin simulation, a photoelectric cooperative stimulation model for improving learning efficiency, and memory functions. The development of heterostructure synaptic transistors and their photoelectric response enhances their application in neuromorphic computation.Current synaptic characteristics focus on replicating basic biological operations, but developing devices that combine photoelectric responsiveness and multifunctional simulation remains challenging. An optoelectronic transistor is presented, utilizing a
Photonics Research
- Publication Date: Jun. 19, 2025
- Vol. 13, Issue 7, 1848 (2025)
Physical Optics
Flying spring and multi-ring ultrashort laser pulses with tunable wavefield dynamics | Spotlight on Optics
Enar Franco, Óscar Martínez-Matos, and José A. Rodrigo
Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications. Controlling their spatiotemporal behavior, tailored to specific applications, can unlock new experimental capabilities. However, achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions, given their polychromatic bandwidth. This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior. We developed a comprehensive approach to directly design and govern these laser pulses. This method elucidates the role jointly played by the pulse’s spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics. It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses. By tailoring the prescribed phase gradient, we demonstrate the creation of, to our knowledge, novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries. The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail. For instance, the intensity peak can be configured as a THz rotating light spot or shaped as a curve, enabling simultaneous substrate illumination at rates of tens of THz, far exceeding the MHz rates typically used in laser material processing. Additionally, the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam. Together, these advancements unveil advantageous capabilities that have been sought after for many years, especially in ultrafast optics and light-matter interaction research.Engineering ultrashort laser pulses is crucial for advancing fundamental research fields and applications. Controlling their spatiotemporal behavior, tailored to specific applications, can unlock new experimental capabilities. However, achieving this control is particularly challenging due to the difficulty in independently structuring their intensity and spatial phase distributions, given their polychromatic bandwidth. This article addresses this challenge by presenting a technique for generating flying structured laser pulses with tunable spatiotemporal behavior. We developed a comprehensive approach to directly design and govern these laser pulses. This method elucidates the role jointly played by the pulse’s spatiotemporal couplings and its prescribed phase gradient in governing the pulse dynamics. It evidences that the often-overlooked design of the phase gradient is indeed essential for achieving programmable spatiotemporal control of the pulses. By tailoring the prescribed phase gradient, we demonstrate the creation of, to our knowledge, novel families of flying structured laser pulses that travel at the speed of light in helical spring and vortex multi-ring forms of different geometries. The achieved control over the dynamics of their intensity peaks and wavefronts is analyzed in detail. For instance, the intensity peak can be configured as a THz rotating light spot or shaped as a curve, enabling simultaneous substrate illumination at rates of tens of THz, far exceeding the MHz rates typically used in laser material processing. Additionally, the independent manipulation of the pulse wavefronts allows local tuning of the orbital angular momentum density carried by the beam. Together, these advancements unveil advantageous capabilities that have been sought after for many years, especially in ultrafast optics and light-matter interaction research..
Photonics Research
- Publication Date: Jun. 26, 2025
- Vol. 13, Issue 7, 1872 (2025)
Quantum Optics
Enhancing the sensitivity of nitrogen-vacancy color-center ensemble sensors using one-dimensional photonic crystals
Yunpeng Yang, Sen Zhang, Kang Liu, Saifei Fan... and Jiaqi Zhu|Show fewer author(s)
The nitrogen-vacancy (NV) color center in diamond is a promising solid-state quantum system at room temperature. However, its sensitivity is limited by its low fluorescence collection efficiency, and its coherence time is limited by spin interference of impurity electrons around the NV color center. Here, we innovatively fabricated a one-dimensional photonic crystal on the surface of diamond, which greatly improved the fluorescence intensity of the NV color centers and increased the sensitivity of NV ensembles by a factor of 2.92. In addition, the laser reflected by the photonic crystal excites impurity electrons around the NV color centers, improving the electric field environment around the NV color centers, which exponentially prolongs the dephasing time (from 209 to 841 ns), opening avenues for NV color-center ensemble sensors.The nitrogen-vacancy (NV) color center in diamond is a promising solid-state quantum system at room temperature. However, its sensitivity is limited by its low fluorescence collection efficiency, and its coherence time is limited by spin interference of impurity electrons around the NV color center. Here, we innovatively fabricated a one-dimensional photonic crystal on the surface of diamond, which greatly improved the fluorescence intensity of the NV color centers and increased the sensitivity of NV ensembles by a factor of 2.92. In addition, the laser reflected by the photonic crystal excites impurity electrons around the NV color centers, improving the electric field environment around the NV color centers, which exponentially prolongs the dephasing time (from 209 to 841 ns), opening avenues for NV color-center ensemble sensors..
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1887 (2025)
Entanglement and quantum coherence of hybrid entangled states
Fengyi Xu, Chenyu Qiao, Shujing Li, Meihong Wang, and Xiaolong Su
A hybrid entangled state that involves both discrete and continuous degrees of freedom is a key resource for hybrid quantum information processing. It is essential to characterize entanglement and quantum coherence of the hybrid entangled state toward the application of it. Here, we experimentally characterize the entanglement and quantum coherence of the prepared hybrid entangled state between a polarization-encoded discrete-variable qubit and a cat-encoded wave-like continuous-variable qubit. We show that the maximum quantum coherence is obtained when the probability of the horizontal-polarization photon is 0.5, and entanglement and quantum coherence of the hybrid entangled state are robust against loss in both discrete- and continuous-variable parts. Based on the experimentally reconstructed two-mode density matrix on the bases of polarization and cat state, we obtain the logarithm negativity of 0.57 and l1-norm of 0.82, respectively, which confirms the entanglement and quantum coherence of the state. Our work takes a crucial step toward the application of the polarization-cat hybrid entangled state.A hybrid entangled state that involves both discrete and continuous degrees of freedom is a key resource for hybrid quantum information processing. It is essential to characterize entanglement and quantum coherence of the hybrid entangled state toward the application of it. Here, we experimentally characterize the entanglement and quantum coherence of the prepared hybrid entangled state between a polarization-encoded discrete-variable qubit and a cat-encoded wave-like continuous-variable qubit. We show that the maximum quantum coherence is obtained when the probability of the horizontal-polarization photon is 0.5, and entanglement and quantum coherence of the hybrid entangled state are robust against loss in both discrete- and continuous-variable parts. Based on the experimentally reconstructed two-mode density matrix on the bases of polarization and cat state, we obtain the logarithm negativity of 0.57 and
Photonics Research
- Publication Date: Jul. 01, 2025
- Vol. 13, Issue 7, 1983 (2025)
Silicon Photonics
Scalable and rapid programmable photonic integrated circuits empowered by Ising-model intelligent computation | On the Cover
Menghan Yang, Tiejun Wang, Yuxin Liang, Ye Jin... and Ming Li|Show fewer author(s)
Programmable photonic integrated circuits (PICs) have emerged as a promising platform for analog signal processing. Programmable PICs, as versatile photonic integrated platforms, can realize a wide range of functionalities through software control. However, a significant challenge lies in the efficient management of a large number of programmable units, which is essential for the realization of complex photonic applications. In this paper, we propose an innovative approach using Ising-model-based intelligent computing to enable dynamic reconfiguration of large-scale programmable PICs. In the theoretical framework, we model the Mach–Zehnder interferometer (MZI) fundamental units within programmable PICs as spin qubits with binary decision variables, forming the basis for the Ising model. The function of programmable PIC implementation can be reformulated as a path-planning problem, which is then addressed using the Ising model. The states of MZI units are accordingly determined as the Ising model evolves toward the lowest Ising energy. This method facilitates the simultaneous configuration of a vast number of MZI unit states, unlocking the full potential of programmable PICs for high-speed, large-scale analog signal processing. To demonstrate the efficacy of our approach, we present two distinct photonic systems: a 4×4 wavelength routing system for balanced transmission of four-channel NRZ/PAM-4 signals and an optical neural network that achieves a recognition accuracy of 96.2%. Additionally, our system demonstrates a reconfiguration speed of 30 ms and scalability to a 56×56 port network with 2000 MZI units. This work provides a groundbreaking theoretical framework and paves the way for scalable, high-speed analog signal processing in large-scale programmable PICs.Programmable photonic integrated circuits (PICs) have emerged as a promising platform for analog signal processing. Programmable PICs, as versatile photonic integrated platforms, can realize a wide range of functionalities through software control. However, a significant challenge lies in the efficient management of a large number of programmable units, which is essential for the realization of complex photonic applications. In this paper, we propose an innovative approach using Ising-model-based intelligent computing to enable dynamic reconfiguration of large-scale programmable PICs. In the theoretical framework, we model the Mach–Zehnder interferometer (MZI) fundamental units within programmable PICs as spin qubits with binary decision variables, forming the basis for the Ising model. The function of programmable PIC implementation can be reformulated as a path-planning problem, which is then addressed using the Ising model. The states of MZI units are accordingly determined as the Ising model evolves toward the lowest Ising energy. This method facilitates the simultaneous configuration of a vast number of MZI unit states, unlocking the full potential of programmable PICs for high-speed, large-scale analog signal processing. To demonstrate the efficacy of our approach, we present two distinct photonic systems: a
Photonics Research
- Publication Date: Jun. 19, 2025
- Vol. 13, Issue 7, 1832 (2025)
Surface Optics and Plasmonics
Microwave-infrared-compatibility enhancement of metasurfaces by decoupling Lorentz resonance of meta-atoms
Huiting Sun, Jun Wang, Yuxiang Jia, Sai Sui... and Jiafu Wang|Show fewer author(s)
To adapt to the complex environment where low infrared emissivity and high infrared emissivity coexist, a radar stealth-infrared camouflage compatibility metasurface requires meta-atoms with customized infrared emissivity. Generally, the infrared emissivity is determined by the occupation ratio. However, the high occupation ratio will interfere with the scattering reduction function due to the Lorentz resonance from the metal patch. To address the problem, a method for decoupling Lorentz resonance is proposed in this paper. By shifting the resonant frequency of the metal patch to a high frequency, the Lorentz resonance is suppressed in the frequency band of scattering reduction. To verify the method, a single functional layer metasurface with microwave scattering reduction and customized infrared emissivity is designed. The scattering reduction at 3.5–5.5 GHz is realized through the polarization conversion. Meanwhile, the infrared emissivity of the metasurface can be gradient-designed by changing the occupation ratios of the meta-atoms. Compared with the initial design, the improved metasurface expands the infrared emissivity range from 0.60–0.80 to 0.51–0.80, and the scattering reduction effect remains unchanged. The experimental results agree with the simulated results. The work enriches the infrared emissivity function, which can be applied to camouflage in complex spectrum backgrounds.To adapt to the complex environment where low infrared emissivity and high infrared emissivity coexist, a radar stealth-infrared camouflage compatibility metasurface requires meta-atoms with customized infrared emissivity. Generally, the infrared emissivity is determined by the occupation ratio. However, the high occupation ratio will interfere with the scattering reduction function due to the Lorentz resonance from the metal patch. To address the problem, a method for decoupling Lorentz resonance is proposed in this paper. By shifting the resonant frequency of the metal patch to a high frequency, the Lorentz resonance is suppressed in the frequency band of scattering reduction. To verify the method, a single functional layer metasurface with microwave scattering reduction and customized infrared emissivity is designed. The scattering reduction at 3.5–5.5 GHz is realized through the polarization conversion. Meanwhile, the infrared emissivity of the metasurface can be gradient-designed by changing the occupation ratios of the meta-atoms. Compared with the initial design, the improved metasurface expands the infrared emissivity range from 0.60–0.80 to 0.51–0.80, and the scattering reduction effect remains unchanged. The experimental results agree with the simulated results. The work enriches the infrared emissivity function, which can be applied to camouflage in complex spectrum backgrounds..
Photonics Research
- Publication Date: Jun. 13, 2025
- Vol. 13, Issue 7, 1800 (2025)
Radiation-type space-time metasurface for arbitrary beamforming by simultaneous and independent modulation of amplitude and phase for orthogonal polarization
Lixin Jiang, Hao Yang, Yongfeng Li, Wanwan Yang... and Shaobo Qu|Show fewer author(s)
Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic (EM) waves. Nevertheless, it is challenging for existing programmable metasurfaces to attain fully independent dynamic modulation of amplitude and phase due to the significant correlation between these two parameters. In this paper, we propose a radiation-type metasurface that can realize radiation space-time coding of the joint amplitude-phase. Hence, independent and arbitrary modulation of amplitudes and phases can be achieved for both x-polarized and y-polarized EM waves. For demonstration, the dynamic beam scanning with ultra-low sidelobe levels (SLLs) is validated. Moreover, we propose a strategy of stochastic coding and non-uniform modulation to suppress the harmonic energy, thereby obtaining the ultra-low sideband levels (SBLs). Prototypes were fabricated and measured, and all simulations and measurements demonstrated the superiority of the proposed strategy. In addition, the proposed strategy is optimization-free and highly integrated, which has unrivaled potential in the field of compact communication systems and radar systems.Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic (EM) waves. Nevertheless, it is challenging for existing programmable metasurfaces to attain fully independent dynamic modulation of amplitude and phase due to the significant correlation between these two parameters. In this paper, we propose a radiation-type metasurface that can realize radiation space-time coding of the joint amplitude-phase. Hence, independent and arbitrary modulation of amplitudes and phases can be achieved for both
Photonics Research
- Publication Date: Jun. 19, 2025
- Vol. 13, Issue 7, 1821 (2025)
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