Researching | PR Issue In Progress

Jiachen Cai, Shuai Wan, Bowen Chen, Jin Li..., Xuqiang Wang, Dongchen Sui, Piyu Wang, Zhenyu Qu, Xinjian Ke, Yifan Zhu, Yang Chen, Wenhui Xu, Ailun Yi, Jiaxiang Zhang, Chengli Wang, Chun-Hua Dong 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 (

{LiNbO}_{3}

) and thin-film lithium tantalate (

{LiTaO}_{3}

), 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

{LiTaO}_{3}

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 (

{LiNbO}_{3}

) and thin-film lithium tantalate (

{LiTaO}_{3}

{LiTaO}_{3}

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1955 (2025)

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Integrated Optics

Spiral resonator referenced low noise microwave generation via integrated optical frequency division

Long Cheng, Mengdi Zhao, Yang He, Yu Zhang..., Roy Meade, Kerry Vahala, Mian 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-

Q

- 69 dBc / Hz

at 10 Hz offset, and

- 144 dBc / Hz

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1991 (2025)

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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..., Wei Yuan, Haolin Xia, Jingxuan Zhang, Junwei Dong, Jihong Xu, Jie Zeng, Feng Wang 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 \times 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

8 \times 3

Photonics Research

Publication Date: Jun. 19, 2025
Vol. 13, Issue 7, 1855 (2025)

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Lasers and Laser Optics

Compact seven-core fiber spatiotemporal mapping system for spatiotemporal mode-locking buildup dynamics

Yu Ning, Jiangyong He, Jin Li, Yuansheng Ma..., Shihai Wang, Zhezhe Li, Mingtong Xiao, Lingyu Shen, Zhi Wang 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.showLess

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1947 (2025)

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Nonlinear Optics

High-harmonic generation in submicron-thick chirped periodically poled thin-film lithium niobate

Lingzhi Peng, Xiaoni Li, Liqiang Liu, Yuanyuan Liu..., Yuanyuan Zhao, Xuanming Duan, Lihong Hong 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

χ^{(2)}

nonlinear up-conversion and

χ^{(3)}

- 25 dB

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)}

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1917 (2025)

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Nonlinear Optics

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.showLess

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1997 (2025)

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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 / {Al}_{2} O_{3}

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

PMHT / {Al}_{2} O_{3}

Photonics Research

Publication Date: Jun. 19, 2025
Vol. 13, Issue 7, 1848 (2025)

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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.showLess

Photonics Research

Publication Date: Jun. 26, 2025
Vol. 13, Issue 7, 1872 (2025)

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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..., Benjian Liu, Bing Dai 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.showLess

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1887 (2025)

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Quantum Optics

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

l_{1}

-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

l_{1}

Photonics Research

Publication Date: Jul. 01, 2025
Vol. 13, Issue 7, 1983 (2025)

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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..., Wei Zhang, Xiangyan Meng, Ang Li, Guojie Zhang, Wei Li, Nuannuan Shi, Ninghua Zhu 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 \times 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 \times 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

4 \times 4

56 \times 56

Photonics Research

Publication Date: Jun. 19, 2025
Vol. 13, Issue 7, 1832 (2025)

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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..., Ruichao Zhu, Yina Cui, Shaobo Qu and Jiafu Wang|Show fewer author(s)

Photonics Research

Publication Date: Jun. 13, 2025
Vol. 13, Issue 7, 1800 (2025)

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Surface Optics and Plasmonics

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..., Yongqiang Pang, Jinming Jiang, Zhe Qin, Mingbao Yan, Yueyu Meng, Lin Zheng, Wenjie Wang, Jiafu Wang 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

x

-polarized and

y

Photonics Research

Publication Date: Jun. 19, 2025
Vol. 13, Issue 7, 1821 (2025)

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Research ArticlesVol. 13, Iss.5-May..1,2025

Holography, Gratings, and Diffraction

Intelligent tailoring of a broadband orbital angular momentum comb towards efficient optical convolution | Editors' Pick

Shiyun Zhou, Lang Li, Yishu Wang, Liliang Gao..., Zhichao Zhang, Chunqing Gao and Shiyao Fu|Show fewer author(s)

Due to the high-dimensional characteristics of photon orbital angular momentum (OAM), a beam can carry multiple OAMs simultaneously thus forming an OAM comb, which has been proved to show significant potential in both classical and quantum photonics. Tailoring broadband OAM combs on demand in a fast and accurate manner is a crucial basis for their application in advanced scenarios. However, obtaining phase-only gratings for the generation of arbitrary desired OAM combs still poses challenges. In this paper, we propose a multi-scale fusion learning U-shaped neural network that encodes a phase-only hologram for tailoring broadband OAM combs on-demand. Proof-of-principle experiments demonstrate that our scheme achieves fast computational speed, high modulation precision, and high manipulation dimensionality, with a mode range of

- 75

+ 75

, an average root mean square error of 0.0037, and a fidelity of 85.01%, all achieved in about 30 ms. Furthermore, we utilize the tailored broadband OAM combs in conducting optical convolution calculation, enabling vector convolution for arbitrary discrete functions, showcasing the extended capability of our proposal. This work opens, to our knowledge, new insight for on-demand tailoring of broadband OAM combs, paving the way for further advancements in high-dimensional OAM-based applications.Due to the high-dimensional characteristics of photon orbital angular momentum (OAM), a beam can carry multiple OAMs simultaneously thus forming an OAM comb, which has been proved to show significant potential in both classical and quantum photonics. Tailoring broadband OAM combs on demand in a fast and accurate manner is a crucial basis for their application in advanced scenarios. However, obtaining phase-only gratings for the generation of arbitrary desired OAM combs still poses challenges. In this paper, we propose a multi-scale fusion learning U-shaped neural network that encodes a phase-only hologram for tailoring broadband OAM combs on-demand. Proof-of-principle experiments demonstrate that our scheme achieves fast computational speed, high modulation precision, and high manipulation dimensionality, with a mode range of

- 75

+ 75

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1148 (2025)

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Holography, Gratings, and Diffraction

Holographic multi-waveguide system: towards implementation in wearable sensor technologies

Pamela Stoeva, Tatsiana Mikulchyk, Suzanne Martin, Maria Antonietta Ferrara..., Giuseppe Coppola and Izabela Naydenova|Show fewer author(s)

Holographic optical elements (HOEs) are integral to advancements in optical sensing, augmented reality, solar energy harvesting, biomedical diagnostics, and many other fields, offering precise and versatile light manipulation capabilities. This study, to the best of the authors’ knowledge, is the first to design and fabricate an HOE mutli-waveguide system using a thermally and environmentally stable photopolymerizable hybrid sol-gel (PHSG) for sensing applications. Using a 476.5 nm recording wavelength, 60% diffraction efficiency PHSG holographic waveguides of spatial frequency of 1720 lines/mm were successfully fabricated to function as in- and out-couplers at 632.8 nm and 700 nm wavelength, respectively. The waveguides were integrated into a polydimethylsiloxane (PDMS) microfluidic system, guiding excitation light of 632.8 nm wavelength into and extracting fluorescence light signal peaking at 700 nm from a location filled with methylene blue water solution. Further, to demonstrate the potential of the proposed optical system, four holographic waveguides were recorded by peristrophic and angular multiplexing in the same location of the material and the input beam was delivered into four spatially separated channels by total internal reflection in the sol-gel layer, thus, successfully highlighting the capabilities and advantages of HOE waveguides for parallel interrogation of multiple locations in a wearable sensor. This study demonstrates the efficiency and versatility of PHSG-based HOE waveguides, underscoring their potential to enhance photonic device design and performance across various optical applications.Holographic optical elements (HOEs) are integral to advancements in optical sensing, augmented reality, solar energy harvesting, biomedical diagnostics, and many other fields, offering precise and versatile light manipulation capabilities. This study, to the best of the authors’ knowledge, is the first to design and fabricate an HOE mutli-waveguide system using a thermally and environmentally stable photopolymerizable hybrid sol-gel (PHSG) for sensing applications. Using a 476.5 nm recording wavelength, 60% diffraction efficiency PHSG holographic waveguides of spatial frequency of 1720 lines/mm were successfully fabricated to function as in- and out-couplers at 632.8 nm and 700 nm wavelength, respectively. The waveguides were integrated into a polydimethylsiloxane (PDMS) microfluidic system, guiding excitation light of 632.8 nm wavelength into and extracting fluorescence light signal peaking at 700 nm from a location filled with methylene blue water solution. Further, to demonstrate the potential of the proposed optical system, four holographic waveguides were recorded by peristrophic and angular multiplexing in the same location of the material and the input beam was delivered into four spatially separated channels by total internal reflection in the sol-gel layer, thus, successfully highlighting the capabilities and advantages of HOE waveguides for parallel interrogation of multiple locations in a wearable sensor. This study demonstrates the efficiency and versatility of PHSG-based HOE waveguides, underscoring their potential to enhance photonic device design and performance across various optical applications.showLess

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1428 (2025)

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Instrumentation and Measurements

Ultrafast ranging using a dispersion-controlled dual-swept laser

Wei Du, Lei Chen, Yujia Li, Jindong Wang..., Yulong Cao, Ligang Huang, Leilei Shi, Lei Gao, Lei Wei and Tao Zhu|Show fewer author(s)

Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.showLess

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1182 (2025)

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Instrumentation and Measurements

Single-shot optical transfer delay measurement with sub-picosecond accuracy and sub-millisecond range

Lihan Wang, Xiangchuan Wang, Xi Liu, Yue Yang..., Shupeng Li, Sihao Yang, Qianwen Sang, Zhijian Zhang, Jingxian Wang and Shilong Pan|Show fewer author(s)

Optical transfer delay (OTD) is essential for distributed coherent systems, optically controlled phased arrays, fiber sensing systems, and quantum communication systems. However, existing OTD measurement techniques typically involve trade-offs among accuracy, range, and speed, limiting the application in the fields. Herein, we propose a single-shot OTD measurement approach that simultaneously achieves high-accuracy, long-range, and high-speed measurement. A microwave photonic phase-derived ranging with a nonlinear interval microwave frequency comb (MFC) and a discrete frequency sampling technique is proposed to conserve both frequency and time resources, ensuring high-accuracy and ambiguity-free measurements. In the proof-of-concept experiment, a delay measurement uncertainty at the

10^{- 9}

level with a single 10 μs sampling time is first reported, to our knowledge. The method is also applied to coherently combine two distributed signals at 31.8 GHz, separated by a 2 km optical fiber. A minimal gain loss of less than 0.0038 dB compared to the theoretical value was achieved, corresponding to an OTD synchronization accuracy of 0.3 ps.Optical transfer delay (OTD) is essential for distributed coherent systems, optically controlled phased arrays, fiber sensing systems, and quantum communication systems. However, existing OTD measurement techniques typically involve trade-offs among accuracy, range, and speed, limiting the application in the fields. Herein, we propose a single-shot OTD measurement approach that simultaneously achieves high-accuracy, long-range, and high-speed measurement. A microwave photonic phase-derived ranging with a nonlinear interval microwave frequency comb (MFC) and a discrete frequency sampling technique is proposed to conserve both frequency and time resources, ensuring high-accuracy and ambiguity-free measurements. In the proof-of-concept experiment, a delay measurement uncertainty at the

10^{- 9}

Photonics Research

Publication Date: Apr. 30, 2025
Vol. 13, Issue 5, 1302 (2025)

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Integrated Optics

Experimental evaluation of continuous and pixelated dispersive optical phased arrays for 2D beam steering

Mennatallah Kandil, Mathias Prost, Jon Kjellman, Wim Bogaerts, and Marcus Dahlem

Dispersive optical phased arrays (DOPAs) offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation, and therefore low control complexity and low power consumption. However, in terms of scalability, state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of long-range LiDAR, including the number of pixels (resolvable points) and beam quality. Here, we experimentally demonstrate the pixelated DOPA concept, which overcomes the scaling challenges of classical (continuous) DOPAs by introducing a new design degree of freedom: the discretization of the optical delay lines distribution network into blocks. We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network, incorporated in both the continuous DOPA and the pixelated DOPA variations. The small-scale demonstration circuits can scan over a field of view of

15 ° \times 7.2 °

, where the continuous DOPA provides

16 \times 25

pixels, while the pixelated DOPA provides

4 \times 25

pixels, for a 1500 to 1600 nm wavelength sweep. The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB, which is higher than that of the continuous version, with a median of 3.6 dB. In addition, the ratio of the main beam to the background radiation pattern is 11 dB (median value) for the pixelated DOPA, while for the continuous DOPA, it is 9.5 dB. This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA. The degree of discretization, combined with other design parameters, will potentially enable better control over the beam quality, while setting practical values for the number of pixels for large-scale DOPAs.Dispersive optical phased arrays (DOPAs) offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation, and therefore low control complexity and low power consumption. However, in terms of scalability, state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of long-range LiDAR, including the number of pixels (resolvable points) and beam quality. Here, we experimentally demonstrate the pixelated DOPA concept, which overcomes the scaling challenges of classical (continuous) DOPAs by introducing a new design degree of freedom: the discretization of the optical delay lines distribution network into blocks. We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network, incorporated in both the continuous DOPA and the pixelated DOPA variations. The small-scale demonstration circuits can scan over a field of view of

15 ° \times 7.2 °

, where the continuous DOPA provides

16 \times 25

pixels, while the pixelated DOPA provides

4 \times 25

Photonics Research

Publication Date: Apr. 30, 2025
Vol. 13, Issue 5, 1330 (2025)

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Integrated Optics

Lithium tantalate microring cavities with a Q factor exceeding 10 million | Spotlight on Optics

Jianfeng He, Xinyi Zhao, Jian-Bin Xu, and Xiankai Sun

Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties. However, its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors. Recently, lithium tantalate, another piezoelectric and nonlinear material, has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction, faster electro-optic response relaxation, higher optical damage threshold, wider transparency window, and lower birefringence compared with lithium niobate. Here, we developed an ultralow-loss lithium tantalate integrated photonic platform, including waveguides, grating couplers, and microring cavities. The measured highest optical

Q

factor of the microring cavities is beyond

10^{7}

, corresponding to the lowest waveguide propagation loss of

\sim 1.88 dB / m

. The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities. This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices, such as periodically poled waveguides, acousto-optic modulators, and electro-optic modulators.Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties. However, its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors. Recently, lithium tantalate, another piezoelectric and nonlinear material, has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction, faster electro-optic response relaxation, higher optical damage threshold, wider transparency window, and lower birefringence compared with lithium niobate. Here, we developed an ultralow-loss lithium tantalate integrated photonic platform, including waveguides, grating couplers, and microring cavities. The measured highest optical

Q

factor of the microring cavities is beyond

10^{7}

, corresponding to the lowest waveguide propagation loss of

\sim 1.88 dB / m

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1385 (2025)

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Integrated Optics

Integrated spatial photonic XY Ising sampler based on a high-uniformity 1 × 8 multi-mode interferometer

Xin Ye, Wenjia Zhang, and Zuyuan He

Spatial photonic Ising machines, as emerging artificial intelligence hardware solutions by leveraging unique physical phenomena, have shown promising results in solving large-scale combinatorial problems. However, spatial light modulator enabled Ising machines still remain bulky, are very power demanding, and have poor stability. In this study, we propose an integrated XY Ising sampler based on a highly uniform multimode interferometer and a phase shifter array, enabling the minimization of both discrete and continuous spin Hamiltonians. We elucidate the performance of this computing platform in achieving fully programmable spin couplings and external magnetic fields. Additionally, we successfully demonstrate the weighted full-rank Ising model with a linear dependence of 0.82 and weighted MaxCut problem solving with the proposed sampler. Our results illustrate that the developed structure has significant potential for larger-scale, reduced power consumption and increased operational speed, positioning it as a versatile platform for commercially viable high-performance samplers of combinatorial optimization problems.Spatial photonic Ising machines, as emerging artificial intelligence hardware solutions by leveraging unique physical phenomena, have shown promising results in solving large-scale combinatorial problems. However, spatial light modulator enabled Ising machines still remain bulky, are very power demanding, and have poor stability. In this study, we propose an integrated XY Ising sampler based on a highly uniform multimode interferometer and a phase shifter array, enabling the minimization of both discrete and continuous spin Hamiltonians. We elucidate the performance of this computing platform in achieving fully programmable spin couplings and external magnetic fields. Additionally, we successfully demonstrate the weighted full-rank Ising model with a linear dependence of 0.82 and weighted MaxCut problem solving with the proposed sampler. Our results illustrate that the developed structure has significant potential for larger-scale, reduced power consumption and increased operational speed, positioning it as a versatile platform for commercially viable high-performance samplers of combinatorial optimization problems.showLess

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1419 (2025)

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Lasers and Laser Optics

Unveiling intracavity soliton evolution dynamics of a mode-locked fiber laser along the dispersion map

Jiarun Zhang, Tianchang Lu, Xiankun Yao, Yusheng Zhang..., Dong Mao, Chao Zeng, Xiang Hao, Longhua Tang, Yudong Cui, Cuifang Kuang and Xu Liu|Show fewer author(s)

Mode-locked fiber lasers are excellent platforms for soliton generation. Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity. Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser. The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity, thereby enabling in-depth observation and manipulation of soliton evolution along the dispersion map. The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution. Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics, fostering advancements in nonlinear and ultrafast optics.Mode-locked fiber lasers are excellent platforms for soliton generation. Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity. Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser. The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity, thereby enabling in-depth observation and manipulation of soliton evolution along the dispersion map. The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution. Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics, fostering advancements in nonlinear and ultrafast optics.showLess

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1130 (2025)

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Lasers and Laser Optics

All-fiber-structure high-power mid-infrared gas-filled hollow-core-fiber amplified spontaneous emission source

Weihua Song, Yu Wen, Qian Zhang, Xin Zhang, and Pu Wang

Hollow-core-fiber (HCF) gas lasers (GLs) have garnered significant interest as a novel approach for generating mid-infrared lasers, owing to their inherent benefits of rich emission wavelength, high beam quality, and high output power potential. However, they are mostly achieved by a free-space coupling structure, which has a major drawback of being prone to vibrations and other environmental variations. Here, we devise and implement an all-fiber-structure gas-filled HCF amplified spontaneous emission (ASE) source at 3.1 μm based on the reverse tapering and angle-cleaved fusion splicing techniques. By optimizing the

C_{2} H_{2}

gas pressure, a maximum mid-infrared output power of 6.59 W was obtained, corresponding to a slope efficiency of 19.74% and near-diffraction-limited beam qualities of

M_{x}^{2} = 1.03

and

M_{y}^{2} = 1.06

. Furthermore, with a similar all-fiber configuration, a

{CO}_{2}

-filled HCF ASE source at 4.3 μm with output power exceeding 1.4 W was generated. To the best of our knowledge, the proposed all-fiber-structure HCF gas light source demonstrates the longest wavelength and highest power reported to date. The development of mid-infrared HCF gas light sources in an all-fiber configuration represents a significant step toward miniaturized HCF lasers, which hold promise as powerful new tools for application in laser medicine, space communication, and other scientific research.Hollow-core-fiber (HCF) gas lasers (GLs) have garnered significant interest as a novel approach for generating mid-infrared lasers, owing to their inherent benefits of rich emission wavelength, high beam quality, and high output power potential. However, they are mostly achieved by a free-space coupling structure, which has a major drawback of being prone to vibrations and other environmental variations. Here, we devise and implement an all-fiber-structure gas-filled HCF amplified spontaneous emission (ASE) source at 3.1 μm based on the reverse tapering and angle-cleaved fusion splicing techniques. By optimizing the

C_{2} H_{2}

gas pressure, a maximum mid-infrared output power of 6.59 W was obtained, corresponding to a slope efficiency of 19.74% and near-diffraction-limited beam qualities of

M_{x}^{2} = 1.03

and

M_{y}^{2} = 1.06

. Furthermore, with a similar all-fiber configuration, a

{CO}_{2}

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1137 (2025)

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Nanophotonics and Photonic Crystals

Floquet hybrid skin-topological effects in checkerboard lattices with large Chern numbers

Yi-Ling Zhang, Li-Wei Wang, Yang Liu, Zhao-Xian Chen, and Jian-Hua Jiang

Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications. Here, we study the non-Hermitian Chern bands and the associated non-Hermitian skin effects in Floquet checkerboard lattices with synthetic gauge fluxes. Such lattices can be realized in a network of coupled resonator optical waveguides in two dimensions or in an array of evanescently coupled helical optical waveguides in three dimensions. Without invoking nonreciprocal couplings, the system exhibits versatile non-Hermitian topological phases that support various skin-topological effects. Remarkably, the non-Hermitian skin effect can be engineered by changing the symmetry, revealing rich non-Hermitian topological bulk-boundary correspondences. Our system offers excellent controllability and experimental feasibility, making it appealing for exploring diverse non-Hermitian topological phenomena in photonics.Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications. Here, we study the non-Hermitian Chern bands and the associated non-Hermitian skin effects in Floquet checkerboard lattices with synthetic gauge fluxes. Such lattices can be realized in a network of coupled resonator optical waveguides in two dimensions or in an array of evanescently coupled helical optical waveguides in three dimensions. Without invoking nonreciprocal couplings, the system exhibits versatile non-Hermitian topological phases that support various skin-topological effects. Remarkably, the non-Hermitian skin effect can be engineered by changing the symmetry, revealing rich non-Hermitian topological bulk-boundary correspondences. Our system offers excellent controllability and experimental feasibility, making it appealing for exploring diverse non-Hermitian topological phenomena in photonics.showLess

Photonics Research

Publication Date: Apr. 30, 2025
Vol. 13, Issue 5, 1321 (2025)

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Nanophotonics and Photonic Crystals

Dual-channel tunable multipolarization adapted terahertz spatiotemporal vortices generating device

Fangze Deng, Ke Ma, Yumeng Ma, Xiang Hou..., Zhihua Han, Yuchao Li, Keke Cheng, Yansheng Shao, Chenglong Wang, Meng Liu, Huiyun Zhang and Yuping Zhang|Show fewer author(s)

Spatiotemporal optical vortices (STOVs) exhibit characteristics of transverse orbital angular momentum (OAM) that is perpendicular to the direction of pulse propagation, indicating significant potential for diverse applications. In this study, we employ vanadium dioxide and photonic crystal plates to design tunable transreflective dual-channel terahertz (THz) spatiotemporal vortex generation devices that possess multipolarization adaptability. In the reflection channel, we achieve active tunability of the topological dark lines by utilizing circularly polarized light, based on the topological dark phenomenon, and observe variations in the number of singularities across the parameter space from different observational perspectives. In the transmission channel, we generate independent vortex singularities using linearly polarized light. This multifunctional terahertz device offers a novel approach for the generation and active tuning of spatiotemporal vortices.Spatiotemporal optical vortices (STOVs) exhibit characteristics of transverse orbital angular momentum (OAM) that is perpendicular to the direction of pulse propagation, indicating significant potential for diverse applications. In this study, we employ vanadium dioxide and photonic crystal plates to design tunable transreflective dual-channel terahertz (THz) spatiotemporal vortex generation devices that possess multipolarization adaptability. In the reflection channel, we achieve active tunability of the topological dark lines by utilizing circularly polarized light, based on the topological dark phenomenon, and observe variations in the number of singularities across the parameter space from different observational perspectives. In the transmission channel, we generate independent vortex singularities using linearly polarized light. This multifunctional terahertz device offers a novel approach for the generation and active tuning of spatiotemporal vortices.showLess

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1408 (2025)

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Nonlinear Optics

Towards high-power and ultra-broadband mid-infrared supercontinuum generation using tapered multimode glass rods

Esteban Serrano, Damien Bailleul, Frédéric Désévédavy, Pierre Béjot..., Grégory Gadret, Pierre Mathey, Frédéric Smektala and Bertrand Kibler|Show fewer author(s)

Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application. We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime. Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm waveband. By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6 μm, a supercontinuum spanning from 2 to 15 μm (3–14 μm) with an average output power of 93 mW (170 mW) is obtained for 500-kHz (1-MHz) repetition rate. Additional experiments on other glass families (silica and tellurite) covering distinct spectral regions are also reported to develop and support our analyses. We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation. Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics, as well as the possible preservation of coherence features. Our study opens a new route, to our knowledge, towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application. We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime. Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm waveband. By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6 μm, a supercontinuum spanning from 2 to 15 μm (3–14 μm) with an average output power of 93 mW (170 mW) is obtained for 500-kHz (1-MHz) repetition rate. Additional experiments on other glass families (silica and tellurite) covering distinct spectral regions are also reported to develop and support our analyses. We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation. Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics, as well as the possible preservation of coherence features. Our study opens a new route, to our knowledge, towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.showLess

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1106 (2025)

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Optical and Photonic Materials

Advancing photonic device capabilities via femtosecond laser modification of LPCVD-SiN microring resonator characteristics

Jia Du, Weixiao Xu, Runwei Zhou, Xiao Chen..., Ting Li, Xiongping Bao, Hong Wang, Weibiao Chen and Libing Zhou|Show fewer author(s)

Femtosecond pulsed lasers offer significant advantages for micro-/nano-modifications in integrated photonics. Microring resonators (MRRs), which are essential components in photonic integrated circuits (PICs), are widely employed in various fields, including optical communication, sensing, and filtering. In this study, we investigate the modification mechanisms associated with femtosecond laser interactions with MRRs fabricated on a low-pressure chemical vapor deposition (LPCVD)-silicon nitride (SiN) photonic platform, with emphasis on the post-fabrication trimming of second-order microring filters and MRR-based four-channel wavelength-division multiplexing (WDM). We examine 10 MRRs located at different positions on a wafer and discovered resonance wavelength shifts exceeding 1 nm due to fabrication-induced variations. Interactions between femtosecond lasers and LPCVD-SiN films resulted in silicon nanoclusters, which significantly redshifted the resonance wavelength of the MRRs. Additionally, the extinction ratio of MRRs improved by over 11.8 dB within the conventional band after laser modification. This technique is employed to enhance the performance of second-order MRRs and the four-channel WDM configuration, thus providing critical experimental evidence for leveraging femtosecond lasers to optimize LPCVD-SiN PICs.Femtosecond pulsed lasers offer significant advantages for micro-/nano-modifications in integrated photonics. Microring resonators (MRRs), which are essential components in photonic integrated circuits (PICs), are widely employed in various fields, including optical communication, sensing, and filtering. In this study, we investigate the modification mechanisms associated with femtosecond laser interactions with MRRs fabricated on a low-pressure chemical vapor deposition (LPCVD)-silicon nitride (SiN) photonic platform, with emphasis on the post-fabrication trimming of second-order microring filters and MRR-based four-channel wavelength-division multiplexing (WDM). We examine 10 MRRs located at different positions on a wafer and discovered resonance wavelength shifts exceeding 1 nm due to fabrication-induced variations. Interactions between femtosecond lasers and LPCVD-SiN films resulted in silicon nanoclusters, which significantly redshifted the resonance wavelength of the MRRs. Additionally, the extinction ratio of MRRs improved by over 11.8 dB within the conventional band after laser modification. This technique is employed to enhance the performance of second-order MRRs and the four-channel WDM configuration, thus providing critical experimental evidence for leveraging femtosecond lasers to optimize LPCVD-SiN PICs.showLess

Photonics Research

Publication Date: Apr. 30, 2025
Vol. 13, Issue 5, 1313 (2025)

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Optical Devices

QBIC-based terahertz metasurface used for the detection of chlorpyrifos in tea

Tianqing Zhou, Binggang Xiao, Yong Du, and Jianyuan Qin

Pesticide residues in tea are an important problem affecting the sustainable development of the tea industry; thus, pesticide detection is the key to ensuring the quality and safety of tea. Here, a terahertz metasurface structure based on the quasi-bound state in the continuum is proposed, which consists of two copper microrods arranged periodically. This design in the metasurface provides strong local enhancement near the surface of the microstructure, significantly improving the interaction of light with the analyte, resulting in increased sensitivity. The simulated and experimental results show that the metasurface structure can be used to detect the refractive index of trace analytes with a high sensitivity and successfully detect low concentrations of chlorpyrifos in tea. This study provides a new idea for the detection of pesticide residues in tea.Pesticide residues in tea are an important problem affecting the sustainable development of the tea industry; thus, pesticide detection is the key to ensuring the quality and safety of tea. Here, a terahertz metasurface structure based on the quasi-bound state in the continuum is proposed, which consists of two copper microrods arranged periodically. This design in the metasurface provides strong local enhancement near the surface of the microstructure, significantly improving the interaction of light with the analyte, resulting in increased sensitivity. The simulated and experimental results show that the metasurface structure can be used to detect the refractive index of trace analytes with a high sensitivity and successfully detect low concentrations of chlorpyrifos in tea. This study provides a new idea for the detection of pesticide residues in tea.showLess

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1158 (2025)

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Optical Devices

Efficient inverse design for tailoring a terahertz metagrating

Jia Shi, Guanlong Wang, Shaona Wang, Wenjing Yu..., Ling Liang, Weiling Fu, Pingjuan Niu, Jianquan Yao and Xiang Yang|Show fewer author(s)

The fast and accurate design of terahertz devices for specific applications remains challenging, especially for tailoring metadevices, owing to the complex electromagnetic characteristics of these devices and their large structural parameter space. The unique functionalities achieved by metadevices come at the cost of structural complexity, resulting in a time-consuming parameter sweep for conventional metadevice design. Here, we propose a general solution to achieve efficient inverse design for a terahertz metagrating via machine learning. Metagratings with different structural parameters were selected as illustrations to verify the effectiveness of this method. As proof-of-principle examples, the metagratings predicted via the inverse design model are numerically calculated and experimentally demonstrated. Initially, the physical modeling of a metagrating is performed via the finite element method (FEM). A spectrum dataset obtained from FEM simulation is prepared for the training of machine learning models. Then, trained machine learning models, including the Elman neural network (Elman), support vector machine (SVM), and general regression neutral network (GRNN), are used to predict probable structural parameters. The results of these models are compared and analyzed comprehensively, which verifies the effectiveness of the inverse design method. Compared with conventional methods, the inverse design method is much faster and can encompass a high degree of freedom to generate metadevice structures, which can ensure that the spectra of generated structures resemble the desired ones and can provide accurate data support for metadevice modeling. Furthermore, a metagrating tailored by an inverse design is used as a biological sensor to distinguish different microorganisms. The proposed data-driven inverse design method realizes fast and accurate design of the metagrating, which is expected to have great potential in metadevice design and tailoring for specific applications.The fast and accurate design of terahertz devices for specific applications remains challenging, especially for tailoring metadevices, owing to the complex electromagnetic characteristics of these devices and their large structural parameter space. The unique functionalities achieved by metadevices come at the cost of structural complexity, resulting in a time-consuming parameter sweep for conventional metadevice design. Here, we propose a general solution to achieve efficient inverse design for a terahertz metagrating via machine learning. Metagratings with different structural parameters were selected as illustrations to verify the effectiveness of this method. As proof-of-principle examples, the metagratings predicted via the inverse design model are numerically calculated and experimentally demonstrated. Initially, the physical modeling of a metagrating is performed via the finite element method (FEM). A spectrum dataset obtained from FEM simulation is prepared for the training of machine learning models. Then, trained machine learning models, including the Elman neural network (Elman), support vector machine (SVM), and general regression neutral network (GRNN), are used to predict probable structural parameters. The results of these models are compared and analyzed comprehensively, which verifies the effectiveness of the inverse design method. Compared with conventional methods, the inverse design method is much faster and can encompass a high degree of freedom to generate metadevice structures, which can ensure that the spectra of generated structures resemble the desired ones and can provide accurate data support for metadevice modeling. Furthermore, a metagrating tailored by an inverse design is used as a biological sensor to distinguish different microorganisms. The proposed data-driven inverse design method realizes fast and accurate design of the metagrating, which is expected to have great potential in metadevice design and tailoring for specific applications.showLess

Photonics Research

Publication Date: Apr. 21, 2025
Vol. 13, Issue 5, 1172 (2025)

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Optical Devices

Dual-frequency-range modulator based on a planar nested multiscale metasurface

Jing Yuan, Guichuan Xu, Zhengang Lu, Xinmeng Zhuang..., Huanping Zhou, Heyan Wang, Lin Han and Jiubin Tan|Show fewer author(s)

Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing. However, the interaction between different spectra and matter varies significantly, making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities. We designed a modulator based on a planar nested multiscale metasurface, incorporating silicon (Si) and perovskite as control materials, to modulate both microwave and terahertz (THz) ranges. Modulation of microwave and THz waves is achieved through visible light and near-infrared light pumping, with modulation depths of 94.03% and 90.77%, respectively. The modulator employs a planar nested multiscale metasurface, utilizing the odd-order nonlinear polarization properties of perovskite in the THz range and the linear absorption properties of Si in the microwave range to realize dual-frequency-range modulation. This research offers innovative insights for designing multi-spectral components applicable in all-optical coding metasurfaces and intelligent light windows.Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing. However, the interaction between different spectra and matter varies significantly, making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities. We designed a modulator based on a planar nested multiscale metasurface, incorporating silicon (Si) and perovskite as control materials, to modulate both microwave and terahertz (THz) ranges. Modulation of microwave and THz waves is achieved through visible light and near-infrared light pumping, with modulation depths of 94.03% and 90.77%, respectively. The modulator employs a planar nested multiscale metasurface, utilizing the odd-order nonlinear polarization properties of perovskite in the THz range and the linear absorption properties of Si in the microwave range to realize dual-frequency-range modulation. This research offers innovative insights for designing multi-spectral components applicable in all-optical coding metasurfaces and intelligent light windows.showLess

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1390 (2025)

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Optical Devices

High-efficiency mode group demultiplexing based on diffractive optical network

Zhibing Liu, Siqing Zeng, Shuixian Yang, Yuetong Shi..., Hongfei Chen, Yaoming Feng, Shecheng Gao, Jiajing Tu, Dawei Wang, Zhaojian Chen and Zhaohui Li|Show fewer author(s)

Space division multiplexing (SDM) can achieve higher communication transmission capacity by exploiting more spatial channels in a single optical fiber. For weakly coupled few-mode fiber, different mode groups (MGs) are highly isolated from each other, so the SDM system can be simplified by utilizing MG multiplexing and intensity modulation direct detection. A key issue to be addressed here is MG demultiplexing, which requires processing all the modes within a single MG in contrast to MG multiplexing. Benefiting from the great light manipulation freedom of the diffractive optical network (DON), we achieve efficient separation of the MGs and receive them with the multimode fiber (MMF) array. To fully exploit the mode field freedom of the MMF, a non-deterministic mode conversion strategy is proposed here to optimize the DON, which enables high-efficiency demultiplexing with a much smaller number of phase plates. As a validation, we design a 6-MG demultiplexer consisting of only five phase plates; each MG is constituted by several orbital angular momentum modes. The designed average loss and crosstalk at the wavelength of 1550 nm are 0.5 dB and

- 25 dB

, respectively. In the experiment, the loss after coupling to the MMF ranged from 4.1 to 4.9 dB, with an average of 4.5 dB. The inter-MG crosstalk is better than

- 12 dB

, with an average of

- 18 dB

. These results well support the proposed scheme and will provide a practical solution to the MG demultiplexing problem in a short-distance SDM system.Space division multiplexing (SDM) can achieve higher communication transmission capacity by exploiting more spatial channels in a single optical fiber. For weakly coupled few-mode fiber, different mode groups (MGs) are highly isolated from each other, so the SDM system can be simplified by utilizing MG multiplexing and intensity modulation direct detection. A key issue to be addressed here is MG demultiplexing, which requires processing all the modes within a single MG in contrast to MG multiplexing. Benefiting from the great light manipulation freedom of the diffractive optical network (DON), we achieve efficient separation of the MGs and receive them with the multimode fiber (MMF) array. To fully exploit the mode field freedom of the MMF, a non-deterministic mode conversion strategy is proposed here to optimize the DON, which enables high-efficiency demultiplexing with a much smaller number of phase plates. As a validation, we design a 6-MG demultiplexer consisting of only five phase plates; each MG is constituted by several orbital angular momentum modes. The designed average loss and crosstalk at the wavelength of 1550 nm are 0.5 dB and

- 25 dB

, respectively. In the experiment, the loss after coupling to the MMF ranged from 4.1 to 4.9 dB, with an average of 4.5 dB. The inter-MG crosstalk is better than

- 12 dB

, with an average of

- 18 dB

. These results well support the proposed scheme and will provide a practical solution to the MG demultiplexing problem in a short-distance SDM system.showLess

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1400 (2025)

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Optoelectronics

High-precision quasi-static sensing method based on WGM resonator self-modulation

Tao Jia, Enbo Xing, Jianglong Li, Jiamin Rong..., Hongbo Yue, Yujie Zhang, Guohui Xing, Yanru Zhou, Wenyao Liu, Jun Tang and Jun Liu|Show fewer author(s)

Whispering gallery mode (WGM) resonators have been widely researched for their high-sensitivity sensing capability, but there is currently a lack of high-sensitivity real-time sensing methods for quasi-static measurement. In this paper, within the framework of dissipative coupling sensing, a new method for quasi-static sensing based on the self-modulation of lithium niobate (

{LiNbO}_{3}

) resonators is proposed. The

{LiNbO}_{3}

resonator actively modulates the signal to be measured, solving the challenge of real-time demodulation of quasi-static signals. The noise background is upconverted to a high frequency region with lower noise, further enhancing the detection limit. In the demonstration of quasi-static displacement sensing, a customized

{LiNbO}_{3}

resonator with a

Q

-factor of

2.09 \times 10^{7}

serves as the high frequency modulation and sensing element, while the movable resonator acts as the displacement loading unit. Experimental and theoretical results show that the sensing response can be improved to 0.0416 V/nm by dissipation engineering to enhance the resonator evanescent field decay rate and orthogonal polarization optimization. The Allan deviation

σ

demonstrates a bias instability of 0.205 nm, which represents the best result known to date for microresonator displacement sensing in the quasi-static range. Our proposed scheme demonstrates competitiveness in high-precision quasi-static sensing and provides solutions for the high-precision real-time detection of low frequency or very low frequency acceleration, pressure, nanoparticles, or viruses.Whispering gallery mode (WGM) resonators have been widely researched for their high-sensitivity sensing capability, but there is currently a lack of high-sensitivity real-time sensing methods for quasi-static measurement. In this paper, within the framework of dissipative coupling sensing, a new method for quasi-static sensing based on the self-modulation of lithium niobate (

{LiNbO}_{3}

) resonators is proposed. The

{LiNbO}_{3}

{LiNbO}_{3}

resonator with a

Q

-factor of

2.09 \times 10^{7}

σ

Photonics Research

Publication Date: May. 01, 2025
Vol. 13, Issue 5, 1375 (2025)

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Physical Optics

Symmetric and asymmetric Hall effect-like splitting of optical Stokes skyrmions via a hybrid multi-zone filter

Tian Xia, Jia Ma, Zhenwei Xie, and Xiaocong Yuan

In recent years, optical skyrmions have garnered increasing attention for their ability to introduce new degrees of freedom in manipulating optical fields. While most research has focused on creating innovative optical topological states such as merons and hopfions, there has been limited exploration into their manipulation, which hinders practical applications in this field. In this study, we utilize a hybrid multi-zone filter to induce a Hall effect-like splitting of optical Stokes skyrmions (HESSs), enabling effective separation and manipulation. By manipulating the horizontal phase gradient parameter, we independently control the separation angle of skyrmions. Additionally, we demonstrate control over the topological charge parameter to achieve symmetric and asymmetric HESSs. This effect not only enhances the manipulation capabilities of optical fields but also opens up potential applications for high precision displacement measurements and preservation quantum information.In recent years, optical skyrmions have garnered increasing attention for their ability to introduce new degrees of freedom in manipulating optical fields. While most research has focused on creating innovative optical topological states such as merons and hopfions, there has been limited exploration into their manipulation, which hinders practical applications in this field. In this study, we utilize a hybrid multi-zone filter to induce a Hall effect-like splitting of optical Stokes skyrmions (HESSs), enabling effective separation and manipulation. By manipulating the horizontal phase gradient parameter, we independently control the separation angle of skyrmions. Additionally, we demonstrate control over the topological charge parameter to achieve symmetric and asymmetric HESSs. This effect not only enhances the manipulation capabilities of optical fields but also opens up potential applications for high precision displacement measurements and preservation quantum information.showLess

Photonics Research

Publication Date: Apr. 30, 2025
Vol. 13, Issue 5, 1365 (2025)

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Silicon Photonics

Micro-transfer printing of O-band InAs/GaAs quantum-dot SOAs on silicon photonic integrated circuits | On the Cover

Yang Liu, Jing Zhang, Laurens Bogaert, Emadreza Soltanian..., Evangelia Delli, Konstantin Morozov, Sergey Mikhrin, Johanna Rimböck, Guy Lepage, Peter Verheyen, Joris Van Campenhout, Peter Ossieur, Geert Morthier and Gunther Roelkens|Show fewer author(s)

Silicon photonics (SiPh) technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing. However, integrating efficient on-chip optical sources and in-line amplifiers remains challenging due to silicon’s indirect bandgap. In this study, we developed prefabricated standardized InAs/GaAs quantum-dot (QD) active devices optimized for micro-transfer printing and successfully integrated them on SiPh integrated circuits. By transfer-printing standardized QD devices onto specific regions of the SiPh chip, we realized O-band semiconductor optical amplifiers (SOAs), distributed feedback (DFB) lasers, and widely tunable lasers (TLs). The SOAs reached an on-chip gain of 7.5 dB at 1299 nm and maintained stable performance across a wide input power range. The integrated DFB lasers achieved waveguide (WG)-coupled output powers of up to 19.7 mW, with a side-mode suppression ratio (SMSR) of 33.3 dB, and demonstrated notable robustness against optical feedback, supporting error-free data rates of 30 Gbps without additional isolators. Meanwhile, the TLs demonstrated a wavelength tuning range exceeding 35 nm, and a WG-coupled output power greater than 3 mW. The micro-transfer printing approach effectively decouples the fabrication of non-native devices from the SiPh process, allowing back-end integration of the III–V devices. Our approach offers a viable path toward fully integrated III–V/SiPh platforms capable of supporting high-speed, high-capacity communication.Silicon photonics (SiPh) technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing. However, integrating efficient on-chip optical sources and in-line amplifiers remains challenging due to silicon’s indirect bandgap. In this study, we developed prefabricated standardized InAs/GaAs quantum-dot (QD) active devices optimized for micro-transfer printing and successfully integrated them on SiPh integrated circuits. By transfer-printing standardized QD devices onto specific regions of the SiPh chip, we realized O-band semiconductor optical amplifiers (SOAs), distributed feedback (DFB) lasers, and widely tunable lasers (TLs). The SOAs reached an on-chip gain of 7.5 dB at 1299 nm and maintained stable performance across a wide input power range. The integrated DFB lasers achieved waveguide (WG)-coupled output powers of up to 19.7 mW, with a side-mode suppression ratio (SMSR) of 33.3 dB, and demonstrated notable robustness against optical feedback, supporting error-free data rates of 30 Gbps without additional isolators. Meanwhile, the TLs demonstrated a wavelength tuning range exceeding 35 nm, and a WG-coupled output power greater than 3 mW. The micro-transfer printing approach effectively decouples the fabrication of non-native devices from the SiPh process, allowing back-end integration of the III–V devices. Our approach offers a viable path toward fully integrated III–V/SiPh platforms capable of supporting high-speed, high-capacity communication.showLess

Photonics Research