Contents
2025
Volume: 13 Issue 6
35 Article(s)
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Research Articles
Fiber Optics and Optical Communications
Concept and experimental demonstration of physics-guided end-to-end learning for optical communication systems
Qiarong Xiao, Chen Ding, Tengji Xu, Chester Shu, and Chaoran Huang
Driven by advancements in artificial intelligence, end-to-end learning has become a key method for system optimization in various fields, including communications. However, applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature. Existing methods typically require developing a precise differentiable digital model of the physical system, which is computationally complex and can cause significant performance loss after deployment. In response, we propose a novel end-to-end learning framework called physics-guided learning. This approach performs the forward pass through the actual transmission channel while simplifying the channel model for the backward pass to a simple white-box model. Despite the simplicity, both experimental and simulation results show that our method significantly outperforms other learning approaches for digital pre-distortion applications in coherent optical fiber systems. It enhances training speed and accuracy, reducing the number of training iterations by more than 80%. It improves transmission quality and noise resilience and offers superior generalization to varying transmission link conditions such as link losses, modulation formats, and scenarios with different transmission distances and optical amplification. Furthermore, our new end-to-end learning framework shows promise for broader applications in optimizing future communication systems, paving the way for more flexible and intelligent network designs.Driven by advancements in artificial intelligence, end-to-end learning has become a key method for system optimization in various fields, including communications. However, applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature. Existing methods typically require developing a precise differentiable digital model of the physical system, which is computationally complex and can cause significant performance loss after deployment. In response, we propose a novel end-to-end learning framework called physics-guided learning. This approach performs the forward pass through the actual transmission channel while simplifying the channel model for the backward pass to a simple white-box model. Despite the simplicity, both experimental and simulation results show that our method significantly outperforms other learning approaches for digital pre-distortion applications in coherent optical fiber systems. It enhances training speed and accuracy, reducing the number of training iterations by more than 80%. It improves transmission quality and noise resilience and offers superior generalization to varying transmission link conditions such as link losses, modulation formats, and scenarios with different transmission distances and optical amplification. Furthermore, our new end-to-end learning framework shows promise for broader applications in optimizing future communication systems, paving the way for more flexible and intelligent network designs..
Photonics Research
- Publication Date: May. 16, 2025
- Vol. 13, Issue 6, 1469 (2025)
Multifunctional fronthaul architecture enabled by electro-optic comb cloning | Editors' Pick
Jingjing Lin, Chenbo Zhang, Weihan Liang, Yi Zou... and Xiaopeng Xie|Show fewer author(s)
Beyond providing user access to the core network, the radio access network (RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality (VR) and drone fleets. To achieve this, fronthaul—the link connecting the central units/distributed units (CUs/DUs) to wireless remote units (RUs) in centralized RAN—must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs. However, existing solutions fall short of supporting these functions within one simple, cost-effective network. In this work, we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simplified DSP, using an electro-optic (EO) comb cloning technique to enable multifunctionality in fronthaul systems. Through the delivery of pilot comb lines, a 1 ps (integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing, realizing frequency synchronization between the CUs/DUs and RUs. Moreover, the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning, and supports wavelength division multiplexing (WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s. Thanks to the clock-synchronized and self-homodyne structure, DSP is streamlined, with digital timing recovery, carrier phase estimation, and frequency offset estimation all omitted. This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing.Beyond providing user access to the core network, the radio access network (RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality (VR) and drone fleets. To achieve this, fronthaul—the link connecting the central units/distributed units (CUs/DUs) to wireless remote units (RUs) in centralized RAN—must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs. However, existing solutions fall short of supporting these functions within one simple, cost-effective network. In this work, we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simplified DSP, using an electro-optic (EO) comb cloning technique to enable multifunctionality in fronthaul systems. Through the delivery of pilot comb lines, a 1 ps (integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing, realizing frequency synchronization between the CUs/DUs and RUs. Moreover, the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning, and supports wavelength division multiplexing (WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s. Thanks to the clock-synchronized and self-homodyne structure, DSP is streamlined, with digital timing recovery, carrier phase estimation, and frequency offset estimation all omitted. This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1591 (2025)
Co-wavelength-channel integration of ultra-low-frequency distributed acoustic sensing and high-capacity communication
Long Gu, Chaocheng Liu, Meng Xiang, Pengbai Xu... and Yuwen Qin|Show fewer author(s)
Integrating distributed ultra-low-frequency vibration sensing and high-speed fiber optical communication can provide additional functionality under the current submarine telecommunication network, such as ocean seismic monitoring and geological exploration. This work demonstrates an integrated sensing and communication (ISAC) system utilizing the same wavelength channel over a 38 km seven-core fiber for concurrent large-capacity transmission and ultra-low-frequency distributed acoustic sensing. Specifically, the digital subcarrier multiplexing (DSM) signal and the chirped-pulse sensing signal are frequency division multiplexed at the same wavelength channel, under the condition of the optimal protection interval bandwidth, relying on the DSM flexibility in spectral allocation. As a result, we successfully achieve a sensitivity of both 3.89 nε/Hz@0.1 Hz and 0.18 nε/Hz@10 Hz under a spatial resolution of 20 m, under the framework of direct detection and cross-correlation demodulation. Meanwhile, a transmission capacity record of 241.85 Tb/s is secured for the ISAC when wavelength and space division multiplexed DP-16QAM DSM signals are successfully transmitted to reach the 20% soft-decision feedforward correction coding threshold of 2×10-2.Integrating distributed ultra-low-frequency vibration sensing and high-speed fiber optical communication can provide additional functionality under the current submarine telecommunication network, such as ocean seismic monitoring and geological exploration. This work demonstrates an integrated sensing and communication (ISAC) system utilizing the same wavelength channel over a 38 km seven-core fiber for concurrent large-capacity transmission and ultra-low-frequency distributed acoustic sensing. Specifically, the digital subcarrier multiplexing (DSM) signal and the chirped-pulse sensing signal are frequency division multiplexed at the same wavelength channel, under the condition of the optimal protection interval bandwidth, relying on the DSM flexibility in spectral allocation. As a result, we successfully achieve a sensitivity of both
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1611 (2025)
High-speed and versatile ONN through parametric-based nonlinear computation
Xin Dong, Yuanjia Wang, Xiaoxiao Wen, Yi Zhou, and Kenneth K. Y. Wong
Neural networks (NNs), especially electronic-based NNs, have been rapidly developed in the past few decades. However, the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware, facing its bottleneck due to the slowdown of Moore’s law. Optical neural networks (ONNs), in which NNs are realized via optical components with information carried by photons at the speed of light, are drawing more attention nowadays. Despite the advantages of higher processing speed and lower system power consumption, one major challenge is to realize reliable and reusable algorithms in physical approaches, particularly nonlinear functions, for higher accuracy. In this paper, a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber (HNLF). With the specially designed mode-locked laser (MLL) and dispersive Fourier transform (DFT) algorithm, the overall computation frame rate can reach up to 40 MHz. Compared to ONNs using only linear computations, this system is able to improve the classification accuracies from 81.8% to 88.8% for the MNIST-digit dataset, and from 80.3% to 97.6% for the Vowel spoken audio dataset, without any hardware modifications.Neural networks (NNs), especially electronic-based NNs, have been rapidly developed in the past few decades. However, the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware, facing its bottleneck due to the slowdown of Moore’s law. Optical neural networks (ONNs), in which NNs are realized via optical components with information carried by photons at the speed of light, are drawing more attention nowadays. Despite the advantages of higher processing speed and lower system power consumption, one major challenge is to realize reliable and reusable algorithms in physical approaches, particularly nonlinear functions, for higher accuracy. In this paper, a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber (HNLF). With the specially designed mode-locked laser (MLL) and dispersive Fourier transform (DFT) algorithm, the overall computation frame rate can reach up to 40 MHz. Compared to ONNs using only linear computations, this system is able to improve the classification accuracies from 81.8% to 88.8% for the MNIST-digit dataset, and from 80.3% to 97.6% for the Vowel spoken audio dataset, without any hardware modifications..
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1647 (2025)
170 Gbps PDM underwater visible light communication utilizing a compact 5-
Zhilan Lu, Zhenhao Li, Xianhao Lin, Jifan Cai... and Nan Chi|Show fewer author(s)
The next generation of mobile communication is committed to establishing an integrated three-dimensional network that encompasses air, land, and sea. The visible light spectrum is situated within the transmission window for underwater communication, making visible light laser communication a focus of intense research. In this paper, we design and integrate a compact 5-λ transmission module based on five laser diodes with different wavelengths, utilizing a self-developed narrow-ridge GaN blue laser. With this transmitter, we have developed a polarization division multiplexing (PDM) 5-λ underwater visible light laser communication (UVLLC) system based on this transmission module. To enhance the transmission quality of the system, we designed a dual-branch ResDualNet network as a reciprocal differential receiver that incorporates common-mode noise cancellation and equalization functions for post-processing the received signals. With the combined contribution of the devices and algorithms, we achieved a total transmission rate of 170.1 Gbps, which represents a 16.1 Gbps increase compared to systems that do not utilize ResDualNet. To the best of our knowledge, this is the highest communication rate currently achievable in a UVLLC system using a single laser transmission module.The next generation of mobile communication is committed to establishing an integrated three-dimensional network that encompasses air, land, and sea. The visible light spectrum is situated within the transmission window for underwater communication, making visible light laser communication a focus of intense research. In this paper, we design and integrate a compact
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1654 (2025)
Imaging Systems, Microscopy, and Displays
Upsampled PSF enables high accuracy 3D superresolution imaging with sparse sampling rate
Jianwei Chen, Wei Shi, Jianzheng Feng, Jianlin Wang... and Yiming Li|Show fewer author(s)
Single-molecule localization microscopy (SMLM) provides nanoscale imaging, but pixel integration of acquired SMLM images limited the choice of sampling rate, which restricts the information content conveyed within each image. We propose an upsampled point spread function (PSF) inverse modeling method for large-pixel single-molecule localization, enabling precise three-dimensional superresolution imaging with a sparse sampling rate. Our approach could reduce data volume or expand the field of view by nearly an order of magnitude, while maintaining high localization accuracy and greatly improving the imaging throughput with the limited pixels available in existing cameras.Single-molecule localization microscopy (SMLM) provides nanoscale imaging, but pixel integration of acquired SMLM images limited the choice of sampling rate, which restricts the information content conveyed within each image. We propose an upsampled point spread function (PSF) inverse modeling method for large-pixel single-molecule localization, enabling precise three-dimensional superresolution imaging with a sparse sampling rate. Our approach could reduce data volume or expand the field of view by nearly an order of magnitude, while maintaining high localization accuracy and greatly improving the imaging throughput with the limited pixels available in existing cameras..
Photonics Research
- Publication Date: May. 16, 2025
- Vol. 13, Issue 6, 1485 (2025)
Hand-held laser for miniature photoacoustic microscopy: triggerable, millimeter scale, cost-effective, and functional | On the Cover
Hanjie Wang, Xingyu Zhu, Xiaobin Weng, Lanxin Deng... and Hongsen He|Show fewer author(s)
Miniaturization of photoacoustic microscopy (PAM) to portable and wearable levels requires special design of scanning, detection, acquisition, and excitation units. Now the first three can be minimized to gram and millimeter levels, but the excitation sources usually remain bulky and also face different challenges, including low pulse energy, wide pulse width, limited wavelength, or high cost. Here, we propose a high-performance laser source specially designed for a miniature PAM system, that is, the pulse-pumped passively Q-switched solid-state laser (PQS-SSL). Its kilohertz repetition rate, nanosecond pulse width, microjoule pulse energy, and UV to NIR spectra are exactly within the requirements of functional PAM imaging, together with the merits of millimeter scale and low cost, originating from the all-crystal-based configuration. The pulsed pump technique empowers the laser with frequency lock and trigger-in ability for system synchronization, overcoming the conventional free-running drawbacks, and the senior multi-pulse pump is also feasible to further compress the laser size and cost. We showcase its PAM performance on the USAF1951, carbon fiber, zebrafish, and lipid (wavelength extension to ∼1.2 μm). The novel, to our knowledge, pulse-pumped PQS-SSL is not only promising for general PAM, but also paves the way to develop miniature PAM systems, such as hand-held or brain-wearable modalities.Miniaturization of photoacoustic microscopy (PAM) to portable and wearable levels requires special design of scanning, detection, acquisition, and excitation units. Now the first three can be minimized to gram and millimeter levels, but the excitation sources usually remain bulky and also face different challenges, including low pulse energy, wide pulse width, limited wavelength, or high cost. Here, we propose a high-performance laser source specially designed for a miniature PAM system, that is, the pulse-pumped passively Q-switched solid-state laser (PQS-SSL). Its kilohertz repetition rate, nanosecond pulse width, microjoule pulse energy, and UV to NIR spectra are exactly within the requirements of functional PAM imaging, together with the merits of millimeter scale and low cost, originating from the all-crystal-based configuration. The pulsed pump technique empowers the laser with frequency lock and trigger-in ability for system synchronization, overcoming the conventional free-running drawbacks, and the senior multi-pulse pump is also feasible to further compress the laser size and cost. We showcase its PAM performance on the USAF1951, carbon fiber, zebrafish, and lipid (wavelength extension to
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1637 (2025)
Single-shot super-resolution imaging via discernibility in the high-dimensional light-field space based on ghost imaging
Zhishen Tong, Chenyu Hu, Jian Wang, Youheng Zhu... and Shensheng Han|Show fewer author(s)
Super-resolution (SR) imaging has been widely used in several fields like remote sensing and microscopy. However, it is challenging for existing SR approaches to capture SR images in a single shot, especially in dynamic imaging scenarios. In this study, we present a single-shot SR imaging scheme that leverages discernibility in the high-dimensional (H-D) light-field space based on a ghost imaging camera via sparsity constraints (GISC camera), which is capable of encoding H-D imaging information into a two-dimensional speckle pattern detected in a single shot. We demonstrate both theoretically and experimentally that while the resolution in the H-D light-field space, characterized by the second-order light-field correlation, remains limited by light-field diffraction, the single-shot spatial resolution is greatly improved beyond classical Rayleigh’s criterion by utilizing the discernibility in the H-D light-field space. We further quantify the effects of the sampling number, signal-to-noise ratio, and object sparsity on the resolution. Our results offer significant potential for the SR observation of high-speed dynamic processes.Super-resolution (SR) imaging has been widely used in several fields like remote sensing and microscopy. However, it is challenging for existing SR approaches to capture SR images in a single shot, especially in dynamic imaging scenarios. In this study, we present a single-shot SR imaging scheme that leverages discernibility in the high-dimensional (H-D) light-field space based on a ghost imaging camera via sparsity constraints (GISC camera), which is capable of encoding H-D imaging information into a two-dimensional speckle pattern detected in a single shot. We demonstrate both theoretically and experimentally that while the resolution in the H-D light-field space, characterized by the second-order light-field correlation, remains limited by light-field diffraction, the single-shot spatial resolution is greatly improved beyond classical Rayleigh’s criterion by utilizing the discernibility in the H-D light-field space. We further quantify the effects of the sampling number, signal-to-noise ratio, and object sparsity on the resolution. Our results offer significant potential for the SR observation of high-speed dynamic processes..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1709 (2025)
Instrumentation and Measurements
Single-shot electro-optic sampling with arbitrary terahertz polarization
Maximilian Lenz, and Pietro Musumeci
With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x- and y-THz fields simultaneously with a single (110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1736 (2025)
Resonant cavity enhanced laser frequency-swept carrier ranging method for noncooperative targets
Weijin Meng, Junkang Guo, Kai Tian, Yuqi Yu... and Zhigang Liu|Show fewer author(s)
Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface. Hence, this paper proposes a laser frequency-swept carrier (LFSC) ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection. Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m, the standard deviation of 10 measurements was less than 70 μm, measurement accuracy exceeded 27 μm, and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak. This method is useful for measurements of noncooperative targets, e.g., large-scale component assembly, industrial measurement, and biomedical testing.Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface. Hence, this paper proposes a laser frequency-swept carrier (LFSC) ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection. Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m, the standard deviation of 10 measurements was less than 70 μm, measurement accuracy exceeded 27 μm, and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak. This method is useful for measurements of noncooperative targets, e.g., large-scale component assembly, industrial measurement, and biomedical testing..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1767 (2025)
Integrated Optics
Passive silicon nitride integrated photonics for spatial intensity and phase sensing of visible light
Christoph Stockinger, Jörg S. Eismann, Natale Pruiti, Marc Sorel, and Peter Banzer
Phase is an intrinsic property of light, and thus a crucial parameter across numerous applications in modern optics. Various methods exist for measuring the phase of light, each presenting challenges and limitations—from the mechanical stability requirements of free-space interferometers to the computational complexity usually associated with methods based on spatial light modulators. Here, we utilize a passive photonic integrated circuit to spatially probe phase and intensity distributions of free-space light beams. Phase information is encoded into intensity through a set of passive on-chip interferometers, allowing conventional detectors to retrieve the phase profile of light through single-shot intensity measurements. Furthermore, we use silicon nitride as a material platform for the waveguide architecture, facilitating multi-spectral utilization in the visible spectral range. Our approach for fast, multi-spectral, and spatially resolved measurement of intensity and phase enables a wide variety of potential applications, ranging from microscopy to free-space optical communication.Phase is an intrinsic property of light, and thus a crucial parameter across numerous applications in modern optics. Various methods exist for measuring the phase of light, each presenting challenges and limitations—from the mechanical stability requirements of free-space interferometers to the computational complexity usually associated with methods based on spatial light modulators. Here, we utilize a passive photonic integrated circuit to spatially probe phase and intensity distributions of free-space light beams. Phase information is encoded into intensity through a set of passive on-chip interferometers, allowing conventional detectors to retrieve the phase profile of light through single-shot intensity measurements. Furthermore, we use silicon nitride as a material platform for the waveguide architecture, facilitating multi-spectral utilization in the visible spectral range. Our approach for fast, multi-spectral, and spatially resolved measurement of intensity and phase enables a wide variety of potential applications, ranging from microscopy to free-space optical communication..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1699 (2025)
Lasers and Laser Optics
Single-mode bending optofluidic waveguides and beam splitters in fused silica enabled by polarization-independent femtosecond-laser-assisted etching
Jianping Yu, Jian Xu, Jinxin Huang, Jianfang Chen... and Ya Cheng|Show fewer author(s)
Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems. The combination of femtosecond (fs)-laser-assisted etching of high-precision microchannels and vacuum-assisted liquid-core filling allows the controllable fabrication of low-loss optofluidic waveguides in fused silica. However, to form high-performance bending optofluidic waveguides in fused silica, facile fabrication of long, homogeneous microchannels with arbitrary shapes remains challenging due to the polarization-dependent limitations of conventional fs-laser-assisted etching. Here, we demonstrate the rational fabrication of homogeneous curved microchannels in fused silica using polarization-independent fs-laser-assisted etching enabled by a low-pulse-overlap scheme. An etching rate exceeding 350 μm/h can be reliably achieved at a pulse overlap of 10 pulses μm-1 regardless of the variation of the laser polarization. Highly interconnected nanocracks are observed along the laser writing direction in the laser-modified regions. Using the polarization-independent fs-laser-assisted etching combined with spatial beam shaping and carbon dioxide laser irradiation, uniform and smooth curved microchannels with centimeter lengths, flexible configurations, and nearly circular cross-sections are initially produced. Subsequently, single-mode bending optofluidic waveguides and beam splitters are created by filling tunable refractive index liquid-core solutions into the channels. The proposed method enables efficient processing of arbitrarily oriented homogeneous microchannels, paving the way for the development of large-scale, complex microfluidic photonic circuits.Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems. The combination of femtosecond (fs)-laser-assisted etching of high-precision microchannels and vacuum-assisted liquid-core filling allows the controllable fabrication of low-loss optofluidic waveguides in fused silica. However, to form high-performance bending optofluidic waveguides in fused silica, facile fabrication of long, homogeneous microchannels with arbitrary shapes remains challenging due to the polarization-dependent limitations of conventional fs-laser-assisted etching. Here, we demonstrate the rational fabrication of homogeneous curved microchannels in fused silica using polarization-independent fs-laser-assisted etching enabled by a low-pulse-overlap scheme. An etching rate exceeding 350 μm/h can be reliably achieved at a pulse overlap of
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1562 (2025)
Non-symmetrical vortex beam shaping in VECSEL laser arrays
Sopfy Karuseichyk, Ilan Audoin, Vishwa Pal, and Fabien Bretenaker
We propose and numerically test, to our knowledge, a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser (DVECSEL). The method is based on a phase-locking ring array of lasers created inside a degenerate cavity with a binary amplitude mask containing circular holes. The diffraction engineering of the mask profile allows for controlling the complex coupling between the lasers. The asymmetry between different lasers is introduced by varying the hole diameters corresponding to different lasers. Several examples of masks with non-uniform or uniform circular holes are investigated numerically and analytically to assess the impact of non-uniform complex coupling coefficients on the degeneracy between the vortex and anti-vortex steady states of the ring laser arrays. It is found that the in-phase solution always dominates irrespective of non-uniform masks. The only solution to make one particular vortex solution dominant over other possible steady-state solutions consists of imprinting the necessary phase shift among neighboring lasers in the argument of their coupling coefficients. We also investigate the role of the Henry factor inherent to the use of a semiconductor active medium in the probabilities to generate vortex solutions. Analytical calculations are performed to generalize a formula previously reported [Opt. Express30, 15648 (2022)OPEXFF1094-408710.1364/OE.456946], for the limiting Henry factor to cover the case of complex couplings.We propose and numerically test, to our knowledge, a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser (DVECSEL). The method is based on a phase-locking ring array of lasers created inside a degenerate cavity with a binary amplitude mask containing circular holes. The diffraction engineering of the mask profile allows for controlling the complex coupling between the lasers. The asymmetry between different lasers is introduced by varying the hole diameters corresponding to different lasers. Several examples of masks with non-uniform or uniform circular holes are investigated numerically and analytically to assess the impact of non-uniform complex coupling coefficients on the degeneracy between the vortex and anti-vortex steady states of the ring laser arrays. It is found that the in-phase solution always dominates irrespective of non-uniform masks. The only solution to make one particular vortex solution dominant over other possible steady-state solutions consists of imprinting the necessary phase shift among neighboring lasers in the argument of their coupling coefficients. We also investigate the role of the Henry factor inherent to the use of a semiconductor active medium in the probabilities to generate vortex solutions. Analytical calculations are performed to generalize a formula previously reported [Opt. Express30 , 15648 (2022 )OPEXFF 1094-4087 10.1364/OE.456946
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1600 (2025)
Origin of SBS-induced mode distortion in high power narrow linewidth fiber amplifiers
Yu Wen, Chun Zhang, Yuan Zhu, Zixiang Gao... and Jianjun Wang|Show fewer author(s)
Stimulated Brillouin scattering (SBS)-induced mode distortion (MD) in high power narrow linewidth fiber amplifiers has been implemented, and the origin has been investigated from the aspect of the evolution of the optical spectrum, spatial beam profiles, and temporal-frequency domain characteristics. It is shown that, following the onset of the backward giant pulses generated by SBS, forward giant pulses were generated, which reached multi-kilowatt level peak power and triggered the onset of stimulated Raman scattering (SRS). After the onset of SRS, the beam quality starts to degrade, and the beam profiles deteriorate obviously. It reveals that the SBS-induced MD is a two-stage physical process: SBS-induced forward giant pulses trigger the SRS effect, and then the SRS effect causes the beam deterioration of the signal laser, which means that SRS is the origin of the MD observed after the onset of SBS. To the best of our knowledge, this is the first revelation of SBS-induced mode distortion in high power narrow linewidth fiber amplifiers, which can facilitate the in-depth understanding and effective suppression of the complicated mode evolution phenomena.Stimulated Brillouin scattering (SBS)-induced mode distortion (MD) in high power narrow linewidth fiber amplifiers has been implemented, and the origin has been investigated from the aspect of the evolution of the optical spectrum, spatial beam profiles, and temporal-frequency domain characteristics. It is shown that, following the onset of the backward giant pulses generated by SBS, forward giant pulses were generated, which reached multi-kilowatt level peak power and triggered the onset of stimulated Raman scattering (SRS). After the onset of SRS, the beam quality starts to degrade, and the beam profiles deteriorate obviously. It reveals that the SBS-induced MD is a two-stage physical process: SBS-induced forward giant pulses trigger the SRS effect, and then the SRS effect causes the beam deterioration of the signal laser, which means that SRS is the origin of the MD observed after the onset of SBS. To the best of our knowledge, this is the first revelation of SBS-induced mode distortion in high power narrow linewidth fiber amplifiers, which can facilitate the in-depth understanding and effective suppression of the complicated mode evolution phenomena..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1631 (2025)
Collisions of heteronuclear dichromatic soliton compounds in a passively mode-locked fiber laser
Yuansheng Ma, Ziyang Zhang, Yu Ning, Jiangyong He... and Zhi Wang|Show fewer author(s)
The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions. In comparison to multimode spatiotemporal mode-locked solitons, expanding the wavelength dimension is also crucial for studying the dynamics of multi-dimensional solitons, with simpler characterization techniques. By inserting a section of zero-dispersion highly nonlinear fiber (HNLF) into a passively mode-locked fiber laser, two heteronuclear dichromatic soliton compounds with different group velocities (GVs) are formed within the resonant cavity of the laser. The cross-phase modulation effect leads to the formation of a robust fast-GV compound (FGC), consisting of a partially coherent dissipative soliton bunch (PCDSB) and dispersion waves (DWs), while a conventional soliton (CS) and a narrow spectral pulse (NSP) form a slow-GV compound (SGC). Multiple SGCs can further interact to form an SGC loosely bound complex. These two types of compounds with different GVs continuously collide and exchange energy through the four-wave mixing (FWM) effect in the HNLF, promoting the annihilation, survival, and regeneration of the SGC complex. This exploration of interactions between asynchronous compounds broadens the study of soliton dynamics in multi-dimensions and offers insights for potential applications in areas such as high-throughput optical communication and optical computing.The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions. In comparison to multimode spatiotemporal mode-locked solitons, expanding the wavelength dimension is also crucial for studying the dynamics of multi-dimensional solitons, with simpler characterization techniques. By inserting a section of zero-dispersion highly nonlinear fiber (HNLF) into a passively mode-locked fiber laser, two heteronuclear dichromatic soliton compounds with different group velocities (GVs) are formed within the resonant cavity of the laser. The cross-phase modulation effect leads to the formation of a robust fast-GV compound (FGC), consisting of a partially coherent dissipative soliton bunch (PCDSB) and dispersion waves (DWs), while a conventional soliton (CS) and a narrow spectral pulse (NSP) form a slow-GV compound (SGC). Multiple SGCs can further interact to form an SGC loosely bound complex. These two types of compounds with different GVs continuously collide and exchange energy through the four-wave mixing (FWM) effect in the HNLF, promoting the annihilation, survival, and regeneration of the SGC complex. This exploration of interactions between asynchronous compounds broadens the study of soliton dynamics in multi-dimensions and offers insights for potential applications in areas such as high-throughput optical communication and optical computing..
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1680 (2025)
Nanophotonics and Photonic Crystals
Dual-band dislocation modes in a topological photonic crystal
Fangyuan Peng, Hongxiang Chen, Lipeng Wan, Xiao-Dong Chen... and Tianbao Yu|Show fewer author(s)
Introducing topological lattice defects, such as dislocations, into topological photonic crystals enables the emergence of many interesting phenomena, including robust bound states and fractional charges. Previous studies have primarily focused on the realization of dislocation modes within a single band gap, which limits the number of dislocation modes and their applications. Here, we design a topological photonic crystal with two topologically non-trivial band gaps. By introducing a dislocation defect into this system, we observe the emergence of localized dislocation modes in both band gaps. Furthermore, we demonstrate a two-channel add-drop filter by coupling two dislocation modes with topological edge modes. These findings are rigorously validated through full-wave numerical simulations and experimental pump-probe transmission measurements. Our results provide a foundation for further exploration of dislocation modes and unlock the potential for harnessing other topological defect modes in dual-band-gap systems.Introducing topological lattice defects, such as dislocations, into topological photonic crystals enables the emergence of many interesting phenomena, including robust bound states and fractional charges. Previous studies have primarily focused on the realization of dislocation modes within a single band gap, which limits the number of dislocation modes and their applications. Here, we design a topological photonic crystal with two topologically non-trivial band gaps. By introducing a dislocation defect into this system, we observe the emergence of localized dislocation modes in both band gaps. Furthermore, we demonstrate a two-channel add-drop filter by coupling two dislocation modes with topological edge modes. These findings are rigorously validated through full-wave numerical simulations and experimental pump-probe transmission measurements. Our results provide a foundation for further exploration of dislocation modes and unlock the potential for harnessing other topological defect modes in dual-band-gap systems..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1554 (2025)
Broadband thin-film lithium niobate rapid adiabatic couplers enabling highly visible two-photon interference
Sunghyun Moon, Jinil Lee, Junhyung Lee, Youngseo Koh... and Hyounghan Kwon|Show fewer author(s)
The integrated quantum interferometer has provided a promising route for manipulating and measuring quantum states of light with high precision, requiring negligible optical loss, broad bandwidth, robust fabrication tolerance, and scalability. In this paper, a rapid adiabatic coupler (RAC) is presented as a compelling solution for implementing the integrated quantum interferometer on a thin-film lithium niobate (TFLN)-based platform, enabling a compact, broadband, and low-loss optical coupler. The TFLN-based RACs are carefully designed by manipulating a curvature along the structures with consideration of inherent birefringence as well as fabrication-induced slanted sidewalls. The high extinction ratio over 20 dB of the RAC-based Mach–Zehnder interferometer (MZI) is achieved in the wavelength range from 1500 to 1600 nm. The beam splitter (BS) with the balanced splitting ratio is exploited for observation of on-chip Hong–Ou–Mandel (HOM) interference with high visibility of 99.25%. We believe TFLN-based RACs hold great potential to be favorably utilized for integrated quantum interferometers, enabling widespread adoptions in myriad applications in integrated quantum optics.The integrated quantum interferometer has provided a promising route for manipulating and measuring quantum states of light with high precision, requiring negligible optical loss, broad bandwidth, robust fabrication tolerance, and scalability. In this paper, a rapid adiabatic coupler (RAC) is presented as a compelling solution for implementing the integrated quantum interferometer on a thin-film lithium niobate (TFLN)-based platform, enabling a compact, broadband, and low-loss optical coupler. The TFLN-based RACs are carefully designed by manipulating a curvature along the structures with consideration of inherent birefringence as well as fabrication-induced slanted sidewalls. The high extinction ratio over 20 dB of the RAC-based Mach–Zehnder interferometer (MZI) is achieved in the wavelength range from 1500 to 1600 nm. The beam splitter (BS) with the balanced splitting ratio is exploited for observation of on-chip Hong–Ou–Mandel (HOM) interference with high visibility of 99.25%. We believe TFLN-based RACs hold great potential to be favorably utilized for integrated quantum interferometers, enabling widespread adoptions in myriad applications in integrated quantum optics..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1579 (2025)
Formation and radiation of unidirectional guided resonances in asymmetric gratings with simultaneously broken up-down mirror and in-plane C2 symmetries
Sun-Goo Lee, Kap-Joong Kim, and Wook-Jae Lee
Unidirectional guided resonances (UGRs) in planar photonic lattices are distinctive resonant eigenstates that emit light in a single direction. A recent study has demonstrated that UGRs can be utilized to implement ultralow-loss grating couplers for integrated photonic applications. In this study, we investigate the formation and radiation of UGRs in two types of L-shaped gratings, type I and type II, which exhibit both broken up-down mirror symmetry and broken in-plane C2 symmetry. In type I gratings, quasi-UGRs are readily identified in the lower band, whereas in type II gratings they appear in the upper band. We demonstrate that, as the relevant grating parameters are gradually varied, these quasi-UGRs evolve into genuine UGRs in the lower band for type I gratings and in the upper band for type II gratings. In type I gratings, UGRs produce negative-angle emission because their Poynting vectors are oriented antiparallel to their wavevectors, while in type II gratings, UGRs yield positive-angle emission due to the parallel alignment of their Poynting vectors and wavevectors. Moreover, the position and emission angle of UGRs can be systematically controlled by varying the lattice parameters. Our findings offer valuable insights for developing high-efficiency optical interconnects that leverage UGRs.Unidirectional guided resonances (UGRs) in planar photonic lattices are distinctive resonant eigenstates that emit light in a single direction. A recent study has demonstrated that UGRs can be utilized to implement ultralow-loss grating couplers for integrated photonic applications. In this study, we investigate the formation and radiation of UGRs in two types of L-shaped gratings, type I and type II, which exhibit both broken up-down mirror symmetry and broken in-plane
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1783 (2025)
Nonlinear Optics
Polarization-dependent neutral nitrogen fluorescence induced by long-distance laser filamentation
Yuezheng Wang, Lu Sun, Zhiwenqi An, Zeliang Zhang... and Weiwei Liu|Show fewer author(s)
Femtosecond laser filamentation has attracted significant attention due to its applications in remote sensing of atmospheric pollutants and artificial weather intervention. Nitrogen is the most abundant gas in the atmosphere, and its stimulated ultraviolet emission is remarkably clean, distinctly different from the fluorescence obtained through electron impact or laser breakdown. While numerous experiments and mechanism analyses have been conducted on its characteristic fluorescence excited by laser filamentation, they predominantly focused on short-distance filamentation (less than 1 m). Contrary to previous reports, we find that at long distances (30 m), the fluorescence intensity of neutral nitrogen molecules excited by linearly polarized laser pulses is approximately 7 times that excited by circularly polarized pulses with the same energy. This enhancement is caused by the enhanced tunneling ionization rate, 3.7 times that under circular polarization, and the elongated filament length, 1.85 times that under circular polarization, when using linear polarization. Additionally, after comparing existing theories for N2(C3Πu)) excitation, the dissociation-recombination model is found to be more appropriate for explaining the formation of N2(C3Πu)) excited states during long-distance filamentation.Femtosecond laser filamentation has attracted significant attention due to its applications in remote sensing of atmospheric pollutants and artificial weather intervention. Nitrogen is the most abundant gas in the atmosphere, and its stimulated ultraviolet emission is remarkably clean, distinctly different from the fluorescence obtained through electron impact or laser breakdown. While numerous experiments and mechanism analyses have been conducted on its characteristic fluorescence excited by laser filamentation, they predominantly focused on short-distance filamentation (less than 1 m). Contrary to previous reports, we find that at long distances (30 m), the fluorescence intensity of neutral nitrogen molecules excited by linearly polarized laser pulses is approximately 7 times that excited by circularly polarized pulses with the same energy. This enhancement is caused by the enhanced tunneling ionization rate, 3.7 times that under circular polarization, and the elongated filament length, 1.85 times that under circular polarization, when using linear polarization. Additionally, after comparing existing theories for
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1691 (2025)
Optical Devices
All-fiber-optic mass sensor based on optomechanical nanofilm resonators
Qiao Lin, Xin Ding, Weiguan Zhang, Yueliang Xiao... and Shen Liu|Show fewer author(s)
Mass detection plays an indispensable role in many fields like medical targeted therapy, biological cytology, and nanophysics. However, traditional mass detection faces the challenge of a complex system, expensive instruments, and long testing time. Here we report an all-fiber-optic mass sensor based on a nanofilm resonator. Using resonant frequency shifts as the readout of analyte mass, the sensor achieves the mass sensitivity of 0.920 kHz/pg with a mass resolution of 1.9×10-14 g, for the first-order mode in the mass range up to 372 pg at room temperature. In this work, we transfer the excitation laser and detection laser to the micro-cavity structure at the end of the optical fiber. Combined with optical fibers, the sensor can be made extremely integrated, making it more stable and collimation-free compared with traditional bulky optical setups. Its good biocompatibility and anti-electromagnetism disturbance ability also make this mass sensor potentially a beneficial tool for cell biology and basic physics measurements.Mass detection plays an indispensable role in many fields like medical targeted therapy, biological cytology, and nanophysics. However, traditional mass detection faces the challenge of a complex system, expensive instruments, and long testing time. Here we report an all-fiber-optic mass sensor based on a nanofilm resonator. Using resonant frequency shifts as the readout of analyte mass, the sensor achieves the mass sensitivity of 0.920 kHz/pg with a mass resolution of
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1526 (2025)
High-performance UV polarization sensitive photodetector for a graphene(2D)/GaN(3D) junction with a non-centrosymmetric electric field | Spotlight on Optics
Can Zou, Qing Liu, Lu Zhang, Xiao Tang... and Fangliang Gao|Show fewer author(s)
This study pioneers a high-performance UV polarization-sensitive photodetector by ingeniously integrating non-centrosymmetric metal nanostructures into a graphene (Gr)/Al2O3/GaN heterojunction. Unlike conventional approaches constrained by graphene’s intrinsic isotropy or complex nanoscale patterning, our design introduces asymmetric metal architectures (E-/T-type) to artificially create directional anisotropy. These structures generate plasmon-enhanced localized electric fields that selectively amplify photogenerated carrier momentum under polarized UV light (325 nm), synergized with Fowler-Nordheim tunneling (FNT) across an atomically thin Al2O3 barrier. The result is a breakthrough in performance: a record anisotropy ratio of 115.5 (E-type, -2 V) and exceptional responsivity (97.7 A/W), surpassing existing graphene-based detectors by over an order of magnitude. Crucially, by systematically modulating metal geometry and density, we demonstrate a universal platform adaptable to diverse 2D/3D systems. This study provides a valuable reference for developing and practically applying photodetectors with higher anisotropy than ultraviolet polarization sensitivity.This study pioneers a high-performance UV polarization-sensitive photodetector by ingeniously integrating non-centrosymmetric metal nanostructures into a graphene
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1544 (2025)
Efficient on-chip waveguide amplifiers in GeSbS-loaded etchless erbium-doped lithium niobate thin film
Chunxu Wang, Jingcui Song, Zhaohuan Ao, Yingyu Chen... and Zhaohui Li|Show fewer author(s)
In this paper, an efficient Ge25Sb10S65 (GeSbS)-loaded erbium-doped lithium niobate waveguide amplifier is demonstrated. By dimensional optimization of the waveguide, an internal net gain of approximately 28 dB and a maximum on-chip output power of 8.2 dBm are demonstrated upon 1480 nm bidirectional pumping. Due to the improved optical mode field distribution within the active erbium-doped lithium niobate film and the mode overlap ratio between the pump and signal sources, a 15% high conversion efficiency can be achieved at a modest pump power of 45 mW. Furthermore, the noise figure of the amplifier can be maintained below 6 dB for low-input-signal power levels. Compared to state-of-the-art erbium-doped waveguide amplifiers (EDWAs), this heterogeneously integrated device shows superior gain performance at the desired optical C-band while avoiding the complex plasma etching process of lithium niobate, providing an inspirative solution for power compensation in the optical telecommunications.In this paper, an efficient
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1674 (2025)
Magnetic fluid enabled hexagonal fiber grating for vector magnetic field sensing
Siyu Chen, Chen Jiang, Yuehui Ma, Yunhe Zhao... and Yunqi Liu|Show fewer author(s)
Optical fiber magnetic field sensors play a crucial role in aerospace and medical fields due to their high sensitivity, fast response time, and resistance to electromagnetic interference. Most current research primarily focuses on detecting magnetic field intensity; however, the magnetic field is a vector field with both intensity and direction, making vector magnetic field measurement significantly important in various fields. Here, we experimentally demonstrated a vector magnetic field sensor using a magnetic fluid (MF) enabled hexagonal fiber grating. Such a specialty optical fiber device features strong asymmetric evanescent field distribution along the index perturbed area, from which the overcoated MF can sense the external magnetic field. When the fiber magnetometer operated at the dispersion turning point, a maximum sensitivity of 10.48 nm/mT was achieved within a range of 0–20.7 mT, which is one order of magnitude greater than that of conventional fiber grating sensors. Utilizing the polygon optical fiber, our demonstrated device simultaneously achieves a maximum orientation sensitivity of 1.17 nm/deg within a range of 0°–30°. This hexagonal fiber grating as an excellent vector magnetic field sensor may be used in military, aerospace, medical sectors, etc.Optical fiber magnetic field sensors play a crucial role in aerospace and medical fields due to their high sensitivity, fast response time, and resistance to electromagnetic interference. Most current research primarily focuses on detecting magnetic field intensity; however, the magnetic field is a vector field with both intensity and direction, making vector magnetic field measurement significantly important in various fields. Here, we experimentally demonstrated a vector magnetic field sensor using a magnetic fluid (MF) enabled hexagonal fiber grating. Such a specialty optical fiber device features strong asymmetric evanescent field distribution along the index perturbed area, from which the overcoated MF can sense the external magnetic field. When the fiber magnetometer operated at the dispersion turning point, a maximum sensitivity of 10.48 nm/mT was achieved within a range of 0–20.7 mT, which is one order of magnitude greater than that of conventional fiber grating sensors. Utilizing the polygon optical fiber, our demonstrated device simultaneously achieves a maximum orientation sensitivity of 1.17 nm/deg within a range of 0°–30°. This hexagonal fiber grating as an excellent vector magnetic field sensor may be used in military, aerospace, medical sectors, etc..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1726 (2025)
Optoelectronics
High-speed avalanche photodiodes for optical communication
Tianhong Liu, Guohao Yang, Jinping Li, and Cunzhu Tong
Advanced technologies such as autonomous driving, cloud computing, Internet of Things, and artificial intelligence have considerably increased data demand. Real-time interactions further drive the development of high-speed, high-capacity networks. Advancements in communication systems depend on developing high-speed optoelectronic devices. Optical communication systems are rapidly evolving, with data rates advancing from 800 Gbps to 1.6 Tbps and beyond, driven by the development of high-performance photodetectors, high-speed modulators, and advanced RF devices. Avalanche photodetectors (APDs) are used in long-distance applications owing to their high internal gain and responsivity. This paper reviews the structural designs of APDs based on various materials for high-speed communication and provides an outlook on developing APDs based on advanced materials.Advanced technologies such as autonomous driving, cloud computing, Internet of Things, and artificial intelligence have considerably increased data demand. Real-time interactions further drive the development of high-speed, high-capacity networks. Advancements in communication systems depend on developing high-speed optoelectronic devices. Optical communication systems are rapidly evolving, with data rates advancing from 800 Gbps to 1.6 Tbps and beyond, driven by the development of high-performance photodetectors, high-speed modulators, and advanced RF devices. Avalanche photodetectors (APDs) are used in long-distance applications owing to their high internal gain and responsivity. This paper reviews the structural designs of APDs based on various materials for high-speed communication and provides an outlook on developing APDs based on advanced materials..
Photonics Research
- Publication Date: May. 07, 2025
- Vol. 13, Issue 6, 1438 (2025)
Electron–phonon coupling enhanced by graphene/PZT heterostructure for infrared emission and optical information transmission
Kaixi Bi, Linyu Mei, Shuqi Han, Jialiang Chen... and Xiujian Chou|Show fewer author(s)
High-performance infrared emitters hold substantial importance in modern engineering and physics. Here, we introduce graphene/PZT (lead zirconate titanate) heterostructure as a new platform for the development of infrared source structure based on an electron–phonon coupling and emitting mechanism. A series of electrical characterizations including carrier mobility [11,361.55 cm2/(V·s)], pulse current (30 ms response time), and cycling stability (2000 cycles) modulated by polarized film was provided. Its maximum working temperature reaches ∼1041 K (∼768°C), and it was broken at 1173 K (∼900°C) within ∼1.2 s rise time and fall time. Based on Wien’s displacement law, the high temperature will lead to near–mid–far thermal infrared when the heterostructure is applied to external voltages, and obvious bright white light could be observed by the naked eye. The changing process has also been recorded by mobile phone. In subsequent infrared emitting applications, 11 V bias voltage was applied on the PZT/graphene structure to produce the temperature change of ∼299 to 445 K within ∼0.96 s rise time and ∼0.98 s fall time. To demonstrate its optical information transmission ability, we exhibited “N, U, C” letters by the time-frequency method at 3 mm×3 mm@20 m condition. Combining with spatial Morse code infrared units, alphabetic information could also be transmitted by infrared array images. Compared with the traditional infrared emitter, the electron–phonon enhancing mechanism and high-performance emission properties of the heterostructure demonstrated a novel and reliable platform for further infrared optical applications.High-performance infrared emitters hold substantial importance in modern engineering and physics. Here, we introduce graphene/PZT (lead zirconate titanate) heterostructure as a new platform for the development of infrared source structure based on an electron–phonon coupling and emitting mechanism. A series of electrical characterizations including carrier mobility [
Photonics Research
- Publication Date: May. 16, 2025
- Vol. 13, Issue 6, 1459 (2025)
Physical Optics
Single-shot common-path encoded coherent diffraction imaging with OAM multiplexing
Mingli Sun, Yingming Xu, Yuanyuan Liu, Chiye Li... and Qiwen Zhan|Show fewer author(s)
Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena, particularly suitable for measuring the density of media with non-repeatable changes and uncertainties. However, traditional single-pattern multiplexed imaging faces challenges in retrieving amplitude and phase information of multiple frames without sacrificing spatial resolution and phase accuracy. In this study, we demonstrate single-shot common-path encoded coherent diffraction imaging with orbital angular momentum (OAM) multiplexing. It employs a sequence of vortex illumination fields, combined with encoding wavefront modulation and a vortex multiplexing phase retrieval algorithm, to achieve the retrieval of complex amplitudes from dynamic samples in single shots. Our experimental validation demonstrated the capability to achieve 9-frame high-resolution phase imaging of the dynamic sample in a single diffraction pattern. The spatial resolution and phase accuracy improve to 9.84 μm and 4.7% with this lensless multiplexed imaging system, which is comparable to single-mode imaging. This technology provides a multiplexed dimension with orbital angular momentum and holds potential in the study of transient continuous phenomena.Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena, particularly suitable for measuring the density of media with non-repeatable changes and uncertainties. However, traditional single-pattern multiplexed imaging faces challenges in retrieving amplitude and phase information of multiple frames without sacrificing spatial resolution and phase accuracy. In this study, we demonstrate single-shot common-path encoded coherent diffraction imaging with orbital angular momentum (OAM) multiplexing. It employs a sequence of vortex illumination fields, combined with encoding wavefront modulation and a vortex multiplexing phase retrieval algorithm, to achieve the retrieval of complex amplitudes from dynamic samples in single shots. Our experimental validation demonstrated the capability to achieve 9-frame high-resolution phase imaging of the dynamic sample in a single diffraction pattern. The spatial resolution and phase accuracy improve to 9.84 μm and 4.7% with this lensless multiplexed imaging system, which is comparable to single-mode imaging. This technology provides a multiplexed dimension with orbital angular momentum and holds potential in the study of transient continuous phenomena..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1620 (2025)
Chirality-assisted local transverse spin angular momentum transfer for enantiospecific detection at the nanoscale
Lü Feng, Ruohu Zhang, Zhigang Li, Bingjue Li... and Guanghao Rui|Show fewer author(s)
The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science, chemistry, and biology. This study presents, to our knowledge, a novel method for chirality detection based on transverse optical torque (OT), which leverages the transverse rotation of achiral particles induced by the transfer of chirality from the chiral particle within interference fields formed by the incident light without spin angular momentum (SAM). We demonstrate, both numerically and analytically, that by modulating the chirality of the chiral particle within a dimer system, it is possible to achieve the transfer of local SAM to the gold particle, thereby generating a transverse OT perpendicular to the light propagation direction. Furthermore, by adjusting the orientation of linear polarization in the excitation field, the respective contributions of electric and magnetic responses to the chirality-transfer-induced transverse OT can be exclusively observed separately, providing deeper insights into the underlying physical mechanisms. More importantly, the transverse OT exhibits an approximately linear dependence on the chirality parameter of the chiral particle, enabling enantiospecific detection of nanosamples. By replacing gold nanoparticles with suitable high-refractive-index dielectric materials such as germanium, the induced transverse magnetic dipolar OT can be further enhanced by more than two orders of magnitude, significantly improving the sensitivity of chirality detection and making it possible to detect weak chiral signals with exceptional precision. This work broadens the application scope of OTs in chirality detection and highlights the potential of chirality transfer mechanisms for advanced optical manipulation and the identification and analysis of chiral substances.The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science, chemistry, and biology. This study presents, to our knowledge, a novel method for chirality detection based on transverse optical torque (OT), which leverages the transverse rotation of achiral particles induced by the transfer of chirality from the chiral particle within interference fields formed by the incident light without spin angular momentum (SAM). We demonstrate, both numerically and analytically, that by modulating the chirality of the chiral particle within a dimer system, it is possible to achieve the transfer of local SAM to the gold particle, thereby generating a transverse OT perpendicular to the light propagation direction. Furthermore, by adjusting the orientation of linear polarization in the excitation field, the respective contributions of electric and magnetic responses to the chirality-transfer-induced transverse OT can be exclusively observed separately, providing deeper insights into the underlying physical mechanisms. More importantly, the transverse OT exhibits an approximately linear dependence on the chirality parameter of the chiral particle, enabling enantiospecific detection of nanosamples. By replacing gold nanoparticles with suitable high-refractive-index dielectric materials such as germanium, the induced transverse magnetic dipolar OT can be further enhanced by more than two orders of magnitude, significantly improving the sensitivity of chirality detection and making it possible to detect weak chiral signals with exceptional precision. This work broadens the application scope of OTs in chirality detection and highlights the potential of chirality transfer mechanisms for advanced optical manipulation and the identification and analysis of chiral substances..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1756 (2025)
Perfect spatiotemporal optical vortices | Spotlight on Optics
Haihao Fan, Qian Cao, Xin Liu, Andy Chong, and Qiwen Zhan
Recently, spatiotemporal optical vortices (STOVs) with transverse orbital angular momentum have emerged as a significant research topic. While various STOV fields have been explored, they often suffer from a critical limitation: the spatial and temporal dimensions of the STOV wavepacket are strongly correlated with the topological charge. This dependence hinders the simultaneous achievement of high spatial accuracy and high topological charge. To address this limitation, we theoretically and experimentally investigate a new class of STOV wavepackets generated through the spatiotemporal Fourier transform of polychromatic Bessel–Gaussian beams, which we term as perfect spatiotemporal optical vortices. Unlike conventional STOVs, perfect STOVs exhibit spatial and temporal diameters that are independent of the topological charge. Furthermore, we demonstrate the generation of spatiotemporal optical vortex lattices by colliding perfect STOV wavepackets, enabling flexible manipulation of the number and sign of sub-vortices.Recently, spatiotemporal optical vortices (STOVs) with transverse orbital angular momentum have emerged as a significant research topic. While various STOV fields have been explored, they often suffer from a critical limitation: the spatial and temporal dimensions of the STOV wavepacket are strongly correlated with the topological charge. This dependence hinders the simultaneous achievement of high spatial accuracy and high topological charge. To address this limitation, we theoretically and experimentally investigate a new class of STOV wavepackets generated through the spatiotemporal Fourier transform of polychromatic Bessel–Gaussian beams, which we term as perfect spatiotemporal optical vortices. Unlike conventional STOVs, perfect STOVs exhibit spatial and temporal diameters that are independent of the topological charge. Furthermore, we demonstrate the generation of spatiotemporal optical vortex lattices by colliding perfect STOV wavepackets, enabling flexible manipulation of the number and sign of sub-vortices..
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1776 (2025)
Quantum Optics
Quantumness of gamma-ray and hard X-ray photon emission from 3D free-electron lattices | Editors' Pick
Leshi Zhao, Linfeng Zhang, Haitan Xu, and Zheng Li
Crystalline undulator radiation (CUR) is emitted by charged particles channeling through a periodically bent crystal. We show that entangled high-energy photons of the order of 100 MeV can be generated from CUR and obtain the quantum entanglement properties of the double-photon emission of CUR with a nonperturbative quantum field theory. We demonstrate that the crystalline undulator (CU) can induce a 3D free-electron lattice with premicrobunched electrons, and the resulting free-electron lattice can enhance the entangled high-energy photon emission for certain angles by phase matching. We also examine the effects of demodulation and dechanneling during the electron beam channeling process, and show the dependence of the dechanneling and demodulation lengths on the undulator parameters.Crystalline undulator radiation (CUR) is emitted by charged particles channeling through a periodically bent crystal. We show that entangled high-energy photons of the order of 100 MeV can be generated from CUR and obtain the quantum entanglement properties of the double-photon emission of CUR with a nonperturbative quantum field theory. We demonstrate that the crystalline undulator (CU) can induce a 3D free-electron lattice with premicrobunched electrons, and the resulting free-electron lattice can enhance the entangled high-energy photon emission for certain angles by phase matching. We also examine the effects of demodulation and dechanneling during the electron beam channeling process, and show the dependence of the dechanneling and demodulation lengths on the undulator parameters..
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1510 (2025)
Efficient coherent optical storage of multi-dimensional states in cold atom ensembles
Xin Yang, Jinwen Wang, Shuwei Qiu, Yan Gu... and Hong Gao|Show fewer author(s)
Photonic multi-dimensional storage capabilities and the high storage efficiency of multiplexed quantum storage devices are critical metrics that directly determine the entanglement distribution efficiency of quantum networks. In this work, we experimentally demonstrate a high-efficiency storage for multi-dimensional photonic states in path, polarization, and orbital angular momentum (with vector beams serving as the photonic dimensional carriers of polarization and orbital angular momentum) in laser-cooled Rb87 atom ensembles with cigar shapes. We achieve path-multiplexed storage of two-channel vector beams at the single-photon level, with storage efficiency exceeding 74% for first-order vector beams and 72% for second-order vector beams. Additionally, the storage fidelity surpasses 89% for both types. Furthermore, we achieve a storage time of approximately 7 μs for two-channel vector beams, and the spatial structure and phase information are preserved during storage through performed projection measurements. The results confirm that our system has the capability for optical storage in photon polarization and orbital angular momentum, as well as in a multi-dimensional photon path. These results show significant potential for advancing large-scale repeater-based quantum networks and distributed quantum computing.Photonic multi-dimensional storage capabilities and the high storage efficiency of multiplexed quantum storage devices are critical metrics that directly determine the entanglement distribution efficiency of quantum networks. In this work, we experimentally demonstrate a high-efficiency storage for multi-dimensional photonic states in path, polarization, and orbital angular momentum (with vector beams serving as the photonic dimensional carriers of polarization and orbital angular momentum) in laser-cooled
Photonics Research
- Publication Date: Jun. 02, 2025
- Vol. 13, Issue 6, 1747 (2025)
Silicon Photonics
GeSn shortwave infrared LED array prepared on GeSn nanostrips for on-chip broad-spectrum light sources
Qinxing Huang, Xiangquan Liu, Jun Zheng, Yupeng Zhu... and Buwen Cheng|Show fewer author(s)
A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip, a very attractive approach for making an infrared broad-spectrum light source. In this work, by applying the Sn content distribution strategy, GeSn shortwave infrared light-emitting diodes (LEDs) arrays with a size of 3 μm×2 μm were fabricated on Si substrate, and the active layer Sn content increased from 2.1% to 5.2% to form a broadband light source. The GeSn LEDs show perfect rectifying behavior about 106 for ±1 V, and room temperature electroluminescence (EL) from the direct bandgap was achieved. The super-linear dependence between the injected current and EL intensity confirms the band-to-band radiative recombination. By utilizing Sn content gradient technology, the EL spectra of Sn gradient GeSn LED arrays can cover from 1600 to 2200 nm with a full width at half-maximum of about 340 nm. These results show a novel method for preparing broad-spectrum shortwave infrared light emitters on a Si chip.A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip, a very attractive approach for making an infrared broad-spectrum light source. In this work, by applying the Sn content distribution strategy, GeSn shortwave infrared light-emitting diodes (LEDs) arrays with a size of
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1572 (2025)
Spectroscopy
Cavity-enhanced infrared quantum dot homojunction arrays
Naiquan Yan, Feng Shi, Xiaomeng Xue, Kenan Zhang... and Menglu Chen|Show fewer author(s)
Infrared spectroscopy has wide applications in the medical field, industry, agriculture, and other areas. Although the traditional infrared spectrometers are well developed, they face the challenge of miniaturization and cost reduction. Advances in nanomaterials and nanotechnology offer new methods for miniaturizing spectrometers. However, most research on nanomaterial-based spectrometers is limited to the visible wavelength or near infrared region. Here, we propose an infrared spectrometer based on diffraction gratings and colloidal quantum dot (CQD) homojunction photodetector arrays. Coupled with a Fabry-Perot cavity, the CQD photodetector covers the 1.4–2.5 μm spectral range, with specific detectivity 4.64×1011 Jones at 2.5 μm at room temperature. The assembled spectrometer has 256 channels, with total area 2.8 mm×40 mm. By optimizing the response matrix from machine learning algorithms, the CQD spectrometer shows high-resolution spectral reconstruction with a resolution of approximately 7 nm covering the short-wave infrared.Infrared spectroscopy has wide applications in the medical field, industry, agriculture, and other areas. Although the traditional infrared spectrometers are well developed, they face the challenge of miniaturization and cost reduction. Advances in nanomaterials and nanotechnology offer new methods for miniaturizing spectrometers. However, most research on nanomaterial-based spectrometers is limited to the visible wavelength or near infrared region. Here, we propose an infrared spectrometer based on diffraction gratings and colloidal quantum dot (CQD) homojunction photodetector arrays. Coupled with a Fabry-Perot cavity, the CQD photodetector covers the 1.4–2.5 μm spectral range, with specific detectivity
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1497 (2025)
Surface Optics and Plasmonics
Solar-blind ultraviolet imaging with a diamond metalens
Wen-Jie Dou, Xun Yang, Cheng-Long Zheng, Hua-Ping Zang... and Chong-Xin Shan|Show fewer author(s)
Imaging in the solar blind ultraviolet (UV) region offers significant advantages, including minimal interference from sunlight, reduced background noise, low false-alarm rate, and high sensitivity, and thus has important applications in early warning or detection of fire, ozone depletion, dynamite explosions, missile launches, electric leakage, etc. However, traditional imaging systems in this spectrum are often hindered by the bulkiness and complexity of conventional optics, resulting in heavy and cumbersome setups. The advent of metasurfaces, which use a two-dimensional array of nano-antennas to manipulate light properties, provides a powerful solution for developing miniaturized and compact optical systems. In this study, diamond metalenses were designed and fabricated to enable ultracompact solar-blind UV imaging. To prove this concept, two representative functionalities, bright-field imaging and spiral phase contrast imaging, were demonstrated as examples. Leveraging diamond’s exceptional properties, such as its wide bandgap, high refractive index, remarkable chemical inertness, and high damage threshold, this work not only presents a simple and feasible approach to realize solar-blind imaging in an ultracompact form but also highlights diamond as a highly capable material for developing miniaturized, lightweight, and robust imaging systems.Imaging in the solar blind ultraviolet (UV) region offers significant advantages, including minimal interference from sunlight, reduced background noise, low false-alarm rate, and high sensitivity, and thus has important applications in early warning or detection of fire, ozone depletion, dynamite explosions, missile launches, electric leakage, etc. However, traditional imaging systems in this spectrum are often hindered by the bulkiness and complexity of conventional optics, resulting in heavy and cumbersome setups. The advent of metasurfaces, which use a two-dimensional array of nano-antennas to manipulate light properties, provides a powerful solution for developing miniaturized and compact optical systems. In this study, diamond metalenses were designed and fabricated to enable ultracompact solar-blind UV imaging. To prove this concept, two representative functionalities, bright-field imaging and spiral phase contrast imaging, were demonstrated as examples. Leveraging diamond’s exceptional properties, such as its wide bandgap, high refractive index, remarkable chemical inertness, and high damage threshold, this work not only presents a simple and feasible approach to realize solar-blind imaging in an ultracompact form but also highlights diamond as a highly capable material for developing miniaturized, lightweight, and robust imaging systems..
Photonics Research
- Publication Date: May. 16, 2025
- Vol. 13, Issue 6, 1452 (2025)
Active control of the toroidal dipole and quasi-bound state in the continuum based on the symmetric and asymmetric hybrid dumbbell aperture arrays
Chen Wang, Meng-Shu Liu, Dong-Qin Zhang, Zhong-Wei Jin... and Fang-Zhou Shu|Show fewer author(s)
Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales. Recent advancements have focused on toroidal dipole (TD) and quasi-bound state in the continuum (quasi-BIC) modes, which are particularly attractive due to their capacity to enhance light-matter interaction. However, most metasurfaces with TD and quasi-BIC modes exhibit passive electromagnetic responses after fabrication, limiting their practical applications. This study presents both numerical and experimental investigations that demonstrate the active control of TD and quasi-BIC modes through the integration of symmetric and asymmetric aluminum dumbbell aperture arrays with the phase-change material Ge2Sb2Te5 (GST). The symmetric hybrid dumbbell aperture array shows a pronounced TD response within the terahertz frequency range. In contrast, modifying the geometric parameters to disrupt the structural symmetry induces a quasi-BIC mode in the asymmetric hybrid dumbbell aperture array. Furthermore, as GST undergoes a phase transition from its amorphous to crystalline state, both TD and quasi-BIC modes become dynamically tunable, driven by changes in the conductivity of GST. Notably, significant modulation of the transmitted terahertz wave occurs around the frequencies corresponding to the TD and quasi-BIC modes during the GST phase transition. Symmetric and asymmetric hybrid dumbbell aperture arrays provide a versatile platform for generating tunable TD and quasi-BIC modes, with promising applications in terahertz modulators and filters.Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales. Recent advancements have focused on toroidal dipole (TD) and quasi-bound state in the continuum (quasi-BIC) modes, which are particularly attractive due to their capacity to enhance light-matter interaction. However, most metasurfaces with TD and quasi-BIC modes exhibit passive electromagnetic responses after fabrication, limiting their practical applications. This study presents both numerical and experimental investigations that demonstrate the active control of TD and quasi-BIC modes through the integration of symmetric and asymmetric aluminum dumbbell aperture arrays with the phase-change material
Photonics Research
- Publication Date: May. 27, 2025
- Vol. 13, Issue 6, 1534 (2025)
Ultrafast Optics
High-precision spatiotemporal profiler of femtosecond laser pulses
Zegui Wang, Qijun You, Yun Gao, Peixiang Lu, and Wei Cao
The precise spatiotemporal characterization of broadband ultrafast laser beams is essential for accurate laser control and holds significant potential in photochemistry and high-intensity laser physics. Existing methods for spatiotemporal characterization, such as frequency-resolved optical gating (FROG) and compressed ultrafast photography (CUP), are often spatially averaged or suffer from limited spatial resolution. Recent advances in imaging techniques based on multiplexed ptychography have enabled high-spatial-resolution diagnostics of ultrafast laser beams. However, the discrete spectral assumption inherent in multiplexed ptychographic algorithms does not align with the continuous spectral structure of ultrafast laser pulses, leading to significant crosstalk between different wavelength channels (WCs). This paper presents a method to reduce the bandwidth of each wavelength channel through spectral modulation, followed by the discretization of the continuous spectrum using interference techniques, which significantly improves the convergence and accuracy of the reconstruction. Using this method, the experiment accurately measured chromatic dispersion, spatial chirp, and other spatiotemporal coupling effects in femtosecond laser beams, achieving a spatial resolution of 9.4 μm, close to the pixel size resolution limit of the angular spectrum method.The precise spatiotemporal characterization of broadband ultrafast laser beams is essential for accurate laser control and holds significant potential in photochemistry and high-intensity laser physics. Existing methods for spatiotemporal characterization, such as frequency-resolved optical gating (FROG) and compressed ultrafast photography (CUP), are often spatially averaged or suffer from limited spatial resolution. Recent advances in imaging techniques based on multiplexed ptychography have enabled high-spatial-resolution diagnostics of ultrafast laser beams. However, the discrete spectral assumption inherent in multiplexed ptychographic algorithms does not align with the continuous spectral structure of ultrafast laser pulses, leading to significant crosstalk between different wavelength channels (WCs). This paper presents a method to reduce the bandwidth of each wavelength channel through spectral modulation, followed by the discretization of the continuous spectrum using interference techniques, which significantly improves the convergence and accuracy of the reconstruction. Using this method, the experiment accurately measured chromatic dispersion, spatial chirp, and other spatiotemporal coupling effects in femtosecond laser beams, achieving a spatial resolution of 9.4 μm, close to the pixel size resolution limit of the angular spectrum method..
Photonics Research
- Publication Date: May. 30, 2025
- Vol. 13, Issue 6, 1666 (2025)
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