Sub-nanometer address grid in variable shaped e-beam lithography for efficient inscription of high-precision large-area optical gratings
Martin Heusinger, Thorsten A. Goebel, Michael Banasch, Daniel Richter, Ria G. Krämer, Christian Voigtländer, Eike Linn, Thomas Siefke, Andreas Tünnermann, Ernst-Bernhard Kley, Stefan Nolte, and Uwe D. Zeitner
High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several cm2. Electron beam lithography with a variable shaped beam (VSB) is well suited but limited by tool-dependent address grid discretization. We adapted address grid interpolation to the VSB method, reducing the effective placement grid to 25 pm, as confirmed by stray light measurements. The technique was further demonstrated on a 0.5 cm×5 cm phase mask for chirped fiber Bragg gratings (100 pm/mm), achieving excellent spectral broadband reflection quality.High-performance, large-area optical gratings for applications like chirped pulse amplification, gravitational wave astronomy, and X-ray optics require sub-nanometer line placement control over several
- Nov. 12, 2025
- Photonics Research
- Vol. 13, Issue 12, 3286 (2025)
- DOI：10.1364/PRJ.541297
Observation of photonic asymmetric topological corner modes driven by periodically staggered onsite edge potentials
Hongyi Li, Chunmei Ouyang, Shiyu Liu, Yuting Yang, Jiajun Ma, Liyuan Liu, Quan Xu, Xueqian Zhang, Jianqiang Gu, Zhen Tian, Yanfeng Li, Jiaguang Han, and Weili Zhang
Controlling topological modes in photonic systems remains a fundamental challenge, as conventional approaches rely on global lattice modifications and lack topological phase engineering of the induced non-trivial states. Here, we reveal that staggered onsite edge potential (SOEP) modulation breaks mirror symmetry in folded edge states, inducing edge-confined Wannier function deviations and thus driving edge bands into distinct topological phases. The emergence of resulting higher-order localized modes is further confirmed. Notably, the hosted corner modes are SOEP-selective, depending on the deviation direction of the Wannier function. Using spoof surface plasmon polariton photonic crystals, we experimentally confirm two SOEP-driven evolution regimes: symmetric evolution enabling corner-mode pumping between adjacent corners and asymmetric evolution restricting corner modes to negative potentials. These results demonstrate spatial control over corner states, linking edge potential engineering to higher-order topology. Our study paves the way for manipulating the band structure and modeling topological phases of photonic states.Controlling topological modes in photonic systems remains a fundamental challenge, as conventional approaches rely on global lattice modifications and lack topological phase engineering of the induced non-trivial states. Here, we reveal that staggered onsite edge potential (SOEP) modulation breaks mirror symmetry in folded edge states, inducing edge-confined Wannier function deviations and thus driving edge bands into distinct topological phases. The emergence of resulting higher-order localized modes is further confirmed. Notably, the hosted corner modes are SOEP-selective, depending on the deviation direction of the Wannier function. Using spoof surface plasmon polariton photonic crystals, we experimentally confirm two SOEP-driven evolution regimes: symmetric evolution enabling corner-mode pumping between adjacent corners and asymmetric evolution restricting corner modes to negative potentials. These results demonstrate spatial control over corner states, linking edge potential engineering to higher-order topology. Our study paves the way for manipulating the band structure and modeling topological phases of photonic states.
- Nov. 12, 2025
- Photonics Research
- Vol. 13, Issue 12, 3274 (2025)
- DOI：10.1364/PRJ.569801
Iterative virtual Moiré reconstruction: simultaneous recovery for topological charge and phase from a single-frame aberrated interferogram
Bo Long, Ning Sun, Ling Wei, Rui Yang, Junling Chen, Rong Yan, Lei Mu, Xiaoyue Hu, and Lei Zhang
Traditional vortex beam parameter determination methods are all designed for aberration-free vortex beams. In the case of aberrations and turbulence, they tend to struggle in mutual restraint between phase recovery and topological charge (TC) detection. Most recent methods depend on complex interferometric setups and precise phase singularity localization. An iterative virtual Moiré reconstruction (IVMR) technique is proposed based on the blind conformal mapping, achieving simultaneous demodulation of TC and phase from a single-frame aberrated interferogram, not needing precise phase singularity positioning. Experimental validation reveals an unprecedented dual-parameter characterization capability, demonstrating robustness across general aberration (root mean square ≤3λ) with an accuracy of 0.1 and Kolmogorov-type turbulence (atmospheric turbulence strength D/r0=12.5) with an accuracy of 0.15 for both integer and fractional topological charges. The simultaneous phase recovery accuracy achieves 3% and 10% root mean square error under general aberrations and turbulence, respectively. This approach demonstrates remarkably robust performance coupled with system simplicity, enabling efficient and accurate parameter quantification of vortex beams in real-world applications.Traditional vortex beam parameter determination methods are all designed for aberration-free vortex beams. In the case of aberrations and turbulence, they tend to struggle in mutual restraint between phase recovery and topological charge (TC) detection. Most recent methods depend on complex interferometric setups and precise phase singularity localization. An iterative virtual Moiré reconstruction (IVMR) technique is proposed based on the blind conformal mapping, achieving simultaneous demodulation of TC and phase from a single-frame aberrated interferogram, not needing precise phase singularity positioning. Experimental validation reveals an unprecedented dual-parameter characterization capability, demonstrating robustness across general aberration (root mean square
- Nov. 12, 2025
- Photonics Research
- Vol. 13, Issue 12, 3264 (2025)
- DOI：10.1364/PRJ.567625
Mode-mixing element 3D-printed directly on a fiber tip for space-division multiplexing
Miri Blau, Moran Bin-Nun and Dan M. Marom
Space-division multiplexing (SDM) offers a promising route to scaling data throughput in fiber-optic networks, but it also introduces challenges such as mode-dependent loss (MDL) and intermodal crosstalk, which increase the computational load on digital signal processing (DSP). Periodic mode mixing has been shown to mitigate these effects by redistributing loss and gain across modes and shortening the effective temporal impulse response over which crosstalk accumulates. In this work, we present a novel and compact mode-scrambling device, 3D-printed directly onto the facet of a few-mode fiber. Our scalable design precisely controls a printed microstructure that strongly couples six spatial modes across a broad spectral range, equalizing modal gains and losses in the SDM link. The device exhibits low insertion loss and small footprint, making it suitable for periodic deployment along the fiber without incurring excessive loss. To the best of our knowledge, this is the first demonstration of a six-mode on-fiber mixer fabricated by 3D printing that meets practical performance requirements, offering a viable path toward scalable, high-capacity SDM transmission systems.Space-division multiplexing (SDM) offers a promising route to scaling data throughput in fiber-optic networks, but it also introduces challenges such as mode-dependent loss (MDL) and intermodal crosstalk, which increase the computational load on digital signal processing (DSP). Periodic mode mixing has been shown to mitigate these effects by redistributing loss and gain across modes and shortening the effective temporal impulse response over which crosstalk accumulates. In this work, we present a novel and compact mode-scrambling device, 3D-printed directly onto the facet of a few-mode fiber. Our scalable design precisely controls a printed microstructure that strongly couples six spatial modes across a broad spectral range, equalizing modal gains and losses in the SDM link. The device exhibits low insertion loss and small footprint, making it suitable for periodic deployment along the fiber without incurring excessive loss. To the best of our knowledge, this is the first demonstration of a six-mode on-fiber mixer fabricated by 3D printing that meets practical performance requirements, offering a viable path toward scalable, high-capacity SDM transmission systems.
- Nov. 12, 2025
- Photonics Research
- Vol. 13, Issue 12, 3257 (2025)
- DOI：10.1364/PRJ.569670
Emerging coding methods for computational imaging
Kai Wu, Yuanfenghe Qu, Ruozhang Wang, Hao Li, Xinrui Ying, Pengyu Tian, Xilai Li, Zongliang Wu, and Xin Yuan
Computational imaging employs the joint design of optical modulation and reconstruction algorithms, overcoming the inherent physical limitations of conventional imaging. From the perspective of information transmission, computational imaging sequentially applies optical encoding, indirect measurement, and computational decoding to capture the desired information. This paradigm demonstrates superiority over conventional imaging in terms of information capacity, information acquisition efficiency, information dimensions, and information acquisition functionality. Optical encoding plays a pivotal role and can be implemented across multiple dimensions of light at various positions along the optical path. This mini-review surveys emerging encoding methods for computational imaging driven by optical element parameter optimization tools, micro-nano manufacturing, and non-classical properties of light. Differentiable optics and end-to-end optimization can model complex physical processes and further strengthen the integration of optical encoding and computational decoding. Advances in material science and micro-nano fabrication give rise to compact, high-performance imaging systems and propel the practical implementation of diverse, bio-inspired imaging. In addition, quantum properties and orbital angular momentum create new possibilities for encoding methods that perform better in specific conditions. The research in these areas represents the latest advances in computational imaging encoding methods and demonstrates the potential for rapid development in the future.Computational imaging employs the joint design of optical modulation and reconstruction algorithms, overcoming the inherent physical limitations of conventional imaging. From the perspective of information transmission, computational imaging sequentially applies optical encoding, indirect measurement, and computational decoding to capture the desired information. This paradigm demonstrates superiority over conventional imaging in terms of information capacity, information acquisition efficiency, information dimensions, and information acquisition functionality. Optical encoding plays a pivotal role and can be implemented across multiple dimensions of light at various positions along the optical path. This mini-review surveys emerging encoding methods for computational imaging driven by optical element parameter optimization tools, micro-nano manufacturing, and non-classical properties of light. Differentiable optics and end-to-end optimization can model complex physical processes and further strengthen the integration of optical encoding and computational decoding. Advances in material science and micro-nano fabrication give rise to compact, high-performance imaging systems and propel the practical implementation of diverse, bio-inspired imaging. In addition, quantum properties and orbital angular momentum create new possibilities for encoding methods that perform better in specific conditions. The research in these areas represents the latest advances in computational imaging encoding methods and demonstrates the potential for rapid development in the future.
- Nov. 12, 2025
- Advanced Imaging
- Vol. 2, Issue 6, A00001 (2025)
- DOI：10.3788/AI.2025.20004
Generation of 1-MHz, 64-W, 26-fs green pulses via second-harmonic generation of nonlinearly compressed pulses at 1.03 μm
Dongliang Wang, Qi Liu, Zhongchao Li, Xinyue Yuan, Hongyue Wu, Zixi Liu, Wei Liu, and Guoqing Chang
High-order harmonic generation (HHG) in noble gases driven by femtosecond lasers is currently a feasible solution to obtain ultrafast pulses in the extreme ultraviolet (EUV) wavelength range. Implementation of high-flux EUV sources requires driving HHG using an ultrafast laser source in the visible wavelength range with MHz repetition rate. In this paper, we employ a multi-pass cell followed by chirped mirrors to compress 1-MHz, 200-W, 300-fs pulses at 1.03 μm to a duration of 35 fs. The resulting 186-W compressed pulses are focused onto 0.5-mm thick beta barium borate crystal to drive second-harmonic generation and produce positively chirped pulses at 520 nm. These green pulses are de-chirped to 26 fs in duration with an average power of 64 W, which, to the best of our knowledge, represents the highest average power of green pulses with a duration below 100 fs.High-order harmonic generation (HHG) in noble gases driven by femtosecond lasers is currently a feasible solution to obtain ultrafast pulses in the extreme ultraviolet (EUV) wavelength range. Implementation of high-flux EUV sources requires driving HHG using an ultrafast laser source in the visible wavelength range with MHz repetition rate. In this paper, we employ a multi-pass cell followed by chirped mirrors to compress 1-MHz, 200-W, 300-fs pulses at 1.03 μm to a duration of 35 fs. The resulting 186-W compressed pulses are focused onto 0.5-mm thick beta barium borate crystal to drive second-harmonic generation and produce positively chirped pulses at 520 nm. These green pulses are de-chirped to 26 fs in duration with an average power of 64 W, which, to the best of our knowledge, represents the highest average power of green pulses with a duration below 100 fs.
- Nov. 11, 2025
- High Power Laser Science and Engineering
- Vol. 13, Issue 5, 05000e74 (2025)
- DOI：10.1017/hpl.2025.10056
Nonreciprocal photonics and its application in thermal radiation
Shuang Xia and Xiaobo Yin
Nonreciprocity denotes the asymmetrical reaction when the sources and observation sites are exchanged. Extensive approaches have been employed to construct nonreciprocal nanophotonic devices in the optical regime. Very recently, this concept was extended to the realm of thermal radiation, emphasizing its significance in overcoming the limitations of Kirchhoff’s law, which asserts that spectral directional absorptivity and emissivity are identical. This facilitates a new understanding of radiative phenomena and paves the way for innovative energy devices. In this review, we summarize the principles of nonreciprocal photonics and outline two primary methods to break Lorentz reciprocity. The extension of nonreciprocal photonics into thermal radiation is highlighted, including a range of nanophotonic structures and their potential applications in photonic energy conversion. We also discuss current challenges in nonreciprocal thermal radiation and provide the outlook for future development.Nonreciprocity denotes the asymmetrical reaction when the sources and observation sites are exchanged. Extensive approaches have been employed to construct nonreciprocal nanophotonic devices in the optical regime. Very recently, this concept was extended to the realm of thermal radiation, emphasizing its significance in overcoming the limitations of Kirchhoff’s law, which asserts that spectral directional absorptivity and emissivity are identical. This facilitates a new understanding of radiative phenomena and paves the way for innovative energy devices. In this review, we summarize the principles of nonreciprocal photonics and outline two primary methods to break Lorentz reciprocity. The extension of nonreciprocal photonics into thermal radiation is highlighted, including a range of nanophotonic structures and their potential applications in photonic energy conversion. We also discuss current challenges in nonreciprocal thermal radiation and provide the outlook for future development.
- Nov. 10, 2025
- Photonics Insights
- Vol. 4, Issue 4, R11 (2025)
- DOI：10.3788/PI.2025.R11
Integrated photonic spectrometers: a critical review
Maarten R. A. Peters, Diana Mojahed, Wenchao Ma, Raphaël Pestourie, Tian Gu, Steven G. Johnson, and Juejun Hu
Integrated photonics, where optical components are fabricated on a chip-scale platform leveraging standard microfabrication technologies, has transformed telecommunications and data communications, quantum optics, and molecular sensing. Optical spectrometry is yet another field that integrated photonics is poised to revolutionize. Unlike traditional bulky, costly benchtop spectrometers, integrated photonics promises miniaturized, rugged, and low-cost spectrometer-on-a-chip modules with broad application prospects ranging from communications to medical imaging. In this review, we survey the various designs of integrated photonic spectrometers through the lens of their underlying operating principles, aiming to reveal quantitative performance scaling laws that transcend specific implementations. This approach enables a general, physically grounded comparison of spectrometer capabilities without being bogged down by device-level details. We further provide guidance on selecting appropriate spectrometer architectures for different applications, taking into account not only their reported advantages but also the practical limitations and implementation challenges.Integrated photonics, where optical components are fabricated on a chip-scale platform leveraging standard microfabrication technologies, has transformed telecommunications and data communications, quantum optics, and molecular sensing. Optical spectrometry is yet another field that integrated photonics is poised to revolutionize. Unlike traditional bulky, costly benchtop spectrometers, integrated photonics promises miniaturized, rugged, and low-cost spectrometer-on-a-chip modules with broad application prospects ranging from communications to medical imaging. In this review, we survey the various designs of integrated photonic spectrometers through the lens of their underlying operating principles, aiming to reveal quantitative performance scaling laws that transcend specific implementations. This approach enables a general, physically grounded comparison of spectrometer capabilities without being bogged down by device-level details. We further provide guidance on selecting appropriate spectrometer architectures for different applications, taking into account not only their reported advantages but also the practical limitations and implementation challenges.
- Nov. 10, 2025
- Photonics Insights
- Vol. 4, Issue 4, R10 (2025)
- DOI：10.3788/PI.2025.R10
LSDNet: a vision graph neural-network-based fast LED light source detector for UWOC systems
Minqi Wu, Hexi Liang, Hang Li, Zhiheng Fang, Yanlong Li, and Yong Ai
In underwater wireless optical communication (UWOC) systems, the alignment between the laser transmitter and receiver is disrupted by light scattering and imaging angle variations, reducing spot imaging quality, positioning accuracy, and link stability. To overcome these limitations, a deep-learning-based light source detection network (LSDNet) is designed for the active link alignment task in UWOC systems. Within the backbone, a locally sparse dynamic graph construction (MDGC) method, guided by multi-dimensional hybrid collaborative attention, is proposed to learn deep representations of underwater optical images, reduce node redundancy, filter out false spots, and suppress scattering. To train and evaluate the model, we construct the UWOC light-emitting diode (LED) light source detection benchmark dataset (UWLED), encompassing 22,770 high-quality images across diverse complex underwater scenarios. Experimental results demonstrate that the proposed LSDNet outperforms other advanced methods, achieving an AP50val of 99.2% and the mean center location error (CLE) below 5.41 pixels on the test set, while also exhibiting outstanding robustness under low-light and scattering conditions. Moreover, LSDNet reduces the number of parameters by 30.8% and achieves an 8.2% higher AP50val compared to the vision graph neural network (ViG). The UWOC system based on LSDNet achieves a bit error rate (BER) at the 10-8 level over a distance of 35 m.In underwater wireless optical communication (UWOC) systems, the alignment between the laser transmitter and receiver is disrupted by light scattering and imaging angle variations, reducing spot imaging quality, positioning accuracy, and link stability. To overcome these limitations, a deep-learning-based light source detection network (LSDNet) is designed for the active link alignment task in UWOC systems. Within the backbone, a locally sparse dynamic graph construction (MDGC) method, guided by multi-dimensional hybrid collaborative attention, is proposed to learn deep representations of underwater optical images, reduce node redundancy, filter out false spots, and suppress scattering. To train and evaluate the model, we construct the UWOC light-emitting diode (LED) light source detection benchmark dataset (UWLED), encompassing 22,770 high-quality images across diverse complex underwater scenarios. Experimental results demonstrate that the proposed LSDNet outperforms other advanced methods, achieving an AP50val of 99.2% and the mean center location error (CLE) below 5.41 pixels on the test set, while also exhibiting outstanding robustness under low-light and scattering conditions. Moreover, LSDNet reduces the number of parameters by 30.8% and achieves an 8.2% higher AP50val compared to the vision graph neural network (ViG). The UWOC system based on LSDNet achieves a bit error rate (BER) at the 10-8 level over a distance of 35 m.
- Nov. 10, 2025
- Chinese Optics Letters
- Vol. 23, Issue 12, 121102 (2025)
- DOI：10.3788/COL202523.121102
Learning-based cross-scale wavefront measurement with a hybrid Shack–Hartmann-digital holographic sensor
Ao Li, Zeyu Gao, Jiawei Sun, Yong Chen, Qiang Yuan, Xinlan Ge, Chao Yang, Licheng Zhu, Shiqing Ma, Ling Wei, Shuai Wang, and Ping Yang
A cross-scale composite wavefront measurement method based on deep learning is proposed to address local large gradient wavefront distortions from aero-optical effects. Since dynamic range and spatial resolution are usually a trade-off for most wavefront sensors, we propose a hybrid Shack–Hartmann-digital holographic wavefront sensing mechanism that includes a Shack–Hartmann wavefront sensor (SHWFS) and off-axis digital holography (OADH). Using the hybrid wavefront sensing mechanism and the data processing method, the reconstructed wavefront of SHWFS and the wrapped phase of OADH are obtained separately. A multi-input efficient network called the multi-system wavefront measurement-net (MSWM-Net) with an attention mechanism is introduced to map the reconstructed wavefront of SHWFS and the wrapped phase of the OADH to the precise wavefront. Numerical simulations and comparisons with the deep learning phase unwrapping (DLPU)-model-based phase unwrapping method and classical phase unwrapping technique demonstrate that this method resolves the challenge of mismatched data scales across the two measurement systems, enabling rapid and high-precision wavefront sensing.A cross-scale composite wavefront measurement method based on deep learning is proposed to address local large gradient wavefront distortions from aero-optical effects. Since dynamic range and spatial resolution are usually a trade-off for most wavefront sensors, we propose a hybrid Shack–Hartmann-digital holographic wavefront sensing mechanism that includes a Shack–Hartmann wavefront sensor (SHWFS) and off-axis digital holography (OADH). Using the hybrid wavefront sensing mechanism and the data processing method, the reconstructed wavefront of SHWFS and the wrapped phase of OADH are obtained separately. A multi-input efficient network called the multi-system wavefront measurement-net (MSWM-Net) with an attention mechanism is introduced to map the reconstructed wavefront of SHWFS and the wrapped phase of the OADH to the precise wavefront. Numerical simulations and comparisons with the deep learning phase unwrapping (DLPU)-model-based phase unwrapping method and classical phase unwrapping technique demonstrate that this method resolves the challenge of mismatched data scales across the two measurement systems, enabling rapid and high-precision wavefront sensing.
- Nov. 10, 2025
- Chinese Optics Letters
- Vol. 23, Issue 12, 121203 (2025)
- DOI：10.3788/COL202523.121203
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Oct. 28, 2025
Special Issue on Advanced Direct Drive Laser Driven Fusion Research and Technology (2025)
Submission Open:1 August 2025; Submission Deadline: 30 November 2025
Editor (s): Dimitri Batani, Sebastien Le Pape, Jianqiang Zhu, Ping Zhu
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Editor (s): Linjie Zhou, Xianshu Luo
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Editor (s): Yuanjie Yang, Yangjian Cai, Qiwen Zhan
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