Volume: 22 Issue 3
25 Article(s)

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Integrated Optics
Photonic analog signal processing and neuromorphic computing [Invited]
James Garofolo, and Ben Wu
In this review paper, we discuss the properties and applications of photonic computing and analog signal processing. Photonic computational circuits have large operation bandwidth, low power consumption, and fine frequency control, enabling a wide range of application-specific computational techniques that are impossible to implement using traditional electrical and digital hardware alone. These advantages are illustrated in the elegant implementation of optical steganography, the real-time blind separation of signals in the same bandwidth, and the efficient acceleration of artificial neural network inference. The working principles and use of photonic circuits for analog signal processing and neuromorphic computing are reviewed and notable demonstrated applications are highlighted.
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 032501 (2024)
Research Articles
Atmospheric, Oceanic, Space, and Environmental Optics
Underwater wireless optical NOMA communication experiment system exploiting GaN-based micro-LED array grouping
Yanjun Liang, Hongxi Yin, An Huang, Xiuyang Ji, and Jianying Wang
This paper has proposed an experimental system for non-orthogonal multiple access (NOMA) wireless optical communication in challenging underwater turbulent environments, employing the gallium nitride (GaN)-based micro-LED array. This design of the GaN-based micro-LED array enables the independent transmission of signals from distinct data streams within the NOMA framework, facilitating direct optical power-domain superposition of NOMA signals. The experimental setup involves emulating oceanic turbulence channels, characterized by varying the level of scintillation intensity, to thoroughly investigate the bit error rate (BER) performance. The outcomes unequivocally demonstrate the superiority of our proposed NOMA scheme, as compared to conventional circuit-driven optical NOMA systems utilizing fixed LED array grouping, particularly in the presence of turbulent underwater channels. The proposed NOMA scheme exhibits consistently superior BER performance and maintains excellent linearity at the lower frequencies while effectively mitigating signal distortion at the higher frequencies.
Chinese Optics Letters
  • Publication Date: Mar. 15, 2024
  • Vol. 22, Issue 3, 030101 (2024)
Stimulated emission–depletion-based point-scanning structured illumination microscopy
Lei Wang, Meiting Wang, Luwei Wang, Xiaomin Zheng, Jiajie Chen, Wenshuai Wu, Wei Yan, Bin Yu, Junle Qu, Bruce Zhi Gao, and Yonghong Shao
Wide-field linear structured illumination microscopy (LSIM) extends resolution beyond the diffraction limit by moving unresolvable high-frequency information into the passband of the microscopy in the form of moiré fringes. However, due to the diffraction limit, the spatial frequency of the structured illumination pattern cannot be larger than the microscopy cutoff frequency, which results in a twofold resolution improvement over wide-field microscopes. This Letter presents a novel approach in point-scanning LSIM, aimed at achieving higher-resolution improvement by combining stimulated emission depletion (STED) with point-scanning structured illumination microscopy (psSIM) (STED-psSIM). The according structured illumination pattern whose frequency exceeds the microscopy cutoff frequency is produced by scanning the focus of the sinusoidally modulated excitation beam of STED microscopy. The experimental results showed a 1.58-fold resolution improvement over conventional STED microscopy with the same depletion laser power.
Chinese Optics Letters
  • Publication Date: Mar. 13, 2024
  • Vol. 22, Issue 3, 031701 (2024)
Noncontact ultrasound sensing based on Mach–Zehnder homodyne interferometer for photoacoustic imaging
Xing Long, Yicheng Hu, Yibing Wang, and Changhui Li
Chinese Optics Letters
  • Publication Date: Mar. 28, 2024
  • Vol. 22, Issue 3, 031702 (2024)
Fiber Optics and Optical Communications
Simple real-time high-sensitivity heterodyne coherent optical transceiver at intraplane satellite communication
Yuanzhe Qu, Qianwu Zhang, Yanyi Wang, Yanhao Chen, Lewei Gong, Ziyue Liu, Junjie Zhang, Yingchun Li, Jian Chen, and Yingxiong Song
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 030601 (2024)
LP modes exchange based on multiplane light conversion
Yanan Zhong, Chuxuan Lin, Juncheng Fang, Ting Lei, and Xiaocong Yuan
Data exchange between different mode channels is essential in the optical communication network with mode-division multiplexing (MDM). However, there are challenges in realizing mode exchange with low insert loss, low mode crosstalk, and high integration. Here, we designed and fabricated a mode exchange device based on multiplane light conversion (MPLC), which supports the transmission of LP01, LP11a, LP11b, and LP21 modes in the C-band and L-band. The simulated exchanged mode purities are greater than 85%. The phase masks were fabricated on a silicon substrate to facilitate the integration with optical systems, with an insert loss of less than 2.2 dB and mode crosstalk below -21 dB due primarily to machining inaccuracies and alignment errors. We carried out an optical communication experiment with 10 Gbit/s OOK and QPSK data transmission at the wavelength of 1550 nm and obtained excellent performance with the device. It paves the way for flexible data exchange as a building block in MDM optical communication networks.
Chinese Optics Letters
  • Publication Date: Mar. 22, 2024
  • Vol. 22, Issue 3, 030602 (2024)
Imaging Systems and Image Processing
Geometric phase helical PSF for simultaneous orientation and 3D localization microscopy
Yongzhuang Zhou, Hongshuo Zhang, Yong Shen, Andrew R. Harvey, and Hongxin Zou
Chinese Optics Letters
  • Publication Date: Mar. 25, 2024
  • Vol. 22, Issue 3, 031103 (2024)
Measurable speckle gradation Hadamard single-pixel imaging
Liyu Zhou, Yanfeng Bai, Qin Fu, Xiaohui Zhu, Xianwei Huang, Xuanpengfan Zou, and Xiquan Fu
The array spatial light field is an effective means for improving imaging speed in single-pixel imaging. However, distinguishing the intensity values of each sub-light field in the array spatial light field requires the help of the array detector or the time-consuming deep-learning algorithm. Aiming at this problem, we propose measurable speckle gradation Hadamard single-pixel imaging (MSG-HSI), which makes most of the refresh mechanism of the device generate the Hadamard speckle patterns and the high sampling rate of the bucket detector and is capable of measuring the light intensity fluctuation of the array spatial light field only by a simple bucket detector. The numerical and experimental results indicate that data acquisition in MSG-HSI is 4 times faster than in traditional Hadamard single-pixel imaging. Moreover, imaging quality in MSG-HSI can be further improved by image stitching technology. Our approach may open a new perspective for single-pixel imaging to improve imaging speed.
Chinese Optics Letters
  • Publication Date: Mar. 25, 2024
  • Vol. 22, Issue 3, 031104 (2024)
Integrated Optics
Ultra-compact and broadband polarization-insensitive mode-order converting power splitter
Haoqi Chen, Runkui Yao, Pengjun Wang, Qiang Fu, Weiwei Chen, Shixun Dai, Dejun Kong, Jian Lin, Tao Jin, Jun Li, Tingge Dai, and Jianyi Yang
A polarization-insensitive mode-order converting power splitter using a pixelated region is presented and investigated in this paper. As TE0 and TM0 modes are injected into the input port, they are converted into TE1 and TM1 modes, which evenly come out from the two output ports. The finite-difference time-domain method and direct-binary-search optimization algorithm are utilized to optimize structural parameters of the pixelated region to attain small insertion loss, low crosstalk, wide bandwidth, excellent power uniformity, polarization-insensitive property, and compact size. Experimental results reveal that the insertion loss, crosstalk, and power uniformity of the fabricated device at 1550 nm are 0.57, -19.67, and 0.094 dB in the case of TE polarization, while in the TM polarization, the relevant insertion loss, crosstalk, and power uniformity are 0.57, -19.40, and 0.11 dB. Within a wavelength range from 1520 to 1600 nm, for the fabricated device working at TE polarization, the insertion loss, crosstalk, and power uniformity are lower than 1.39, -17.64, and 0.14 dB. In the case of TM polarization, we achieved an insertion loss, crosstalk, and power uniformity less than 1.23, -17.62, and 0.14 dB.
Chinese Optics Letters
  • Publication Date: Mar. 19, 2024
  • Vol. 22, Issue 3, 031301 (2024)
Ultralow cross talk arrayed waveguide grating integrated with tunable microring filter array | On the Cover
Heming Hu, Shiping Liu, Tianwen Li, Yongjie Fan, Hua Chen, and Qing Fang
Chinese Optics Letters
  • Publication Date: Mar. 07, 2024
  • Vol. 22, Issue 3, 031303 (2024)
Microwave photonic sideband selector based on thin-film lithium niobate platform
Yuedi Ding, Chenglin Shang, Wenqi Yu, Xiang Ma, Shaobo Li, Cheng Zeng, and Jinsong Xia
Chinese Optics Letters
  • Publication Date: Mar. 25, 2024
  • Vol. 22, Issue 3, 031304 (2024)
Lasers, Optical Amplifiers, and Laser Optics
Power output correction model of narrow linewidth ring fiber laser filtered with whispering gallery mode resonator
Ziyun Wang, Zaibin Xu, Jiwen Cui, and Jiubin Tan
A whispering gallery mode resonator (WGMR) filter can narrow laser linewidth while significantly changing the output power characteristics of fiber laser system. It is found that traditional laser output power model is invalid. We report a correction model of a narrow linewidth fiber laser filtered with a WGMR to analyze its power. We believe that the loss of the laser system and the threshold gain increase caused by the WGMR filter lead to the predominate amplified spontaneous emission during the original laser period. According to that, we assume the correction coefficient is an exponential decay related to the Er-doped fiber length in the large loss situation, and we verify it experimentally. As a result, the correction model is valid for WGMR-filtered fiber laser.
Chinese Optics Letters
  • Publication Date: Mar. 19, 2024
  • Vol. 22, Issue 3, 031401 (2024)
22 kW near-diffraction-limited Yb:YAG slab laser amplifier without adaptive optics correction
Dan Wang, Ping He, Tangjian Zhou, Mi Li, Yingchen Wu, Yanan Wang, Jianli Shang, Qingsong Gao, Kai Zhang, Chun Tang, and Rihong Zhu
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 031402 (2024)
Bright/dark switchable mode-locked fiber laser based on alcohol
Wenyan Zhang, Huijie Jiang, Kun Yang, Nannan Liu, Lijie Geng, Yunqi Hao, Tianhao Xian, and Li Zhan
A passively switchable erbium-doped fiber laser based on alcohol as the saturable absorber (SA) has been demonstrated. The SA is prepared by filling the gap between two optical patch cords with alcohol to form a sandwich structure. The modulation depth of the alcohol–SA is measured to be 6.4%. By appropriately adjusting the pump power and the polarization state in the cavity, three kinds of mode-locked pulse patterns can be achieved and switched, including bright pulse, bright/dark soliton pair, and dark pulse. These different soliton emissions all operate at the fundamental frequency state, with a repetition rate of 20.05 MHz and a central wavelength of ∼1563 nm. To the best of our knowledge, this is the first demonstration of a switchable soliton fiber laser using alcohol as the SA. The experimental results further indicate that organic liquid-like alcohol has great potential for constructing ultrafast lasers.
Chinese Optics Letters
  • Publication Date: Mar. 07, 2024
  • Vol. 22, Issue 3, 031403 (2024)
Stable ultraviolet ultrafast laser based on all-polarization-maintaining fiber femtosecond laser
Hao Tian, Zhe Zhu, Wei Lin, Zihao Li, Junpeng Wen, Hao Xiu, Yiheng Fan, Chiyi Wei, Xiaoming Wei, and Zhongmin Yang
We report a high-stability ultrafast ultraviolet (UV) laser source at 352 nm by exploring an all-fiber, all-polarization-maintaining (all-PM), Yb-doped femtosecond fiber laser at 1060 nm. The output power, pulse width, and optical spectrum width of the fiber laser are 6 W, 244 fs, and 17.5 nm, respectively. The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB3O6 (BIBO) and sum frequency generation in a 5.1-mm-long BIBO. The maximum UV output power is 596 mW. The root mean square error of the output power of UV pulses is 0.54%. This laser, with promising stability, is expected to be a nice source for frontier applications in the UV wavelength window.
Chinese Optics Letters
  • Publication Date: Mar. 22, 2024
  • Vol. 22, Issue 3, 031404 (2024)
Light-matter Interaction
Microstructured fluorescence in liquid crystals with femtosecond laser excitation
Xia Meng, Ping Jin, Shijun Ge, Jiao Liu, Bingxiang Li, Lei Wang, and Yanqing Lu
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 033801 (2024)
Nanophotonics, Metamaterials, and Plasmonics
Vortex localization and OAM selective conversion via cylindrical metagratings
Zhanlei Hao, Shan Zhu, Cheng-Wei Qiu, Yadong Xu, and Huanyang Chen
Vortex waves with orbital angular momentum (OAM) are a highly active research topic in various fields. In this paper, we design and investigate cylindrical metagratings (CMs) with an even number of unit cells that can efficiently achieve vortex localization and specific OAM selective conversion. The multifunctional manipulation of vortex waves and the new OAM conservation law have further been confirmed through analytical calculations and numerical simulations. In addition, we qualitatively and quantitatively determine the OAM range for vortex localization and the OAM value of vortex selective conversion and also explore the stability for performance and potential applications of the designed structure. This work holds potential applications in particle manipulation and optical communication.
Chinese Optics Letters
  • Publication Date: Mar. 04, 2024
  • Vol. 22, Issue 3, 033601 (2024)
Recent progress in thin-film lithium niobate photonic crystal [Invited] | Editors' Pick
Rui Ge, Jiangwei Wu, Xiangmin Liu, Yuping Chen, and Xianfeng Chen
Lithium niobate is a material that exhibits outstanding electro-optic, nonlinear optical, acousto-optic, piezoelectric, photorefractive, and pyroelectric properties. A thin-film lithium niobate photonic crystal can confine light in the sub-wavelength scale, which is beneficial to the integration of the lithium niobate on-chip device. The commercialization of the lithium niobate on insulator gives birth to the emergence of high-quality lithium niobate photonic crystals. In order to provide guidance to the research of lithium niobate photonic crystal devices, recent progress about fabrication, characterization, and applications of the thin-film lithium niobate photonic crystal is reviewed. The performance parameters of the different devices are compared.
Chinese Optics Letters
  • Publication Date: Feb. 20, 2024
  • Vol. 22, Issue 3, 033602 (2024)
Nonlinear Optics
Talbot effect in anti-PT symmetric synthetic photonic lattices
Zhaofeng Liu, Siwei Tang, Zengrun Wen, Yuanmei Gao, Yangjian Cai, and Liren Zheng
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 031901 (2024)
Nonlinear photonic quasi-periodic spiral | Editors' Pick
Jing Zeng, Sen Wang, Ruwei Zhao, Yongxing Liu, Tiefeng Xu, Yan Sheng, and Tianxiang Xu
Chinese Optics Letters
  • Publication Date: Mar. 21, 2024
  • Vol. 22, Issue 3, 031902 (2024)
Broadband second-harmonic generation in thin-film lithium niobate microdisk via cyclic quasi-phase matching
Jiefu Zhu, Tingting Ding, Xuerui Sun, Fengchao Ni, Hao Li, Shijie Liu, Yuanlin Zheng, and Xianfeng Chen
Whispering-gallery-mode (WGM) microresonators can greatly enhance light–matter interaction, making them indispensable units for frequency conversion in nonlinear optics. Efficient nonlinear wave mixing in microresonators requires stringent simultaneous optical resonance and phase-matching conditions. Thus, it is challenging to achieve efficient frequency conversion over a broad bandwidth. Here, we demonstrate broadband second-harmonic generation (SHG) in the x-cut thin-film lithium niobate (TFLN) microdisk with a quality factor above 107 by applying the cyclic quasi-phase-matching (CQPM) mechanism, which is intrinsically applicable for broadband operation. Broadband SHG of continuous-wave laser with a maximum normalized conversion efficiency of ∼15%/mW is achieved with a bandwidth spanning over 100 nm in the telecommunication band. Furthermore, broadband SHG of femtosecond lasers, supercontinuum lasers, and amplified spontaneous emission in the telecommunication band is also experimentally observed. The work is beneficial for integrated nonlinear photonics devices like frequency converters and optical frequency comb generator based on second-order nonlinearity on the TFLN platform.
Chinese Optics Letters
  • Publication Date: Mar. 22, 2024
  • Vol. 22, Issue 3, 031903 (2024)
Optical Materials
Saturable absorption and visible pulse modulation of few-layer topological nodal-line semimetal HfGeTe
Qiming Zhao, Shouyan Zhang, Shuxian Wang, Gang Wang, Haohai Yu, and Huaijin Zhang
Topological nodal-line semimetals attract growing research attention in the photonic and optoelectronic fields due to their unique topological energy-level bands and fascinating nonlinear optical responses. Here, to the best of our knowledge, we first report the saturable absorption property of topological nodal-line semimetal HfGeTe and the related pulse modulation in passively Q-switched visible lasers. Few-layer HfGeTe demonstrates outstanding saturable absorption properties in the visible-light band, yielding the saturation intensities of 7.88, 12.66, and 6.64 µJ/cm2 at 515, 640, and 720 nm, respectively. Based on an as-prepared few-layer HfGeTe optical switch and a Pr:LiYF4 gain medium, Q-switched visible lasers are also successfully achieved at 522, 640, and 720 nm. The minimum pulse widths of the green, red, and deep-red pulsed lasers are 150, 125.5, and 420 ns, respectively. Especially for the green and red pulsed laser, the obtained pulse width is smaller than those of the low-dimensional layered materials. Our work sheds light on the application potential of topological nodal-line semimetals in the generation of visible pulsed lasers.
Chinese Optics Letters
  • Publication Date: Mar. 25, 2024
  • Vol. 22, Issue 3, 031601 (2024)