A water track laser Doppler velocimeter (LDV) is developed with advantages of high update rate, high real-time performance, high concealment, light weight, and small dimensions. The water track LDV measures the advance velocity of the under-water vehicle with respect to the surrounding water. The experimental results show that the water track LDV has an accuracy of 96.4% when the moving velocity of the vehicle with respect to the ground exceeds 0.25 m/s. Thus, the water track LDV is promising in the application of underwater navigation to aid the strapdown inertial navigation system.
{"title":"Water track laser Doppler velocimeter [Invited]","authors":"è�£ 黄, ç�¦ 王, 志毅 å�‘, 晓明 è�‚, å�¥ 周, æ™– ç½—","doi":"10.3788/col202321.090005","DOIUrl":"https://doi.org/10.3788/col202321.090005","url":null,"abstract":"A water track laser Doppler velocimeter (LDV) is developed with advantages of high update rate, high real-time performance, high concealment, light weight, and small dimensions. The water track LDV measures the advance velocity of the under-water vehicle with respect to the surrounding water. The experimental results show that the water track LDV has an accuracy of 96.4% when the moving velocity of the vehicle with respect to the ground exceeds 0.25 m/s. Thus, the water track LDV is promising in the application of underwater navigation to aid the strapdown inertial navigation system.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135600661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.110008
Liang Chen, Huiyi Guo, Zekun Shi, Wenzhe Chang, Boyu Chen, Zhi Wang, Yan-ge Liu
Broadband mode converters are essential devices for space-division and wavelength-division multiplexing systems. There are great challenges in the generation of higher-order modes above the third order with low loss and high mode purity employing all-fiber devices. In this paper, an all-fiber LP41 mode converter is proposed and fabricated by tapering a nine-core single-mode fiber bundle. Experimental results indicate that this all-fiber LP41 mode converter is low-loss, high-purity, and ultrabroadband. The insertion loss is less than 0.4 dB. The purity of odd LP41 at 1310 nm is 95.09%, and the operating bandwidth exceeds 280 nm.
{"title":"Low-loss, high-purity, and ultrabroadband all-fiber LP41 mode converter employing a mode-selective photonic lantern [Invited]","authors":"Liang Chen, Huiyi Guo, Zekun Shi, Wenzhe Chang, Boyu Chen, Zhi Wang, Yan-ge Liu","doi":"10.3788/col202321.110008","DOIUrl":"https://doi.org/10.3788/col202321.110008","url":null,"abstract":"Broadband mode converters are essential devices for space-division and wavelength-division multiplexing systems. There are great challenges in the generation of higher-order modes above the third order with low loss and high mode purity employing all-fiber devices. In this paper, an all-fiber LP41 mode converter is proposed and fabricated by tapering a nine-core single-mode fiber bundle. Experimental results indicate that this all-fiber LP41 mode converter is low-loss, high-purity, and ultrabroadband. The insertion loss is less than 0.4 dB. The purity of odd LP41 at 1310 nm is 95.09%, and the operating bandwidth exceeds 280 nm.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135612365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.113602
Jingcheng Zhao, Nan Li, Yongzhi Cheng
In this paper, we propose an ultrabroadband chiral metasurface (CMS) composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate. This innovative structure enables ultrabroadband and high-efficiency linear polarization (LP) conversion, as well as asymmetric transmission (AT) effect in the microwave region. The enhanced interference effect of the Fabry–Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect. Through numerical simulations, it has been revealed that the cross-polarization transmission coefficients for normal forward (-z) and backward (+z) incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz, accompanied by a polarization conversion ratio of over 99%. Furthermore, our microwave experimental results validate the consistency among simulation, theory, and measurement. Additionally, we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles, total transmittance, AT coefficient, and electric field distribution. The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar, remote sensing, and satellite communication.
{"title":"Ultrabroadband chiral metasurface for linear polarization conversion and asymmetric transmission based on enhanced interference theory","authors":"Jingcheng Zhao, Nan Li, Yongzhi Cheng","doi":"10.3788/col202321.113602","DOIUrl":"https://doi.org/10.3788/col202321.113602","url":null,"abstract":"In this paper, we propose an ultrabroadband chiral metasurface (CMS) composed of S-shaped resonator structures situated between two twisted subwavelength gratings and dielectric substrate. This innovative structure enables ultrabroadband and high-efficiency linear polarization (LP) conversion, as well as asymmetric transmission (AT) effect in the microwave region. The enhanced interference effect of the Fabry–Perot-like resonance cavity greatly expands the bandwidth and efficiency of LP conversion and AT effect. Through numerical simulations, it has been revealed that the cross-polarization transmission coefficients for normal forward (-z) and backward (+z) incidence exceed 0.8 in the frequency range of 4.13 to 17.34 GHz, accompanied by a polarization conversion ratio of over 99%. Furthermore, our microwave experimental results validate the consistency among simulation, theory, and measurement. Additionally, we elucidate the distinct characteristics of ultrabroadband LP conversion and significant AT effect through analysis of polarization azimuth rotation and ellipticity angles, total transmittance, AT coefficient, and electric field distribution. The proposed CMS structure shows excellent polarization conversion properties via AT effect and has potential applications in areas such as radar, remote sensing, and satellite communication.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135612369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aiming at coherence degradation during target detection, a suppressing method based on frequency-modulated continuous wave coherent lidar is proposed. Combined with a random iteration algorithm, a long-pulse echo signal with coherent degradation is matched with random phase noise of a certain frequency and achieves coherence restoration. Simulation and field experiment results show that this proposed method can recover the intrapulse coherence in long-pulse echo signals. In addition, for the real target echo signal at 4.2 and 19.8 km, the peak signal-to-noise ratio processed by this method is increased by 0.35 times and 4 times after pulse compression, respectively.
{"title":"Intrapulse coherence degradation suppressing method of echo signal in coherent lidar","authors":"Haisheng Cong, Jianfeng Sun, Zhiyong Lu, Hongyu He, Weijie Ren, Yuxin Jiang, Lingling Xu, Chaoyang Li, Longkun Zhang, Zhengwei Zhang","doi":"10.3788/col202321.071201","DOIUrl":"https://doi.org/10.3788/col202321.071201","url":null,"abstract":"Aiming at coherence degradation during target detection, a suppressing method based on frequency-modulated continuous wave coherent lidar is proposed. Combined with a random iteration algorithm, a long-pulse echo signal with coherent degradation is matched with random phase noise of a certain frequency and achieves coherence restoration. Simulation and field experiment results show that this proposed method can recover the intrapulse coherence in long-pulse echo signals. In addition, for the real target echo signal at 4.2 and 19.8 km, the peak signal-to-noise ratio processed by this method is increased by 0.35 times and 4 times after pulse compression, respectively.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"3 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84934657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we demonstrate the spectral manipulation in an ultrafast fiber laser system that generates ultrashort pulses with a repetition rate of 1.2 GHz and two switchable modes — a 1064-nm fundamental laser mode with a maximum output power of 66.6 W, and a 1125-nm Raman laser mode with a maximum output power of 17.23 W. The pulse width, beam quality, and power stability are carefully characterized. We also investigate a method to switch between the two modes by manipulating the duty cycle of the modulation signal. It is anticipated that this bi-mode ultrafast fiber laser system can be a promising ultrafast laser source for frontier applications, such as micromachining, bioimaging, and spectroscopy.
{"title":"Spectral manipulation in a high-power ultrafast fiber laser system generating ultrashort pulses with GHz repetition rate","authors":"Yingtao Zhang, Zihao Li, Tianxi Wang, Hao Xiu, Chiyi Wei, Luyi Wang, Molei Hao, Xiaoming Wei, Zhong-zhu Yang","doi":"10.3788/col202321.091401","DOIUrl":"https://doi.org/10.3788/col202321.091401","url":null,"abstract":"In this work, we demonstrate the spectral manipulation in an ultrafast fiber laser system that generates ultrashort pulses with a repetition rate of 1.2 GHz and two switchable modes — a 1064-nm fundamental laser mode with a maximum output power of 66.6 W, and a 1125-nm Raman laser mode with a maximum output power of 17.23 W. The pulse width, beam quality, and power stability are carefully characterized. We also investigate a method to switch between the two modes by manipulating the duty cycle of the modulation signal. It is anticipated that this bi-mode ultrafast fiber laser system can be a promising ultrafast laser source for frontier applications, such as micromachining, bioimaging, and spectroscopy.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"13 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86979549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.082701
Miao Cai, Zhi-Xiang Li, Hao Wu, Ya-Ping Ruan, Lei Tang, Jiangshan Tang, Ming-Yuan Chen, Han Zhang, K. Xia, M. Xiao, Yanqing Lu
The sensitivity of optical measurement is ultimately constrained by the shot noise to the standard quantum limit. It has become a common concept that beating this limit requires quantum resources. A deep-learning neural network free of quantum principle has the capability of removing classical noise from images, but it is unclear in reducing quantum noise. In a coincidence-imaging experiment, we show that quantum-resource-free deep learning can be exploited to surpass the standard quantum limit via the photon-number-dependent nonlinear feedback during training. Using an effective classical light with photon flux of about 9 × 10 4 photons per second, our deep-learning-based scheme achieves a 14 dB improvement in signal-to-noise ratio with respect to the standard quantum limit.
{"title":"Surpassing the standard quantum limit of optical imaging via deep learning","authors":"Miao Cai, Zhi-Xiang Li, Hao Wu, Ya-Ping Ruan, Lei Tang, Jiangshan Tang, Ming-Yuan Chen, Han Zhang, K. Xia, M. Xiao, Yanqing Lu","doi":"10.3788/col202321.082701","DOIUrl":"https://doi.org/10.3788/col202321.082701","url":null,"abstract":"The sensitivity of optical measurement is ultimately constrained by the shot noise to the standard quantum limit. It has become a common concept that beating this limit requires quantum resources. A deep-learning neural network free of quantum principle has the capability of removing classical noise from images, but it is unclear in reducing quantum noise. In a coincidence-imaging experiment, we show that quantum-resource-free deep learning can be exploited to surpass the standard quantum limit via the photon-number-dependent nonlinear feedback during training. Using an effective classical light with photon flux of about 9 × 10 4 photons per second, our deep-learning-based scheme achieves a 14 dB improvement in signal-to-noise ratio with respect to the standard quantum limit.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"232 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82749335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.011408
Y. Guan, Ruixuan Sun, N. Zhuo, Xiyu Lu, Jinchuan Zhang, S. Zhai, Jun-qi Liu, Shuman Liu, Lijun Wang, Feng-qi Liu
We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser (QCL) by optimizing the design of a homogeneous active region and combining superposed distributed feedback gratings. Coaxial, single-mode emissions at two different wavelengths were achieved only through adjusting the bias voltage. Room temperature con-tinuous-wave operation with output powers of above 30 mW and 75 mW was realized for single-mode emission at 7.61 μ m and 7.06 μ m, respectively. The simplified fabrication process and easy wavelength control of our designed dual-wavelength QCL make it very attractive for developing miniature multi-species gas sensing systems.
{"title":"Room temperature continuous-wave operation of a dual-wavelength quantum cascade laser","authors":"Y. Guan, Ruixuan Sun, N. Zhuo, Xiyu Lu, Jinchuan Zhang, S. Zhai, Jun-qi Liu, Shuman Liu, Lijun Wang, Feng-qi Liu","doi":"10.3788/col202321.011408","DOIUrl":"https://doi.org/10.3788/col202321.011408","url":null,"abstract":"We report on the design and fabrication of a dual-wavelength switchable quantum cascade laser (QCL) by optimizing the design of a homogeneous active region and combining superposed distributed feedback gratings. Coaxial, single-mode emissions at two different wavelengths were achieved only through adjusting the bias voltage. Room temperature con-tinuous-wave operation with output powers of above 30 mW and 75 mW was realized for single-mode emission at 7.61 μ m and 7.06 μ m, respectively. The simplified fabrication process and easy wavelength control of our designed dual-wavelength QCL make it very attractive for developing miniature multi-species gas sensing systems.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"19 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82546437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.011202
Yongjian Li, Shuai Zhang, Jinyi Li, Xiaotao Yang, Yunfei Meng, Xu Liu, Z. Du
Studies on the kinetics of gas-phase chemical reactions currently rely on calculations or simulations and lack simple, fast, and accurate direct measurement methods. We developed a tunable laser molecular absorption spectroscopy measurement system to achieve direct measurements of such reactions by using wavelength modulated spectroscopy and performed online measurements and diagnostics of molecular concentration, reaction temperature, and pressure change during the redox reaction of ozone with nitrogen oxides (NO x ) with 0.1 s temporal resolution. This study provides a promising diagnostic tool for studying gas-phase chemical reaction kinetics.
{"title":"Preliminary study on direct measurements and diagnostics for chemical reaction dynamics of NOx by using laser wavelength modulation spectroscopy","authors":"Yongjian Li, Shuai Zhang, Jinyi Li, Xiaotao Yang, Yunfei Meng, Xu Liu, Z. Du","doi":"10.3788/col202321.011202","DOIUrl":"https://doi.org/10.3788/col202321.011202","url":null,"abstract":"Studies on the kinetics of gas-phase chemical reactions currently rely on calculations or simulations and lack simple, fast, and accurate direct measurement methods. We developed a tunable laser molecular absorption spectroscopy measurement system to achieve direct measurements of such reactions by using wavelength modulated spectroscopy and performed online measurements and diagnostics of molecular concentration, reaction temperature, and pressure change during the redox reaction of ozone with nitrogen oxides (NO x ) with 0.1 s temporal resolution. This study provides a promising diagnostic tool for studying gas-phase chemical reaction kinetics.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"5 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87374118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.3788/col202321.030501
Ran Ning, Dayong Wang, L. Rong, Jie Zhao, Yunxin Wang, Shufeng Lin
The converging lens is one of the key components in high-resolution terahertz imaging. In this Letter, a binary diffractive lens is proposed for the scanning imaging system working at 278.6 GHz, in which a convergent beam with a waist diameter of 0.65 mm is generated, and 1 mm lateral imaging resolution is realized. This low-cost terahertz lens, constituted by concentric rings with different radii, is optimized by stimulated annealing algorithm and fabricated by three-dimensional printing. Compared with the conventional transmissive convex lens, higher resolution and enhanced imaging quality are achieved via smaller focal spot of the illumination beam. This type of lens would promote terahertz imaging closer to practical applications such as nondestructive testing and other scenarios.
{"title":"Binary diffractive lens with subwavelength focusing for terahertz imaging","authors":"Ran Ning, Dayong Wang, L. Rong, Jie Zhao, Yunxin Wang, Shufeng Lin","doi":"10.3788/col202321.030501","DOIUrl":"https://doi.org/10.3788/col202321.030501","url":null,"abstract":"The converging lens is one of the key components in high-resolution terahertz imaging. In this Letter, a binary diffractive lens is proposed for the scanning imaging system working at 278.6 GHz, in which a convergent beam with a waist diameter of 0.65 mm is generated, and 1 mm lateral imaging resolution is realized. This low-cost terahertz lens, constituted by concentric rings with different radii, is optimized by stimulated annealing algorithm and fabricated by three-dimensional printing. Compared with the conventional transmissive convex lens, higher resolution and enhanced imaging quality are achieved via smaller focal spot of the illumination beam. This type of lens would promote terahertz imaging closer to practical applications such as nondestructive testing and other scenarios.","PeriodicalId":10293,"journal":{"name":"Chinese Optics Letters","volume":"43 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76940924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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