Optical analysis method for fast plasma characterization of high-speed miniaturized synthetic jet
Ye Yuan, Yan Zhang, Cheng Guo, Xiaolu Kang, Zhong Yan, Xiaoping Huang, and Qing Zhao
In this paper, a new optical analysis method for plasma characterization is proposed. Plasma characteristics are obtained directly by measuring the plasma luminous color, rather than the complex spectral diagnosis method, which is difficult to obtain at high speed. By using the light transmittance curve of the human cornea, the RGB coordinates are calculated from the measured plasma spectrum data. Plasma characteristics are diagnosed using the Boltzmann plot method and the Stark broadening method. The corresponding relationship of the electron temperature, electron density data points, and luminous color is established and analyzed. Our research results indicate that this optical analysis method is feasible and promising for fast plasma characterization.In this paper, a new optical analysis method for plasma characterization is proposed. Plasma characteristics are obtained directly by measuring the plasma luminous color, rather than the complex spectral diagnosis method, which is difficult to obtain at high speed. By using the light transmittance curve of the human cornea, the RGB coordinates are calculated from the measured plasma spectrum data. Plasma characteristics are diagnosed using the Boltzmann plot method and the Stark broadening method. The corresponding relationship of the electron temperature, electron density data points, and luminous color is established and analyzed. Our research results indicate that this optical analysis method is feasible and promising for fast plasma characterization.
- May. 06, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 073001 (2022)
- DOI：10.3788/COL202220.073001
In-situ laser-induced surface damage inspection based on image super-resolution and adaptive segmentation method
Fengdong Chen, Jingyang Sun, Qian Wang, Hongbo Zhu, Fa Zeng, Yueyue Han, Cheng Lu, and Guodong Liu
In-situ laser-induced surface damage inspection plays a key role in protecting the large aperture optics in an inertial confinement fusion (ICF) high-power laser facility. In order to improve the initial damage detection capabilities, an in-situ inspection method based on image super-resolution and adaptive segmentation method is presented. Through transfer learning and integration of various attention mechanisms, the super-resolution reconstruction of darkfield images with less texture information is effectively realized, and, on the basis of image super-resolution, an adaptive image segmentation method is designed, which effectively adapts to the damage detection problems under conditions of uneven illumination and weak signal. An online experiment was carried out by using edge illumination and the telescope optical imaging system, and the validity of the method was proved by the experimental results.In-situ laser-induced surface damage inspection plays a key role in protecting the large aperture optics in an inertial confinement fusion (ICF) high-power laser facility. In order to improve the initial damage detection capabilities, an in-situ inspection method based on image super-resolution and adaptive segmentation method is presented. Through transfer learning and integration of various attention mechanisms, the super-resolution reconstruction of darkfield images with less texture information is effectively realized, and, on the basis of image super-resolution, an adaptive image segmentation method is designed, which effectively adapts to the damage detection problems under conditions of uneven illumination and weak signal. An online experiment was carried out by using edge illumination and the telescope optical imaging system, and the validity of the method was proved by the experimental results.
- Apr. 29, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 071101 (2022)
- DOI：10.3788/COL202220.071101
Underwater Bessel-like beams with enlarged depth of focus based on fiber microaxicon
Xiaoying He, Mengyuan Li, and Lan Rao
Underwater optical wireless communication, which is useful for oceanography, environmental monitoring, and underwater surveillance, suffers the limit of the absorption attenuation and Mie–Rayleigh scattering of the lights. Here, Bessel-like beams generated by a fiber microaxicon is utilized for underwater wireless propagation. Underwater, the cone angle for generating Bessel-like beams starts from 46°, which is smaller than that in air for Bessel-like beams. When the cone angle of the fiber microaxicons is about 140°, the depth of focus underwater, which is four times as long as the depth of focus in air, has enlarged about 28 µm, 36.12 µm, and 50.7 µm for 470 nm, 520 nm, and 632 nm visible lights. The transmission distance of the Bessel beams for visible lights has been simulated by using Henyey–Greenstein–Rayleigh phase function methods and spectral absorption by bio-optical model due to Monte Carlo methods. The results show that the propagation distance could reach 4000 m, which overcome the limit of the Mie–Rayleigh scattering and absorption attenuation underwater.Underwater optical wireless communication, which is useful for oceanography, environmental monitoring, and underwater surveillance, suffers the limit of the absorption attenuation and Mie–Rayleigh scattering of the lights. Here, Bessel-like beams generated by a fiber microaxicon is utilized for underwater wireless propagation. Underwater, the cone angle for generating Bessel-like beams starts from 46°, which is smaller than that in air for Bessel-like beams. When the cone angle of the fiber microaxicons is about 140°, the depth of focus underwater, which is four times as long as the depth of focus in air, has enlarged about 28 µm, 36.12 µm, and 50.7 µm for 470 nm, 520 nm, and 632 nm visible lights. The transmission distance of the Bessel beams for visible lights has been simulated by using Henyey–Greenstein–Rayleigh phase function methods and spectral absorption by bio-optical model due to Monte Carlo methods. The results show that the propagation distance could reach 4000 m, which overcome the limit of the Mie–Rayleigh scattering and absorption attenuation underwater.
- May. 07, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 072601 (2022)
- DOI：10.3788/COL202220.072601
Inverse design of 1D color splitter for high-efficiency color imaging
Jiahao Li, Mengwei Cao, Weili Liang, Yilin Zhang, Zhenwei Xie, and Xiaocong Yuan
We introduce a simple one-dimensional (1D) structure in the design of 1D color splitters (1D-CSs) with RGB unit cells for color imaging and propose a single-to-double-layer design in 1D-CSs. Based on inverse design metasurfaces, we demonstrate numerically a single-layer 1D-CS with a full-color efficiency of 46.2% and a double-layer 1D-CS with a full-color efficiency of 48.2%; both of them are significantly higher than that of traditional color filters. Moreover, we demonstrate a 1D-CS that has application value by evaluating the double-layer 1D-CS’s performances in terms of incident angle sensitivity, polarization angle sensitivity, and assembly tolerance.We introduce a simple one-dimensional (1D) structure in the design of 1D color splitters (1D-CSs) with RGB unit cells for color imaging and propose a single-to-double-layer design in 1D-CSs. Based on inverse design metasurfaces, we demonstrate numerically a single-layer 1D-CS with a full-color efficiency of 46.2% and a double-layer 1D-CS with a full-color efficiency of 48.2%; both of them are significantly higher than that of traditional color filters. Moreover, we demonstrate a 1D-CS that has application value by evaluating the double-layer 1D-CS’s performances in terms of incident angle sensitivity, polarization angle sensitivity, and assembly tolerance.
- May. 06, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 073601 (2022)
- DOI：10.3788/COL202220.073601
Low-threshold continuous operation of fiber gas Raman laser based on large-core anti-resonant hollow-core fiber
Xinyue Zhu, Fei Yu, Dakun Wu, Yan Feng, Shufen Chen, Yi Jiang, and Lili Hu
Continuous operation of fiber gas Raman lasing at the 1135 nm wavelength is experimentally demonstrated with an output power exceeding 26 W. Rotational stimulated Raman scattering (Rot-SRS) is generated in the hydrogen gas filled 50 m homemade anti-resonant hollow-core fiber (AR-HCF). A single-frequency fiber laser at the 1064 nm wavelength is used as the pump source, and a minimum threshold of 31.5 W is measured where the core diameter of AR-HCF reaches 37 µm. Up to 40.4% power conversion efficiency of forward Rot-SRS is achieved in the single-pass configuration, corresponding to a quantum efficiency of 43.1%. Over 1 W strong backward Rot-SRS is observed in the experiment, ultimately limiting the further increase of Rot-SRS generation in the forward direction.Continuous operation of fiber gas Raman lasing at the 1135 nm wavelength is experimentally demonstrated with an output power exceeding 26 W. Rotational stimulated Raman scattering (Rot-SRS) is generated in the hydrogen gas filled 50 m homemade anti-resonant hollow-core fiber (AR-HCF). A single-frequency fiber laser at the 1064 nm wavelength is used as the pump source, and a minimum threshold of 31.5 W is measured where the core diameter of AR-HCF reaches 37 µm. Up to 40.4% power conversion efficiency of forward Rot-SRS is achieved in the single-pass configuration, corresponding to a quantum efficiency of 43.1%. Over 1 W strong backward Rot-SRS is observed in the experiment, ultimately limiting the further increase of Rot-SRS generation in the forward direction.
- May. 07, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 071401 (2022)
- DOI：10.3788/COL202220.071401
LiNbO3 channel and ridge waveguides based on helium ion implantation combined with lithography and precise diamond dicing
Sumei Wang, Jinhua Zhao, Jinjun Gu, Mingyang Bu, Li Fan, Shuang Li, Xifeng Qin, Yicun Yao, Yingying Ren, and Lei Wang
Lithium niobate (LiNbO3, LN) channel and ridge waveguides have been successfully fabricated by He ion implantation, which has energy of 500 keV and fluence of 1.5×1016 ions/cm2 and is combined with lithography and the precise diamond dicing technique. The refractive index profile of the annealed LN planar waveguide was reconstructed. The propagation loss of the channel waveguide with a width of 10 µm and that of the ridge waveguides with widths of 25 µm and 15 µm were investigated by the end-face coupling method. In our work, the factors that affect the waveguide properties of channel and ridge waveguides were revealed.Lithium niobate (
- May. 07, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 071301 (2022)
- DOI：10.3788/COL202220.071301
Probing fluorescence quantum efficiency of single molecules in an organic matrix by monitoring lifetime change during sublimation
Penglong Ren, Shangming Wei, Pu Zhang, and Xue-Wen Chen
Quantum efficiency is a critical piece of information of a quantum emitter and regulates the emitter’s fluorescence decay dynamics in an optical environment through the Purcell effect. Here, we present a simple way to experimentally probe fluorescence quantum efficiency of single dibenzoterrylene molecules embedded in a thin anthracene microcrystal obtained through a co-sublimation process. In particular, we correlate the fluorescence lifetime change of single dibenzoterrylene molecules with the variation of the matrix thickness due to natural sublimation. With the identification of the molecule emission dipole orientation, we could deduce the near-unity intrinsic quantum efficiency of dibenzoterrylene molecules in the anthracene matrix.Quantum efficiency is a critical piece of information of a quantum emitter and regulates the emitter’s fluorescence decay dynamics in an optical environment through the Purcell effect. Here, we present a simple way to experimentally probe fluorescence quantum efficiency of single dibenzoterrylene molecules embedded in a thin anthracene microcrystal obtained through a co-sublimation process. In particular, we correlate the fluorescence lifetime change of single dibenzoterrylene molecules with the variation of the matrix thickness due to natural sublimation. With the identification of the molecule emission dipole orientation, we could deduce the near-unity intrinsic quantum efficiency of dibenzoterrylene molecules in the anthracene matrix.
- May. 06, 2022
- Chinese Optics Letters
- Vol.20 Issue, 7 073602 (2022)
- DOI：10.3788/COL202220.073602
LD Pumped Watt-Level Actively Q-switched Alexandrite Laser
Wang Jingchong, Guan Chen, Liu Zhaojun, Cong Zhenhua, Wang Shiwu, Nie Yi, Liu Yang, and Zhao Zhigang
ConclusionsThis paper presents a red LD pumped Q-switched Alexandrite laser. A watt-level pulsed laser is obtained in a V-shaped cavity. The corresponding repetition rate is 10 kHz, the pulse duration is 961 ns, and the pulse energy is 116 μJ. Wavelength tuning from 728 to 793 nm is demonstrated with BRF. Based on the Q-switched rate equations, a well-matched numerical simulation is obtained, and the effect of pump energy on pulse duration is analyzed. A shorter pulse laser of 10 ns is also achieved by cavity dumping and the peak power is over 3 kW. In the future work, we will continue to optimize the design of the cavity and the experimental parameters. Based on the need of specific applications, we will try to achieve higher-energy, higher-efficiency, shorter pulse duration, and narrower linewidth Alexandrite lasers pumped by red LDs.Conclusions
This paper presents a red LD pumped Q-switched Alexandrite laser. A watt-level pulsed laser is obtained in a V-shaped cavity. The corresponding repetition rate is 10 kHz, the pulse duration is 961 ns, and the pulse energy is 116 μJ. Wavelength tuning from 728 to 793 nm is demonstrated with BRF. Based on the Q-switched rate equations, a well-matched numerical simulation is obtained, and the effect of pump energy on pulse duration is analyzed. A shorter pulse laser of 10 ns is also achieved by cavity dumping and the peak power is over 3 kW. In the future work, we will continue to optimize the design of the cavity and the experimental parameters. Based on the need of specific applications, we will try to achieve higher-energy, higher-efficiency, shorter pulse duration, and narrower linewidth Alexandrite lasers pumped by red LDs.
- Apr. 22, 2022
- Chinese Journal of Lasers
- Vol.49 Issue, 13 1301001 (2022)
- DOI：10.3788/CJL202249.1301001
1.65 µm square-FP coupled cavity semiconductor laser for methane gas detection | Editors' Pick
Yingrun Fan, Jinlong Xiao, Zhengzheng Shen, Youzeng Hao, Jiachen Liu, Ke Yang, Yuede Yang, and Yongzhen Huang
We report a 1.65 µm square-Fabry–Pérot (FP) coupled cavity semiconductor laser for methane gas detection. The laser output optical power can reach 7.4 mW with the side mode suppression ratio about 40 dB. The wavelength tuning range is 2 nm by adjusting the FP cavity injection current, covering the methane absorption line at 1653.72 nm. The lasing wavelength can also be tuned by adjusting the square microcavity injection current or temperature, respectively. Methane gas detection is successfully demonstrated utilizing this laser.We report a 1.65 µm square-Fabry–Pérot (FP) coupled cavity semiconductor laser for methane gas detection. The laser output optical power can reach 7.4 mW with the side mode suppression ratio about 40 dB. The wavelength tuning range is 2 nm by adjusting the FP cavity injection current, covering the methane absorption line at 1653.72 nm. The lasing wavelength can also be tuned by adjusting the square microcavity injection current or temperature, respectively. Methane gas detection is successfully demonstrated utilizing this laser.
- Apr. 29, 2022
- Chinese Optics Letters
- Vol.20 Issue, 6 061401 (2022)
- DOI：10.3788/COL202220.061401
High efficiency of spectral beam combining by using large optical cavity lasers
Xiaoxu Xing, Xuyan Zhou, Hongwei Qu, Weiqiao Zhang, Lingqian Meng, Jing Liu, Yufei Wang, and Wanhua Zheng
We studied the spectral beam combining (SBC) of a large optical cavity (LOC) laser array to achieve high-power and high-brightness laser output. We discussed the characteristics of the external cavity feedback efficiency and the focal length of the transform lens for lasers with different waveguide thicknesses. We have found that using LOC laser diodes can increase the proportion of external cavity feedback, thereby improving the SBC efficiency. At a current of 90 A, the CW output power of the SBC system is 59.2 W, and the SBC efficiency reaches up to 102.8%. All emitters of the laser array have achieved spectral locking with a spectral width of 11.67 nm, and the beam parameter product is 4.38 mm·mrad.We studied the spectral beam combining (SBC) of a large optical cavity (LOC) laser array to achieve high-power and high-brightness laser output. We discussed the characteristics of the external cavity feedback efficiency and the focal length of the transform lens for lasers with different waveguide thicknesses. We have found that using LOC laser diodes can increase the proportion of external cavity feedback, thereby improving the SBC efficiency. At a current of 90 A, the CW output power of the SBC system is 59.2 W, and the SBC efficiency reaches up to 102.8%. All emitters of the laser array have achieved spectral locking with a spectral width of 11.67 nm, and the beam parameter product is 4.38 mm·mrad.
- May. 06, 2022
- Chinese Optics Letters
- Vol.20 Issue, 6 061402 (2022)
- DOI：10.3788/COL202220.061402
Monolithic thin film lithium niobate electro-optic modulator with over 110 GHz bandwidth
Chinese Optics Letters, Vol. 20,Issue 2, 022502 (2022)
Soliton frequency comb generation in CMOS-compatible silicon nitride microresonators
Photonics Research, Vol. 10,Issue 5, 05001290 (2022)
High-performance distributed feedback quantum dot lasers with laterally coupled dielectric gratings
Photonics Research, Vol. 10,Issue 5, 05001271 (2022)
Engineering photonic angular momentum with structured light: a review
Advanced Photonics, Vol. 3,Issue 6, 064001 (2021)
Review of bio-optical imaging systems with a high space-bandwidth product
Advanced Photonics, Vol. 3,Issue 4, 044001 (2021)
Chinese Optics Letters, Vol. 19,Issue 10, 102202 (2021)
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