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.
  • Apr. 22, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 13 1301001 (2022)
  • DOI:10.3788/CJL202249.1301001
Dichroic Mirror Based on Dense Wavelength Combining of High-Brightness Laser Diode
Guo Linhui, Zhang Lanping, Fu Yun, Jiang Quanwei, Tan Hao, Du Weichuan, Gao Songxin, Wu Deyong, and Tang Chun
ConclusionsWe used dichroic mirror dense spectral beam combing to model and analyse the impact on incident angle, centre wavelength and thin-film transmission. Further, we developed an experimental study on three sub-beam combing wavelengths of 969, 976, 981 nm, achieving an output power of 311.9 W, a beam combining of 95.88%, a brightness of 58.42 MW/(cm2·sr), a spectral width of 12 nm, and a beam quality deterioration of less than 1.06 times. Compared to traditional beam combing based on the dichroic mirror, we can decrease the spectral width from several tens of nm to only 7 nm, and the combing channels substantially increased, allowing us to achieve higher brightness and power LD output relatively easily. In addition, when compared with dense spectral beam combing of about 0.5 nm, this type of beam combing has the disadvantages of a wider spectral interval, but this method can play the role of secondary beam combing and the output from dense spectral beam combing can be regarded as sub-beam. These findings are important in terms of increasing the power and brightness of direct diode lasers.
  • Apr. 22, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 9 0901001 (2022)
  • DOI:10.3788/CJL202149.0901001
Generation of Laser System Using for Rydberg Atom Excitation
Jin Gang, Cheng Yongjie, Huang Chengzu, Liu Xingxun, Qi Wanquan, and He Jun
ConclusionsIn ladder type EIT, decreasing probe optical power and increasing coupling beam power can minimize the population of the middle state in vapor cell. This is essential for the lifetime of coherent state between Rydberg atom and ground state. Due to the broadening of the atomic spectral by increasing probe power, we set the probe power below the saturated intensity. In comparison, the EIT peak increases as the coupling laser power increases; however, the spectrum linewidth is only broadened slightly. For a high electric-field strength, we should increase the coupling laser power to distinguish AT splitting peaks. We have developed strong engineering applicability and high stability Rydberg atomic excitation light system based on CEDL. The laser linewidth is about tens of kHz, with a flexible wavelength tuning, providing fast and slow feedback channels for locking center frequency. The 1018 nm CEDL is the ideal seed laser for YDFA. Based on the fiber-coupled single-pass crystal frequency doubling, the power of the single-frequency narrow line width of 509 nm laser is about 470 mW. Meanwhile, its power and the linewidth parameter can meet the Cs atomic Rydberg atom EIT spectrum applications. The preparation and optimization of EIT signal measurement is the next step in building a reliable microwave field strength measurement system based on the above laser system.
  • Mar. 25, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 7 0701003 (2022)
  • DOI:10.3788/CJL202249.0701003
Development of 261 nm Single-Longitudinal Mode Ultraviolet Laser
Li Xinqi, Pu Shuangshuang, Niu Na, Dou Wei, Zhao Yue, Liu Ying, and Zheng Quan
ConclusionsA 444 nm blue laser diode and a 469 nm blue laser diode, whose maximum pump powers are 1.4 W and 1.5 W, respectively, are used as the pumping source. The two blue laser diodes are fixed in the π polarization direction. A 45° combiner is used to combine the pump light of the two blue laser diodes. An aspherical lens with a focal length of 4 mm is used as a collimator to collimate the pump light emitted by the blue laser diode. A spherical lens with a focal length of 12 mm is used as a focusing lens to focus the pump light emitted by the blue laser diode. The cavity structure of the laser is V-shaped. The Fabry-Perot etalon is used to select a single-longitudinal mode. The Pr∶YLF crystal with a size of 3 mm×3 mm×5 mm and doping concentration (mass fraction) of 0.5% is used as the gain medium. The type-I phase-matched BBO crystal with a size of 3 mm×3 mm×3 mm is used as the frequency-doubling crystal. By optimizing the resonator parameters and the parameters of two Fabry-Perot etalons, the maximum output power of 261 nm single-longitudinal ultraviolet laser is 110 mW when the incident pump power is 2500 mW.
  • Mar. 03, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 9 0901002 (2022)
  • DOI:10.3788/CJL202249.0901002
High-Efficiency Ignition Laser Source Based on Diode Laser Beam Combination Technology
Han Jinliang, Zhang Jun, Shan Xiaonan, Peng Hangyu, Qin Li, and Wang Lijun
ConclusionsAn optical structure with a single fiber dual-wavelength output and self-inspection function is designed using spatial combining, wavelength beaming, and beam shaping techniques. We obtain a 976 nm ignition laser with an output power greater than 10 W and a 1310 nm detection laser with an output power greater than 1 mW. The structure can simultaneously realize the power and optical path self-inspection of 976 nm ignition and 1310 nm detection laser. The divergence angle and beam size of the laser are effectively reduced using a self-focusing lens. This can improve laser power density and solve the randomness problem of the PD detector. It is crucial to realize the quantitative detection of optical detection system feedback and improve the effectiveness of the optical path continuity testing.
  • Mar. 02, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 7 0701002 (2022)
  • DOI:10.3788/CJL202249.0701002
Research on Thermal-Frequency Characteristics of 633 nm Internal-Mirror He-Ne Laser
Xi Lu, Yin Cong, Wang Jianbo, Shi Chunying, Cai Shan, Liu Ruonan, Li Mengyao, and Zhang Chaochao
ConclusionsIn this paper, the free-running characteristics of the 633 nm internal-mirror He-Ne laser tube at the ambient temperature of -20-40 ℃ are studied. The experimental results show that when the laser tube reaches the thermal equilibrium at different ambient temperatures, the difference between the laser tube temperature and the ambient temperature is fixed, the expansion rate is also the same, and the voltage difference of the double longitudinal mode changes for the same period. According to these characteristics, the preheating and frequency stabilization control scheme of the laser system is designed, and the frequency stabilization of the 633 nm internal-mirror He-Ne laser is realized. When the room temperature is about 24 ℃, the beat frequency results of the locked thermally stabilized laser and the high-precision iodine stabilized laser show that the relative standard uncertainty of frequency within 3 h is u=6.4×10-9. When the sampling time τ=1 s, the corresponding Allen variance is 7.0×10-11. When 0.1 s≤τ≤2000 s, the Allan variance is better than 4.3×10-10, and the frequency reproducibility within 3 months is better than 4.6×10-9. This paper also studies the frequency drift law of the output laser after locking at the ambient temperature of -20-40 ℃. The experimental results show that the temperature of the laser tube wall changes linearly with the ambient temperature after frequency stabilization. At the same time, the drift of the laser output frequency with the ambient temperature after frequency stabilization is about 293 kHz/℃, which is consistent with the drift value of 268 kHz/℃ calculated by the pressure estimation model. In this regard, when the laser is working in a large temperature range (such as -20-40 ℃), interpolation calibration can be used to obtain a more accurate reference output frequency.
  • Mar. 02, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 6 0601002 (2022)
  • DOI:10.3788/CJL202249.0601002
Electrical Aging Test and Lifetime Analysis of Whispering-Gallery-Mode Micro-Cavity Lasers
Fan Yingrun, Xiao Jinlong, Yang Yuede, Hao Youzeng, Huang Yongtao, and Huang Yongzhen
  • Mar. 02, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 6 0601001 (2022)
  • DOI:10.3788/CJL202249.0601001
Research on Frequency Locking of 1560 nm Fiber Laser Based on Rubidium Atomic Modulation Transfer Spectroscopy Technology
Yu Xiao, Lv Mengjie, Zhang Xu, Jia Aiai, Wang Guochao, Zhu Lingxiao, Yan Shuhua, and Yang Jun
ConclusionsThis study investigates the MTS frequency stabilisation method based on 1560 nm laser frequency doubling, optimises the analysis of the modulation transfer signal and finally locks the 1560 nm fiber laser frequency doubling to the 34 cross peak of the rubidium atom D2 line. After the laser is frequency-locked, it beats with an optical frequency comb and the standard deviation of the beat frequency value after locking for 1 h is 0.049. The Allan variance is used to characterise the performance of the system frequency locking, and the relative frequency stability after frequency locking reaches the minimum within the integration time of 10 s. The system results show that the 1560 nm fiber laser frequency locking system based on rubidium MTS can achieve excellent frequency stabilisation performance. Moreover, the frequency stabilisation system can output high-frequency stability at 1560 and 780 nm narrow-linewidth lasers simultaneously, which can be directly applied to fiber sensing, lidar and rubidium atoms as experimental media, quantum information, atomic and molecular physics and other fields.
  • Jan. 24, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 3 0301002 (2022)
  • DOI:10.3788/CJL202249.0301002
Controllable All-Solid-State Pulsed Laser Based on Graphene Capacitor Devices
Chen Tiantian, Dai Tengfei, Chen Chaoran, Liu Xiang, and Chang Jianhua
ConclusionsThe paper introduces the fabrication, characterization and analysis of a novel graphene capacitor, which can be used as an effective saturable absorber modulator in a passive Q-switched system. The photoelectric interaction mechanism of the device is studied based on its electrical transmission and spectral absorption properties. Due to the change of Fermi level and carrier density, the absorption properties of graphene in the device can be adjusted by gate voltage without changing the properties of SA material. The output characteristics of all-solid-state pulse laser can be adjusted flexibly under ultra-low electric modulation power (~13 pA current and 1 nW power). It is applied to the Nd∶ YVO4 all solid state laser system, and the stable pulse output at 532.04 nm wavelength is achieved. The laser absorption pump power is kept constant, and the gate voltage is changed. The pulse duration of the Q-switched output can be compressed from 1.1 μs to 345 ns. This structure is expected to further promote the development of tunable pulse lasers from visible light to mid-infrared band. In particular, passive Q-switching/mode-locking devices based on graphene devices will be used in future applications such as infrared measurement, projection display, and optical modulation.
  • Jan. 18, 2022
  • Chinese Journal of Lasers
  • Vol.49 Issue, 3 0301003 (2022)
  • DOI:10.3788/CJL202249.0301003