张程程, 张东亮, 王锐, 罗明馨, 林青华, 郑显通, 祝连庆, 王伟平. 大功率脉冲量子级联激光器锥形波导光学与热学仿真设计[J]. 红外与激光工程, 2024, 53(5): 20240015. DOI: 10.3788/IRLA20240015
引用本文: 张程程, 张东亮, 王锐, 罗明馨, 林青华, 郑显通, 祝连庆, 王伟平. 大功率脉冲量子级联激光器锥形波导光学与热学仿真设计[J]. 红外与激光工程, 2024, 53(5): 20240015. DOI: 10.3788/IRLA20240015
Zhang Chengcheng, Zhang Dongliang, Wang Rui, Luo Mingxin, Lin Qinghua, Zheng Xiantong, Zhu Lianqing, Wang Weiping. Optical and thermal simulation design of tapered waveguide for high-power pulsed quantum cascade laser[J]. Infrared and Laser Engineering, 2024, 53(5): 20240015. DOI: 10.3788/IRLA20240015
Citation: Zhang Chengcheng, Zhang Dongliang, Wang Rui, Luo Mingxin, Lin Qinghua, Zheng Xiantong, Zhu Lianqing, Wang Weiping. Optical and thermal simulation design of tapered waveguide for high-power pulsed quantum cascade laser[J]. Infrared and Laser Engineering, 2024, 53(5): 20240015. DOI: 10.3788/IRLA20240015

大功率脉冲量子级联激光器锥形波导光学与热学仿真设计

Optical and thermal simulation design of tapered waveguide for high-power pulsed quantum cascade laser

  • 摘要: 针对脊形波导结构的大功率脉冲量子级联激光器面临的光束质量差和热积累严重的问题,研究了一种新型锥形波导量子级联激光器结构设计方法。通过COMSOL软件仿真优化脉冲功率60 W,重复频率10 kHz输出的锥形量子级联激光器光学和热学特性,分析了不同几何参数对波导光场模式分布、传输特性和最大内部温度的影响以及不同热沉材料、热沉温度和脉冲宽度对核心层内部温度分布的影响。结果表明,在4.6 μm的波长下,直波导宽度为5 μm,在锥度角为1.9°,直波导/锥形波导长度比为1∶3,可以保证直波导产生TM基模输出,整个端口的透射率、反射率、损耗、光限制因子达到最好效果。在同脊宽条件下,对于3 mm腔长,该锥形波导结构激光器核心区的面积对比条形的脊波导结构大10倍左右,更有利于大功率输出。此外,基于该结构进行了不同脉冲模式下的热学仿真分析,为器件工作模式和封装方式的选择提供有益参考。文中研究相关结论可为后续工艺设计和实验验证提供数据支持。

     

    Abstract:
      Objective  Quantum cascade laser has the advantages of unipolarity and easy wavelength adjustment, which has become an important laser source for mid-wave infrared. To satisfy the demand for pulsed high-power quantum cascade lasers, wide-ridge waveguide technology is often used to obtain ultra-high pulse peak power, which will cause the transverse heat dissipation path of the active layer to become longer, make the heat accumulation of the core layer more serious, and reduce the performance of the device. In addition, increasing the ridge width leads to an increase in the number of intrinsic modes supported in the waveguide, which lases higher-order modes and eventually degrades the beam quality. Therefore, in this article, a longer cavity length and a narrower ridge structure are designed to significantly enhance the fundamental mode and increase the heat dissipation capacity simultaneously. Additionally, a long tapered structure is incorporated on the output surface to elevate the optical loss threshold. To a certain extent, high beam quality propagation is guaranteed and the optical power density of the device is reduced. It has important research significance.
      Methods  A new tapered waveguide structure model is established by COMSOL simulation software. The optical and thermal characteristics of a tapered high-power quantum cascade laser are simulated with an output of 60 W and a pulse frequency of 10 kHz in pulse mode. The optical field mode distribution under different ridge widths (Fig.3) and the influence of different geometric parameters on the port transmittance, the optical limiting factor of the waveguide (Fig.5-7), and the heat dissipation effect are mainly analyzed. The impact of different heat sink materials, varying heat sink temperatures (Fig.8), and diverse pulse widths (Fig.9) on the core region temperature of the fixed device structure under identical pulse mode is investigated.
      Results and Discussions  In the waveguide optical field mode analysis, for 4.6 μm wavelength, when the waveguide width is less than 5.6 μm, the luminescence mode of QCL laser is TM fundamental mode, and the higher order mode is restrained (Fig.4). In the analysis of output port characteristics, for 3 mm or longer cavity length, the waveguide loss is kept at a low level of 0.17 dB/cm, and the core area of the tapered waveguide laser is about 10 times larger than that of the strip ridge waveguide structure, which is more conducive to high-power output (Fig.7). In the heat dissipation analysis, when copper heat sink is used and the total cavity length is 4 mm, the entire core layer has a lower maximum internal temperature and a faster heat dissipation rate (Fig.9).
      Conclusions  The optical and thermal structures for the pulsed high-power quantum cascade laser which incorporates a novel tapered waveguide design are modeled and simulated by using COMSOL optical finite element simulation software. The impact of various geometric parameters on the mode distribution and transmission characteristics of waveguides is analyzed. In conclusion, at a wavelength of 4.6 μm, the ridge waveguide width is 5 μm, the taper Angle is 1.9°, and the ridge/taper length ratio is 1:3, which can ensure that the ridge waveguide will produce TM fundamental mode output, and the transmission, reflectivity, loss, and light limiting factor of the entire port can achieve the best effect. In addition, the structure is subjected to thermal simulation analysis under various pulse modes, which provides a useful reference for the selection of device operating mode and packaging mode. The relevant conclusions of this study can provide data support for the subsequent process design and experimental verification.

     

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