分布布拉格反射器半导体激光器中光栅结构设计  

Design of Grating Structure in Distributed Bragg Reflector Semiconductor Laser

作　　者：朱坤 李辉 郝永芹 钱冉 王东岳 Zhu Kun;Li Hui;Hao Yongqin;Qian Ran;Wang Dongyue(National Key Laboratory on High Power Semiconductor Lasers,Changchun University of Science and Technology,Changchun 130022,Jilin,China)

机构地区：[1]长春理工大学高功率半导体激光国家重点实验室,吉林长春130022

出　　处：《中国激光》2023年第11期255-264,共10页Chinese Journal of Lasers

基　　金：国家自然科学基金(61864002);长春市科技发展计划项目(21ZY59)。

摘　　要：半导体激光器发射光谱中的边模存在恶化了其光束质量,严重限制了其在通信领域中的应用。基于分布布拉格反射器(DBR)半导体激光器中光栅的占空比、耦合系数、材料折射率三者之间的关系,研究了光栅占空比分布对边模抑制的影响,同时对矩形均匀光栅和矩形渐变占空比光栅结构的边模进行了分析与比较。优化了DBR光栅结构,分析了矩形均匀光栅与锥形渐变占空比光栅结构的旁瓣强度大小。利用时域有限差分(FDTD)法对器件结构进行仿真模拟,在不同光栅占空比分布下,分析了光栅的占空比和反射率的关系,并讨论了渐变占空比光栅反射峰值与光栅长度的关系。结果表明,渐变占空比光栅相比于矩形均匀光栅,边模得到有效抑制。当注入电流为63 mA时,在温度300 K下,矩形渐变占空比光栅结构的器件边模抑制比达到48 dB,并且渐变占空比光栅的反射峰值达到96%。通过分析矩形均匀光栅和锥形渐变占空比光栅结构在远场侧向切面上的光场分布,发现利用锥形渐变占空比光栅制作DBR有助于降低DBR半导体激光器的旁瓣强度。Objective The existence of edge modes in the distributed Bragg reflector(DBR)semiconductor laser emission spectrum has a significant influence on the beam quality.The output multi-edge modes and high side lobes deteriorate the semiconductor laser beam and output power.The F-P effect formed on the sides of the DBR laser with a homogeneous duty cycle is one reason for this,resulting in side-mode resonance enhancement.Second,the energy coupled to the narrow-ridge waveguide through the grating decreases near the rim of the narrow ridge.This study proposes a modification scheme of the regular DBR structure to inhibit the edge mode on the DBR laser spectrum,ensuring maximized reflectance at the central wavelength while weakening the side lobe strength.Methods Based on coupled-mode theory,a rectangular grating model with a gradual duty cycle is established for the DBR laser.The influence of the duty cycle distribution on the edge mode suppression and the reflectivity maximization at the central wavelength is analyzed using the finite-difference time-domain(FDTD)method and changing the DBR duty cycle.The electro-optic model of the rectangular grating with gradient duty cycle is simulated,and the reflectance at the central wavelength and the side mode suppression ratio are obtained after device optimization.A tapered duty cycle model for the DBR is established,and the influence of the grating structure with tapered duty cycle on the output side lobe intensity of the DBR laser is analyzed.Results and Discussions In DBR lasers,the F-P effect exists in rectangular uniform duty cycle gratings,resulting in edge-mode oscillation enhancement(Fig.5).From the relationship of coupling coefficient and duty cycle(Fig.6)and the duty cycle under the maximum reflectivity at the central wavelength,the grating duty-cycle range can be determined.Within the gradient range,the simulation of grating when the duty cycle is truncated sinc function distribution is carried out.Within the gradient ranges of 0.545‒0.580 and 0.580‒0.545,the refl

关 键 词：激光器 分布布拉格反射半导体激光器 边模抑制 渐变占空比光栅 旁瓣 

分 类 号：TN248.4[电子电信—物理电子学]