分布反馈量子级联激光器光栅反馈特性北大核心CSCD

为探究Bragg光栅结构对TM模反馈特性的影响,利用有限时域差分法对具有TM模的分布反馈(DFB)量子级联激光器Bragg光栅结构进行仿真研究。重点分析了侧向耦合光栅的光学特性以及光栅侧壁倾角对光栅反射谱、损耗的影响及原因,并探究了光栅刻蚀深度及占空比与TM模的耦合系数、损耗的关系。结果表明有效折射率是影响Bragg波长的主要因素,而光限制因子是不同周期的侧向耦合光栅结构耦合系数产生巨大差别的原因,当光栅侧壁倾角90°时镜面损耗最小。光栅周期、占空比、刻蚀深度与耦合系数的关系表明:这些参数不仅影响光栅的相对介电常数,也会对光限制因子产生作用,从而影响耦合系数的大小;耦合系数与刻蚀深度具有正比关系,大周期光栅耦合系数随占空比的变化率较小。对光栅光反馈特性的理论研究有利于提升对DFB量子级联激光器的认识,促进激光器性能的提升和发展。

Study on grating feedback characteristics of distributed feedback quantum cascade laser

The grating feedback characteristics of distributed feedback (DFB) quantum cascade lasers with TM mode were simulated by difference time domain method. Comparative analysis was mainly focused on the optical properties of lateral coupled grating and ridge waveguide grating. The causes of differences, the effects of side wall angle on reflection spectrum and loss of grating were also investigated. The results show that the main factor influencing the Bragg wavelength is the effective refractive index, the optical limiting factor is the reason for the great difference of coupling coefficient between the two grating structures, the specular loss is minimum when the side wall angle of the grating is 90°. The relationship between grating period, duty cycle, etching depth and the coupling coefficient shows that the parameters not only affect the relative dielectric constant of grating, but also affects the light limiting factor, thus affecting the coupling coefficient; the coupling coefficient is proportional to the etching depth, and the variation of the coupling coefficient with duty cycle is smaller. Theoretical research on grating optical feedback characteristics is beneficial to improve the understanding of DFB quantum cascade lasers and promote the improvement and development of laser performances.