Jiang Lingrong, Liu Jianping, Zhang Liqun, Qiu Bocang, Tian Aiqin, Hu Lei, Li Deyao, Huang Siyi, Zhou Wei, Ikeda Masao, Yang Hui
Opt Express. 2020 May 11;28(10):15497-15504. doi: 10.1364/OE.389880.
Parasitic substrate mode readily appears in GaN-based laser diodes (LDs) because of insufficient optical confinement, especially for green LDs. Substrate modes affect the behavior of a LD severely, including the laser beam quality, the optical output power, the longitudinal mode stability, and the maximum modulation speed. In this article, systematic studies on the n-cladding layer (CL) design to suppress the substrate mode of GaN-based green LDs were carried out. We established a contour map to describe the relationship between the optical confinement (determined by the thickness and the refractive index) of n-CL and the substrate mode intensity by simulating the near-field pattern and the far-field pattern. We found that it was difficult to obtain the Gaussian-shape far-field pattern using AlGaN as a cladding layer due to the appearance of cracks induced by tensile strain. However, this can be realized by introducing quaternary AlInGaN as a cladding layer since refractive index and strain can be tuned separately for quaternary alloy.
由于光限制不足，寄生衬底模式很容易出现在基于氮化镓的激光二极管（LD）中，尤其是对于绿色激光二极管。衬底模式严重影响激光二极管的性能，包括激光束质量、光输出功率、纵向模式稳定性和最大调制速度。在本文中，我们对用于抑制基于氮化镓的绿色激光二极管衬底模式的n型包层（CL）设计进行了系统研究。通过模拟近场图案和远场图案，我们建立了一个等高线图来描述n型包层的光限制（由厚度和折射率决定）与衬底模式强度之间的关系。我们发现，由于拉伸应变引起的裂纹出现，使用AlGaN作为包层很难获得高斯形状的远场图案。然而，通过引入四元AlInGaN作为包层可以实现这一点，因为对于四元合金，折射率和应变可以分别进行调整。
