Lateral Divergence in High Power Laser Diodes: Method of Analysis for Assessing Contributing Factors

Lateral far field blooming or slow axis divergence is a common problem of high-power diode lasers and there are many different factors that contribute. Some of the major factors include temperature, carrier-induced effects, high order modes, mode types, and optical confinement. In this study, these properties were characterized and quantified in order to build a model to assess and simulate lateral divergence. A novel device called a spectral mapper was built to separate out lateral and longitudinal modes and their changes as current is varied. The collected and calculated data was input into LaserMOD, where simulations were run to determine the extent to which core width, mode number and refractive index changes modify the divergence of the device. While the modelling software was unable to support large numbers of modes due to weak confinement and also underestimated refractive index change in multimodal devices, the model and simulations were still able to quantify that more modes led to more lateral divergence. These tests and models can be used to improve coupling performance and hopefully provide insight into how high-power laser diodes can be further integrated with fiber lasers