Numerical studies of thermal lensing effects on high-CW-power single-spatial- mode diode lasers

Abstract

Three-dimensional (3-D) above-threshold analyses have been performed on laterally antiguided laser structures operated on leaky modes and twin-waveguide structures operated on guided modes for generating watt-range CW powers in a single, stable spatial mode. The 3-D numerical code takes into account carrier diffusion in the quantum well, thermooptic effects as well as edge radiation losses. Additionally, higher-order optical modes on a 'frozen background' provided by the fundamental mode operation are computed by the Arnoldi algorithm. Approaching the threshold for a competing higher-order mode puts a limit on the range for stable, single-mode operation. The modal structure and stability for both device types are studied over a wide range of the active core width and widths of the buried waveguides bordering the low-index device core. The numerical analyses results indicate an essential role of thermal lensing in transformations of optical-modes shapes and in mode stability loss with the drive current increase. The CW operation in a stable, single spatial mode to powers as high as 2 W is predicted for 2-mm length lasers operated on leaky modes. The maximum CW power in single-guided-mode is predicted as high as 2.46 W for 2-mm length and 3.4 W for 3-mm length devices.