Design and Analysis of Laser Diodes

High-power low-vertical-divergence laser diodes based on the longitudinal photonic band crystal (PBC) concept are investigated at a wavelength of 900 nm. The thicknesses of the layers in the longitudinal PBC waveguide are prudently optimized by mode analysis, and the lowest vertical far-field angle is found to be achieved by mode coupling. A self-consistent model is also utilized to study the device performances in detail, which shows excellent optical properties without obvious electronic performance degradation.

In the experiment, continuous wave power up to 1 W/facet and vertical far-field angles of less than 10° (full-width at half-maximum) and ~50° (with 95%power content) are achieved simultaneously, with epitaxial wafer containing PBC layers of ten periods. The agreement among the design, simulation, and experiment shows a bright prospect for further reduced vertical divergence angle with high power output.