High-performance 640-nm-range GaInP-AlGaInP lasers based on the longitudinal photonic bandgap crystal with narrow vertical beam divergence

Abstract

We address the design and performance issues of 640-nm range GaInP-AlGaInP laser diodes based on a longitudinal photonic bandgap crystal (PBC). The all-epitaxial design is based on selective filtering of high-order modes and allows extending of the fundamental mode over a PBC waveguide achieving very large vertical modal spot size. At the same time the robustness of the narrow far-field vertical beam divergence is remarkably high with respect to layer thickness variations. Optimal design ensures that all high-order optical modes show high absolute values of leakage loss (> 30 cm/sup -1/), which are order (orders) of magnitude higher than the leakage loss for the fundamental mode. This PBC-induced resonant tunneling effect for high-order modes leads to preferential excitation of the fundamental mode and the high-order modes are not excited even at the highest injection current densities. Broad-area (100 /spl mu/m) devices show vertical beam divergence of 8' (full-width at half-maximum) and lateral beam divergence of 7'-8'. The far-field pattern is circular shaped and stable upon an increase in injection current. Differential quantum efficiency is as high as 85 %. Maximum pulsed total optical output power is 20 W for 100-tim-wide stripe lasers with uncoated fac.