High-power, single-mode 751nm laser diode with facet passivation for enhanced COMD resistance

Developing high-power, single-mode laser diodes at 740-760 nm remain challenging due to carrier leakage, facet oxidation, and material limitations. Low COMD threshold limits high current operation, particularly for single waveguide mode applications. We designed and fabricated ridge-waveguide InGaAsP/GaAs lasers emitting at 751 nm, featuring an Al-free active region and an optimized asymmetric epitaxial structure with graded doping. These devices achieve maximum slope efficiency of 1.02 W/A with a threshold current of 54 mA and a lateral far-field divergence angle of 7.89°. They maintain stable single-mode emission (M2 < 1.2) under CW at room temperature. As confirmed by SEM analysis, ZnSe passivation of ultra-high vacuum (UHV)-cleaved facets increases the COMD threshold by over 300% under QCW operation, enabling high-current operation without facet degradation. These advances enable robust, high-performance visible single-mode diode lasers for emerging photonic applications.