High power885 nm laser diodes with graded optical expand structures for small divergence angle

In order to decrease the generated heat during pumping laser crystals, and enhance the efficiency of optical coupling with pumped materials,885 nm high power laser diodes with small vertical divergence angle were theoretically designed and fabricated. By means of introducing a grade optical expand layer into cladding layers, and combining optimized design the epitaxy material structure, the vertical divergence angle of devices was effectively decreased. AlGalnAs/AlGaAs quantum wells structure was used to increase the compressive strain, optical gain coefficient was enhanced, and material composition and thickness of quantum wells were optimized theoretically. The epitaxy material was prepared by LP-MOCVD technology, and the standard1 cm laser bar was fabricated. Measured results indicate that the vertical divergence angle of devices is decreased to17.6°, the output power and slope efficiency are20.1 W and1.05 W/A respectively, and the corresponding center wavelength is888.2 nm