Single transverse mode GaSb-based ridge waveguide lasers with low lateral beam divergence

Abstract

GaSb-based narrow Ridge Waveguide (RW) laser diodes providing high optical power with low lateral beam divergence single-transverse-mode operation are fabricated and characterized. The typical Separate-Confinement-Heterostructure (SCH) Multi-Quantum-Well (MQW) structure is grown by the solid-state Molecular Beam Epitaxy (MBE). The 1 mm long uncoated RW lasers yield single-transverse-mode output power exceeding 170 mW in the 1950 nm wavelength range under continuous-wave (cw) operation at an injection current of 800 mA and room temperature of 20 ℃. The shallow-etched 7 μm width RW design produces a lateral beam divergence angle as narrow as 9° Full Width at Half Maximum (FWHM) with an excellent beam quality of M²factor < 2 at the maximum output power, enabling it for simple and inexpensive bulk coupling into the typical SM1950 or PM1950 fiber which has a core diameter of 7 μm and numerical aperture (NA) of 0.2. The RW lasers with high output power, good beam quality, and low divergence are promising candidates for a wide range of demanding and advanced applications including pumping fiber amplifiers and solid-state lasers, seeding external cavity lasers, and frequency conversion.