Single Transverse Mode GaSb-based Ridge Waveguide Lasers with Low Lateral Beam Divergence

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 degrees C. The shallow-etched 7 mu m width RW design produces a lateral beam divergence angle as narrow as 9 degrees full width at half maximum (FWHM) with an excellent beam quality of M-2 factor < 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 mu m 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.