Distributed feedback 3.27 μm diode lasers with continuous-wave output power above 15 mW at room temperature

GaSb-based type-I quantum well laterally coupled distributed feedback diode lasers emitting in the methane absorption band near 3.27 μm were designed and fabricated. The first-order index grating with a period of 480 nm was defined by e-beam lithography and etched on both sides of 6 μm-wide shallow ridge waveguide. Coated 2 mm-long devices demonstrated stable continuous-wave single-frequency operation in a wide temperature range with an output power of 15 mW at +17°C and 40 mW at -20°C. The Bragg wavelength temperature tuning rate was ∼0.27 nm/K.