GaSb based midinfrared equilateral-triangle-resonator semiconductor lasers

Theoretical calculations of the mode characteristics of an equilateral-triangle resonator (ETR) with a 10 μm cavity side length show that the fundamental mode, with longitudinal mode index of 25, has a wavelength of 2.185 μm and a longitudinal mode separation of 100 nm. This mode has a quality factor (∼2× 105) that is much larger than the first (∼5× 104) and second (∼3× 104) order modes, indicating that single fundamental mode lasing should be accessible over a broad wavelength tuning range. An electrically injected ETR based on this design is fabricated from an InGaAsSbAlGaAsSbGaSb, graded-index separate-confinement heterostructure, laser diode wafer with a 2.1 μm emission wavelength. This device achieved single mode, continuous wave operation at 77 K with a threshold current of 0.5 mA and a single mode wavelength tuning range of 3.25 nm, which is accomplished by varying the injection current from 0.5 to 6.0 mA.