Two-Step Narrow Ridge Cascade Diode Lasers Emitting Near 2 um

Nearly diffraction limited GaSb-based type-I quantum well cascade diode lasers emitting in the spectral region 1.95-2μ were designed and fabricated. Two-step 5.5-μm -wide shallow and 14-μ m-wide deep etched ridge waveguide design yielded devices generating stable single lobe beams with 250 mW of continuous wave output power at 20 °C. Quantum well radiative recombination current contributes about 13% to laser threshold as estimated from true spontaneous emission and modal gain analysis. Recombination at etched sidewalls of the 14-μ m-wide deep ridges controls about 30% of the threshold.