Continuous-wave operation and differential gain of InGaN/GaN quantum dot ridge waveguide lasers (λ = 420 nm) on c-plane GaN substrate

The differential gain and coherent output characteristics of blue-emitting In0.18Ga0.82N/GaN quantum dot ridge waveguide lasers have been measured. The laser heterostructures were grown by molecular beam epitaxy. Injected carrier lifetimes in the quantum dots have been measured by temperature dependent and time resolved photoluminescence measurements. The radiative lifetime at 280 K is 480 ps. The threshold current densities at room temperature are 930 and 970 A/cm2 for pulsed and continuous wave bias operation, respectively. The measured differential gain is 2 × 10−16 cm2. The output slope and wall plug efficiency at 1050 A/cm2 under continuous wave operation are 0.4 W/A and 0.4%, respectively. The measured blue shift in the emission wavelength due to screening of the piezoelectric field with injection is as small as 4.4 nm.