High-power multimode semiconductor lasers (976 nm) based on asymmetric heterostructures with a broadened waveguide and reduced vertical divergence

Abstract: The effect of the active region design on the vertical far field divergence of high-power semiconductor lasers based on asymmetric heterostructures with a broadened waveguide of 4 μm thickness, with one (SQW) and two (DQW) InGaAs quantum wells is studied. It is shown that the number of quantum wells has a significant effect on the divergence, that is determined by the angle containing 95 % of the radiated power (Θ_95%). The beam divergence at the half-maximum level of 12.9° for asymmetric heterostructures with the SQW active region is demonstrated. It is experimentally shown that the change-over to the DQW from the SQW design of the active region leads to the increase in the value of Θ_95% from 23.2° to 41.8°. For both types of the structures the internal optical losses and the internal quantum efficiency of 0.27 cm^–1 and 99 %, respectively, is demonstrated. Basing on asymmetric heterostructures with the active SQW region we demonstrate high-power semiconductor lasers emitting the power of 9 W in the continuous mode at the temperature and pump current: 25 °C/10 A, 55 °C/11.4 A.

Keywords: high-power semiconductor lasers, vertical far field divergence, active region design, angle containing 95 % of the radiated power.