Design and optimization of VECSELs for the IR and mid-IR

An approach based on fully microscopically computed material properties like gain/absorption, radiative and Auger recombination rates are used to design, analyze and develop optimization strategies for Vertical External Cavity Surface Emitting Lasers for the IR and mid-IR with high quantitative accuracy. The microscopic theory is used to determine active regions that are optimized to have minimal carrier losses and associated heating while maintaining high optical gain. It is shown that in particular for devices in the mid-IR wavelength range the maximum output power can be improved by more than 100% by making rather minor changes to the quantum well design. Combining the sophisticated microscopic models with simple one-dimensional macroscopic models for optical modes, heat and carrier diffusion, it is shown how the external efficiency can be strongly improved using surface coatings that reduce the pump reflection while retaining the gain enhancing cavity effects at the lasing wavelength. It is shown how incomplete pump absorption can be reduced using optimized metallization layers. This increases the efficiency, reduces heating and strongly improves the maximum power. Applying these concepts to VECSELs operating at 1010nm has already resulted in more than twice as high external efficiencies and maximum powers. The theory indicates that significant further improvements are possible - especially for VECSELs in the mid-IR.