Figure-of-merit analysis of distributed sidewall loss method to suppress high-order modes in broad area quantum cascade lasers

We have modeled broad-area ridge-waveguide quantum cascade lasers (QCLs) using COMSOL and generated a rank-ordering of high-order transverse lateral modes as a function of cavity width on the basis of a figure-of-merit. In particular, we corroborate experimental results previously obtained using the distributed sidewall loss (DSL) method to suppress high-order transverse lateral modes and extract fundamental mode in broad-area QCLs. COMSOL modeling shows that waveguide losses preferentially incurred by the high-order modes, due to the direct sidewall contact with metal as prescribed by the DSL method, can be used to obtain single-lobed emission with enhanced brightness in broad-area QCLs.