Enhancing oscillator strength for second harmonic generation in AlGaAs/InGaAs quantum cascade lasers

This paper explores tunable oscillator strength and nonlinear susceptibility in strained quantum cascade lasers (QCLs) that lead to frequency mixing within a GaAs matrix. The study involves a QCL cavity design with emission near the 3.8 mum range, a region within the atmospheric water transparency window that is useful for various sensing applications. A self-consistent Schrodinger-Poisson solver was employed to analyze the effects of strain within an AlGaAs/InGaAs active region between AlGaAs/GaAs injectors on a [111] GaAs matrix for the purpose of enhancing nonlinear susceptibility. A neural network simulator was employed to model the influence of indium composition in the active region based on oscillator strength. Results from neural network modeling highlight critical regions within the design space where the oscillator strength is maximized. Results demonstrate the feasibility of strained AlGaAs/InGaAs devices on GaAs for producing higher order harmonics that lay below the 4-mum spectral limit.