Modelling second harmonic generation at mid-infrared frequencies in waveguide integrated Ge/SiGe quantum wells

A promising alternative to bulk materials for the nonlinear coupling of optical fields is provided by photonic integrated circuits based on heterostructures made of asymmetric-coupled quantum wells. These devices achieve a huge nonlinear susceptivity but are affected by strong absorption. Here, driven by the technological relevance of the SiGe material system, we focus on Second-Harmonic Generation in the mid-infrared spectral region, realized by means of Ge-rich waveguides hosting p-type Ge/SiGe asymmetric coupled quantum wells. We present a theoretical investigation of the generation efficiency in terms of phase mismatch effects and trade-off between nonlinear coupling and absorption. To maximize the SHG efficiency at feasible propagation distances, we also individuate the optimal density of quantum wells. Our results indicate that conversion efficiencies of & AP; 0.6%/W can be achieved in WGs featuring lengths of few hundreds & mu;m only. & COPY; 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

A promising alternative to bulk materials for nonlinear optical field coupling is photonic integrated circuits based on asymmetric-coupled quantum wells, which have a huge nonlinear susceptivity but are affected by strong absorption. This study focuses on Second-Harmonic Generation in the mid-infrared spectral region using Ge-rich waveguides hosting p-type Ge/SiGe asymmetric-coupled quantum wells, and explores the efficiency in terms of phase mismatch effects and the trade-off between nonlinear coupling and absorption. The optimal density of quantum wells is identified to maximize SHG efficiency at feasible propagation distances, with conversion efficiencies of & AP; 0.6%/W achievable in waveguides of lengths of a few hundred μm only.