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

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Quantum Electronics

Background:

• Photonic integrated circuits (PICs) offer alternatives to bulk materials for nonlinear optical applications.
• Asymmetric-coupled quantum wells (ACQWs) exhibit high nonlinear susceptibility but suffer from significant absorption.
• The silicon-germanium (SiGe) material system is technologically relevant for mid-infrared (MIR) applications.

Purpose of the Study:

• To theoretically investigate Second-Harmonic Generation (SHG) efficiency in Ge-rich waveguides with p-type Ge/SiGe ACQWs.
• To analyze the impact of phase mismatch, nonlinear coupling, and absorption on SHG.
• To determine the optimal quantum well density for maximizing SHG efficiency at practical propagation lengths.

Main Methods:

• Theoretical modeling of nonlinear optical effects in heterostructures.
• Analysis of phase mismatch and absorption trade-offs in Ge/SiGe waveguides.
• Optimization of quantum well density for Second-Harmonic Generation.

Main Results:

• Identified optimal quantum well density to balance nonlinear coupling and absorption.
• Demonstrated theoretical SHG conversion efficiencies of approximately 0.6%/W.
• Achieved efficient SHG in waveguides with lengths of only a few hundred micrometers.

Conclusions:

• Ge/SiGe ACQWs in waveguides are a viable platform for efficient MIR nonlinear optics.
• Optimized quantum well density is crucial for maximizing SHG performance.
• Compact photonic devices can achieve significant nonlinear optical conversion.