Second-Harmonic Generation in Suspended AlGaAs Waveguides: A Comparative Study.

Area of Science:

• Optoelectronics
• Nonlinear Optics
• Materials Science

Background:

• Aluminum gallium arsenide (AlGaAs) optical waveguides offer tunable modal birefringence for phase-matched frequency mixing.
• Suspended AlGaAs waveguides provide high nonlinearities and low losses, surpassing other AlGaAs waveguide designs.
• Achieving efficient second-harmonic generation (SHG) is crucial for optical signal processing and telecommunications.

Purpose of the Study:

• To compare the second-harmonic generation (SHG) performance of two suspended AlGaAs waveguide designs: nanowire and nanorib.
• To evaluate SHG efficiency, injection losses, and propagation losses for both waveguide types.
• To assess the suitability of these waveguides for applications such as liquid sensing.

Main Methods:

• Fabrication of suspended AlGaAs nanowire and nanorib waveguides from a 123 nm thick epitaxial layer.
• Characterization of second-harmonic generation (SHG) efficiency under telecom-range wavelengths.
• Measurement of injection and propagation losses for both waveguide structures.

Main Results:

• Both suspended nanowire and nanorib AlGaAs waveguides demonstrate efficient second-harmonic generation (SHG).
• The nanorib waveguide exhibits performance comparable to the nanowire waveguide.
• The nanorib waveguide shows significantly improved mechanical robustness compared to the nanowire design.

Conclusions:

• Suspended AlGaAs nanorib waveguides are a viable and robust platform for efficient frequency mixing, particularly for SHG.
• The nanorib design's mechanical stability makes it well-suited for integration into sensing devices, including liquid sensing.
• These findings highlight the potential of suspended AlGaAs waveguides for advanced photonic applications.