Tunable Four-Wave Mixing in AlGaAs Waveguides of Three Different Geometries

TL;DR

This study introduces a new half-core etched AlGaAs waveguide geometry that balances the advantages of nanowire and strip-loaded designs, demonstrating high-efficiency four-wave mixing suitable for on-chip nonlinear photonics.

Contribution

The paper presents a novel half-core AlGaAs waveguide geometry with improved FWM efficiency and reduced multiphoton absorption compared to traditional geometries.

Findings

Half-core waveguides achieve near-highest FWM efficiencies in AlGaAs.

Signal-to-idler conversion spans over 150 nm in tested geometries.

Half-core geometry shows fewer multiphoton absorption issues.

Abstract

The AlGaAs material platform has been intensively used to develop nonlinear photonic devices on-a-chip, thanks to its superior nonlinear optical properties. We propose a new AlGaAs waveguide geometry, called half-core etched, which represents a compromise between two previously studied geometries, namely the nanowire and strip-loaded waveguides, combining their best qualities. We performed tunable four-wave mixing (FWM) experiments in all three of these geometries in the telecommunications C-band (wavelengths around 1550 nm), with a pulsed pump beam and a continuous-wave (CW) signal beam. The maximum FWM peak efficiencies achieved in the nanowire, strip-loaded and half-core geometries were about -5 dB, -8 dB and -9 dB, respectively. These values are among the highest reported in AlGaAs waveguides. The signal-to-idler conversion ranges were also remarkable: 161 nm for the strip-loaded and half-core waveguides and 152 nm for the nanowire. Based on our findings, we conclude that the half-core geometry is an alternative approach to the nanowire geometry, which has been earlier deemed the most efficient geometry, to perform wavelength conversion in the spectral region above the half-bandgap. Moreover, we show that the half-core geometry exhibits fewer issues associated with multiphoton absorption than the nanowire geometry.