Suspended AlGaAs waveguide for integrated nonlinear photonics

Abstract

AlxGa1-xAs compound is one of the promising platforms to realize high performance nonlinear optical devices, which provide ultra-high third order nonlinearity and negligible two-photon absorption in the range of telecom wavelength. To achieve highly efficient optical confinement, the conventional AlGaAs waveguide cladding layer is achieved by using SiO2 via the wafer bonding process or AlGaAs with higher Al concentration, which requires a complex fabrication process. In this work, we demonstrate a suspended Al0.5Ga0.5As waveguide structure directly grown on the GaAs substrate by using the molecular beam epitaxy system. Both self-phase modulation and four-wave-mixing experiments are performed. By solving the nonlinear Schrödinger equations and the degenerated parametric amplification process, the n2 value is calculated to be 1.6 × 10−17 m2/W, and the nonlinear parameter is determined to be 155 W−1 m−1. As the AlGaAs thin film can be directly grown on the Si based substrate, this suspended waveguide platform could potentially be developed on a large scale silicon wafer for integrated nonlinear photonic devices.