Near-infrared OPO in an AlGaAs/AlOx waveguide

Abstract

Within the ambitious quest for an electrically pumped version of the optical parametric oscillator (OPO), we demonstrate the first near-infrared integrated OPO in a direct gap semiconductor. This nonlinear device is based on a selectively oxidized GaAs/AlAs heterostructure, the same "AlOx" technology that is at the heart of VCSEL fabrication. The heterostructure and waveguide design allows for type-I form-birefringent phase matching, with a TM 00 pump around 1 µm and TE 00 signal and idler around 2 µm. Relying on the high non-resonant χ (2) of GaAs, relatively weak guidedwave optical losses, and monolithic SiO 2 /TiO 2 dichroic Bragg mirrors, we observe a threshold of 210 mW at degeneracy in the continuous-wave regime, with a single-pass-pump doubly resonant scheme. Further improvement can be achieved by adopting a double-pump-pass scheme and, in a more fundamental way, by further optimizing the waveguide optical losses. The latter are induced by a not entirely mastered AlAs oxidation process and are of two distinct types: Rayleighlike scattering at signal and idler wavelength (α ≤ 1cm -1 ), due to the interface roughness between GaAs and AlOx layers; and absorption at pump wavelengths (α ≈ 3cm -1 ), due to volume defects in the GaAs layers adjacent to the aluminum oxide. This result marks a milestone for integrated nonlinear photonics and represents a significant step toward the goal of a broadly tunable coherent light source on chip.