Continuously tunable sources with room-temperature operation are required in the mid-infrared region for applications
such as spectroscopy or pollutants monitoring. In this spectral range, optical parametric oscillators (OPOs) are more
versatile than laser diodes.
Guided-wave OPOs constitute a promising perspective, thanks to higher conversion efficiency provided by the
confinement of the interacting waves. While LiNbO3 has been the crystal of choice for a long time, GaAs is a good
alternative thanks to higher nonlinearity, broader transparency range, and optoelectronic integrability. So far, a GaAs
integrated OPO has not yet been demonstrated due to technology induced propagation losses.
Here we present a detailed investigation of the propagation losses in partially oxidized multilayer GaAs/AlAs
waveguides. We have studied the impact of oxidation on the roughness of the multilayer interfaces, via transmission
electron microscopy. While the roughness of our MBE-grown GaAs/AlAs heterostructures is the standard 0.3 nm, it
increases to at least 0.53 nm after AlAs oxidation. Semi-analytical modeling shows that this level of roughness is
responsible for scattering losses, in fair agreement with the measured values. Optimization of the oxidation process is
currently under way with the aim of reaching the OPO oscillation threshold.