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.

Date Published: 4 June 2010
PDF: 9 pages
Proc. SPIE 7728, Nonlinear Optics and Applications IV, 772808 (4 June 2010);

Published in SPIE Proceedings Vol. 7728:
Nonlinear Optics and Applications IV
Benjamin J. Eggleton; Alexander Luis Gaeta; Neil G. R. Broderick, Editor(s)