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We report on the observation of self-amplified parametric downconversion in a selectively oxidized AlGaAs cavity that was designed to perform as a guided-wave optical parametric oscillator in the near infrared. To date, two technological factors preclude such oscillation and are thoroughly investigated here: oxidation-induced optical propagation losses and the reflectivity of the waveguide resonator facets. The spectral study of the former has singled out two distinct mechanisms: scattering at the oxide interfaces and absorption by point defects in the oxide neighboring layers. Regarding the latter, dielectric mirrors have been designed and deposited on the ridge waveguide facets, with modal reflectivities of ∼10% at pump wavelength and ∼90% at signal/idler wavelengths. With respect to the case of a mirrorless waveguide, the monolithic cavity enabled a factor-2 enhancement of the conversion efficiency, indicating the close proximity of the oscillation threshold.

A theoretical and experimental study has been carried out on a macroscopic cholesteric structure. The authors establish a physical model which allows us to calculate the reflected and transmitted electromagnetic fields on a stack of uniaxial layers submitted to a normal incidence plane wave. Experimental measurements are in good agreement with the predicted values.