Theoretical study of Bragg reflection waveguide laser structures with surface gratings for spontaneous parametric down conversion

Abstract Bragg reflection waveguides (BRW) enable the generation of photon pairs in non-birefringent AlGaAs through spontaneous parametric down conversion (SPDC). Furthermore, the development of an electrically driven laser source from a passive BRW by introducing a suitable doping profile and an active region allows the simultaneous lasing of the pump field and the SPDC process within the same cavity. Here, we present an optimized design of a BRW to allow lasing at 775 nm and simultaneous conversion into photon pairs at 1550 nm. Based on the computed modes at 775 nm and 1550 nm, the non-linear emission characteristics of both SPDC and second harmonic generation of the proposed device is calculated. The design is particularly optimized regarding the monolithic integration of a distributed Bragg reflector (DBR) section to stabilize the laser wavelength. This is necessary because SPDC is highly sensitive to the pump wavelength. By using an eigenmode expansion approach, we calculate the reflection spectra of a 1 mm long, 9th order surface grating in dependence of various parameters. We demonstrate that a peak reflectivity of > 80% can be achieved with technologically feasible etch depths and groove widths. This paves the way for the promising application of DBR surface gratings for the selection of the pump wavelength for the SPDC process in BRW lasers, with the objective of improving the photon output.