High-efficiency non-ideal quarter-wavelength Bragg reflection waveguide for photon-pair generation

Quantum light source is a promising resource for quantum-enhanced technologies and tests of quantum mechanics. In the race towards scalable quantum information processing, integrated photonics has recently emerged as a powerful platform. Semiconductor AlGaAs is arising as an outstanding platform due to its strong second-order nonlinearities, direct bandgap, manufacturability and reconfigurability. Here, we conduct an analytical investigation of semiconductor Bragg reflection waveguide (BRW), in which the core layer is surrounded by periodic claddings. A general solution to the mode dispersion equation is deduced independently of whether each cladding layer has an ideal quarter-wavelength thickness or not, and used for the analysis of AlGaAs/GaAs material. Different than before, we propose a novel structure with the core layer having high-index and achieve high modal overlap after full parameter optimization in a BRW slab structure, which can provide a practical way for designing high efficiency devices. The influence of thickness variation on overlap factor and system dispersion as well as biphoton spectral properties generated from type-II spontaneous parametric down conversion are also shown. Our approach can serve as a quick guideline for the design of polarization-entangled sources and contribute to large scale processing devices for practical applications by leveraging the structure's versatile architecture.