We propose a strategy for designing Bragg reflection waveguides with no polarization sensitivity. Via spontaneous parametric downconversion, such waveguides produce both cross-polarized and co-polarized entangled photons, acting as integrated sources of optical Bell states.
In this paper, we present Bragg reflection waveguides as a novel universal platform for reaching the phasematching
of spontaneous parametric downconversion process in semiconductor materials. We have designed two
different waveguide structures. The first one is based on AlGaN and it is able to produce spectrally uncorrelated
photon pairs. The second one is based on AlGaAs and it allows us to generate entangled photon pairs with
ultra-broad spectra. Spontaneous-parametric-downconversion and second-harmonic-generation experiments are
presented.
We explore the potential of versatile and efficient entangled photon pair generation by spontaneous parametric downconversion in Bragg reflection waveguides. By employing a quantum treatment of modes in channel waveguides, and by accounting for group velocity dispersion in the modes, the quantum state of the generated biphotons is realistically calculated. The pair production rate is predicted to reach 4×108 pairs/s/nm/mW of pump light in a 2 mm-long structure, on par with or exceeding the performance of previously reported designs. This is attributable to an enhanced nonlinear interaction through tight mode confinement in the waveguide. Strategies for device performance optimization and phase matching wavelength tunability are outlined and numerically demonstrated. The proposed design platform is versatile and allows photon pair generation with controllable flux, bandwidth, Schmidt number, and degree of polarization entanglement. The possibility of monolithic integration with a diode laser pump offers a way to design an electrically pumped entangled photon source.
AlGaAs Bragg reflection waveguides are promising systems for the generation of single and entangled photons through the process of spontaneous parametric down-conversion (SPDC) [1]. We use a type II SPDC process where the downconverted photons are orthogonally polarized. The produced photons are inherently polarization-entangled eliminating the need for any additional entanglement setup. The material AlGaAs is our preferred choice as a nonlinear medium because it features a high nonlinear coefficient allowing for room temperature operation and has the advantage of being a non-birefringent material. Further, the material platform allows for the direct integration of a pump laser into the same chip.
We demonstrate efficient photon pair generation for quantum communication using an all-semiconductor approach. In an AlGaAs Bragg-reflection waveguide we employ spontaneous parametric down-conversion to produce photon pairs at telecommunication wavelengths. The various phase-matching solutions present in our device can be used to create timebin or polarization entanglement. This approach can to lead to a fully integrated photon pair source with the pump laser, active and passive optical devices all on a single semiconductor chip.