Lithium niobate thin film represents as an ideal material substrate for quantum photonics due to its strong electro-optic effect and high-speed modulation capability. Here, we propose a novel platform which heterogeneously integrates single self-assembled InAs/GaAs quantum dots for a single-photon source on a lithium niobate photonic chip. The InAs/GaAs quantum dots can be transferred to the lithium niobate waveguide via a substrate transfer procedure with nanometer precision and be integrated through van der Waals force. A down-tapered structure is designed and optimized to deliver the photon flux generated from the InAs quantum dots embedded in a GaAs waveguide to the lithium niobate waveguide with an overall efficiency of 42%. In addition, the electro-optical effect is used to tune, and therefore to tune the beam splitting ratio of the integrated lithium niobate directional coupler, which can simultaneously route multiple photons to different spatial modes, and subsequently fan out through grating couplers to achieve single-photon sub-multiplexing. The proposed device opens up novel opportunities for achieving multifunctional hybrid integrated photonic chips.
Advanced Electrode Design for Low-Voltage High-Speed Thin-Film Lithium Niobate Modulators