Efficient Sources of Entangled Single-Photon Pairs with Nonlinear Plasmonic Metasurfaces

The Spontaneous Parametric Down-Conversion (SPDC) process is a fundamental method for the generation of entangled and correlated single-photon pairs. This research investigates the use of a plasmonic metasurface consisting of metallic nanostripes deposited on a bulk lithium niobate (LiNbO3) crystal to significantly increase efficiency of photon pair generation. The geometric parameters of the metasurface features can be set to create resonances with the signal and idler frequencies, boosting the electric field in the LiNbO3 crystal and enhancing the SPDC process. The photon pair generation rate is found by invoking the quantum-classical correspondence principle and computing the rate for the classical sum frequency generation (SFG) process. Efficient room temperature SPDC single-photon nanophotonic sources show promise for developing free space quantum optical communications and have multiple applications across the field of quantum optics.