Spontaneous Parametric Down-Conversion Photon Pair Generation in a Small Footprint X-Cut Periodic Poled Lithium Niobate Micro-Resonator

Spontaneous parametric down-conversion (SPDC) has been utilized in generating non-classical light, such as correlated photon pairs and squeezed light, significantly influencing optical quantum information research. Advances in thinfilm lithium niobate (TFLN) technologies have brought the benefits of χ<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(2)</sup> nonlinearity from bulk optics to integrated photonics. Targeting fully exploitation of high Electro-optic (EO) controllability and the periodic poled lithium niobate (PPLN), enabling quasi-phase matching (QPM), offer the realization especially under the X-cut based platform [1]–[3]. Moreover, the small footprint is also key figure of merit for efficient processing of SPDC spectrum. In this work, we demonstrate SPDC photon pair generation in a small footprint size with a 0.614 nm FSR at the IR wavelength, based on X-cut PPLN racetrack resonator.