Optimizing Spontaneous Parametric Down Conversion in Metasurfaces with Inverse Design

Spontaneous parametric down conversion (SPDC) is one of the most versatile techniques for the generation of correlated photon pair, whose quantum state is essential for photon entanglement that underpins many quantum applications like secure communication, quantum metrology and lithography and quantum imaging [1]. Inverse design of effective SPDC has been achieved by structured crystals with shaped pump beams [2]. Another popular platform for SPDC is nanofabricated structures with sub-wavelength thickness called metasurfaces, as they could achieve drastic enhancement of nonlinear light-matter interactions [3]. There remains the possibility to use inverse design to optimize metasurfaces for SPDC.