Enhanced generation of angle correlated photon-pairs in nonlinear metasurfaces

Abstract We reveal that strongly enhanced generation of photon pairs with narrow frequency spectra and sharp angular correlations can be realised through spontaneous parametric down-conversion in metasurfaces. This is facilitated by creating meta-gratings nano-structuring nonlinear films sub-wavelength thickness to support the extended bound state continuum resonances, associated ultra-high Q -factors, at biphoton wavelengths across a wide range emission angles. Such spectral features photons beneficial for various applications, including quantum imaging. Our modelling demonstrates pronounced enhancement, compared unpatterned films, total photon-pair rate normalized pump power reaching 1.75 kHz mW ?1 , which robust respect bandwidth pump, supporting feasibility future experimental realisations.