Floquet frequency-bin photon-pair generation in time-modulated nonlinear metasurfaces

We propose Floquet (periodically driven) control of spontaneous parametric downconversion in electrically biased nonlinear metasurfaces, enabling programmable frequency-bin photon pairs. A Floquet expansion of the time-dependent nonlinear interaction derived here expresses the biphoton amplitude as a coherent sum over discrete pathways, predicting tunable correlations spaced by the drive frequency. The modulation phase provides an electrical knob that coherently redistributes frequency-bin coincidences, including dark bins from interference between overlapping Floquet contributions. For predominantly phase-modulated sinusoidal drive, Bessel-function weights furnish a universal rule for suppressing selected Floquet orders without per-channel redesign. Numerical simulations validate the predicted coincidence statistics under finite-bandwidth, filter-based detection.