High-sensitivity future single-photon detection via optical rectification in asymmetric gold gratings

In this work, we explore how asymmetric gold gratings can enhance optical rectification (OR), a second-order nonlinear effect enabled by inversion symmetry breaking, which was previously reported experimentally. We engineer the grating asymmetry to enhance the rectified electric fields generated at the interface c, leading to detectable photocurrents even for weak incident light. We analyze theoretically how OR responds to the spatial asymmetry and polarization of incident photons. We predict that spin-momentum locking of surface plasmon polaritons (SPPs) on asymmetric gratings provides polarization-sensitive photon detection. The sensitivity of OR in this system enables detecting single photons by correlating rectified currents with photon arrival. Asymmetric gold gratings can act as plasmonic sensors. OR on asymmetric gold gratings could open new frontiers for ultrasensitive optical sensors, relevant for quantum technologies, quantum sourcing of entangled photons via spontaneous parametric down conversion (if (2) arising from a coating in the presence of the plasmonic metasurface exhibiting OR is large enough), remote sensing, and single photon counting.