Exploiting Time-Varying Radiative Coupling Modulation To Boost Second Harmonic Generation

The nonlinear processes are triggered by short high-intensity laser pulses. The most effective harmonics generation is realised when bandwidth of metasurface resonances correlates with the pulse bandwidth. Here we propose a theoretical approach, based on coupled mode theory, to investigate time-varying optical systems to boost second harmonic generation beyond the time-bandwidth limit. We perform numerical simulation to obtain general guidelines by unveiling the role of pulse duration and quality factors. Our results pave the way to fully exploit metasurfaces to boost nonlinear interactions with ultrafast laser pulses.