Third-harmonic generation of ultraviolet light in silicon nitride metasurface: a numerical study of pulse duration dependence

Dielectric metasurfaces are being studied as an alternative compact platform for the nonlinear generation of ultraviolet light. Resonant modes existing in metasurfaces may significantly boost those processes. However, the optimal excitation pulse duration is dependent on the resonance Q-factor. Here, we report a comprehensive numerical analysis of the third-harmonic generation efficiency from a silicon nitride metasurface by pulses of different durations. We show that the pulse duration should be long enough that its bandwidth is comparable to or smaller than the bandwidth of resonances. This consideration is vital to designing efficient metasurfaces for wavelength conversion.