Resonant fully dielectric metasurfaces for ultrafast terahertz pulse generation

Metasurfaces represent a new frontier in materials science paving for unprecedented methods of controlling electromagnetic waves, with a range of applications spanning from sensing to imaging and communications. For pulsed terahertz (THz) generation, metasurfaces offer a gateway to tuneable thin emitters that can be utilized for large-area imaging, microscopy, and spectroscopy. In literature, THz-emitting metasurfaces generally exhibit high absorption, being based either on metals or on semiconductors excited in highly resonant regimes. Here, the use of a fully dielectric semiconductor exploiting morphology-mediated resonances and inherent quadratic nonlinear response is proposed. This system exhibits a remarkable 40-fold efficiency enhancement compared to the unpatterned at the peak of the optimized wavelength range, demonstrating its potential as a scalable emitter design.