  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 generation, metasurfaces offer a gateway to tuneable thin emitters
that can be utilised 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 we propose the use of a fully dielectric semiconductor exploiting
morphology-mediated resonances and inherent quadratic nonlinear response. Our
system exhibits a remarkable 40-fold efficiency enhancement compared to the
unpatterned at the peak of the optimised wavelength range, demonstrating its
potential as scalable emitter design.
