Shift of the resonance frequency of split-ring resonators induced by high THz electric field strengths

摘要

We show that the resonance frequency of gold split-ring resonators with nano-gaps featuring giant field enhancement is redshifted when irradiated with intense single-cycle THz pulses. While the redshift is reversible at low field strengths, it becomes permanent at higher field strengths. To elucidate the underlying mechanism, we investigate the effect for different substrate materials (high resistivity Ge, Si, GaAs, and ZnS), for different gap widths, and for samples where the substrate underneath the gap has been removed.