Terahertz emission from thin metal films with porous nanostructures

摘要

We characterized the terahertz emission from a thin metal film with quasi-randomly distributed porous nanostructures. Unlike many demonstrated nanostructured metal terahertz sources, the emission is in the forward direction when the laser excitation illuminates the metal film at normal incidence, making its integration in a time-domain terahertz system straightforward. We attribute the generation mechanism to optical rectification. Moreover, we observe a deviation from the expected linear scaling of the terahertz electric field with excitation laser pulse energy, which we relate to thermal heating of the emitter.