Terahertz emission by diffusion of carriers and metal-mask dipole inhibition of radiation

TL;DR

This paper investigates how metal masks inhibit dipole radiation, leading to asymmetry and enabling terahertz emission in semiconductors, combining simulations, analytic calculations, and experimental validation.

Contribution

It reveals that metal-mask dipole inhibition causes THz emission by creating asymmetry, a novel mechanism supported by simulations and experiments.

Findings

Metal masks inhibit dipole radiation, causing asymmetry.

Simulations and experiments confirm THz emission due to dipole inhibition.

Metal-mask dipole inhibition can be used to create THz emitters.

Abstract

Terahertz (THz) radiation can be generated by ultrafast photo-excitation of carriers in a semiconductor partly masked by a gold surface. A simulation of the effect taking into account the diffusion of carriers and the electric field shows that the total net current is approximately zero and cannot account for the THz radiation. Finite element modelling and analytic calculations indicate that the THz emission arises because the metal inhibits the radiation from part of the dipole population, thus creating an asymmetry and therefore a net current. Experimental investigations confirm the simulations and show that metal-mask dipole inhibition can be used to create THz emitters.