Optical excitation of surface plasmons and terahertz emission from metals

TL;DR

This paper develops a microscopic theory for terahertz radiation generation from metal gratings under femtosecond laser pulses, emphasizing low-frequency currents and plasmon-enhanced thermal effects, explaining experimental observations.

Contribution

It introduces a novel model focusing on internal low-frequency currents and thermal effects, differing from previous electron emission-based models.

Findings

Resonant optical-to-THz conversion explained by the model

Reproduces delayed THz response observed experimentally

Accounts for low conversion efficiency with deep gratings

Abstract

We propose a microscopic theory of terahertz (THz) radiation generation on metal gratings under the action of femtosecond laser pulses. In contrast to previous models, only low-frequency currents inside the metal are considered without involving electron emission. The presented model is based on plasmon-enhanced thermal effects and explains the resonant character of optical-to-THz conversion giving an adequate estimation for the full signal energy. Numerical modeling reproduces specific experimental features like delayed character of THz response and low conversion efficiency when the grating depth is too large.