Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

TL;DR

This study demonstrates sub-cycle electron emission driven by intense terahertz pulses across a split-gap dipole antenna, revealing ultrafast electron dynamics and field enhancement effects at THz frequencies.

Contribution

The paper introduces a method to induce and analyze sub-cycle electron emission using resonant terahertz excitation in a micro-fabricated antenna with a vacuum gap.

Findings

Field emission occurs above ~10 MV/cm in-gap electric field.

Electrons are accelerated to about one-tenth of the speed of light.

Emission occurs within a fraction of the THz cycle.

Abstract

We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ~170. Above an in-gap E-field threshold amplitude of ~10 MVcm-1, THz-induced field electron emission is observed (TIFEE) as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.