Terahertz pulsed photogenerated current in microdiodes at room temperature

TL;DR

This paper demonstrates that a vacuum microdiode can generate tunable terahertz signals at room temperature by exploiting space-charge effects and beamlet formation, with optimal operation at high electric fields and small gaps.

Contribution

It reveals how temperature and space-charge forces influence beamlet formation and shows room-temperature THz oscillation in microdiodes with specific electric fields and dimensions.

Findings

Room-temperature THz oscillation is achievable in microdiodes.

Single beamlet operation enhances current modulation stability.

High electric fields (>10 MV/m) are essential for effective THz generation.

Abstract

Space-charge modulation of the current in a vacuum diode under photoemission leads to the formation of beamlets with time periodicity corresponding to THz frequencies. We investigate the effect of the emitter temperature and internal space-charge forces on the formation and persistence of the beamlets. We find that temperature effects are most important for beam degradation at low values of the applied electric field, whereas at higher fields intra-beamlet space-charge forces are dominant. The current modulation is most robust when there is only one beamlet present in the diode gap at a time, corresponding to a macroscopic version of the Coulomb blockade. It is shown that a vacuum microdiode can operate quite well as a tunable THz oscillator at room temperature with an applied electric field above 10 MV/m and a diode gap of the order of 100 nanometers.