Impact of DC bias on Weak Optical-Field-Driven Electron Emission in Nano-Vacuum-Gap Detectors

TL;DR

This paper explores how applying a small DC bias to nanoscale vacuum-gap detectors significantly enhances electron emission driven by optical fields, enabling ultrafast, room-temperature detection for advanced communication and metrology.

Contribution

It demonstrates that a modest DC bias can drastically lower the emission threshold and boost photocurrent in nanoscale vacuum-gap detectors, facilitating ultrafast optical detection.

Findings

DC bias greatly alters photocurrent properties

Bias reduces threshold for optical-field tunneling

Potential for sub-femtosecond response in detectors

Abstract

In this work, we investigate multiphoton and optical-field tunneling emission from metallic surfaces with nanoscale vacuum gaps. Using time-dependent Schrodinger equation (TDSE) simulations, we find that the properties of the emitted photocurrent in such systems can be greatly altered by the application of only a few-volt DC bias. We find that when coupled with expected plasmonic enhancements within the nanometer-scale metallic gaps, the application of this DC bias significantly reduces the threshold for the transition to optical-field-driven tunneling from the metal surface, and could sufficiently enhance the emitted photocurrents, to make it feasible to electronically tag fJ ultrafast pulses at room temperature. Given the petahertz-scale instantaneous response of the photocurrents, and the low effective capacitance of thin-film nanoantenna devices that enables < 1 fs response time, detectors that exploit this bias-enhanced surface emission from nanoscale vacuum gaps could prove to be useful for communication, petahertz electronics, and ultrafast optical-field-resolved metrology.