Harmonics in the tunneling current for a nanocircuit with a mode-locked laser

TL;DR

This paper investigates how a mode-locked laser influences tunneling currents in a scanning tunneling microscope, revealing potential high-frequency harmonics up to 45 THz within the nanocircuit.

Contribution

It introduces a model showing that harmonics generated in a nanocircuit can extend to very high frequencies without significant attenuation.

Findings

Harmonics at hundreds of multiples of laser repetition rate are superimposed on tunneling current.

Power at each harmonic decreases with the square of frequency in measurement circuit.

Harmonics may have no appreciable roll-off up to 45 THz within the tunneling junction.

Abstract

Focusing a mode-locked laser on the tip-sample tunneling junction of a scanning tunneling microscope superimposes currents at hundreds of harmonics of the laser pulse-repetition rate on the DC tunneling current. The power at each harmonic is inversely proportional to the square of the frequency because of the measurement circuit. However, analysis suggests that within the tunneling junction the harmonics may have no appreciable roll-off at frequencies up to 45 THz. We consider a nanocircuit with an optical antenna receiving the laser radiation, metal-insulator-metal (MIM) tunneling diodes to generate the harmonics, and filters to select microwave and terahertz harmonics that are transmitted by a second antenna.