Enhanced generation of VUV radiation by four-wave mixing in mercury using pulsed laser vaporization

TL;DR

This paper reports a significant enhancement in VUV radiation generation via four-wave mixing in mercury vapor, achieved by pulsed laser vaporization, leading to higher efficiency and potential applications in lithography and photochemistry.

Contribution

It introduces a novel method of locally heating mercury vapor with pulsed laser to significantly boost VUV generation without complex heating systems.

Findings

Up to 2 orders of magnitude increase in VUV yield.

Achieved energies up to 5 μJ at room temperature.

Observed saturation and broadening effects at high power densities.

Abstract

The efficiency of a coherent VUV source at 125 nm, based on 2-photon resonant four-wave mixing in mercury vapor, has been enhanced by up to 2 orders of magnitude. This enhancement was obtained by locally heating a liquid Hg surface with a pulsed excimer laser, resulting in a high density vapor plume in which the nonlinear interaction occurred. Energies up to 5 μJ (1 kW peak power) have been achieved while keeping the overall Hg cell at room temperature, avoiding the use of a complex heat pipe. We have observed a strong saturation of the VUV yield when peak power densities of the fundamental beams exceed the GW/cm2 range, as well as a large intensity-dependant broadening (up to ~30 cm-1) of the two-photon resonance. The source has potential applications for high resolution interference lithography and photochemistry.