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

摘要

The efficiency of a coherent VUV source at 125 nm, based on 2-photon resonantfour-wave mixing in mercury vapor, has been enhanced by up to 2 orders ofmagnitude. This enhancement was obtained by locally heating a liquid Hg surfacewith a pulsed excimer laser, resulting in a high density vapor plume in whichthe 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 saturationof the VUV yield when peak power densities of the fundamental beams exceed theGW/cm2 range, as well as a large intensity-dependant broadening (up to ~30cm-1) of the two-photon resonance. The source has potential applications forhigh resolution interference lithography and photochemistry.