Generation Of Coherent VUV Radiation Research Articles

Resonant sum-difference frequency mixing enhanced by electromagnetically induced transparency in krypton

We report experiments that investigate the generation of coherent VUV radiation at 123.6 nm via a resonant sum-difference frequency mixing scheme in Kr. One of the mixing fields at 212.55 nm was in two-photon resonance with the transition between the ${4p}^{6}{}^{1}S$ ground state and the ${4p}^{5}5p[0,\frac{1}{2}]$ excited state $(94093.7 {\mathrm{cm}}^{\ensuremath{-}1}).$ The second field (the coupling field) at 759 nm was in single-photon resonance with the transition between the ${4p}^{5}5p[0,\frac{1}{2}]$ state and the ${4p}^{5}5s[1,\frac{1}{2}]$ state at $80917.6 {\mathrm{cm}}^{\ensuremath{-}1}.$ The presence of the coupling field leads to electromagnetically induced transparency (EIT) at the wavelength of the generated field, 123.6 nm. This is predicted to enhance the four-wave-mixing efficiency by a large factor. We have studied the dependence of the four-wave mixing process on the detuning and strength of the coupling field. The efficiency for four-wave mixing was found to be enhanced by a significant factor (>5) by the EIT effect when the resonant coupling field strength exceeded about half the Doppler width $(0.1 {\mathrm{cm}}^{\ensuremath{-}1}).$ A calculation for monochromatic fields and a uniform slab of gas provided qualitative agreement with the results of experiment. The relative conversion efficiency for this resonant mixing scheme is found to be ${10}^{4}$ times greater than that for a similar scheme where the coupling laser is tuned far $(1270 {\mathrm{cm}}^{\ensuremath{-}1})$ off resonance. A substantial part of this resonant enhancement can thus be attributed to the EIT effect.

Generation of coherent VUV radiation using annular laser beams

Generation of a tunable third harmonic of the fundamental laser light in xenon was studied using laser beams with ring-shaped amplitude profiles. The conversion efficiencies and the tuning ranges were compared for different annular and ordinary Gaussian beams. Some advantages of the annular beams in generation of coherent VUV radiation are discussed.

Generation of coherent VUV radiation using resonance-enhanced four-wave difference-mixing of nanosecond and femtosecond laser pulses in Kr

A four-wave difference-mixing scheme based on resonance-enhanced two-photon excitation of Kr with a narrow bandwidth nanosecond laser and a tunable femtosecond laser is used to generate tunable, intense (10 7 photons/pulse), coherent, short pulse radiation around 124 nm.

Generation of coherent VUV radiation and its application to plasma diagnostics

The generation of narrow-bandwidth tunable VUV radiation for plasma diagnostic applications is described. The characteristics of VUV radiation obtained by four-wave mixing in noble gases and mercury vapour and stimulated anti-Stokes Raman scattering in molecular hydrogen are compared. Examples of the application of VUV radiation generated by various methods to diagnose atomic and molecular hydrogen are presented.