Observation of VUV radiation at wavelengths in the ωp- and 2ωp-wavelength range emitted from femtosecond laser-plasmas

Abstract

Electromagnetic emission close to multiples of the plasma frequency ωp has been observed experimentally from short-pulse laser-irradiated solid targets. Such radiation may be generated by a two-step process in which hot electron jets excite Langmuir waves in the overdense region, which then undergo parametric conversion to electromagnetic emission at harmonics of the plasma frequency ωp. The observations are supported by particle-in-cell simulations, suggesting that this radiation may be exploited as a density diagnostic.