Nonlinear-optical processes in the near-resonant two-photon excitation of xenon by femtosecond KrF-excimer-laser pulses

The nonlinear response of xenon gas due to a near-resonant two-photon excitation at the 5p⁶ ¹{S}₀→6p[1/2{]}₀$ transition with a femtosecond KrF-excimer-laser system is investigated for the intensity range ${10}¹⁰$--${10}¹⁵$ W/${cm}²$. Stimulated hyper-Raman scattering and amplified spontaneous emission of atomic xenon are observed at wavelengths around 823 and 828 nm. These emissions are superimposed by four-wave parametric-oscillation processes leading to strong ultrashort continuum radiation in the visible and near-infrared (650--850 nm), uv (185--400 nm), and vacuum ultraviolet (147--155 nm) spectral ranges with output powers up to 100 MW. From difference-frequency-mixing experiments microscopic nonlinear susceptibilities in the range of {}χ⁽³⁾{}=10^-48 to 10^-50 m⁵/V² have been determined, which are in good agreement with calculations.