Generation of infrared and extreme-ultraviolet radiation in krypton with picosecond irradiation at 193 nm

The nonlinear interaction of neutral krypton atoms with picosecond 193-nm radiation with intensities ≤1013 W/cm2 has been studied. Because of the relatively high intensity of the applied radiation field and the two-photon resonance of the 4p-6p transition, several competing nonlinear processes were observed that result in the generation of coherent radiation. Amplified spontaneous emission (ASE) from the two-photon-resonant level was observed in the IR frequency at ∣2 μm. Additionally, a tunable IR wave, in the same frequency range, was generated by stimulated hyper-Raman scattering of the incident laser. The observed self-generated IR waves induced other nonlinear interactions, which resulted in the generation of extreme-ultraviolet (XUV) radiation in the same medium. Tunable XUV frequency was shown to be generated by four-wave sum mixing of the laser and the hyper- Raman wave. Vacuum-ultraviolet frequency was shown to be generated by four-wave oscillation, and other nontunable XUV frequencies resulted from anti-Stokes Raman scattering of the ASE IR waves. © 1988, Optical Society of America.