Generation Of Intense Short Pulses In The VUV By Four Wave mixing

By the interaction of intense short pulse laser radiation ( < 1ps; ) with atomic or molecular gases and vapors strong nonlinear polarizations are induced, allowing the generation of coherent radiation by a variety of nonlinear processes. To obtain a short response time of the medium, off resonant excitation schemes have to be considered. Such schemes may still yield high conversion efficiencies, due to the high peak intensities of the pump laser and the occurance of transient resonances by ponderomotive level shifts. Compared to us-experiments saturation effects which limit the conversion efficiency, as the formation of an optically thick plasma by a catastrophic breakdown in the medium, are reduced.