Abstract

The nonlinear optical processes of four- wave sum mixing (FWSM) and harmonic generation (HG) are well-established techniques for producing tunable or untunable coherent radiation in the spectral regions of the vacuum ultraviolet (VUV) and the extreme ultraviolet (XUV). However, most experiments have been performed in the negative dispersive region of gaseous media and have usually used a resonant-enhancement process. Since only a limited spectral region satisfies the requirements of negative dispersion, a systematic study in the positive dispersive region is necessary. In this paper we report that tunable VUV (or XUV) coherent radiation can be generated by nonresonant FWSM in both the positive and negative dispersive regions of nonlinear media of Ar and Kr, and the complete, detailed investigation and analysis are presented. To our knowledge this is the first report of the generation of tunable VUV coherent radiation by FWSM with no regard to the sign of dispersion of inert gases.

© 1993 Optical Society of America