Research on ultrashort-wavelength vacuum ultraviolet generation by using stimulated Raman scattering

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We have improved laser-induced damage tolerance of CsLiB6O10 (CLBO), and attempted to construct vacuum-ultraviolet (VUV) laser source below 190 nm as a new pump source of anti-Stokes (AS) stimulated Raman scattering (SRS). By using an Nd:YAG laser, the fifth harmonic and infrared (IR) OPO at 1697.9 nm were generated via several frequency conversion stages. At the final stage, VUV light below 190 nm was generated by sum-frequency generation with the fifth-harmonic and IR in a CLBO. A 189 nm output was produced with a conversion efficiency of 7.3% from the 213 nm input. Based on the experimental result, we have newly designed VUV laser system at 185 nm using a 20-W Nd:YAG laser with high-peak power density. Although we are currently constructing the final stage in the system, we estimate the average power over 100 mW at 185 nm and expect ultrashort-wavelength VUV radiation by SRS in H2 such as 1st, 3rd, and 8th AS lines at 172, 150, and 115 nm.