193 nm Generation by Optical Frequency Conversion Using CsLiB6O10 Crystal (CLBO)

Two sum-frequency mixing scheme for 193-nm generation have been investigated using CLBO as the final mixing crystal. One scheme mixes the output of an optical parametric oscillator, operating at 2.1μm, with the 5th harmonic of a Nd: YAG laser. The second scheme mixes the fundamental wave of a Nd: YAG laser (1064.2 nm) with ultraviolet light at 236.4 nm. In the latter scheme, according to the Sellmeier equations obtained from the published refractive index data, Type I CLBO should critically phase-match to generate 193.4-nm output. However, in our experiments, no phase matching at room temperature was observed. The CLBO did show non-critical phase-matching (NCPM) at the wavelength combination: λ1=1064.2 nm, λ2=238.8 nm and λ3=195.0 nm at room temperature (24°C). In a temperature tuning experiment performed with this mixing scheme (λ1 fixed at 1064.2 nm and λ2 varied), it was discovered that CLBO needs to be cooled below -180°C in order to generate 193.4 nm.