High-power CW deep-UV coherent light sources around 200 nm based on external resonant sum-frequency mixing

We report pure continuous-wave (CW) high-power (>100 mW) deep-ultraviolet (DUV) light sources emitting around 200-nm spectral region based on singly resonant sum-frequency mixing (SRSFM). Efficient DUV generation is made possible by use of a Brewster-cut CsLiB₆O₁₀ (CLBO) crystal near noncritically phase-matched (NCPM) condition for the SFM of 1-μm output of neodymium lasers. The CW radiation of fifth-harmonic wavelength of a neodymium laser at 213 nm was generated by the SFM of enhanced 1064-nm radiation with single-passing 266-nm radiation produced by external-resonant frequency doubling of a 532-nm green laser. With 1.8 W of 266-nm radiation incident upon a CLBO crystal, as much as 180 mW of CW 213-nm power has been produced. The sub-200-nm CW radiation with 140-mW power has also been achieved by SFM of 1064 nm with 244-nm radiation from a frequency-doubled Argon-ion laser in the CLBO crystal operated near the NCPM condition.