Currently, efficiencies of frequency quadrupled 236.5-nm DUV lasers from 946-nm Nd:YAG output are low and beam quality is not even close to LUSTER specifications, due to the unfavorable quasi- three-level laser transition and the spatial walk-off of the nonlinear optical (NLO) crystals during frequency conversions. Therefore, the approach is inefficient for cw laser and would require very large equipment. BBO is presently the only viable NLO crystal for conversion to DUV and has an especially large walk-off angle of >4. The proposed approach will overcome the current limitations and problems of the technology, using: A Nd:YAG 946 nm pump laser designed as a diode pumped crystal fiber waveguide (CFW), modeled to result in close to theoretical beam quality and efficiency for quasi-three-level system. Walk-off compensated LBO and BBO stacks to extend the useful length of LBO and especially BBO, increase efficiency and beam quality for conversion to 236.5 nm.
