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High-power and high-conversion efficiency deep ultraviolet (DUV) laser at 258  nm generation in the CsLiB6O10 (CLBO) crystal with a beam quality of M2<1.5.

We report a 10 kHz, 10.5 W deep ultraviolet (DUV) laser at 258 nm with a pulse duration of 3 ns by fourth-harmonic generation (FHG) in a CsLiB6O10 crystal with high-conversion efficiency. The fundamental laser is at 1030 nm with 35 W output power consisting of a Yb:YAG ceramics thin rod amplifier. The M2 of the DUV laser was confirmed to be <1.5. To the best of our knowledge, this is the best beam quality for DUV laser power higher than 10 W generated by FHG of a solid-state laser, as well as the highest conversion efficiency of 31% from infrared to DUV so far.