Generation of Ultraviolet Radiation at 266 nm with RbBe2BO3F2 Crystal

High-average-power fourth-harmonic generation (4th HG) of an Nd:YAG laser is achieved with a RbBe2BO3F2 (RBBF) crystal. A maximum output power of 3 W at 266 nm is obtained. To our knowledge, this is the first time that efficient 4th HG is realized with RBBF. The angular bandwidth of 4th HG is also measured.