Second harmonic generation from KBBF crystal in the deep ultraviolet

By using a KBe/sub 2/BO/sub 3/F/sub 2/ (KBBF) crystal with a size of 10 /spl times/ 10 /spl times/ 1.2 mm/sup 3/ and a special prism coupling technique (PCT), the fourth-harmonic generation of Ti:sapphire laser systems from 200 nm to 179.4-nm has been achieved for the first time. Moreover, by a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate. A conversion efficiency as high as 13% from 400 nm to 200 nm has also been obtained without any surface loss correction.