Review of research on ultraviolet and deep-UV nonlinear optical crystals in the last decade

Investigations on ultraviolet (UV) and deep-UV nonlinear optical (NLO) crystals over the last decade in our research group, including successes and failure, are discussed. Successes include the discovery of KBBF (KBe/sub 2/BO/sub 3/F/sub 2/) and KABO (K/sub 2/Al/sub 2/B/sub 2/O/sub 7/) crystals. By using a special prism coupling technique for KBBF, our group and Watanabe´s group at the University of Tokyo have jointly shown that this crystal is suitable for fourth harmonic generation of the Ti:sapphire laser. On the other hand, we are surprised that SBBO (Sr/sub 2/Be/sub 2/B/sub 2/O/sub 7/) crystal, which has good linear and nonlinear optical properties, lacks structural completeness. As a result, the crystal has very poor optical homogeneity, and can not be used to produce deep-UV harmonic generation yet.