  A continuous-wave Ti:sapphire laser at 795 nm is frequency doubled in a
bow-tie type enhancement four-mirror ring cavity with LiB3O5 (LBO), BiB3O6
(BiBO), and periodically polled KTiOPO4 (PPKTP) crystals, respectively. The
properties of 397.5 nm ultra-violet (UV) output power, beam quality, stability
for these different nonlinear crystals are investigated and compared. For PPKTP
crystal, the highest doubling efficiency of 58.1% is achieved from 191 mW of
795 nm mode-matched fundamental power to 111 mW of 397.5 nm UV output. For LBO
crystal, with 1.34 W of mode-matched 795 nm power, 770 mW of 397.5 nm UV output
is achieved, implying a doubling efficiency of 57.4%. For BiBO crystal, with
323 mW of mode-matched 795 nm power, 116 mW of 397.5 nm UV output is achieved,
leading to a doubling efficiency of 35.9%. The generated UV radiation has
potential applications in the fields of quantum physics
