GdYCOB is a promising nonlinear optical crystal that possesses characteristics of an effective nonlinear coefficient, noncritical phase matching operation, and high chemical stability. In this paper, we report about fabrication and characteristics of a monolithic wavelength converter, which generates ultraviolet light by the incidence of near infrared laser. The converter consists of GdYCOB for third-harmonic generation, KTP for second-harmonic generation, and a wave plate for polarization-control. These constituents are integrated with an optical contact bonding. The extreme downsizing of ultraviolet generator is possible with this converter as compared to the conventional method. GdYCOB has the advantage of wide angular bandwidth whereas KTP exhibits wide temperature bandwidth. Consequently, the combination of these crystals results in highly efficient and stable ultraviolet conversion. The converter does not necessitate any high-temperature curing or desiccators since the constituent crystals are non-hygroscopic. Thus the monolithic wavelength converter enables a very compact and highly reliable ultraviolet laser.
