Frequency conversion of near-infrared diode lasers provides an efficient method to generate tunable laser radiation in the near-UV, violet and blue-green spectral range. High-power, coherent fundamental laser sources such as master oscillator-power amplifier (MOPA) configurations are now state of the art and commercially available.
A new, highly efficient material for second-harmonic generation (SHG) is Bismuth Triborate ("BiBO", stoichiometry BiB3O6). The material has a high effective non-linearity deff, is non-hygroscopic and transparent for wavelengths between 286 nm and 2.5 μm. Compared to other non-linear crystals, "walk-off" effects between fundamental laser radiation and frequency-doubled beam are considerably lower. We used a BiBO crystal in a resonant doubling cavity to convert the output of a 780 nm, 900 mW tapered amplifier system. A maximum UV power of 400 mW (conversion efficiency 44%) was attained. This value is 3-4 times higher than previous results obtained with LBO or BBO crystals and, to the best of our knowledge, represents the highest tunable cw power of a frequency-converted diode laser.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.