626-nm single-frequency semiconductor laser system operated near room temperature for mW-level second-harmonic generation at 313 nm

We report a 626-nm, single-frequency generation based on laser diodes operated near room temperature and the second-harmonic generation with an output power of 2 mW at 313 nm. A fundamental single-frequency laser at 626 nm consists of an external-cavity diode laser and a tapered semiconductor amplifier with 200 mW output. Antireflection coating of the laser diode expands the wavelength tuning range and realizes single-frequency output at 626 nm at room temperature. 313 nm light is generated by cavity-enhanced frequency doubling with a β-BaB2O4 crystal. A 313 nm laser with mW-level output power is useful for various experiments using laser cooling of beryllium ions.