Continuous-wave single-frequency 295 nm laser source by a frequency-quadrupled optically pumped semiconductor laser

Up to 136 mW of cw single-frequency output at 295 nm was obtained from a frequency-quadrupled optically pumped semiconductor laser. The highly strained InGaAs quantum-well semiconductor laser operates at 1178 nm in a single frequency. The single-frequency intracavity-doubled 589 nm output is further converted to 295 nm in an external resonator using β-BaB₂O ₄.