Narrow linewidth ultraviolet semiconductor disk laser

Single-frequency, narrow-linewidth laser sources emitting in the UV-visible range are of interest for applications such as spectroscopy, high-precision metrology and interference photolithography. Optically-pumped semiconductor disk lasers (SDLs) have shown their ability to deliver high brightness output, both spatially and spectrally, and have been able to target the UV via frequency-doubling from the visible or frequency tripling and quadrupling from the infrared [1]; however, most demonstrations of narrow linewidth (sub-MHz) SDLs have been in the infrared (e.g. [2]). Here we combine active stabilisation of an AlGaInP-based red SDL with intracavity frequency doubling in the same cavity in order to achieve narrow linewidth, <25 kHz, and tuning at the second harmonic. As compared to other frequency stabilised UV laser systems which require successive external enhancement cavities, each with separate stabilisation [3], we benefit here from a much simpler setup thanks to the short fundamental wavelength which allows direct intracavity doubling to the UV.