A frequency quintupled laser at 308 nm for spectroscopy of intercombination lines in zinc

Many experiments in atomic physics and quantum optics, among them optical atomic clocks, require laser sources in the ultra-violet wavelength range with very low intensity noise and phase noise. The development of such lasers is a challenge, especially when a robust and transportable system is required. Here, we report on the development of a novel continuous wave (cw) frequency-quintupled laser at 308 nm with an output power of 0.5 mW, based on a fiber laser operating in the telecom band. Three consecutive frequency conversion stages in nonlinear crystals are employed. The performance of the laser system is demonstrated by linear absorption spectroscopy of a narrow intercombination line in zinc.