We present and characterize a laser system for the spectroscopy on highly charged 209 Bi 82+ ions at a wavelength of 243.87 nm. For absolute frequency stabilization, the laser system is locked to a near-infra-red laser stabilized to a rubidium transition line using a transfer cavity based locking scheme. Tuning of the output frequency with high precision is achieved via a tunable rf offset lock. A sampleand-hold technique gives an extended tuning range of several THz in the UV. This scheme is universally applicable to the stabilization of laser systems at wavelengths not directly accessible to atomic or molecular resonances. We determine the frequency accuracy of the laser system using Dopplerfree absorption spectroscopy of Te 2 vapor at 488 nm. Scaled to the target wavelength of 244 nm, we achieve a frequency uncertainty of σ 244 nm = 6.14 MHz (one standard deviation) over six days of operation.

A highly efficient Talbot array illuminator for single-shot, laser-induced-damage test measurements of optical thin-film coatings is proposed. With a periodic binary phase grating, a laser beam is transformed into an ensemble of Gaussian-like spots, which are known as the Fresnel image of the grating. For this purpose hexagonal phase gratings were fabricated and analyzed. With a peak fluence distribution of approximately 1 order of magnitude, the damage threshold of thin films can be deduced by use of the data from only a single shot.

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