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Transmission of fused silica, CaF(2), LiF, and MgF(2) is measured using 450-fsec, 248-nm pulses in the range 10-120 GW/cm(2). Different loss mechanisms such as scattering of transmitted radiation, color-center formation, and multiphoton absorption were studied separately. For fused silica a two-photon absorption mechanism is found, while for CaF(2), LiF, and MgF(2) three-photon absorption and absorption due to color-center formation are found as dominant absorption mechanisms.

A set-up for automated measurement of damage thresholds on UV optical components is presented, being part of the EUREKA program "High Power Excimer Lasers". It includes on-line monitoring of probe beam parameters as well as sample condition, using digital image processing techniques for both laser beam profiling and high sensitivity damage detection. The latter is performed with a video microscopy system by pixel-to-pixel comparison of the video frames taken before and after the test laser pulse.

An interferometric method is presented to characterize the most important parameters of beams from large aperture femtosecond excimer laser systems. With the use of a special interferometer the shape of both the pulse and the phase fronts can simultaneously be studied. With minor changes, conventional autocorrelation measurements can also be performed.

Polymethyl-methacrylate doped with organic dye molecules can be photoablated with 308 or 351 nm nanosecond excimer laser pulses. For comparison, pure polymethyl-methacrylate cannot be photoablated at these wavelengths. The definition of the ablation pattern is comparable to the results achieved by the use of 248 nm pulses on pure polymethyl-methacrylate. Etch rates of about 50 μm per pulse can be reached, which is ten times the maximum etch rate of 248 nm pulses. An example of an effective dopant molecule is 1,3-diphenyltriazene. The ablation process is governed by gas production due to laser-induced photodissociation of the dopant. The ablation rate increases with growing laser fluence up to a saturation level, which is approximately proportional to the reciprocal dopant concentration (0.2 to 2 wt%).

Since laser induced damage of optical components has become a severe problem for the development of high power lasers during the last years, great efforts are made to improve the quality of the employed optics. This requires, however, the use of controlled damage testing experiments, which not only allow the accurate determination of damage thresholds, but can also give insight into the fundamental damaging processes [1].

The noise characteristic of available laser sources limits the sensitivity of saturated absorption spectroscopy. Time averaging is one method to improve the signal-to-noise ratio. A computer controlled dye-laser spectrometer is described which has the capability to scan several times any selected frequency range with an absolute accuracy of ±200 kHz. The sensitivity of this system is demonstrated by measuring the isotope shift of the low abundant38Ar and by detecting a weak83Kr-hyperfine component.

The 6s-7p transitions in cesium at 459.3 nm (72P1/2) and 455.5 nm (72P3/2) have been investigated by saturation spectroscopy in vapor cells, using a laser spectrometer with 500 kHz bandwidth in the blue spectral range. Isotope shifts as well as hyperfine splittings were determined for the isotopes 133, 135 and 137.

We have used a cw color center laser near 2.6 μm to study highly excited states in helium and neon atoms by Doppler- free intermodulated optogalvanic spectroscopy in a hollow cathode discharge tube. For helium n = 4 to 6 transitions, the resolution was limited to about 320 MHz (FWHM) by Holtzmark broadening due to the presence of charged particles in the discharge. Lines as narrow as 60 MHz were observed for neon 3s 5 -5p 10 .

We report the production of stable CW single mode UV radiation around 295 nm at powers exceeding 50 mW, using a passive enhancement cavity for second harmonic generation. With this laser we have investigated the 2 3 S−5 3 P transition at 294.5 nm in 3 He and 4 He by intermodulated fluorescence spectroscopy. The measurements of the hyperfine splittings of the 5 3 P levels agree with semi-empirical calculations.

A cw single mode color center laser was used to study infrared transitions between n = 4 and n = 6 states in helium by Doppler-free intermodulated fluorescence spectroscopy. Excited helium atoms are produced by bombarding ground-state helium atoms with low energy electrons. With pulsed excitation and gated detection, the resolution approaches the natural linewidth.

A high resolution cw dye laser spectrometer with a frequency calibration system of 100 kHz resolution is described. Two examples of measured isotope shifts will be discussed.

A high resolution polarization experiment performed on the 1s 5 − 2p 3 transition in even krypton isotopes is described. A least square analysis of the data shows a good agreement with existing theoretical calculations.

The spectral and temporal behaviour of subpicosecond DFDLs are studied. A simple and sensitive spectral diagnostic method is proposed to exhibit the presence and determine the temporal separation and relative amplitude of any following pulse. The measurements were performed in a hybrid excimer-dye laser system generating less than 100 fs pulses at 248 nm.

A single frequency, jet stream cw dye laser spectrometer locked to a stable high finesse optical reference cavity is described. This system is capable of maintaining a frequency stability of ± 1 MHz/min and a continuous scan of up to 6 GHz.

High-spectral purity of pulsed dye lasers is required by many experiments. Unfortunately, the dye laser output is usually accompanied by a spectrally broadband background of spontaneous emission (ASE). We have carried out detailed studies of the ASE background using a dye laser operating with an oscillator, pre- and main amplifier.