Resonant third harmonic generation of KrF laser in Ar gas.

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

Changes in DRIFT spectra of wood irradiated by lasers of different wavelength.

An exact wavelength separation of the spectrum cannot be accomplished when utilizing common ultraviolet (UV) light sources, so the dependence of photodegradation on wavelength cannot be done directly. The photodegradation of wood resulted in by laser irradiation on various wavelengths can be studied by comparing the changes in the DRIFT spectra of various wood materials. The analysis of the difference spectrum is a widely used method to investigate the changes in the infrared spectrum. As this procedure cannot be used to compare the changes quantitatively, a new indicator was introduced, termed Band Damage Index (BDI). The BDI and the results obtained by its analysis are going to be discussed.

Two-step preionization scheme for discharge pumped KrF excimer lasers.

The beam homogeneity and stored energy of discharge pumped KrF excimer amplifiers are critically dependent on the preionization level of the active medium and on the rise time of the electric excitation pulse. Here a scheme is presented to increase the effectiveness of the preionization and to improve the rise time of the pump pulse by the use of the auto-spark-gap UV preionization of increased gap separation. The modified charging circuit has been proven to enhance the discharge quality and the amplification properties of the excimer module. The increased temporal jitter of the preionization sparks of large gap separation is eliminated by an additional pre-preionization scheme. The circuit is especially well suited for short-pulse KrF amplifiers.