No abstract available

[en] High reflecting mirrors for the wavelength of 514nm were produced with ion-beam sputtering using different process parameters. The optical characteristics were determined by cavity decay time measurement, laser calorimetry and total integrated scatter measurements. The results for single layers of SiO₂ and Ta₂O₅ were evaluated with respect to an optimisation of the deposition process. Furthermore, coatings were investigated by infrared spectroscopy and RBS. Laser induced damage thresholds of coatings were measured with a pulsed Nd:YAG-laser. Mirrors produced with optimised parameters show absorption values less than 5ppm, and the scatter losses are in the range of 6ppm at 514nm. Adding the transmission loss of the mirrors, this is in good agreement with the results of the cavity decay time measurement. The damage threshold values and the optical losses are discussed and compared to the results of conventional coatings

[en] The anti-Stokes Raman laser (ASRL) process has proved to be a method that works well for frequency upconversion and for the generation of powerful tunable narrowband (pulsed) laser radiation in the UV and VUV spectral range. This conversion process allows large-frequency shifts in single step, high output energies, and high efficiencies. A basic requirement is population inversion on a two-photon transition, where, in general, the upper level of the transition should be metastable. Up to now the ASRL technique has only been demonstrated for the pulsed regime, where the necessary population inversion was generated by photodissociation or inner shell photoionization. These inversion techniques, however, cannot be transferred to cw operation of an ASRL, and, therefore, other inversion techniques have to be developed. Here a novel approach for the creation of the necessary population inversion is proposed, that uses well-known cw gas lasers as the active material for the conversion process. The basic idea is to use either existing two-photon population inversions in a cw laser material or to generate the necessary population inversion by applying a suitable population transfer process to the material. A natural two-photon inversion situation in a laser material is evident whenever a cascade laser can be operated. Cascade laser-based anti-Stokes schemes are possible in a He-Ne laser discharge, and investigations of these schemes are discussed

[en] First cw laser oscillation with thresholds below 1 mW was observed for various B¹PIsub(u) → X¹Σ⁺sub(g) transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454-488 nm. For pump powers of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm^-1 were obtained. Some properties of the heat pipe laser system are discussed. (orig.)

[en] A study on thin film optical materials is presented. Single layers of oxides, fluorides, and mixtures of various dielectrics are fabricated on suprasil substrates. Optimized parameters are used for deposition of each material. Optical characteristics of dielectric materials are determined. A Nd-YAG laser with a maximum output energy of 250 mJ and pulse duration of 14 ns (FWHM) is used for damage experiments. X-ray diffraction analysis of various dielectric materials for bulk and film specimen is also presented. Morphology of damage sites is done by Nomarsky and scanning electron microscopy. (author)

[en] Innershell photoionization of atomic gases and vapors by soft x rays from a laser-produced plasma is a potential method for making lasers at short wavelengths. Normally, in such experiments only a single plasma spot or plasma line is created for the excitation. This gives high excitation rates but only a short excitation length. At high excitation rates detrimental influences, such as amplified spontaneous emission, optical saturation, or quenching processes, may decrease or even destroy a possible inversion. Therefore, it seems to be more favorable to use a number of separated plasma spots with smaller excitation rates and larger excitation lengths. As a test, a three-plasma spot device was constructed and used in the well-known Cd-photoionization laser at 442 nm. With a 600-mJ Nd:YAH laser (pulse length, 8 ns) for plasma production, output energies up to 300 μJ have been measured, which is more than a doubling of so far obtained data. On innershell excitation, levels may be populated that allow direct lasers as in the case of Cd or that are metastable and cannot be directly coupled to lower levels. In this case modifications in the excitation process are necessary. Such modifications may be an optical pump process in the atom prior to the innershell photoionization or an optical pump process (population transfer process) after the innershell ionization, leading to Raman or anti-Stokes Raman-type laser emissions. With these techniques and the developed multiplasma spot excitation device a variety of new laser emissions in K and Cs ions have been achieved which are indicated in the level schemes

[en] Interferometric gravitational wave detectors require high optical power, single frequency lasers with very good beam quality and high amplitude and frequency stability as well as high long-term reliability as input light source. For GEO 600 a laser system with these properties is realized by a stable planar, longitudinally pumped 12 W Nd:YAG rod laser which is injection-locked to a monolithic 800 mW Nd:YAG non-planar ring oscillator. Frequency control signals from the mode cleaners are fed to the actuators of the non-planar ring oscillator which determines the frequency stability of the system. The system power stabilization acts on the slave laser pump diodes which have the largest influence on the output power. In order to gain more output power, a combined Nd:YAG-Nd:YVO₄ system is scaled to more than 22 W