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We report a novel cavity feedback mechanism for stabilizing single-longitudinal-mode (SLM) operation of diamond Raman lasers. Polarization-dependent Raman gain and in-grown stress birefringence in diamond were investigated as sources for Hansch-Couillaud-type locking signals. The power range of SLM operation increased from 2.1 W to 7.2 W, compared to the free-running laser, for a simple standing-wave laser cavity without frequency-selective elements. Methods for further increasing power range and frequency stability are discussed.

In this work we study the effect of laser conditioning on laser-induced damage of ion-beam sputtered, anti-reflection coated laser optics with ns-pulsed laser radiation at a wavelength of 355 nm. With respect to applications in aerospace, measurements were performed under high vacuum. At laser fluences below 20 J/cm2, laser-induced damage appears as pin-point damage (small explosion pits with sizes in the range of 1 micro-meter), sometimes referred to as "grey haze". We find that ramped laser conditioning is an effective tool to reduce not only the abundance but also the average size of pin-point damage at laser fluences exceeding the optic’s unconditioned laser-induced damage threshold. We discuss our results in the context of the small absorber model for damage crater formation.

Field exposition experiments have been initiated by the German Federal Office for Radiation Protection (Bundesamt für Strahlenschutz – BfS) to examine genotoxic effects of THz radiation in vitro. Two different human skin cell types are exposed to continuous-wave radiation at six distinct frequencies between 100 GHz and 2.52 THz originating from different sources of THz radiation under defined environmental conditions. The cell containers are irradiated with free space power flux densities between 0.1 mW/cm2 and 2 mW/cm2 measured traceable to the SI units. For meaningful results, dosimetric calculations using the finite differences time-domain method have been performed in order to access the fields and consequently the specific absorption rate (SAR) in the cell layer.

In order to investigate the complex relative dielectric constant of different materials over a frequency range of 50 MHz to 3 GHz a setup has been built that allows rf-measurements in a climate chamber. Within this chamber the temperature and humidity can be changed and be measured by accurate sensors. The construction of the rf-part of the setup has been made with an outer cylindrical shell that allows climate interactions through its large orifices. Methods for calculating the complex relative dielectric constant from the measured scattering parameters are presented and the changes of the relative constants due to different humidity conditions are shown.