Single crystal fibers doped with Er or Tm and clad with a sapphire sol-gel were tested for both laser performance and super-continuum generation. Laser performance was explored for multiple sol-gel cladding deposition cycles (0 to 5) in addition to variable concentration (0.25% to 3%). A single sample showed exemplary performance (2% Tm with 3 deposition cycles) achieving 44.5% slope-efficiency. Super-continuum generation was compared in pure and doped fibers of both 150μm and 50μm diameters at five different pump wavelengths with an 80 fs source. Super-continuum was generated covering 1.5 octaves (790 nm pump) and <2.5 octaves (1645 nm pump) with a threshold pulse energy of 0.4 μJ (5 MW peak power).
The diode-pumped rare gas laser (DPRGL) has been suggested as a potential high-gain, high-energy laser which requires densities on the order of 1013 cm−3 at pressures around 1 atmosphere for efficient operation. Argon 1s5 number densities have been measured in micro-hollow cathode discharges with electrode gaps of 127 and 254 μm and hole diameters from 100-400 μm. The dependency of the metastable argon (1s5) density on total gas pressure, electrode gap distance and hole diameter were explored. The measured densities were all in the range of 0.5 − 2 × 1013 cm−3 with the 400 μm hole diameters being the lowest.
Fine-structure mixing cross-sections for the alkalis in collisions with the rare gases are reviewed. Included in the review are all the rare gases in collisions with all of the first excited state of the alkalis, the second excited state for K, Rb and Cs and the third excited state for Rb and Cs. The cross-sections are converted to probabilities for energy transfer using a quantum-defect calculated cross-section and are then presented as a function of adiabaticity. The data shows a clear decreasing trend with adiabaticity but secondary factors prevent the probabilities from decreasing as quickly as expected. Polarizability is introduced as a proxy for the secondary influences on the data as it increases with both rare gas partner and alkali excited state. The polarizability is shown to cause the probability of fine structure transition to be higher than expected. An empirical model is introduced and fit to the data. Future work will develop a model using time-independent perturbation theory in order to further develop a physical rational for the dependence of fine structure cross sections on adiabaticity and to further understand the secondary influences on the probability for fine structure transition.