A decreased laser threshold has been observed for a flashlamp-pumped Rhodamine B dye laser as the temperature of the solution is reduced. The change in threshold is attributed to an increase in the fluorescence quantum yield and can be characterized by an activation energy of 880 cm−1.

Results of a development program for light-emitting-diode (LED)-pumped neodymium-doped yttrium aluminum garnet (Nd: YAG) lasers highlight a significant design feature: an index-matching method to increase the coupling efficiency of the laser. A solid-glass half-cylinder measuring 5.0×5.6 cm was used for index matching and also as a pumping cavity reflector. An array of twenty 0.034×0.254-cm GaAlAs diodes, connected in series, aligned such that the emission area formed a straight line, was used to excite a 1.5×56-mm laser rod. The interfaces between the diode array, glass half-cylinder, and laser rod were filled with viscous fluid of refractive index n = 1.55. Experiments performed with both the glass half-cylinder and a gold-coated stainless steel reflector under the same operating conditions indicated that the index-matching half-cylinder gave 160–200% improvement of coupling efficiency over the metal reflector at various operating temperatures. For a 207-A/cm2 driving current density the laser produced cw output power of 27 mW.

Experimental data comparing peak emission wavelength with organic dye laser cell length are presented. These data and knowledge of the variation of peak emission wavelength with organic dye concentration make reasonable the hypothesis that the observed effects are caused by self-absorption. A simple theory is developed on this hypothesis and the results of numerical calculations compared with the experimental data. Good agreement is obtained, but some departures from agreement suggest improvement may be expected from a time-dependent theory.

The output from a transverse-pumped organic dye laser has been investigated using time-resolved spectroscopy. It is found that for the specific case of DTTC-Iodide dissolved in either DMSO or methanol the peak wavelength in the emission band shifts during the output pulse.

No abstract