SINGLE PASS GAIN OF EXCIPLEX 4-MU AND RHODAMINE 6G DYE LASER AMPLIFIERS

Abstract

Single pass gain has been measured in N2 laser pumped exciplex 4-Methylumbelliferone (4-MU) and rhodamine 6G dye lasers using a technique developed by Silfvast and Deech for high-gain pulsed metal vapor lasers. The gain is measured by comparing the intensities of amplified spontaneous emission in single and double cell lengths with the maximum unsaturated single-pass gain being limited by the saturation of the spontaneous emission. Maximum unsaturated gains on the order of 20 dB/cm were measured for both dyes. The gain was found to vary linearly with pump power. The technique was also used to measure the variation of gain with wavelength for a given pump power. The maximum gain for exciplex 4-MU occurred at the fluorescence peak, whereas for rhodamine 6G it was shifted to a longer wavelength due to ground-state reabsorption. By fitting the measured gain versus wavelength to the theory, it was possible to deduce the fractional excited singlet population in the rhodamine 6G solution.