Photophysical properties and laser performance of photostable UV laser dyes. Part 1. Substituted p-quaterphenyls

Abstract

The photophysical properties of nine ring-bridged p-quaterphenyls, such as the singlet and triplet absorption spectra, the fluorescence spectra, the fluorescence quantum yield, and fluorescence decay time, as well as the laser performance data, such as the tuning range, conversion efficiency, and photochemical stability, have been measured in ethanol and dioxane at room temperature. Compared to the methyl-substituted p-quaterphenyls, ring-bridging shifts the absorption maximum by 20-25 nm toward longer wavelengths which results in a better match of the absorption maximum with emission of the XeCl excimer laser. The ring-bridged p-quaterphenyls exhibit laser dye emission in the 363-385-nm range with conversion efficiencies (slope efficiency) between 3 and 17% and with low lasing thresholds. Ring-bridging of p-quaterphenyl with methylene, oxygen, and ethylene causes a considerable decrease of the conversion efficiency in the order given, while the photochemical stability in dioxane increases with the same order of ring-bridging. 2,7-Diphenyl-9,10-dihydrophenanthrene is one of the most stable UV laser dyes. Knowing the fluorescence quantum yield and decay time, one can predict the possibility of laser action and the conversion efficiency of a potential UV laser dye.