Characterisation of solid-state dyes and their use as tunable laser amplifiers

This paper reports on the spectroscopic and photo physical characteristics of solid-state dyes and their use as tunable high-gain laser amplifiers. A comparison of the absorption and fluorescence spectra is made for the dyes pyrromethene 567, pyrromethene 597, pyrromethene 650, rhodamine 6G in the solid hosts, polymethyl methacrylate, polycom and ormosil, and compared to the case of the dyes in the solvent methanol. Results show a reduced Stokes' shift and an increased fluorescence lifetime for dyes in the solid hosts compared to the solvent. The use of pyrromethene 650 in polymethyl methacrylate as a tunable laser amplifier was investigated. The dye amplifier was shown to exhibit photo-induced birefringence, and the fluorescence polarisation and intensity dependent anisotropy effects of gain and refractive index was characterised. The molecular reorientation time for pyrromethene 650 in the solid host was calculated to be 6.8 ns. The solid-state dye exhibited a single pass gain of 500 at 616 nm. The saturation behaviour was investigated and values of emission cross-section determined. Operation of the solid-state dye in a laser oscillator showed effects of strong shift in the lasing wavelength as a function of the cavity Q due to the small Stokes' shift of the dye in the solid host.