EFFECTIVE STIMULATED-EMISSION CROSS-SECTIONS DETERMINED BY TRANSIENT FLUORESCENCE AMPLIFICATION IN A FABRY-PEROT RESONATOR

The amplification of fluorescence light of an active medium in a Fabry -Perot resonator, transversely pumped with picosecond pulses, is explo ited to determine the effective stimulated emission cross-section spec trum, sigma(em,eff)(lambda). A theory is presented for the ratio of am plified fluorescence output to spontaneous emission signal (resonator mirrors removed). The detection sensitivity is enhanced by the multi-p ass amplification. Its dependence on the output mirror reflectivity an d residual ground-state absorption in the emission region is analysed. As an example the effective stimulated emission cross-section spectru m of coumarin 2 in methanol is measured in the wavelength region 435 n m to 610 nm.