Optical gain characteristics of C 460 and C 450

Dye concentration dependent gain spectra for Coumarin 460 (C 460) and Coumarin 450 (C 450) in ethanol have been studied using Amplified Spontaneous Emission (ASE) technique under Nitrogen laser (337.1 nm) excitation in the concentration range 10(-2)-10(-5) m/l. The dependence of lasing wavelength and peak gain on concentration have been understood in terms of variation of fluorescence lifetime, which is due to photo-physical processes such as radiation trapping and concentration-quenching. Pump intensity dependence of efficiency is also explained in terms of fluorescence lifetime. A comparison of the stability of the two dyes has also been made on the basis of the functional groups at different positions of the basic coumarin.