Ritty J, Nedumpara; Binoy, Paul; Santhi, A; Radhakrishnan, P; Nampoori, V P N(Elsevier, January , 2004)
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Abstract:
In this paper, we present a laser-induced photoacoustic study on the photostability of laser dye Coumarin 540 doped in PMMA matrix and modified by the incorporation of low-molecular weight additives. The dependence of photostability of the dye on various experimental conditions, such as nature of solvents, incident optical power and dye concentration, is investigated in detail. The activation rates for the bleaching process are calculated for different concentrations and they suggest the possibility of two distinct mechanisms responsible for photodegradation. Further, analysis of the data confirms the linear dependence of photodegradation on the intensity of incident radiation. The role of different externally influencing parameters, such as wavelength and modulation frequency of incident radiation, is also discussed.
Achamma, Kurian; Nibu, A George; Binoy, Paul; Nampoori, V P N; Vallabhan, C P G(Taylor & Francis, 2002)
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Abstract:
In this paper we report the use of the dual beam thermal lens technique as a quantitative
method to determine absolute fluorescence quantum efficiency and concentration
quenching of fluorescence emission from rhodamine 6G doped Poly(methyl
methacrylate) (PMMA), prepared with different concentrations of the dye. A
comparison of the present data with that reported in the literature indicates that the
observed variation of fluorescence quantum yield with respect to the dye
concentration follows a similar profile as in the earlier reported observations on
rhodamine 6G in solution. The photodegradation of the dye molecules under cw laser
excitation is also studied using the present method.