Determination of femtosecond dephasing times of organic dyes confined in a single spherical microparticle

When the fluorescing atoms or molecules are placed inside such a micro-cavity, the fluorescence gets coupled to the morphology dependent resonances (MDR) as an electromagnetic field. This results in alternatively enhancement or inhibition of the fluorescence depending on whether or not the fluorescence emission spectrally coincides with a cavity resonance. The effect of MDR on the radiative rate of chelated Europium ions as well as the shortening of fluorescence lifetime of Rhodamine 6G due to the effect of MDR are reported in micro-droplets. However, a study of a few dyes of higher fluorescence quantum yield in polymer micro-particles does not show any change in the fluorescence lifetime even though the modification of the fluorescence spectra is observed. In this chapter, morphology dependent resonances (MDR) are observed in the fluorescence of 9-amino acridine hydrochloride hydrate (9AAHH) impregnated single microparticles. These MDRs influence the radiative rate of the molecule. From the time-resolved measurement with a resolution of nanosecond, the femtosecond dephasing time of the molecule in a polymer matrix at room temperature is determined.