Method for measuring the extinction coefficient of fluorescing media within the emission band

We propose and test a method for determining a fluorescent medium's absorption or extinction index while it is fluorescing. The method uses an optical arrangement that records changes in fluorescence intensity at a fixed viewing angle as a function of the angle of incidence of an excitation lig...

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Bibliographic Details
Published in:Applied optics (2004) 2023-03, Vol.62 (8), p.C106
Main Authors: Reyes-Alberto, Miguel, García-Valenzuela, Augusto, Gutierrez-Herrera, Enoch
Format: Article
Language:English
Subjects:
Absorption spectra
Anisotropy
Emission analysis
Emissions control
Excitation
Fluorescence
Incidence angle
Light beams
Measurement methods
Polymer films
Rhodamine 6G
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Summary:We propose and test a method for determining a fluorescent medium's absorption or extinction index while it is fluorescing. The method uses an optical arrangement that records changes in fluorescence intensity at a fixed viewing angle as a function of the angle of incidence of an excitation light beam. We tested the proposed method on polymeric films doped with Rhodamine 6G (R6G). We found a strong anisotropy in the fluorescence emission and, thus, limited the method to TE-polarized excitation light. The method proposed is model dependent, and we provide a simplified model for its use in this work. We report the extinction index of the fluorescing samples at a selected wavelength within the emission band of the fluorophore R6G. We found that the extinction index at the emission wavelengths in our samples is appreciably larger than the extinction index at the excitation wavelength, which is the opposite of what one might expect from measuring the absorption spectrum of the medium with a spectrofluorometer. The proposed method could be applied to fluorescent media with additional absorption other than by the fluorophore.
ISSN:1559-128X
2155-3165
DOI:10.1364/AO.478433