[OPTICAL REVIEW Vol. 10, No. 1 (2003) 31-37]
© 2003 The Optical Society of Japan

Proposal for Fourier-Transform Phase-Modulation Fluorometer

Tetsuo IWATA*

Department of Mechanical Engineering, Faculty of Engineering, University of Tokushima, Minami-Jyosanjimacho-2, Tokushima 770-8506, Japan

(Received October 2, 2002; Accepted November 5, 2002)

I propose a concept of a novel Fourier-transform phase-modulation fluorometer by which a fluorescence decay waveform can be obtained. In the fluorometer, the modulation frequency of the excitation light source is swept continuously from a start frequency fmin to an end frequency fmax with a time duration T. The resultant fluorescence signal waveform is Fourier-transformed to obtain amplitude and phase spectra. The ratio of the amplitude spectrum and the difference of the phase spectrum over those of the reference spectra that are obtained from a non-fluorescent material are calculated, respectively, and the pair of both spectral data is inverse-Fourier-transformed again to obtain the fluorescence decay waveform. To verify and demonstrate the effectiveness of the concept, I carried out (1) numerical simulations, (2) determination of a time constant of a passive resistor-capacitor (RC) differential circuit, and (3) measurement of a fluorescent decay waveform of YAG materials packed in Nichia’s white LED.

Key words: Fourier-transform phase-modulation fluorometer, fluorescence lifetime, multi-component, instrumentation