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Journal of Biomedical Optics

Dual closed-loop, optoelectronic, auto-oscillatory detection circuit for monitoring fluorescence lifetime-based chemical sensors and biosensors
Author(s): Emmanuel M. Rabinovich; Tengiz Sviminoshvilli; Michael J. O'Brien; Steven Roy Julien Brueck; Gabriel P. Lopez
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Paper Abstract

We present a new detection instrument for sensor measurements based on excited-state fluorescence lifetimes. This system consists of a primary optoelectronic loop containing a resonance-type rf amplifier, a modulatable fluorescence-excitation light source, a fiber optic feedback loop (with a gap for a fluorescent sensor), and a photomultiplier tube. A secondary, phase-feedback optoelectronic circuit consists of a long-wavelength-pass optical filter, a second photomultiplier tube, a photodiode, an electronic phase detector, a dc amplifier, and an electronic phase shifter (inserted into the main loop). This phase-feedback circuit is new with respect to our previous work. Under the appropriate conditions, the main loop exhibits self-oscillations, manifesting themselves as sinusoidal rf modulation of light intensity. The phase-feedback circuit detects the modulation phase shift resulting from the finite excited-state lifetimes of a fluorophore. As the excited state lifetime changes, the phase shift from the electronic phase shifter also changes, which results in a shift in self-oscillation frequency. The detection system uses self-oscillation frequency as the detection parameter and has excellent resolution with respect to changes in excited-state lifetime (~1 ps).

Paper Details

Date Published: 1 May 2004
PDF: 9 pages
J. Biomed. Opt. 9(3) doi: 10.1117/1.1688814
Published in: Journal of Biomedical Optics Volume 9, Issue 3
Show Author Affiliations
Emmanuel M. Rabinovich, Univ. of New Mexico (United States)
Tengiz Sviminoshvilli, Univ. of New Mexico (United States)
Michael J. O'Brien, Univ. of New Mexico (United States)
Steven Roy Julien Brueck, CHTM/Univ. of New Mexico (United States)
Gabriel P. Lopez, Univ. of New Mexico (United States)

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