Optoelectronic closed loop auto-oscillator for fluorescence lifetime detection: A new fluorimetry technique with applications to chemical/biosensors
We present a new approach to excited state fluorescence lifetime-based measurements which is inexpensive and highly sensitive. The detection system consists of a closed-loop optoelectronic arrangement containing an intermediate frequency resonance amplifier, a fluorescence excitation light source (for example, a light emitting diode or a semiconductor laser), a fiber optic delay line, and a photodetector. The system exhibits self-oscillations in the vicinity of the frequency Ω∼l/τ (where τ is the excited state lifetime) which manifest themselves as modulation of the light. Changes in the excited state lifetime alter the phase delay of the loop, which in turn causes a frequency shift in the modulation signal. The frequency shift can be measured very precisely with a frequency counter. With appropriate averaging, this technique can yield subpicosecond resolution of shifts in lifetime. This technique is suited for chemical/biological sensing applications, and can be easily duplicated for chemical/biological sensor arrays.
II, MJO; Rabinovich, E; Svimonishvilli, T; Brueck, SRJ; Lopez, GP
Proceedings of SPIE - The International Society for Optical Engineering
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