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Proceedings Paper

Fluorescence advantages with microscopic spatiotemporal control
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Paper Abstract

We present a clever design concept of using femtosecond laser pulses in microscopy by selective excitation or de-excitation of one fluorophore over the other overlapping one. Using either a simple pair of femtosecond pulses with variable delay or using a train of laser pulses at 20-50 Giga-Hertz excitation, we show controlled fluorescence excitation or suppression of one of the fluorophores with respect to the other through wave-packet interference, an effect that prevails even after the fluorophore coherence timescale. Such an approach can be used both under the single-photon excitation as well as in the multi-photon excitation conditions resulting in effective higher spatial resolution. Such high spatial resolution advantage with broadband-pulsed excitation is of immense benefit to multi-photon microscopy and can also be an effective detection scheme for trapped nanoparticles with near-infrared light. Such sub-diffraction limit trapping of nanoparticles is challenging and a two-photon fluorescence diagnostics allows a direct observation of a single nanoparticle in a femtosecond high-repetition rate laser trap, which promises new directions to spectroscopy at the single molecule level in solution. The gigantic peak power of femtosecond laser pulses at high repetition rate, even at low average powers, provide huge instantaneous gradient force that most effectively result in a stable optical trap for spatial control at sub-diffraction limit. Such studies have also enabled us to explore simultaneous control of internal and external degrees of freedom that require coupling of various control parameters to result in spatiotemporal control, which promises to be a versatile tool for the microscopic world.

Paper Details

Date Published: 13 March 2013
PDF: 9 pages
Proc. SPIE 8573, Design and Quality for Biomedical Technologies VI, 857302 (13 March 2013); doi: 10.1117/12.2009500
Show Author Affiliations
Debabrata Goswami, Indian Institute of Technology Kanpur (India)
Debjit Roy, Indian Institute of Technology Kanpur (India)
Arijit K. De, Indian Institute of Technology Kanpur (India)

Published in SPIE Proceedings Vol. 8573:
Design and Quality for Biomedical Technologies VI
Ramesh Raghavachari; Rongguang Liang, Editor(s)

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