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Proceedings Paper

Stimulated emission depletion following two photon excitation
Author(s): Richard Marsh; Daven Armoogum; Angus J. Bain
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Paper Abstract

The technique of stimulated emission depletion of fluorescence (STED) from a two photon excited molecular population is demonstrated in the S1 excited state of fluorescein in ethylene glycol and methanol. Two photon excitation (pump) is achieved using the partial output of a regeneratively amplified Ti:Sapphire laser in conjunction with an optical parametric amplifier whose tuneable output provides a synchronous depletion (dump) pulse. Time resolved fluorescence intensity and anisotropy measurements of the fluorescein emission are made using picosecond time-correlated single photon counting. Pump-dump time delayed fluorescence intensity measurements are used to characterise the response of the system and to provide additional data on saturation dynamics of the dump transition. Two photon STED is modelled using both approximate analytical techniques in the weak dump limit and by numerical solutions to the appropriate rate equations. The latter are used to fit experimental data from which it is possible to determine the cross-section for the stimulated transition and lifetime of the upper vibrational levels of the ground state.

Paper Details

Date Published: 1 November 2002
PDF: 10 pages
Proc. SPIE 4812, Nonlinear Spectroscopy, (1 November 2002); doi: 10.1117/12.451385
Show Author Affiliations
Richard Marsh, Univ. College London (United Kingdom)
Daven Armoogum, Univ. College London (United Kingdom)
Angus J. Bain, Univ. College London (United Kingdom)

Published in SPIE Proceedings Vol. 4812:
Nonlinear Spectroscopy
David L. Andrews, Editor(s)

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