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Elimination of two-photon excited fluorescence using a single-beam coherent anti-Stokes Raman scattering setup

Authors

  • Alexander Wipfler,

  • Jean Rehbinder,

  • Tiago Buckup,

  • Marcus Motzkus

    Corresponding author
    1. Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg, Germany
    • Correspondence to: Marcus Motzkus, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany.

      E-mail: marcus.motzkus@pci.uni-heidelberg.de

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  • This article is from the ECONOS part of the joint special issue on the European Conference on Nonlinear Optical Spectroscopy (ECONOS 2012) with Guest Editors Johannes Kiefer and Peter Radi and the II Italian Conference of the National Group of Raman Spectroscopy and Non-Linear Effects (GISR 2012) with Guest Editor Maria Grazia Giorgini.

Abstract

In this report, we demonstrate how to obtain Raman spectra from single-beam CARS measurements under the condition of strong overlapping two-photon excited fluorescence (2PEF). Our approach is based on the use of a narrowband phase gate implemented via femtosecond laser pulse shaping from a single broadband laser source, without any use of polarization or amplitude modulation. The decisive quantity regarding the creation of 2PEF with shaped laser pulses is the second harmonic power spectrum, which shows a different dependence on the excitation phase from the CARS signal generation. By shifting the phase or the position of the gate in an appropriate way, it is possible to keep the second harmonic power spectrum and 2PEF constant, paving the way for an elimination of it. This allows to reconstruct the Raman signal and to retrieve quantitative information of resonances even when the fluorescence is about 160 times larger than the CARS signal. Copyright © 2013 John Wiley & Sons, Ltd.

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