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Monitoring of Orientation in Molecular Ensembles by Polarization Sensitive Nonlinear Microscopy

Veronique Le Floc'h·Sophie Brasselet·Jean-Francois Roch·Joseph Zyss
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Abstract

We present high resolution two-photon excitation microscopy studies combining two-photon fluorescence (TPF) and second harmonic generation (SHG) in order to probe orientational distributions of molecular ensembles at room temperature. A detailed polarization analysis of TPF and SHG signals is used in order to unravel the parameters of the molecular orientational statistical distribution, using a technique which can be extended and generalized to a broad variety of molecular arrangements. A polymer film containing molecules active for TPF and/or SHG emission is studied as a model system. Polarized TPF is shown to provide information on specific properties pertaining to incoherent emission in molecular media, such as excitation transfer. SHG, being highly sensitive to a slight departure from centrosymmetry such as induced by an external electric field in the medium, complements TPF. The response of each signal to a variable excitation polarization allows investigation of molecular behavior in complex environments which affect their orientations and interactions.

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Veronique Le Floc'h, Sophie Brasselet, Jean-Francois Roch, Joseph Zyss. 2003-07-29. Monitoring of Orientation in Molecular Ensembles by Polarization Sensitive Nonlinear Microscopy. https://arxiv.org/abs/cond-mat/0307708

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