Measurements of nonlinear refractive index in scattering media.

Loading...
Thumbnail Image

Date

2010-06-07

Journal Title

Journal ISSN

Volume Title

Repository Usage Stats

480
views
806
downloads

Abstract

We have recently developed a spectral re-shaping technique to simultaneously measure nonlinear refractive index and nonlinear absorption. In this technique, the information about the nonlinearities is encoded in the frequency domain, rather than in the spatial domain as in the conventional Z-scan method. Here we show that frequency encoding is much more robust with respect to scattering. We compare spectral re-shaping and Z-scan measurements in a highly scattering environment and show that reliable spectral re-shaping measurements can be performed even in a regime that precludes standard Z-scans.

Department

Description

Provenance

Subjects

Citation

Scholars@Duke

Warren

Warren S. Warren

James B. Duke Distinguished Professor of Chemistry

Our work focuses on the design and application of what might best be called novel pulsed techniques, using controlled radiation fields to alter dynamics. The heart of the work is chemical physics, and most of what we do is ultrafast laser spectroscopy or nuclear magnetic resonance. It generally involves an intimate mixture of theory and experiment: recent publications are roughly an equal mix of pencil- and-paper theory, computer calculations with our workstations, and experiments. Collaborations also play an important role, particularly for medical applications.

Fischer

Martin Fischer

Research Professor in the Department of Chemistry

Dr. Fischer’s research focuses on exploring novel nonlinear optical contrast mechanisms for molecular imaging. Nonlinear optical microscopes can provide non-invasive, high-resolution, 3-dimensional images even in highly scattering environments such as biological tissue. Established contrast mechanisms, such as two-photon fluorescence or harmonic generation, can image a range of targets (such as autofluorescent markers or some connective tissue structure), but many of the most molecularly specific nonlinear interactions are harder to measure with power levels one might be willing to put on tissue. In order to use these previously inaccessible interactions as structural and molecular image contrasts we are developing ultrafast laser pulse shaping and pulse shape detection methods that dramatically enhance measurement sensitivity. Applications of these microscopy methods range from imaging biological tissue (mapping structure, endogenous tissue markers, or exogenous contrast agents) to characterization of nanomaterials (such as graphene and gold nanoparticles). The molecular contrast mechanisms we originally developed for biomedical imaging also provide pigment-specific signatures for paints used in historic artwork. Recently we have demonstrated that we can noninvasively image paint layers in historic paintings and we are currently developing microscopy techniques for use in art conservation and conservation science.

Dr. Fischer is also the director of the Advanced Light Imaging and Spectroscopy (ALIS) facility at Duke University.


Unless otherwise indicated, scholarly articles published by Duke faculty members are made available here with a CC-BY-NC (Creative Commons Attribution Non-Commercial) license, as enabled by the Duke Open Access Policy. If you wish to use the materials in ways not already permitted under CC-BY-NC, please consult the copyright owner. Other materials are made available here through the author’s grant of a non-exclusive license to make their work openly accessible.