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Depth Profiling In Diffusely Scattering Media Using Raman Spectroscopy And Picosecond Kerr Gating.

Matousek, P, Everall, N, Towrie, M and PARKER, AW 2005, 'Depth Profiling In Diffusely Scattering Media Using Raman Spectroscopy And Picosecond Kerr Gating.' , Applied Spectroscopy, 59 (2) , pp. 200-205.

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Abstract

We demonstrate how pulsed laser Raman excitation (approximately 1 ps) followed by fast optical Kerr gating (approximately 4 ps) can be used to effectively separate Raman signals originating from different depths in heterogeneous diffusely scattering media. The diffuse scattering slows down photon propagation through turbid samples enabling higher depth resolution than would be obtained for a given instrumental time resolution in an optically transparent medium. Two types of experiments on two-layer systems demonstrate the ability to differentiate between surface and sub-surface Raman signals. A Raman spectrum was obtained of stilbene powder buried beneath a 1 mm over-layer of PMMA (poly(methyl methacrylate)) powder. The signal contrasts of the lower stilbene layer and upper PMMA layer were improved by factors >or=5 and >or=180, respectively, by rejecting the Raman component of the counterpart layer. The ability to select the Raman signal of a thin top surface layer in preference to those from an underlying diffusely scattering substrate was demonstrated using a 100 mum thick optically transparent film of PET (poly(ethylene terephthalate)) on top of stilbene powder. The gating resulted in the suppression of the underlying stilbene Raman signal by a factor of 1200. The experiments were performed in back-scattering geometry using 400 nm excitation wavelength. The experimental technique should be well suited to biomedical applications such as disease diagnosis.

Item Type: Article
Themes: Subjects / Themes > Q Science > Q Science (General)
Subjects outside of the University Themes
Schools: Colleges and Schools > College of Science & Technology
Colleges and Schools > College of Science & Technology > School of Environment and Life Sciences
Journal or Publication Title: Applied Spectroscopy
Publisher: Society for Applied Spectroscopy
Refereed: Yes
ISSN: 0003-7028
Depositing User: H Kenna
Date Deposited: 10 Aug 2007 14:49
Last Modified: 20 Aug 2013 16:46
URI: http://usir.salford.ac.uk/id/eprint/246

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