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Ultrafast Raman loss spectroscopy (URLS): instrumentation and principle

Authors


  • This article is part of the Journal of Raman Spectroscopy special issue entitled “Proceedings of the 9th European Conference on Nonlinear Optical Spectroscopy (ECONOS), Bremen, Germany, June 21–23, 2010” edited by Peter Radi, PSI, Villigen, Switzerland, and Arnulf Materny, Jacobs University, Bremen, Germany.

Abstract

In this paper, we report on the concept and the design principle of ultrafast Raman loss spectroscopy (URLS) as a structure-elucidating tool. URLS is an analogue of stimulated Raman scattering (SRS) but more sensitive than SRS with better signal-to-noise ratio. It involves the interaction of two laser sources, namely, a picosecond (ps) Raman pump pulse and a white-light (WL) continuum, with a sample, leading to the generation of loss signals on the higher energy (blue) side with respect to the wavelength of the Raman pump unlike the gain signal observed on the lower energy (red) side in SRS. These loss signals are at least 1.5 times more intense than the SRS signals. An experimental study providing an insight into the origin of this extra intensity in URLS as compared to SRS is reported. Furthermore, the very requirement of the experimental protocol for the signal detection to be on the higher energy side by design eliminates the interference from fluorescence, which appears on the red side. Unlike CARS, URLS signals are not precluded by the non-resonant background and, being a self-phase-matched process, URLS is experimentally easier. Copyright © 2011 John Wiley & Sons, Ltd.

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