Use of multi-notch filter for simultaneous recording of stokes and anti-Stokes Raman signals close to the exciting line

• Published in: Journal of Raman spectroscopy Vol. 30; no. 9; pp. 745 - 755
• Main Authors: Barbillat, Jacques, Roussel, Bernard, Da Silva, Edouard
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.09.1999
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/(SICI)1097-4555(199909)30:9<745::AID-JRS422>3.0.CO;2-7

An optical prefilter called Xtranotch, incorporating multiple holographic notch filters (or more generally Bragg diffraction notch filters) has been designed to record, with a single‐stage spectrograph, both Stokes and anti‐Stokes regions of the Raman spectrum simultaneously, with the smallest possible blind region around the Rayleigh line compatible with the best performance of current supernotch holographic filters. Thus, with this arrangement it is possible to observe simultaneously low‐wavenumber Raman lines down to ca 28 cm−1 on each side of the Rayleigh line together with a high signal throughput along the entire spectrum. Optical alignment of this multi‐notch filter is made easier owing to the use of a mechanical system which compensates for the beam deviation occurring when Bragg diffraction notch filters are rotated. Better laser line rejection can also be obtained by replacing one of the holographic notch filters by a more efficient grating filter but at the expense of throughput in the low‐wavenumber region. Copyright © 1999 John Wiley & Sons, Ltd.