In Raman spectroscopy applications, a laser beam is used to create Raman scattered light from a sample under test. The Raman 'finger print' is measured by a spectrometer. Optical filters are critical components in Raman spectroscopy systems to prevent undesired light from reaching the spectrometer.
There are four basic types of filters to choose from: LPF (long pass) edge filters, SPF (short pass) edge filters, notch filters and laser-line filters. Laser-line filters are an obvious choice as laser transmitting filters, and notch and edge filters can both be used as laser blocking filters. Which one you choose depends on the application. If both stokes and anti-stokes Raman scattering should be measured simultaneously one would choose a notch; if we are looking at the smallest stokes shifts, one would choose a steep edge filter.
Iridian Spectral Technologies offers the steepest edge pass filter on the market. For a regular edge pass filter, the Raman shift goes from 100 to 50cm-1.
If you wish to see stokes and anti-stokes at the same time, the notches offer a very good solution.
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Iridian Spectral Technologies Ltd.is based in Ottawa, ON, Canada. www.iridian.ca