In Raman spectroscopy applications, intense laser beams are 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 all undesired light from reaching the spectrometer.
Our RazorEdge filters provide the widest selection of Raman-spectroscopy grade edge filters available, with edge wavelengths from 224 to 1550 nm. These filters are so steep and highly transmitting that they out-perform even the leading holographic notch filters. Now you can see the weakest signals closer to the laser line than you ever have before. With their deep laser-line blocking, ultra-wide and low-ripple passbands, proven hard-coating reliability, and high laser damage threshold, they offer performance that lasts.
For preventing laser light from reaching the detector and drowning out the relatively weak Raman signal, we offer a collection of StopLine filters, both single-notch and multi-notch filters, which block one or more laser line while transmitting light on both sides. For the most discriminating Raman measurements, you can eliminate laser spectral noise leakage by cleaning up your laser spectrum with a matched MaxLine™ laser clean-up filter
The general layout is like this; Laser transmitting filters inserted between the laser and the sample block all undesired light from the laser. Laser blocking filters inserted between the sample and the spectrometer block the Rayleigh scattered light at the laser wavelength. There are four basic types of filters to choose from: long-wave-pass edge filters, short-wave-pass edge filters, notch filters and laser-line filters. Laser-line filters are an obvious choice as laser transmitting filters, and notch filters and edge filters can both be used as laser blocking filters.
Which one to choose depends on the application, for example if both Stokes and Anti-Stokes Raman scattering should be measured simultaneously, or if the steepest possible edge for looking at the smallest Stokes shifts is desired.
However, in many high-performance Raman systems – such as those with microscopic imaging capabilities or highly sensitive remote probes –complex focusing and collection optics are used to couple the system to the sample region. For these systems it is desirable for the excitation laser beam and the Raman-shifted signal light to share a common light path, and this is done by a BrightLine dichroic beamsplitter.