Raman Spectroscopy

General Introduction to Raman Spectroscopy

Raman spectroscopy directly probes the vibrational and rotational states of a molecule via scattering from a molecule of merely one photon in a million. Unlike infrared spectroscopy, no sample preparation is required, nor is there interference due to water content in the sample. Samples can be analyzed against a library in the field using non-destructive, point-and-click instruments.

For this reason, Raman spectroscopy has become a popular technique for identification and analysis in diverse fields like process and pharmaceuticals, explosives detection, semiconductor processing quality control, and biotechnology. It is also used in many fields of research, including carbon nanomaterials.

The high power of the excitation laser and extremely low signal levels generated require optical filters with high efficiency and high laser damage threshold. Longpass detection filters with steep edges offer more Raman spectral information than low-cost filters, while high quality shortpass filters offer the broad passbands needed for useful anti-Stokes spectra to be acquired.

High Performance Raman Spectroscopy

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Raman spectroscopy allows for the detection and identification of molecules through their unique vibrational and rotational energy level structure. As opposed to fluorescence methods, which require the addition of a separate fluorescing molecule as a “tag” attached to the actual molecule of interest, Raman spectroscopy allows direct detection of a molecule with no chemical alteration. Another important difference, however, is that the scattered Raman signal (as a percentage of the excitation power) is several orders-of-magnitude weaker than the corresponding fluorescence signal. Because of this, lasers are typically used as excitation sources to provide high power in a tightly focused spot, and very sensitive detectors are used to detect the very faint signal. Excellent filtering is therefore essential to block the very intense laser light while still allowing high transmission of the slightly wavelength-shifted Raman scattered signal.

SNIOE provides the widest selection of Raman-spectroscopy 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, yet are less than half the price.  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 both single-notch filters and multi-notch filters, which block one or more laser line while transmitting light on both sides.  For the most discriminating Raman measurements, eliminate laser spectral noise leakage by cleaning up your laser spectrum with a matched laser clean-up filter