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Raman spectroscopy relies on the inelastic scattering of photons. The laser light interacts with molecular vibrations within a molecule, which shifts the energy of the light up and down, which alters the spectra of the returned light. Thus, creating a spectra of light, which is the signature of the molecule. However, the amount of light returned from inelastic scatter is very low compared with Rayleigh scattered light. In addition, for many materials the fluorescence that is induced in the material by the laser light swamps out the light from the inelastic scatter. Therefore, choosing the optimal wavelength to minimize fluorescence and maximize the signal from the molecules is critical in creating an effective Raman system. In addition, with the increasing emergence of spontaneous and enhanced Raman spectroscopy, creating an optimized laser source becomes progressively more important. Single-mode operation allows higher precision through your optical train.
Many Raman applications utilize 785, 830, and 1064 nm. Wavelengths in the NIR range are best for fluorescence suppression. Sheaumann has high-power, single-mode TO-Can and Butterfly packages that deliver reliable, continuous-wave power and best-in-class spectral performance at these critical wavelengths.
Excitation with this wavelength results in a high signal-to-noise ratio and provides excellent spectral resolution with lower power draw. The sensitivity of Raman at 785 nm also means that lower laser powers can be used, thus protecting sensitive samples from destruction. 785 nm also provides weaker fluorescence than 532 nm
Fluorescence suppression with less risk to sample compared to 1064nm.
In some applications, it may be preferable to use 1064nm excitation instead of the more traditional 785nm excitation in order to reduce fluorescence, thereby improving the Raman spectral quality and specificity.
Sheaumann can fabricate single-mode fiber packages that can include polarization-maintaining (PM) fiber and wavelength locked packages based on fiber Bragg gratings (FBG). This new internal capability is the result of bringing online new high precision fiber aligners that can align to the tight tolerances required for 5-micron core single-mode fiber. These single-mode packages are perfect for Raman or any other applications, where locking the wavelength to a few nanometers is crucial.
Sheaumann supports companies in providing a high degree of flexibility in choosing their optimal wavelength. We can create custom packages at a range of wavelengths from 780 to 1070 nm. Our ability to tailor products to meet specific needs helps mitigate common risks associated with Raman Spectroscopy. Plus, our new capability in locking the wavelength of the laser will make for very effective packages that create the best signal-to-noise ratio.