The most commonly used wavelength in Raman spectroscopy is 785 nm. It offers the best balance between scattering efficiency, influence of fluorescence, detector efficiency and availability of cost-efficient and compact, high-quality laser sources. To understand more on how the choice of wavelength can affect the Raman spectroscopy measurements, see our post on How to choose lasers for Raman Spectroscopy. In this post, we introduce the different laser technologies available at 785 nm and discuss how the different technologies perform in relation to the critical performance specifications to consider when selecting lasers for Raman spectroscopy.

Laser performance parameters

There is a number of different kinds of lasers available at 785 nm. They offer different performance and cost characteristics, which means a careful selection can be important to find the best solution for a particular Raman spectroscopy set-up.

Critical performance parameters are:

  1. Spectral bandwidth
    • This should be less than a few 10s of pm in order not to limit the resolution of the system. In some high resolutions applications a linewidth of much less than that can be required
  2. Spectral purity (or side-mode suppression ration – SMSR):
    • Of the illumination source should be at least better than 60 dB in the spectral region where Raman peaks are to be detected
  3. Wavelength stability:
    • Must be low, in the order of few pm, both over time and temperature in order not to limit the resolution of the system
  4. Mode:
    • For high resolution imaging applicat