532nm laser. This is a cheap green laser, good as it avoids fluorescence common at shorter wavelengths (e.g. 400nm violet) but still gives strong Raman signals.
These then need cleaning up, using a bandpass filter, E.g. there's dirt or something in the laser which causes it to emit at other frequencies.
Some research is needed into suitable light sources:
The comments here https://publiclab.org/notes/emontoya57/12-16-2015/a-homemade-cost-effective-raman-spectrometer-with-high-performance Suggest the following:
532nm laser. This is a cheap green laser, good as it avoids fluorescence common at shorter wavelengths (e.g. 400nm violet) but still gives strong Raman signals. These then need cleaning up, using a bandpass filter, E.g. there's dirt or something in the laser which causes it to emit at other frequencies.
Potential filter https://www.newport.com/f/laser-line-filters £100?