I’ve previously explained why my laser is useless for Raman spectroscopy. To briefly reiterate the problem; it’s not a single frequency laser. It was simply too cheap for that.
It is entirely possible to construct a single frequency laser from relatively cheap laser diodes and a diffraction grating. There are many excellent instructions around including this open access article.¹
However, it quickly becomes apparent that there’s a reason for the hefty pricetags of nice slm lasers. For starters a diffraction grating is not inexpensive – I know, I already bought one. Then there’s controlling the temperature of the diode, and maybe also an optical feedback – because constant current is not enough.
Oh, and you also need to be able to verify that whatever you end up putting together is indeed lasing in single longitudinal mode, so throw in time and money to make your own Fabry-Perot interferometer as well.
I don’t know the translation for the danish expression for almost cheating, but Indiana Jones sums it up nicely:
I decided my life would be better spent if I simply bought a used lab laser, and here it is:
I love pictures, so here it is from a second angle:
It came with all the extra optics you see in the photo and a nice ½” thick piece aluminium, that I will probably anodize black and use as base in the spectrograph, that will hopefully be ready in the not-to-far future..
¹ Construction and Characterization of External Cavity Diode Lasers for Atomic Physics
Hardman, K. S., Bennetts, S., Debs, J. E., Kuhn, C. C. N., McDonald, G. D., Robins, N. J. Vis. Exp. (86), e51184 (2014)