Raman spectroscopy is a technique in which light from a laser interacts with a sample to shift the laser wavelength. Recording the shifts with a spectrometer gives information about the sample. We’ve covered general cheap spectroscopy more than once here.
OpenRAMAN is a project to assemble a Raman spectroscopy setup using about $3000 in (mostly ThorLab) equipment, with a thorough set of assembly instructions along with pictures. A bill of materials, part drawings, and STEP files are available here. The project is separated into two sections, one for the device and the other for the cuvette.
There is a lot of discussion about the device in a blog style manner, as well as a lot of data of the devices performance. The creator of OpenRAMAN has an entire website of similar posts including other DIY projects.