First attempt at DIY Raman Spectrometry

For the past couple weeks I have been working on my (super-budget) Raman Spectrometer. Last night I finally (maybe) got a spectral image. First let me talk about my set up. My goal is to make a handheld Raman spectrometer so I can analyze samples while I am out in the field. Eventually I wish to build something similar to this: http://bwtek.com/products/nanoram/

This is the fist time I have built something like this and I do not know much about the process of actually processing digital data, but it will be a learning experience I guess.

In my spectrometer I am using a 532 nm green laser pointer with 5mW of output power. The light travels to a 50/50 beam splitter. My beam then travels up to a microscope objective and focused on a sample. In my first test this was Polystyrene foam. The Raman signal travels back through the objective lens through the beam splitter again and into a 550 nm longpass filter form Throbs. The raman signal then travels though a small gemology diffraction grating spectrometer which I picked up on eBay for about $30. Underneath the spectrometer I placed my phone (Samsung galaxy S3).



With the lights turned off I then took several spectra photos. Each of the photos were taken with ISO 1600 focused at inf and a 60 second exposure. The first one with light shining down from above the longpass filter. I think some light leaked by the filter because I was not holding the led flashlight directly above the spectroscope.




As you can see though there is a a sharp intensity drop at at about 550 nm beaning that the filter was working. I do not know why there is a second image to the right of the spectrum but I expect it was because I was not holding the flashlight directly vertical to the spectrometer.

The next image I took with the flashlight directly above the objective. I got an overexposed image because the light coming back was far too intense, but again there is a nice sharp cut off if it wasn't for the glair.



It was then time to take the image of the polystyrene. With the same camera settings and conditions I turned on the laser. At first I thought that I wasn't getting any image, but after a minute I found this on my camera.



It is incredibly weak and there are no well defined peaks but there is something there. I am going to put my images through photoshop and see if I can figure out what frequencies the image is displaying and see if it resembles anything close to polystyrene.