@mullermuttu It's a PIN photodiode with preamp from Hamamatsu, S6468 series https://docs.rs-online.com/fbe9/0900766b80870611.pdf

Hi, any recommendations on the mirrors / beamsplitter? 

Hi, this is great! I also have a project to build an interferometric vibrometer that I began yesterday here: https://hackaday.io/project/19247-laser-interferometric-vibrometer

Its based on self mixing topology as opposed to the classical Michelson appoach which would allow smaller volume occupied by the setup as opposed to a lab setup.

I can see you connected your photodiode to the mic input of your soundcard. Is this right? Did you use a transimpedance amp in between the soundcard and the photodiode by any chance?

Hi! Thanks for sharing your project, I'll follow it! Yes it's right, I connected my photodiode directly to the mic input of my sound card. I didn't use a transimpedence amp because there is already a pretty good one in the chip of the photodiode (preamp) http://www.ebay.com/itm/-/201061866496?ssPageName=ADME:L:OC:CA:3160 . I was just too lazy to build my own high-frequency amplification circuit, and it lets you connect a scope probe directly on it which reduces noise exposure (and the voltage is in the range of 0-500mV which is ok to plug directly in a sound card too)

Hey very interesting project. I am curious to know about the detector used. The link given above is broken. Can you tell more about detector? @Frédérik Berthiaume