The (likely?) cheapest home-made Michelson interferometer

Summary

The (likely?) cheapest home-made Michelson interferometer Posted 2026-01-04 Lately, I’ve been really into 3D printing along with asking myself what we can do with this technology now that it’s become, well, a technology. (At least, in the “this is a thing that can now be used, is robust, and is generally accessible to many people” sense of technology.) The first thing to print on a 3D printer is obviously another 3D printer, but, barring that, I started to ask myself what would be an interesting thing to print that would make some use of my previous fun experiences in photonics. One might ask, “why photonics?” but the quick tl;dr is that most off-the-shelf pieces of optomechanical equipment are very expensive. (Also, messing around with lasers is cool.) So I gave myself the very basic challenge of building a Michelson interferometer with a very tiny budget along things I could easily get off of Amazon. (And a 3D printer, of course.) As a quick taste of the end result, below is a simple render of the final CAD assembly, along with the print and complete running set up. A picture of the build: Running the actual interferometer after some basic alignment: The output of the interferometer, after adjusting for exposure: I will at some point put this up on Thingiverse or Printables but this’ll do for now. All of the CAD for this project was done in Python using build123d and the designs + step files are available on my Github CAD page. What is a Michelson interferometer? I won’t get too into the details, but the high-level idea of a Michelson interferometer1 is that it is a device for measuring very tiny changes in distance of a specific “arm” of the interferometer by using constructive and destructive interference.2 The rough layout looks like this: ┌ ─ ─ ─ ─ ─ Mirror 2 │ └ ─ ─ ─ ─ ─ ┌──────────────────────┐ │ │ └──────────────────────┘ ▲│ ││ ┌───┐ ││ │ │ ││ ┌─┐ │ │ ││ │█│ │ │ ┌──┼┼─┐ │█│ │ │ │╲ ││ │ │█│ ┌ ─ ─ ─ ─ ─ ─ ─ ┐ ┌ ─ ─ ─ ─ ─ │ │─────────────┼▶╲│▼─┼────────────▶│...