The Michelson Interferometer

This is a demonstration of the sensitivity of the Michelson Interferometer for the members of the LaserCommunity forum. A Michelson Interferometer is made by splitting a laser-beam. Bounce each beam from a mirror and back into the beam-splitter to recombine those two beams. They will cause interference patterns in the resultant beam. Project this beam through a diverging lens and onto a wall or a screen to see the patterns more clearly. They are usually used for detecting very small movements or vibrations, especially during the setup of a holography bench. They will also show the instability in the frequency of a laser. This type of interferometer will register movements of less than 1 tenth of the wavelength of the light being used. In this case, I am using 532nm and should be able to detect a movement of less than 50nm. It's sensitive enough to show the vibrations from my wife in the kitchen or walking across the floor some 5 or more metres away. It will even show the tiny vibrations from a little fluffy toy dropped from only a couple of inches onto the table where the interferometer is set up. If I was to be making holograms, each time you see those fringes (the technical term for the green stripes) move, that would equate to a ruined hologram exposure. The hardest part about setting one of these up is the alignment of the co-incident beams. It's very tricky to line up the two beams so that they exit the beam-splitter together. I'm not using an optical bench, the mirrors and lens are simply stuck down with blutac and were adjusted by hand.