Simple Michelson Interferometer Setup

A simple Michelsons Interferometer setup designed such that a highschool teacher could recreate the setup and get similar results. Furthermore, the setup fits inside the budget such a teacher would have and can then easily be taken apart after usage.

Materials:

1. Mounts
2. Any color PLA filament. Have enough for all mounts used in the setup.
3. 10 x Screws, 2 - 4mm. A minimum of 2 screws per mount, but all mounts were made with 4 screw holes.
4. 4 x M4 nuts, 35mm
5. 4 x M4 bolts, 35mm
6. 1 x 0.7x7x20mm, 4.67LBF/IN spring
7. 1 x 0.65x7x15mm, 5.68LBF/IN spring
8. 1 x 0.5x6x15mm, 2.3LBF/IN spring
9. 1 x 0.65x7x25mm, 3.41LBF/IN spring
10. Components for mounts
11. 1 x Beamsplitter/Half mirror, 70x35x3mm
12. 2 x Normal mirror, 70x35x3mm
13. 1 x Convex lens
14. 1 x Class 2, 650nm laser pointer. Because this setup was designed for a highschool teacher to be able to recreate, a laser of a higher class than 2 cannot be used.
15. Inner tube. Exact diamater is not important, as long as it fits under the plank without leaving too much extra space. The thinkness
16. Mounting plank
17. 1 x MDF plank, 400x400mm . The plank does not need to be these exact measurements, but the setup must be able to fit. An MDF plank was used for ease of screwing the components onto it, but other (cheap) soft woods can be used.
18. Arduino circuit
19. 1 x Bread board
20. 1 x Arduino UNO board
21. Solid core wires (Optional: pre-cut solid core wires)
22. 1 x Tactile push-button switch. Other switches can be used or the laser can be manually disconnected from the circuit.

Tools:

1. Screwdriver, flat top or cross slot depending on which scews you use.
2. Wire stripper, if your wires are not pre-cut
3. Hex key

Software:

1. Any 3D-printing and splicing software

All models shown were printed with the standard infill settings and all models were sliced with the same colour settings.

The large and small mirror holder mounts still need some assembly before they can be used. Both mounts come with a pair of boxes with a slit at the top. Fit a M4 nut into each of these slits. These slitted boxes also have a hole, following where the hole is pointing you will find another part of the mount also with a hole. The M4 bolt must go through this hole to be screwed with the nut placed earlier.

For the large mount you need the 0.7x7x20mm, 4.67LBF/IN and 0.65x7x25mm, 3.41LBF/IN springs. Place the larger spring between the holes where the mirror will be then screw the bolt in the nut, whilst threading it through the spring. Do the same with smaller spring on the other pair of holes.

For the small mount, repeat these steps with the 0.65x7x15mm, 5.68LBF/IN and 0.5x6x15mm, 2.3LBF/IN springs.

The tire holder mount must be printen atleast 3 times to ensure the plank stays balanced on the innertube.

The models of all mounts have been attached, upon downloading all models can be directly printed and sliced.

Begin by inflating the inner tube until it retains it shape but is still bouncy. Place the inflated inner tube in the centre of the plank and mark where you want the mounts to be. Keep in mind, that however you place the mounts that the plank and the setup will need to then be able to balance on the inner tube. Now screw in the tire mounts into the plank.

Now flip the plank and placing it on the inner tube by aligning it with the mounts.

The exact distances between each mount aren't important on their own. The setup should still remain as compact as possible however, because the laser loses its sharpness the further it travels. What is important is the distances between the beamsplitter and the mirrors. The difference between these distances cannot be larger than the coherence length of our laser. In our case this ranges between tens of millimeters to a centimeter.

Using the fotos as a guide, place all the mounts in their positions. In our case we have a lens mount instead of a detector device. Don't scew down any mounts down yet.

Important

1. Place all other mounts the same distance away from the beamsplitter mount, ensure that both mirror mounts are the same distance away within a millimeter. A distance no longer than 15cm should be used.
2. All mounts must be place perpendicularly to each other.
3. All mounts must be centred relative to the beamsplitter mount.

Refer to the fotos above once more to make sure all mounts are in the correct positions. If everything is correctly in place, scew down all mounts to the plank. Now place all components in their respective mounts. Of course, making sure the laser and mirrors are facing the beamsplitter.

Set up the following circuit and connect the wires of the laser diode. Copy the code to your device and connect it to your Arduino board. Upon running the code, the laser can be turned on and off with the tactile push-botton switch.

The circuit used was made with breadboard and Arduino. The code thus also being made in Arduino. Other methods of powering the laser diode are fully acceptable.