Quantum Tunnelling DEMO - Part 3

Quantum tunneling with prisms involves a laser that needs to incrementally scan the prisms. This is needed to show the difference between total internal reflection and frustrated total internal reflection (or: between non-tunneling and tunneling). By being able to move the laser, the place where the light starts to penetrate the barrier can be found.

In this instructable, you'll be guided to make a holder for this laser. This device uses a precise bolt and a spring to slowly advance the lazer over the rails.

P.s. This is part of a bigger project where I, Helen van Rooij, worked together with Larissa Krab and Mark Lemmens. When I refer to myself, I mean Helen van Rooij.

You will need the following materials:

• 0.95 mW red lazer
• Accompanying holder for the lazer
• About 80 cm^2, 3mm thick, plywood for lazer cutting
• One bolt with fitting nut, metric fine and 10 cm long
• One small bolt with fitting nut
• Two metal rings with an inner diameter larger than the bolts
• One small spring
• One elastic band
• Two cables to connect the lazer
• Battery
• Wooden stick with a diameter of 5 cm
• Wood glue

For the laser holder, a design was created to allign it with the prism holder (see instructable part 1). You can view the pictures and file to see what was done to create this, as well as the sketch.

Also, it is needed to saw two 8mm bits out of the wooden sticks before continuing.

Now it's time to use laser cutting to cut out the components of the plywood plate!

With the lasercutter having done it's job, we first plug in the little poles into the small holes of the baseplate.

Then some glue has to be added to the slits of the triangle supports. Slide these into the plate with the single hexagonal hole. Glue the plate with supports to the baseplate, on the side without a large hole.

And finaly, add the small strips of wood to the sides to create some rails to keep everything in a straight line.

Now some bolts have to be added, do this by first drilling a hole a bit below the hexagon hole. Then screw a small bolt into the hole, with just a bit poking out to attach the spring to. After this is done, put a fitting nut into the hexagonal hole.

To ensure the (metal) rings are fastened, some glue was used on either side of the nut.

Lastly, insert a long bolt into the secured nut, this bolt will regulate the lazer!

Before our laser holder is fully done, a spring has to be added to help the moving of the laser.

In order to do this, put an elastic band through the end of the spring, with the spring being in the middle of the band. Then make a hole out of both ends of the band, and put that hole over the laser holder. If it is not tight enough, stretch the band, twist it and pull it over another time.

After this, hook the other end of the spring to the small bolt.

Now we can add the laser to the holder! Use the screw on top to make it fit snugly.

Hook the lazer up to a power source, and the setup is finished!