Laser

The laser was a cheap laser pointer. To avoid running out of batteries, we removed the batteries and switched it to a power supply. We used a mount which had several adjustments.

Problems

• Switching the laser to a power supply proved somewhat challenging as soldering the wires to the spring contact inside the tube without creating a short-circuit with the side of the tube was difficult. We originally tried to solder the other wire to the inside of the tube, but it was too smooth so we wound up taping it to the outside. Also, if we hooked it up backwards, we would blow up the laser. We were very careful and managed not to do this.
• The beam of our original laser wasnÕt collimated enough, so we couldnÕt get interference fringes. We had to remount another laser and attach it to the power supply.
• We got back-reflection from the system. Adding an attenuator fixed that problem.