Detector
This is a fairly standard photodiode. The current output is proportional to the intensity of the input, which is in turn affected by the relative phase of the two beams.
Problems
- Due to other limitations in aiming the beam, we had trouble getting the beam to hit both photodiodes. Fortunately, only one is really necessary, since you can watch the output on the oscilloscope, and determine the maximum and minimum values of output that the interferometer produces. Additionally, removing one of the diodes simplified the aiming process for recombining the beams.
- The photodiode produces a current output, while the oscilloscope measues a voltage input. Therefore, we built a current-voltage converter, using an op amp.
Used with permission from C. Howe