Educational Objectives
l He-Ne Laser
l Contrast Function
l Coherence Length
l Two Beam Interference
l Homodyne Interferometer
l Fringe Detection, Counting andInterpolation
l Definition of Length
The basic version of a Michelson interferometer is used to teach thehandling, alignment, and measurement of a homodyne interferometer system. By interferingtwo laser beams, fundamental properties of Gaussian beams as well as wavefronts and interference patterns are demonstrated and investigated. With oneinterferometer mirror on a mechanical rack and pinion drive the beam pathdifference can be varied and hence the interferometer contrast function can beprobed. The measurement of coherence length of the He-Ne laser introduces thestudent to the spectral emission bandwidth of the laser source.