Many scientific applications have made great use of the wave nature of light. Until the first half of the century the nature of light remained completely a mystery. Some thought light to be a particle while others believed it to be a wave. Scientists now know that wave exhibits properties of both waves and particles. It is this dual nature of light that produced the branch of physics known as quantum physics. However, engineers have found many ways to exploit the wave characteristics of light. One instrument that capitalizes on the wave ....