Investigation on phase jump in a differential interferometer

This article presents a new phase jump phenomenon in a differential heterodyne interferometer. When the intensity of one arm of an interferometer changes from greater to less (or less to greater) than that of another, a phase jump of 180° will take place if the phase difference between two arms is prefixed at π. We call this phenomenon phase jump. To demonstrate phase jump, a modified differential heterodyne interferometer has been setup. The intensity of one arm is modulated as the arm is scanning across an edge. Both theoretical and experimental investigations are conducted in detail. The theoretical and experimental results indicate that the phase slope of the phase jump is infinite and the amplitude of output signal is zero when a phase jump occurs. Meanwhile the position of phase jump is very sensitive to the displacement. Therefore, both phase and amplitude signals of phase jump are suitable for precise position index and may find wide potential applications in the fields of edge detection, alignment, optical storage, and so on.