Generation of Phase-Modulated Periodic Optical Signals by use of a Polarization Interferometer

Polarization phase-shifting interferometry is an established technique in optical metrology. In the present study it is shown that, by use of this technique, not only is it possible to realize any discrete magnitude of a predetermined phase difference (from 0 to 2pi) between two light beams but also phase-modulated periodic optical signals can be generated simply by rotation of a polarizer or a retarder or both placed at the input of a conventional two-beam interferometer. Some representative linear and nonlinear periodic polarization-induced phase-modulated optical signals are shown. A linear phase modulation of 0-2pi with constant output intensity is obtained in some cases. The Poincaré sphere representation is introduced as a convenient tool for visualizing the dynamics involved in the generation of polarization-phase-modulated waveforms and as a possible aid to intelligent modification of the generated waveform as required. This all-optical technique of continuous and periodic phase variation should prove useful for introducing phase modulation without the need for electro-optic devices.