Phase-sensitive switching in a rocking rotator fiber filter

Abstract

To date all-optical switching experiments in fibers and channel waveguides have relied on having a high intensity beam switch itself between two waveguides or two polarization states or on switching a low intensity beam by a strong control beam. We demonstrate for the first time, to our knowledge, phase-sensitive switching in a periodically twisted birefringent fiber where the switching of a strong signal beam is controlled by the phase of a weak control beam. The switching was implemented by using 30 ps pulses from a dye laser tuned to the resonant filter wavelength of 590 nm. The fiber was cut to a coupling length of 185 cm, and a strong signal beam, which contained 90% of the input power, was launched along one of the two principal axes. The remaining 10% was coupled orthogonal to the signal polarization direction. The phase difference between the two polarization states was controlled by a Soleil–Babinet compensator. When the phase was varied between 0 and 2π, phase-sensitive switching was observed at input powers of 1.3 kW. The contrast of the bar state could be varied between 22% and 75% of the input power by using the configuration described above. The phase-sensitive process vanished at input powers much smaller than the critical power.