Liquid-crystal polarization stabilizers on fiber arrays

We have built polarization stabilizer arrays of ultrathin liquid-crystal (LC) polarization controller (PC) arrays and a tap-type photodetector array on a fiber array. The ultrathin (35-μm-thick) LC cells are inserted into trenches cut across the fiber array, which is affixed to V grooves in a glass plate and are used to change the phase of 1.55-μm lights from 0.5 to 3.9π with the application of less than 3 Vrms. Two cascaded ultrathin LC cells, where the directions of alignment of the LCs are rotated by 45° relative to each other, are capable of converting light with an arbitrary input polarization to the transverse electric (TE) or transverse magnetic (TM) polarization. We fabricated a multichannel TE- and TM-polarization stabilizer of the previously mentioned 16-channel LC PC array and a feedback system made up of a multichannel tap-type photodetector array, sheet polarizer, and a computer and analog-to-digital converters. Feedback control was applied to maximize and minimize the tapped light, to convert an arbitrary input polarization to TM or TE output polarization, and stabilize it in the given state.