Liquid-crystal polarization controller arrays on planar waveguide circuits

We have developed thin liquid crystal (LC) arrays for use as simple polarization-controller arrays on planar lightwave circuits (PLCs). The 30-μm thick LC arrays are vertically inserted into trenches cut across PLC substrates. Two such LC cells that are in line and parallel to each other, one of which has a direction of alignment that is rotated by 45/spl deg/ relative to that of the other, are able to convert an arbitrary input polarization to a desired one. Twisted-nematic LC cells can switch the polarization of input light between the TE and TM modes with an extinction ratio of 15 dB.