Feed-forward continuous and complete polarization control with a PLZT rotatable-variable waveplate and inline polarimeter

A Pb_1-xLa_x(Zr_yTi_z)_1-x4/O₃ (PLZT) electrooptic ceramic variable-rotatable waveplate and a compact inline polarimeter have been used to develop a fast feed-forward-controlled module for the continuous and complete conversion of polarization. This requires the control of only two parameters: the direction θ and strength of the applied voltage V₀. Feed-forward control speed is fast, taking only 24 μs. The chip plates were made by cutting T-shaped trenches into the four sides of a 500×400×300-μm³ PLZT chip and coating the trenches with electrodes. The PLZT waveplate is inserted into a 330-μm gap between thermally expanded core fibers. The input polarization states are monitored by a newly developed compact and fast inline polarimeter, which is placed in front of the polarization controller. The optimum θ and V₀ values for the required conversion are calculated by a computer, and the corresponding voltages are then applied to PLZT waveplate.