Study Of The Transparent Electro-optic Ceramics Based Polarization Controller And Its Control Algorithm

The development of the polarization controllers (PCs) is summarized and the PCs are classified into three categories: the direction-control PCs, the retardation-control PCs and the direction-retardation-control PCs according to the retarders used in polarization control devices. Mathematics models of SOP and the optical propagation characteristics in electric-optical crystal are reviewed. The properties of transparent electro-optic ceramics are studied in detail.A 4-plate electro-optic polarization controller is constructed with the plates fast axes oriented alternately 45°, 0°, 45° and 0° with respect to horizontal. On controlling, the output polarization state is modified by changing the phase delay of the plates and fixing their fast axes. Using Jones matrix, the polarization state of polarization light through the polarization controller is analyzed.The mutation operation is substituted by random dither for modified genetic algorithms applied in polarization control. The simulation for 4-plate polarization controller shows that the random input state of polarization (SOP) can be converted into a fixed linear output state of polarization by the modified genetic algorithms. On the controlling the output state of polarization is stable and the fluctuation of intensity of the desired output light is less than 2%.A new endless polarization control algorithm based on simulated annealing (SA) algorithm is proposed and demonstrated. The SA algorithm can quickly search the solution in the whole region and easily escape from the saddle points. To employ the SA in the PCs, the control parameters of the SA are studied. The simulating results of the SA-based 4-plate polarization controller which phase delay vary from 0 to 2n show that this controller is endless and the output polarization state is stabile while the light intensity fluctuates less than 1%.To verify the SA control ability, an application of the algorithm in a fast feedback polarization controller (PC) constructed by four electro-optic ceramic variable waveplates for the continuous conversion of the state of polarization (SOP) is investigated. The experiment results show that the fluctuation of the light intensity in the desired output SOP is less than 2% and the extinction is larger than 20 dB for a random input SOP. This SA-based PC can run reset-freely and the response time is less than 400μs.The endless reset of simulated annealing algorithm based polarization controller is analyzed. The Noe reset method is used to overcome reset fluctuation in this controller and simulatingresearch shows that the disadvantageous reset surge was found with Noe reset method in this controller. To ensure the endless property of the controller, a coercing reset method is introduced for reset. This is based on the fact that at least two plates of fat are used.Equivalent rotatable quarter-wave plates and rotatable half-wave plates are constructed from sequences of adjustable linear retarders with fixed retardation axes. To avoid resetting, the adjustable linear retarders based polarization controller using rotating plates based polarization controlling algorithm is proposed and demonstrated. Simulation results show that the 4-plate polarization controller is endless while the range of retardation is confined into 2n and the transformation of SOPs is continuous, and rest-free and the phase shifts are smooth.The feedback single rotatable-variable OptoCeramic waveplate polarization controller is constructed based on the variable retardation and rotatable axes of a waveplate. For this controller, the simulated annealing algorithm is applied to dither optimization considering the limit of phase shift and the endless rotatable axes. Simulated researches show that this controller can transform any varying general input polarization state into an arbitrary linear output polarization state. On controlling the phase shift vary within 0~2n, so the fluctuation caused by resetting can be avoided.