双重复合式液晶/聚合物电调谐光栅的制备

Electrically tunable multiplexed grating with alternate liquid crystal-polymer structure

采用一次性全息曝光的方法同时在样品上制备了周期分别为1μm和4μm,衍射效率电场可调的双重复合式液晶/聚合物光栅.使用He-Ne激光器对复合光栅的衍射特性进行了实验研究,发现光栅存在两个1级衍射极强峰.对峰值衍射效率的测定结果表明,周期1μm的光栅衍射效率为90%,周期4μm的光栅,60%.结合耦合波理论计算了周期1μm和4μm光栅的衍射效率理论值,分别为92.57%和63.68%.实验结果与理论值符合得非常好.对电光特性的测试表明该复合光栅内的两套子光栅的驱动电压V90比较接近,分别为7 V/μm(周期1μm)和6 V/μm(周期4μm),从而保证了电调谐的同步性.

In this paper, we report a kind of electrically tunable multiplexed grating which is prepared conveniently with a single step holographic exposure on the mixture of nematic liquid crystals and photosensitive monomers. The periods of two sub-gratings contained in the multiplexed grating are tested with scanning electronic microscopy （ SEM）, the results show that their periods are 1 μm and 4 μm, respectively. Diffraction properties of this multiplexed grating are tested, and it is found that there are two diffraction peaks when the testing beam incidents at two different incidence angles. The corresponding diffraction efficiencies of the two sub-gratings are 90% （for ∧ = 1μm） and 643% （for ∧ = 4μm）, which have a good agreement with the theoretical results obtained by coupled wave theory （the theoretical values being 92.57% for ∧ = 1μm and 63.68% for ∧= 1 μm）. In addition, the electro-optical performance indicates, that the threshold voltage for the sub-gratings are similar with each other, the V90 of ∧ = 1 μm is 7 V/μm and 6 V/μm for ∧=4μm, respectively. Such results show the good synchronized electrically-tunable property of multiplexed grating.