Electrically tunable multiplexed grating with alternate liquid crystal-polymer structure

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 mu m and 4 mu m, 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 Lambda = 1 mu m) and 60% (for Lambda = 4 mu m), which have a good agreement with the theoretical results obtained by coupled wave theory (the theoretical values being 92.57% for Lambda = 1 mu m and 63.68% for Lambda = 1 mu m). In addition, the electro-optical performance indicates, that the threshold voltage for the sub-gratings are similar with each other, the V-90 of Lambda = 1 mu m is 7 V/mu m and 6 V/mu m for Lambda = 4 mu m, respectively. Such results show the good synchronized electrically-tunable property of multiplexed grating.