Ellabban Mostafa A, Glavan Gašper, Klepp Jürgen, Fally Martin
Physics Department, Faculty of Science, Tanta University, Tanta 31527, Egypt.
Physics Department, Faculty of Science, Taibah University, P.O. Box 30002, Al-Madina Al-Monaoura 42353, Saudi Arabia.
Materials (Basel). 2016 Dec 24;10(1):9. doi: 10.3390/ma10010009.
A detailed investigation of the recording, as well as the readout of transmission gratings in composites of poly(ethylene glycol) dimethacrylate (PEGDMA) and ionic liquids is presented. Gratings with a period of about 5.8 micrometers were recorded using a two-wave mixing technique with a coherent laser beam of a 355-nm wavelength. A series of samples with grating thicknesses d 0 = 10 … 150 micrometers, each for two different exposure times, was prepared. The recording kinetics, as well as the post-exposure properties of the gratings were monitored by diffracting a low intensity probe beam at a wavelength of 633 nm for Bragg incidence. To obtain a complete characterization, two-beam coupling experiments were conducted to clarify the type and the strength of the recorded gratings. Finally, the diffraction efficiency was measured as a function of the readout angle at different post-exposure times. We found that, depending on the parameters, different grating types (pure phase and/or mixed) are generated, and at elevated thicknesses, strong light-induced scattering develops. The measured angular dependence of the diffraction efficiency can be fitted using a five-wave coupling theory assuming an attenuation of the gratings along the thickness. For grating thicknesses larger than 85 microns, light-induced scattering becomes increasingly important. The latter is an obstacle for recording thicker holograms, as it destroys the recording interference pattern with increasing sample depth. The obtained results are valuable in particular when considering PEGDMA-ionic liquid composites in the synthesis of advanced polymer composites for applications, such as biomaterials, conductive polymers and holographic storage materials.
本文详细研究了聚（乙二醇）二甲基丙烯酸酯（PEGDMA）与离子液体复合材料中透射光栅的记录及读出情况。使用波长为355 nm的相干激光束，通过双波混频技术记录了周期约为5.8微米的光栅。制备了一系列光栅厚度d0 = 10…150微米的样品，每个样品有两种不同的曝光时间。通过在布拉格入射角下衍射波长为633 nm的低强度探测光束，监测光栅的记录动力学以及曝光后特性。为了获得完整的表征，进行了双光束耦合实验以阐明所记录光栅的类型和强度。最后，测量了不同曝光后时间下衍射效率随读出角度的变化。我们发现，根据参数的不同，会产生不同类型的光栅（纯相位和/或混合），并且在厚度增加时，会出现强光诱导散射。假设光栅沿厚度方向存在衰减，使用五波耦合理论可以拟合所测量的衍射效率的角度依赖性。对于厚度大于85微米的光栅，光诱导散射变得越来越重要。后者是记录更厚全息图的障碍，因为随着样品深度的增加，它会破坏记录干涉图案。当考虑将PEGDMA - 离子液体复合材料用于合成先进聚合物复合材料（如生物材料、导电聚合物和全息存储材料）时，所获得的结果尤其有价值。
