Blaya S, Acebal P, Carretero L, Murciano A, Madrigal R F, Fimia A
Departamento de Ciencia de Materiales, Optica y Tecnología Electrónica Universidad Miguel Hernández, Av. de la Universidad s/n Apdo. 03202 Ed. Torrevaillo, Elx (Alicante) Spain.
Opt Express. 2010 Jan 18;18(2):799-808. doi: 10.1364/OE.18.000799.
The recent results reported in reference 1 have produced an increased interest in explaining deviations from the ideal behavior of the energetic variation of the diffraction efficiency of holographic gratings. This ideal behavior occurs when uniform gratings are recorded, and the index modulation is proportional to the energetic exposure. As a result, a typical sin(2) curve is obtained reaching a maximum diffraction efficiency and saturation at or below this value. However, linear deviations are experimentally observed when the first maximum on the curve is lower than the second. This effect does not correspond to overmodulation and recently in PVA/acrylamide photopolymers of high thickness it has been explained by the dye concentration in the layer and the resulting molecular weight of the polymer chains generated in the polymerization process. In this work, new insights into these deviations are gained from the analysis of the non-uniform gratings recorded. Therefore, we show that deviations from the linear response can be explained by taking into account the energetic evolution of the index modulation as well as the fringe bending in the grating.
参考文献1中报道的最新结果引发了人们对解释全息光栅衍射效率能量变化偏离理想行为的兴趣增加。当记录均匀光栅时会出现这种理想行为，且折射率调制与能量曝光成正比。结果，会得到一条典型的sin(2)曲线，在该值或低于该值时达到最大衍射效率并饱和。然而，当曲线上的第一个最大值低于第二个最大值时，会在实验中观察到线性偏差。这种效应与过调制不符，最近在高厚度的PVA/丙烯酰胺光聚合物中，已通过层中的染料浓度以及聚合过程中生成的聚合物链的分子量来解释。在这项工作中，通过对所记录的非均匀光栅的分析，对这些偏差有了新的认识。因此，我们表明，考虑折射率调制的能量演变以及光栅中的条纹弯曲，可以解释与线性响应的偏差。
