A volume grating based holographic sensor on a flexible substrate for real-time characterization of the bending deformation of polymer has been studied. Two kinds of deformations, i.e., unilateral and bilateral bending, are analyzed by using the diffraction spectrum of a transmission grating. The dependence of the peak wavelength on the angle displacement in unilateral bending presents a linear relationship. The relation between the peak wavelength and the curvature radius in bilateral bending is also a linear relationship. The maximum bending angle is 18 deg in unilateral bending, and the curvature radius reduces to 44 mm in bilateral bending. The diffraction spectrum coverage is up to 200 nm. In straightening a curved grating, the spatial width of the rainbow spectrum presents a linear relation to the curvature radius. The sensing feedback of bending deformation provides an effective method for characterizing the bending movement of polymer. It can even qualitatively present the deformation by observing the center color and its width with the naked eye. The optical measurement of bending deformation further validates the practical applicability of the holographic sensor.

中文翻译：

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利用全息光栅在柔性基板上的衍射光谱表征聚合物的弯曲变形

已经研究了在柔性基板上基于体积光栅的全息传感器，用于实时表征聚合物的弯曲变形。利用透射光栅的衍射光谱分析了单向弯曲和双向弯曲两种变形。峰值波长对单边弯曲角度位移的依赖性呈线性关系。双向弯曲中的峰值波长与曲率半径之间的关系也是线性关系。单向弯曲的最大弯曲角度为18度，双侧弯曲的曲率半径减小至44 mm。衍射光谱覆盖范围高达200 nm。在矫直弯曲的光栅时，彩虹光谱的空间宽度与曲率半径呈线性关系。弯曲变形的感测反馈提供了表征聚合物弯曲运动的有效方法。它甚至可以通过肉眼观察中心颜色及其宽度来定性地显示变形。弯曲变形的光学测量进一步验证了全息传感器的实际适用性。