聚合物分散液晶电控全息变间距光栅

Electrically controlled holographic varied line--spacing grating based on polymer dispersed liquid crystal

本文报道了一种基于聚合物分散液晶的电控全息变间距光栅。采用柱面波和平面波干涉得到具有变间距的干涉条纹,并将此条纹记录于聚合物分散液晶材料中。实验分析研究了该光栅的空间频率、衍射特性和电场调控特性。光栅的空间频率变化范围和趋势与理论计算公式相匹配,实验结果表明光栅衍射效率与曝光光强和时间存在一定的关系。空间频率在530 mm^(-1)~650 mm^(-1)内的光栅衍射效率能达到70%以上。光栅的阈值电压为2.4 V/μm,上升沿和下降沿时间分别为300μs和750μs。该光栅不但具备了普通变间距光栅的优点,而且还具备了聚合物分散液晶的电场调控的特性,在光纤通信,光电探测及光谱探测等领域具有一定的应用前景。

Electrically controlled holographic varied-line-spacing （VLS） grating based on polymer dispersed liquid crystal （PDLC） is reported. Varied-line-spacing interference pattern is generated through interference between cylindrical wave and plane wave, and recorded in PDLC. Characteristics, such as spatial frequency, diffraction and electric-optic, are analyzed by experiments. The results show that the trend and range of grating period match well with the theoretical simulation. The relationships between diffraction efficiency and exposure intensity as well as exposure time are studied. The grating diffraction efficiency can be achieved more than 70% with spatial frequency from 530 mm-1 to 650 mm-1. Meanwhile, the grating has good electrically controlled property. The threshold voltage is 2.4 V/μm, and the rise time and fall time are 300 μs and 750 μs, respectively. The grating not only has advantages of ordinary VLS grating but also has electric-optic characteristics of PDLC. It has potential applications in the fields of optical fiber communication, photoelectric detection and spectrograph.