光定域化蓝相软晶格结构的光学应用

实验利用表面光取向技术控制蓝相晶格的有序生长,将光定域化取向与分子自组装相结合。通过对基板表面进行交替的取向/非取向控制,平面内获得周期排列的微结构,使蓝相图形化结构的反射光强度在空间上形成周期性调制,同时设计制备了振幅型衍射器件;通过对基板表面做正交取向方向交替排列的微结构,使蓝相图形化结构的反射光相位在空间上形成周期性调制,设计制备了相位型衍射器件。这两类衍射器件均具有对入射光的波段选择性,即只有当入射光的波长局域在蓝相的反射带时才会呈现衍射效应。蓝相液晶软物质的特性又赋予它在电场下可调谐的波段选择性,即反射带位置随电场的增加发生红移从532nm到610nm,电场撤除则回复到初始状态。同时,借助于光取向材料的光可擦写特性,蓝相晶格的取向微结构能够重复的擦写与重构,从而实现不同衍射器件乃至不同衍射调制方式的转换。

Light-patterned blue phase soft cubic superstructure in optical applications

Combining light-patterning process with self-assembly trait, we applied photo-alignment technique to control the arrangement of liquid crystal blue phase (BP) cubic superstructure. By means of generating alternate aligned areas and non-aligned areas, the amplitude-modulation diffraction devices can be designed, which derives from the periodic reflection intensity of the patterned BP. By means of generating alternate orthogonal alignment directions, the phase-modulation diffraction devices can be designed, which are owing to the periodic reflected phase from the patterned BP. These two types of diffraction devices exhibit peculiarly wavelength-selectivity, which means that light diffraction occurs selectively to certain wavelength. Based on the soft attribute of BP, these devices can respond to applied electric field leading to a tunable wavelength-selectivity. When the external electric field was applied, the corresponding reflection waveband of BP exhibited a continuous red-shifting from 532 nm to 610 nm. Furthermore, a preferable feature of the devices is photo-induced dynamical erasability and rewritability due to rewritable characteristic of the photoalignment film, which results in realizing the conversion of different diffractive devices and even diffractive modulation modes.