Optically Tunable Diffraction Gratings in Polymer-Stabilized Liquid Crystals

Optically Tunable Diffraction Gratings in Polymer-Stabilized Liquid Crystals 

Materials Design and Switching Mechanism. The dynamic holographic grating recorded with azobenzene SCLCPs is erased once the writing beams are turned off. It is of interest to develop materials with which one can record a stable diffraction grating that, after formation, can be repeatedly 

CHAPTER 11 TUNABLE DIFFRACTION GRATINGS BASED ON AZO MATERIALS 

LC in nonirradiated areas and can be further polymerized upon flood irradiation (photomask removed). Basically, the grating is formed by alternating polymer-rich and LC-rich regions. As shown in Fig. 11.24, the grating can not only be switched by an electric field because of different responses of the two regions but is also sensitive to UV and visible light by virtue of the photoisomerization of the small amount of azobenzene polymer in nonirradiated areas. 

With this design, it is easy to understand that a concentration of azobenzene monomer before polymerization ( 10wt%) is needed. Generally, azobenzene compounds have a Hmited solubility in LCs ( 3%). To overcome this problem, we prepared a dimethacrylate azobenzene monomer that is Hquid crystaUine on its own (following structure), with the following phase transition temperatures (°C) on heating Cr 70 S 99 N 145 Iso. 

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