Fig. 1. Fabrication process of patterned PVA structures.

Fig. 2. (a) and (b) Photographs of LC cell under ambient light and between cross polarizers; (c)–(f) SEM images of the fabricated PVA relief structures with periods of 11.7, 13.6, 15.6, and 17.3 μm, respectively; (g) AFM image of the sample with a period of 15.6 μm; (h) depth profile of the PVA relief structures highlighted by the dotted line in Fig. 2(g).

Fig. 3. (a) Structure of POSS molecule used in our experimental work; (b)–(e) polarizing microscope images of LC cells doped with 0.2, 0.5, 0.6, and 0.8 wt. % POSS, respectively. All the LC cells have the same cell gap d∼9  μm.

Fig. 4. (a) and (b) Images of the 15.6 μm LC phase grating observed under a cross polarizer POM when the angles between the rubbing direction and the analyzer are 0° and 45°, respectively; (c) schematic diagram of LC phase gratings based on an alternating VA/HAN geometry.

Fig. 5. First-order diffraction efficiency of the 15.6 μm LC phase grating as a function of the applied AC (1 kHz) voltage for a fixed input wavelength of 635 nm. Red and black open symbols, experimental data probed using a polarized laser beam with its polarization parallel and perpendicular to the rubbing direction, respectively. Inset A, diffraction pattern of LC phase grating. Inset B, measured response time of the first order.

Fig. 6. Experimental and theoretical first-order diffraction efficiencies of the 15.6 μm LC phase grating as a function of the applied AC voltage. Red symbols, experimental result; blue symbols, theoretical prediction.