Study On Two-dimensional Photonic Crystals With Liquid Crystal By Simulative And Experimental Methods

The invention of photonic crystal, which has been a hot area of research in recent years, brings the revolutionary change to the optoelectronics field. Since photonic crystal is similar to the semiconductor with the structure of photonic forbidden band, it is known as the optical semiconductor. The introduction of liquid crystal to in photonic crystals, solve the problem that the photonic crystal device once made and the character such as photonic band gap will not be able to change. What’s more, the devices not only have the characteristics of liquid crystal, but also have the characteristics of photonic crystals, which broaden the application range of the photonic crystal.Triangular lattice photonic crystals, filled with liquid crystal in the air column while the basal materials respectively are Si and Ge, won’t generate absolute photonic band gap. On this basis, this paper probes into the band gap structure characteristic of the two-dimensional Honeycomb lattice photonic crystal filled with liquid crystal and the semiconductor materials Si and Ge. The simulation results demonstrate that photonic crystal could generate absolute photonic band gap under the normal liquid crystal refractive index, while not under the anomalous refractive index. So these photonic ctystals can be used for fabricating optical switch devices. And we also analyzed the influences of the structural parameters, such as pillar shapes, filling ratio, on the photonic band gap, and optimized the structural parameters. The optimized structure identified in our study should provide better guidance for the implementation of LC based PC devices.The phase separation between polymer and liquid crystal is induced by the 532 nm laser beam interference pattern. In this paper, the electrically-controlled twodimensional polymer dispersed liquid crystal photonic crystals are fabricated through exposing the polymer dispersed liquid crystal sample twice within the holographic optical path. After the first exposure, the sample is rotated about 60° along the central normal line of the base plate and then is exposed again. The experimental results demonstrate that the times of twice exposures have influence on the phase separation between polymer and liquid crystal. In addition, the optimized two-dimensional photonic crystal shows regular triangular lattice periodicity distribution with an ordinary microscope. The diffraction efficiency of photonic crystal can be effectively adjusted through electric field. The results provide potential application in electronic tuning photonic crystal lasers and other photonic crystal photo-electric conversion devices.