We studied the electro-optical property and photorefractive effects in a semiconductor CdSe nanorod doped neamtic liquid crystal [NLC] system. The nonlinear index coefficient is measured to be n2=2.05×10−2cm2/W, which is 10 times larger than that of an equivalent pure liquid crystal system. Electro-optical switching investigation shows that the Freedericksz transition voltage of this system is also noticeably lower than that of un-doped NLC. These enhanced electro- and nonlinear optical properties are attributed to the photoconductivity of CdSe nanorods and the enlarged electric conductivity and dielectric anisotropies of the doped system. An AC field assisted photorefractive effect in CdSe nanorod doped liquid crystal system has also been studied.
We have fabricated 1-, 2- and 3-D photonic crystalline structures in polymer dispersed nematic and isotropic phase liquid crystals. It is observed that a particular mixture of isotropic liquid crystals and the photo-polymer will also polymerize and phase separate, forming high quality optical gratings, just as typical nematic liquid crystals. Liquid crystal droplet sizes obtained could be as small as a few 10’s of nm, i.e., nano-droplets. The resultant structure exhibits excellent optical qualities, and high efficiency Bragg diffraction properties.
We report theoretical and experimental studies of supra-photorefractive nematic liquid crystals doped with C60 and/or Carbon nanotubes. Theoretical estimate shows that the nonlinear refractive index change coefficient n2 in such systems can be >> 1 cm2/Watt. Experimentally, we have observed n2 of ~ 10 cm2/W, with typical nematic response times.
We report on theoretical and experimental studies of all-optical polarization conversion of cw 1.55 μm lasers using nematic liquid crystal in their ordered and isotropic phases. Almost complete conversion of the linearly polarized laser is achieved in a 400 μm thick film at mW power.