We study the enhancement and control of the refractive index of liquid crystals with
dispersed gold and silver nanoparticles. The maximum obtainable variation in the real
and imaginary parts of the effective refractive index of the solution by reorientation of
the liquid crystal molecules is calculated, and the results obtained with gold and silver
nanospheres are compared. The effect of size, concentration, and composition of the
nano-particulates (solid spheres vs. silver- or gold-coated silica nanoshells) on the
refractive index and its wavelength dependence is also considered.
We present the results of nonlinear transmission in various ordered and disordered mesophases of liquid crystals,
and demonstrate that in bulk or guided wave geometry, they are capable of clamping the transmission of pulsed or cw
lasers to below the Maximum Permissible Exposure level of eyes and optical sensors in the entire visible - infrared
We present a theoretical model and some experiment demonstrations of all-optical passive switching processes with 90°
twist-aligned nano-doped nematic liquid crystal cells sandwiched between two crossed polarizers. The photosensitive
dopants give rise to laser induced dye-assisted director axis reorientation and order parameter modifications, which in
turn produce an intensity dependent polarization switching and hence a transmission modulation capability.
Experimental observations are in good agreement with our expectation derived from modified Jones matrix analysis and
also demonstrate the feasibility of an efficient [microwatt power] low threshold polarization and fast switching
[microseconds] all optical limiting device for visible as well as infrared lasers or bright light sources.
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 <i>n</i><sub>2</sub>=2.05×10<sup>−2</sup><i>cm</i><sup>2</sup>/<i>W</i>, 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.