This work focuses on experimentally demonstrating the modification in diffusion kinetics, formation of holographic polymer dispersed liquid crystal gratings and an improvement in its electro optic response by doping them with multi-walled carbon nanotubes. Results indicate a faster rise and fall times which is attributed to the reduction in size of the liquid crystal droplets formed and a reduction in switching voltage due to change in dielectric properties of the medium as manifested by a rise in capacitance. Real time diffraction efficiency measurements reveal a time delay in the appearance of the diffracted order due to non-participation of the nanotube in the polymerization induced phase separation process. An analysis of this effect is presented based on the Stoke-Einstein's diffusion equation incorporating shape anisotropy of the nanotubes.
Published by the AIP PublishingArticles you may be interested in Coherent diffraction and random scattering in thiol-ene-based holographic polymer-dispersed liquid crystal reflection gratings
In this work we demonstrate the feasibility of using a holographically formed thin film electro-optic stack for the development of an airborne hyperspectral imaging system in the visible wavelength range of 600nm to 800nm. Each wavelength filtering element in the stack is formed by photo-induced phase separation of a homogenous mixture of liquid crystals and photopolymers, exhibiting a uniform reflection efficiency of up to 80% across a 35mm optical aperture with non-normalized baseline transmission, polarization insensitivity for normal incidence and a spectral resolution of 10nm. Fast switching time on the order of microseconds and techniques to improve view angle in the individual wavelength filtering elements in the stack are discussed and the improvements are discussed from a morphological standpoint. Two techniques for stacking the thin films have been developed which requires lesser number of substrates hence improving transmission throughput and radiometric efficiency through the stack. An advantage of using such a stack is the ability to modulate each wavelength filtering element at a different frequency to obtain a spectral multiplex, thereby enabling synchronous detection and demodulation of each wavelength with a high update rate for the hyperspectral cube. A system level integration of such a stack into the prototype drive and detection unit is discussed in this work.
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