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Holographic polymer dispersed liquid crystals (H-PDLCs), which is one of promising material for LC display, when doped with nanoscale silver (nano Ag) exhibit a unique electro-optical response to frequency modulation. We established an equivalent circuit model for H-PDLC doped nano Ag gratings according to Maxwell-Wagner effect and calculated relaxation frequency for three concentrations of nano Ag. We found that the frequency modulation and doping concentration have a close effect on threshold driving voltage of H-PDLC gratings. It is experimentally shown that the lowest threshold driving voltage can be obtained when the driving frequency is located just around the recipe's dielectric relaxation frequency. It is possible to decrease the driving voltage of H-PDLC through selection of suitable driving frequency as well as via doping with appropriate concentration of nano Ag.

A four-channel frequency division multiplexed fluorescent microscope (FDMFM) modulated by holographic polymer dispersed liquid crystal (H-PDLC) grating array is presented in this paper. The four-channel H-PDLC grating array is developed and employed to generate frequency modulation. Fluorescent signals at four different locations on a rat neural cell have been successfully modulated with four different frequencies, collected by a single high-sensitivity photodetector, such as photomultiplier tubes, and distinguished by taking the Fourier transform of the detected sum signal. The experimental and simulation results agree well. The new system offers the advantages of (1) multiple channel modulation capability, (2) no mechanical noise and (3) flexible and controllable modulation profile (e.g. square wave, triangular wave, etc.). Thus this four-channel FDMFM system can be very helpful for studying fast-changing transient events in biological samples.

We experimentally demonstrated an electrically controlled variable focus optical system based on cascading polymer dispersed liquid crystal (PDLC) lens. Through adjusting external electric field applied on the hole-type electrode of PDLC lens to change the spatial distribution of refractive index of PDLC, the plane PDLC cell can be functioned as a focusing lens with the variable focus length. In this article, we simulate the electromagnetic field distribution of the external electrical field, as well as analysis the corresponding principle and mathematic equation of its electrically controlled focusing length. The experimental results show that as external alternate current (AC) voltage is increased from 0 to 80 V, the focal length of single lens decreases from ∞ to 1.073 m, and that of the double lens from ∞ to 0.484 m. These experimental results are in good accordance with the simulation results. The experimental response time of PDLC tunable lens is less than 1 ms, which will bring benefits for the applications especially for the fast imaging system. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2830–2835, 2013

Photonic crystals (PCs) with infiltrating liquid crystals (LCs) have many potential applications because of their ability to continuously modulate the band-gaps. Using the plane-wave expansion method (PWM), we simulate the band-gap distribution of 2D honeycomb lattice PC with different pillar structures (circle, hexagonal and square pillar) and with different filling ratios, considering both when the LC is used as filling pillar material and semiconductors ( Si , Ge ) are used in the substrate, and when the semiconductors ( Si , Ge ) are pillar material and the LC is the substrate. Results show that unlike LC-based triangle lattice PC, optimized honeycomb lattice PC has the ability to generate absolute photonic band-gaps for fabricating optical switches. We provide optimization parameters for LC infiltrating honeycomb lattice PC structure based on simulation results and analysis.

We report on the synthesis and characteristics of a holographic polymer dispersed liquid crystal (H-PDLC) switchable grating based on nano-Ag particles. The influence of doping different concentrations of nano-Ag on the diffraction efficiency, driving voltage, and response time of the H-PDLC grating is investigated. The best grating characteristics were achieved with 0.05% nano-Ag doping. Calculated and experimental results reveal that the improvement of the characteristics is likely due to the surface plasmon effect of nano-Ag.