Based on the equivalence theorem of a unitary optical system. We proposed an analytical approach to characterize the
cell parameters of a twisted nematic liquid crystal device (TNLCD) with full field resolution. The spatial distribution of
three characteristic parameters of a TNLCD were measured by using a polarizer-sample-analyzer imaging ellipsometer,
thus the untwisted phase retardation, cell thickness and twisted angle of a TNLCD can be directly calculated through the
explicit expressions as a function of its characteristic parameters. The measured results are very close to the design
values provided by TNLCD manufacture. This method shows that both the system setup and parameters calculating
process are quite simple. It would be more helpful to characterize a TNLCD in the manufacturing process.
We report the experimental manipulation of liquid crystal spatial distribution in micro-scale optical waveguide via
ultrashort pulse lithography. The frequency-doubled Ti:sapphire laser pulse focuses on the liquid crystal/monomer
mixtures at high scanning speed, and well-defined liquid crystal/polymer triple-layer and periodic micro-waveguide is
observed through phase separation and self organization mechanism.
Simultaneous two-dimensional nanometric-scale position monitoring can be achieved in a simple interferometric
setup by real-time probing a hexagonal photonic crystal glass substrate. The minimum detectable translational movement
is determined by the period of photonic crystal array, and can be as high as 8 nm in the present work.
Optical liquids can be used to engineer the dispersion characteristics of fibers by serving as
the core or cladding. The short-/long-pass filters are so made and concatenated to achieve
widely tunable Gaussian-shaped filters for bio-imaging.
A simple dispersion measurement of fiber gratings using an un-balanced Michelson interferometer is proposed. A broadband source and an optical spectrum analyzer are used to scan the interference spectrum, and then the group time delay can be obtained rapidly by Fourier transform processing the interference spectrum. We measured the group time delays of a uniform-period FBG, a chirped FBG, an arrayed-waveguide grating interleaver, and a thin-film filter type OADM by an un-balanced Michelson and Mach-Zehnder interferometers, respectively. The experimental results excellent match the measured results of the optical network analyzer. The experimental repeatability is shown to be better than 1ps.
This article describes light-induced reorientation effects on a homeotropical dye-doped liquid crystal (DDLC) cell. The photo-excited azo dye, methyl red (MR), diffuses and adsorbs onto the substrate, thus forming a ripple structure. The adsorbed dye and laser-induced ripple structure then reorient the liquid crystal molecules and induce a holographic grating. Initially, the LC directors are reoriented primarily by the adsorbed dye. However, given sufficiently large ripple groove amplitude, the torque imposed by the ripple grooves overcomes that owing to the adsorbed dyes, and the LCs are realigned along the groove direction.
The dynamic behavior of a holographic grating induced in a homeotropically aligned dye-doped liquid-crystal film is investigated. In the presence of an applied dc voltage, photoexcited azo dyes induce a photorefractive grating and then diffuse and are absorbed onto cell substrates. The reorientation of liquid crystals as a result of adsorbed dyes leads to a phase grating that is phase shifted 90° from the photorefractive grating. Competition of these two gratings induces two-beam couplings of the writing beams, initially transferring energy from beam 1 to beam 2 and then, after a pause, from beam 2 to beam 1.
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