Aligned Layers of Silver Nano-Fibers

We describe a new dichroic polarizers made by ordering silver nano-fibers to aligned layers. The aligned layers consist of nano-fibers and self-assembled molecular aggregates of lyotropic liquid crystals. Unidirectional alignment of the layers is achieved by means of mechanical shearing. Aligned layers of silver nano-fibers are partially transparent to a linearly polarized electromagnetic radiation. The unidirectional alignment and density of the silver nano-fibers determine degree of polarization of transmitted light. The aligned layers of silver nano-fibers might be used in optics, microwave applications, and organic electronics

Electro-Optic Effects in Colloidal Dispersion of Metal Nano-Rods in Dielectric Fluid

In modern transformation optics, one explores metamaterials with properties that vary from point to point in space and time, suitable for applications in devices such as an "optical invisibility cloak" and an "optical black hole". We propose an approach to construct spatially varying and switchable metamaterials that are based on colloidal dispersions of metal nano-rods (NRs) in dielectric fluids, in which dielectrophoretic forces, originating in the electric field gradients, create spatially varying configurations of aligned NRs. The electric field controls orientation and concentration of NRs and thus modulates the optical properties of the medium. Using gold (Au) NRs dispersed in toluene, we demonstrate electrically induced change in refractive index on the order of 0.1.Comment: 27 pages, 23 figure

Nematic Cells for Digital Light Deflection

Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction

55.2: Fast Switching Dual-Frequency Liquid Crystal Optical Retarder, Driven by an Amplitude and Frequency Modulated Voltage

Abstract We Introduction Nematic cells are widely used as optical retarders in various applications where 0 ε is the electric constant, 1 γ is the rotational viscosity of the nematic liquid crystal, ∆ε=ε II -ε ⊥ is the dielectric anisotropy, ε II and ε ⊥ are the principal dielectric permittivities referred to the nematic director, threshold value of the applied voltage, K is the characteristic elastic constant. According to Eq.(1), one can decrease τ on by increasing the applied voltage. However, the relaxation time τ off depends only on the material parameters and the thickness of the cell and cannot be shortened by a higher electric field, see Eq.(2) τ off ~d 2 . The drawback is that smaller d causes smaller optical retardation (the optical path difference for ordinary and extraordinary waves) ∆L, as ∆L~d. The goal of our work was to resolve contradictory requirements of fast (sub-millisecond) switching and the broad range of switched optical retardations (∆L ≥1µm). Fast Switching Dual-Frequency Liquid Crystal Optical Retarder We use the so-called dual-frequency nematic materials in cells with a high pretilt angle (α≈45 degrees) driven by a sequence of electric pulses of different frequency and amplitude. We assembled nematic cells with an anti-parallel fashion from plates with a high pretilt angle, which was achieved by oblique deposition of SiO layers We used the optical setup with the cell placed between two crossed polarizer prisms to measure the time evolution of the optical response of the cell

Digital Beam Deflectors Based Partly on Liquid Crystals

A digital beam deflector based partly on liquid crystals has been demonstrated as a prototype of a class of optical beam-steering devices that contain no mechanical actuators or solid moving parts. Such beam-steering devices could be useful in a variety of applications, including free-space optical communications, switching in fiber-optic communications, general optical switching, and optical scanning. Liquid crystals are of special interest as active materials in nonmechanical beam steerers and deflectors because of their structural flexibility, low operating voltages, and the relatively low costs of fabrication of devices that contain them

Smectic A Filled Birefringent Elements and Fast Switching Twisted Dual Frequency Nematic Cells Used for Digital Light Deflection

We describe the application of smectic A (SmA) liquid crystals for beam deflection. SmA materials can be used in digital beam deflectors (DBDs) as fillers for passive birefringent prisms. SmA prisms have high birefringence and can be constructed in a variety of shapes, including single prisms and prismatic blazed gratings of different angles and profiles. We address the challenges of uniform alignment of SmA, such as elimination of focal conic domains. Fast rotation of the incident light polarization in DBDs is achieved by an electrically switched 90 twisted nematic (TN) cell

Fast Switching Dual-Frequency Liquid Crystal Optical Retarder, Driven by an Amplitude and Frequency Modulated Voltage

We demonstrate theoretically and experimentally a fast-switching nematic optical retarder capable to switch a few microns of optical retardation in less than 1 ms. For example, a nematic cell of thickness 14.5 mum switches 0.3 mum of retardation within 0.15 ms and 2.5 mum within 0.5 ms for single passage of beam. The corresponding figure of merit is two orders of magnitude higher than the one known for the best nematic materials synthesized so far. The fit is achieved by employing a dual-frequency nematic liquid crystal in high-pretilt angle cells and a special addressing scheme that features amplitude and frequency modulated voltage. The scheme can be used in spatial light modulators, retarders, beam deflectors, polarization rotator, and displays. </p

Fast switching optical modulator based on dual frequency nematic cell,”

We demonstrate a fast optical modulator capable of switching large amount of optical retardation (a few microns) in less than 1 ms. The result is achieved by employing a dual frequency nematic in cells with high pre-tilt alignment and by providing a special addressing scheme that features amplitude and frequency modulated voltage. We explore the effect of surface alignment and dielectric heating on the switching time. We also report the measurements of dielectric permittivities and crossover frequency of dual frequency nematic