Methods of manufacturing a liquid crystal device including depositing a layer of liquid crystal material on a substrate and imprinting a pattern on the layer of liquid crystal material using an imprint template are disclosed. The liquid crystal material can be jet deposited. The imprint template can include surface relief features, Pancharatnam-Berry Phase Effect (PBPE) structures or diffractive structures. The liquid crystal device manufactured by the methods described herein can be used to manipulate light, such as for beam steering, wavefront shaping, separating wavelengths and/or polarizations, and combining different wavelengths and/or polarizations.

Virtual and augmented reality systems and methods

The review describes the status of the studies and the recent achievements in the field of photoalignment of liquid crystals. An update classification of photoaligning materials and exposure schemes, and analyzes of the relationship between the molecular structure of the materials and characteristics of LC alignment are provided. In addition, bulk mediated photoalignment and combination of photoalignment with other alignment methods are discussed. Along with traditional, recently proposed applications of the photoalignment technique are considered.

Photoalignment of liquid crystals: basics and current trends

Nonmechanical steering of optical beams will enable revolutionary systems with random access pointing, similar to microwave radar phased arrays. An early approach was birefringent liquid crystals writing a sawtooth phase profile in one polarization, using 2pi resets. Liquid crystals were used because of high birefringence. Fringing fields associated with voltage control required to implement the 2pi resets have limited the efficiency and steering angle of this beam steering approach. Because of steering angle limitations, this conventional liquid crystal steering approach is usually combined with a large angle step-steering approach. Volume holograms, birefringent prisms or sawtooth-profile birefringent phase gratings, and circular-type polarization gratings are the large angle step steering approaches that will be reviewed in this paper. Alternate steering approaches to the combined liquid crystal and step-steering approach exist. Microelectromechanical system mirrors, lenslet arrays, electrowetting, and a variable birefringent grating approach will be reviewed and compared against the conventional liquid crystal and step-steering approaches. Step-steering approaches can also be combined with these approaches. Multiple nonmechanical steering approaches are developing that will allow high-efficiency steering, excellent steering accuracy, and wide fields of view.

A Review of Phased Array Steering for Narrow-Band Electrooptical Systems

We demonstrate a broadband, thin-film, polarizing beam splitter based on an anisotropic diffraction grating composed of reactive mesogens (polymerizable liquid crystals). This achromatic polarization grating (PG) manifests high diffraction efficiency (~100%) and high extinction ratio (⩾1000:1) in both theory and experiment. We show an operational bandwidth Δλ/λ0~56% (roughly spanning visible wavelength range) that represents more than a fourfold increase of bandwidth over conventional PGs (and significantly larger than any other grating). The diffraction angle and operational region (visible, near-infrared, midwave infrared, and ultraviolet wavelengths) may be easily tailored during fabrication. The essence of the achromatic design is a stack of two chiral PGs with an opposite twist sense and employs the principle of retardation compensation. We fully characterize its optical properties and derive the theoretical diffraction behavior.

Achromatic diffraction from polarization gratings with high efficiency.

1 What is a liquid crystal 2 1.1 Nematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Cholesterics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Smectics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.4 Columnar phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.5 Lyotropic liquid crystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Introduction to Liquid Crystals

We report experimental results of a liquid crystal polarization grating (LCPG) modulating unpolarized light with high contrast for the first time. Striking results are observed: nearly ideal diffraction into the first orders at > 99%, contrast ratios of up to 600:1 for monochromatic light, switching times of ∼ 2 ms for nematic LCs, and threshold voltage of 1.65 Vrms.

39.4: Polarization-Independent Switching With High Contrast from a Liquid Crystal Polarization Grating

We report our recent experimental results on a new polarization-independent, liquid crystal (LC) spatial light modulator (SLM) Based on a periodic nematic director profile, the modulator acts as a switchable diffraction grating with only 0th- and ±1st-orders at efficiencies of ≥ 99%, manifests contrast ratios ~600:1 (for laser light), switching times of ~2ms, and threshold voltages of < 1V/μm Results of modulating broadband, unpolarized light from light-emitting-diodes (LEDs) indicates that contrast ratios are ~100:1 so far Note that incoherent scattering for visible light is very low, and that samples are typically completely defect-free over large areas An important feature of this diffractive polarization-independent SLM compared to its predecessors is its potential to achieve much larger diffraction angles, which enables a larger aperture (and etendue) In addition to describing the fabrication and characteristics of this SLM in general, we report on our initial progress in implementing a projection display system All of the surprising and useful results from this grating arise from its continuous nematic director, which is most properly classed as a switchable polarization grating (PG) The SLM described here offers the inherent advantages polarization-independence at the pixel-level and fairly fast switching with nematic LCs, while maintaining similar switching voltages, cell thickness, contrast ratios, and materials

A polarization-independent liquid crystal spatial light modulator

— Progress in the use of liquid-crystal polarization grating (LCPG) to modulate unpolarized (and polarized) light with a grating period as small as 6.3 μm is reported. Similar to LCPGs formed at larger periods (11 μm) reported previously, polarization-independent switching, predominantly three diffraction orders, maximum contrast ratios of ∼100:1 for unpolarized broadband light, very low scattering, and diffraction efficiencies >98% continue to be observed. The smaller period led to an expected lower threshold voltage, even though the thickness was greater. Because the smaller grating period enables a brighter result from a Schlieren projection scheme for a microdisplay using the LCPG light valve, the inherent tradeoffs involved with both material and design parameters are discussed, and prospects for a polarization-independent projection display are commented upon.

Polarization-independent modulation for projection displays using small-period LC polarization gratings

We report on our first experimental comparison of polarizationindependent projection schemes using the liquid crystal polarization grating (LCPG) modulator as the active element. This recently-demonstrated LC grating has unique diffraction properties, and we evaluate its performance using the bright- and dark-field Schlieren configurations and consider its use with a TIR-prism assembly. Each scheme shows promise for highbrightness and good-contrast projection for different applications. 1. Introduction crystal polarization gratings (LCPGs) show great promise as projection display modulators of unpolarized light, exhibiting high contrast and experimentally-demonstrated 100% diffraction efficiency [1]. This type of modulator is particularly suited for mobile, battery-powered “pocket” projectors that demand high contrast and brightness with minimal power consumption. As with the other types of projection display systems using diffractive modulators, the contrast and brightness of our system depends on the projection scheme employed. Since the principle of operation in the LCPG is distinct from previous LC gratings, we anticipate comparably improved projected image properties (contrast and brightness). As only very limited experimental and theoretical investigations into LCPG switches have been carried out (and none utilizing a realistic projection scheme), here we report on the first examination of such. This information should strongly inform the design of any realistic projection system based on the LCPG modulator. The key feature of our polarization-independent modulator is the diffractive LCPG, whose operation and structure is outlined in Fig. 1. This grating is unique from conventional gratings in that only three orders (m=±1,0) are present, and its diffraction efficiency for unpolarized light follows [1]:

P-209: Evaluation of Projection Schemes for the Liquid Crystal Polarization Grating Operating on Unpolarized Light

As data converter sample rates increase there is a push to quantify the feasibility of all-digital beamforming solutions in L/S/C-band and beyond. For those systems requiring multiple channels to achieve the performance required, measured data on both the individual and combined-channel transmitter and receiver performance using these new converters is warranted for system architects to derive the required system-level models. This paper discusses measured multi-channel phase noise, noise spectral density, linearity and spurious improvements when using a direct-S-band-sampled digitizer transceiver as the backbone of the design. Over-the-air all-digital beamforming is also demonstrated using the hardened DSP on these new digitizer integrated circuits.

W. Michael Jones

Papers

39.4: Polarization-Independent Switching With High Contrast from a Liquid Crystal Polarization Grating

A polarization-independent liquid crystal spatial light modulator

Polarization-independent modulation for projection displays using small-period LC polarization gratings

P-209: Evaluation of Projection Schemes for the Liquid Crystal Polarization Grating Operating on Unpolarized Light

Novel All-Digital Beamforming Techniques for L/S/C-Band Multi-Channel Systems Leveraging Hardened DSP on Integrated Circuits