Michael J. O'Callaghan

Fast beam steering with a ferroelectric-liquid-crystal optical phased array.

We demonstrate fast, efficient beam steering using a single 1x32 analog ferroelectric liquid crystal (FLC) spatial light modulator. A high-tilt FLC material with 82 degrees optic-axis switching provides, in a reflective-mode device with a passive quarter-wave retarder between a half-wave FLC layer and a mirror, 91% of full 0-2pi phase modulation. Electronic drive based on applied charge gives 200 micros response-time analog modulation.

Bistable FLCOS devices for doubled‐brightness micro‐projectors

— Optical output is of paramount importance to emerging ultra-miniature projector products. Experimental bistable ferroelectric liquid-crystal-on-silicon (FLCOS) projection microdisplay devices using newly developed FLC materials aligned on obliquely deposited SiO2 have been developed. These devices enable the doubling of the illumination duty cycle, and hence doubling of the achievable projector light output, while maintaining a DC-balanced electrical drive.

High-Tilt, High-PS, de Vries FLCs for Analog Electro-Optic Phase Modulation

Four new de Vries I-A-C* ferroelectric liquid crystal mixtures have been formulated to have high tilt (45°), high polarization, and low smectic layer shrinkage for use in analog electro-optic phase modulators. The mixtures are based on a high-tilt anti-ferroelectric compound which, when combined with other compounds, results in ferroelectric I-A-C* materials. Three of the mixtures include a new germanium-containing liquid crystal compound. X-ray diffraction measurements show layer contraction as small as 7%, while the temperature-dependence of birefringence shows a sharp increase at the A → C* transition as expected of a de Vries material. Charge control drive produced V-shaped switching with low hysteresis.

Second harmonic generation in laterally azo-bridged H-shaped ferroelectric dimesogens

This contribution describes the analysis of experimental results on second harmonic generation (SHG) in a novel laterally azo-bridged H-shaped ferroelectric liquid crystal (FLC) 2, incorporating a disperse red 1 (DR-1) chromophore along the FLC polar axis, and its two mixtures with a laterally azo-bridged H-shaped FLC host 1, incorporating an azobenzene chromophore. The largest dij coefficient at the fundamental wavelength of λ = 1.6 μm is d22 = 4.5 pm/V, the coefficient along the polar axis that is optimized from the viewpoint of the chemical design of NLO FLC molecules. A linear dependence of d22 on the mole fractions of 2 in mixtures has been found, indicating that i) both 1 and 2 have a similar degree of polar order, and ii) dipole–dipole interaction in the DR-1 chromophore of 2 is not strong due to low chromophore density. This work highlights the importance of synthetic tailorability of FLC materials with extra functionality to second-order nonlinear optics applications.

Anticlinic Ferroelectric Bananas for Electro-Optic Modulators

Five bent-core compounds structurally analogous to 8OPIMB6* were synthesized using three types of non-imine linkages for better stability. Only two showed liquid crystal phases, and neither possessed the SmC A P F phase. Four compounds were synthesized with the Tschierske core to determine whether or not fluorinated tails can be used to improve stability while maintaining the SmC A P F phase. All four exhibited polar smectic C phases, and two showed the SmC A P F phase. Racemic 8OPIMB6* was synthesized to test the importance of chirality in SmC A P F compounds, it was found to have properties identical to the chiral 8OPIMB6*.

Analog electro-optic modulators for ferroelectric-liquid-crystal/VLSI spatial light modulators

We report here on analog modulation effects in ferroelectric liquid crystal (FLC) materials and electrical drive schemes that are appropriate to FLC/VLSI spatial light modulations (SLMs). The deformable-helix ferroelectric (DHF) effect paired with fixed-charge drive can give sub- millisecond grey-scale response with VLSI-compatible drive voltages. New DHF materials with long-pitch nematic phases give superior alignment quality and contrast ratio. We present analog FLC driver circuits suitable for VLSI implementation, and show that providing adequate read/write isolation in optically addressed FLC/VLSI SLMs requires special care.

18.2: Bistable FLCOS Devices for Doubled-Brightness Micro-Projectors

Optical efficiency is of paramount importance to emerging ultra-miniature projector products. We have developed experimental bistable ferroelectric-liquid-crystal-on-Silicon (FLCOS) projection microdisplay devices using newly developed FLC materials aligned on obliquely-deposited SiO2. These devices enable doubling of illumination duty cycle, and hence doubling of achievable projector light output, while maintaining DC-balanced electrical drive.

Spatial Light Modulators with Integrated Phase Masks for Holographic Data Storage

A phase mask formed as a planarized relief structure within a few microns of the pixel plane of a ferroelectric liquid crystal SLM eliminates the DC Fourier-plane hotspot, eliminating the need for precision-aligned relay optics

Single-chip correlator implementation for PCI-bus personal computers

We have previously reported on the design and operation of a novel single-chip optical correlator prototype. Two ferroelectric liquid crystal SLMs and a high-speed APS camera were built into a single CMOS integrated circuit. Diffractive Fourier transform lenses were fabricated onto the surface of a window which was mounted on top of the chip. We are now working towards implementing the correlator as a business card-sized module mounted on a PCI card which can be plugged into the motherboard of industry standard PCs. We are also upgrading the SLMs to have analog optical modulation capability. The PCI card contains input and output image buffers, plus high-speed circuitry which digitizes the four analog output channels of the correlators camera. This paper describes the system we are developing, some of the electronic and optical engineering issues involved, and the present status of our work.

Highly integrated single-chip optical correlator

Barriers to commercialization of optical correlators include the complexity and cost of their manufacture, their large size compared to typical electronic processors, and the cost of their components. Using sub-micron CMOS VLSI fabrication processes it is possible to build the two SLMs and photodetector array of a Vander Lugt correlator on a single silicon die. The correlators lenses can be fabricated on a single piece of glass using diffractive optics technology and then attached to the CMOS die to form a monolithic assembly. This approach greatly reduces the mechanical degrees of freedom that must be controlled by the correlators housing thus lowering cost, reducing size, and improving reliability. Here we report on the design and performance of a prototype.