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In this work, we computationally investigate liquid crystal (LC) droplets in the size range 0.03–1 μm, confined within shells of combined anchoring conditions. Two different types of surface were d...

Liquid crystal (LC) droplets have been investigated for a wide range of applications, from displays to sensors. Over the years, a need has arisen for complete understanding of the behaviour of LCs in droplets under different conditions for the development of advanced devices, for which accurate modelling is necessary. We show here, for the first time, both qualitative and quantitative agreement between coarse-grained molecular models and Q-tensor theory calculations for liquid crystal (LC) droplets. The approach is demonstrated for two types of droplet surfaces, which possess strong planar degenerate and strong homeotropic anchoring, respectively. Once its reliability has been proven, our approach was used to identify defects due to changes in anchoring in a small region on the LC droplet surface, which could be triggered, for example, by the adsorption of a nano-particle or a protein. Both coarse-grained simulations and Q-tensor analysis show the appearance of defects in well-determined locations within the LC droplet, albeit sometimes affected by degeneracy due to the symmetry of the systems being investigated. These results suggest the possibility of using LC droplets, in the future, as platforms for advanced sensing as well as for signal intensification.

Consumer demand for high resolution and high refresh-rate displays has naturally led to the fabrication of liquid crystal displays with ever smaller pixels. As a consequence, fringing fields between adjacent pixels grow in magnitude, leading to abrupt changes in orientation. Electric field strengths above some threshold can lead to order melting and, in turn, disclinations. This paper presents accurate modeling of disclinations induced by fringing fields due to interdigitated electrodes in a nematic liquid crystal calculated by means of the Landau–de Gennes theory. Disclination paths are determined while taking into account the flow of the liquid crystal. Making use of interdigitated electrodes, precise electrical control over the creation and positioning of defects is demonstrated for homeotropic, planar, hybrid, and in-plane surface alignments.

This paper proposes a general design method for microstrip devices using liquid crystals (LCs) at microwave frequency. The method employs lumped element modelling to first optimise the filter at the working frequency. Then EM simulation is used for the second optimisation and the full-wave simulation. LC is used as the tunable material since the anisotropy can be changed with low voltages. The approach of modelling of LC as a homogeneous anisotropy demonstrated with Computer Simulation Technology (CST) Microwave Studio is an acceptable approximation, which accurately predicts the tuning range. A new tunable inverted microstrip filter using nematic LCs at millimetre-wave frequencies is designed to verify the method. The proposed design utilises interdigital capacitors in parallel with two inductive loops to form a bandpass filter. It is fabricated and measured, and shows that the centre frequency varies from 5.01 to 5.51GHz (10% tunability) and achieves a 3-dB bandwidth of 450MHz, which is in good agreement with simulation results. A finite-element simulation is used to investigate the detailed behaviour of LC directors in the fully switched state; the effective permittivity is extracted from the finite-element simulation and used in CST to achieve an even more accurate agreement with experimental results.

Liquid crystals with a varying phase profile enable reconfigurable and intelligent devices to be designed, which are capable of manipulating incident electromagnetic fields in display, telecommunications as well as wearable applications. The active control of defects in these devices is becoming more important, especially since the electrodes used to manipulate them are shrinking to nanometer length scales. In this paper, a simple subwavelength, 1D, interdigitated metal electrode structure that can be reconfigured using nematic liquid crystals aligned in the homeotropic, planar, and hybrid methods are demonstrated. Accurate electro‐optic modeling of the directors and the defects are shown, which are induced by the fringing electric fields. Applied voltages result in liquid crystal reorientation near the bottom surface, such that defects are induced between the electrodes. The height of the electrodes does not affect the lateral position of these defects. Rather, this can be achieved by increasing the biasing voltage on the top electrode, which also leads to greater splay‐bend in the bulk of the material. These results therefore aim to generalize the control of defects in complex anisotropic nematic liquid crystals using simple interdigitated structures for a range of reconfigurable intelligent surface applications.

Q-tensor simulation of the liquid crystal structure at the edge of electrodes has been carried out. The modeling shows a twist wall, which reverses direction to form a zig-zag structure. The results are compared with experiment. Also a defect loop is found in micro-lenses formed using a hole electrode structure.

Liquid crystal substrates have been shown to provide the means to develop low-cost, reconfigurable, adaptive and tuneable microwave and MM-wave devices for mobile and wireless communication systems. However, techniques for the characterisation of materials, device fabrication and design are necessary in order to take maximum advantage of the possibilities that these materials offer. This includes appropriate modelling methods to simulate accurately the switching behaviour of the liquid crystal and the characteristics of the wave propagation through the devices, taking full consideration of the point-by-point variation of the material tensor permittivity. We describe these techniques here and show their application in the design of a meander-line phase shifter.

A procedure combining accurate liquid crystal and electromagnetic modelling is developed for the analysis of wave propagation through liquid crystal devices. This is required to study the optics of high resolution liquid crystal cells or cells containing very small features, where diffraction effects occur. It is also necessary for the study of optical waveguiding devices using liquid crystal as variable permittivity substrates. An accurate finite element modelling program is used to find the permittivity tensor distribution, which is then used to find the response of the device to an excitation electromagnetic field by means of a finite difference in the frequency domain (FDFD) approach.

Modelling has been carried out of the Liquid Crystal structures at the edges of electrodes for planar aligned devices, used as phase modulators. The voltage dependence and a threshold voltage of the defect formation is found. The effect of adjacent pixels used in high resolution in LCOS is investigated.

El efecto de la combinacion de tecnicas de establecimiento se evaluo sobre el crecimiento inicial de Grevillea robusta, en el norte de la provincia de Corrientes, Argentina. Los tratamientos incluyeron la combinacion de dos factores. El primero de ellos aplicado previo a la plantacion de G. robusta y consistio en el manejo de residuos con dos niveles: a) conservacion de residuos y b) quema de residuos. El segundo factor consistio en la aplicacion de fertilizante con tres niveles: a) sin aplicacion de fertilizante, b) aplicacion de fertilizante luego del establecimiento de la plantacion y, c) aplicacion de fertilizante despues de un ano del establecimiento de la plantacion. La combinacion de tecnicas de establecimiento de la plantacion modifico el crecimiento inicial de G. robusta. La mejor combinacion fue la quema de residuos con fertilizacion durante el establecimiento. Con dicha combinacion, la plantacion logro un incremento en diametro de 43.7 % a los 36 meses de edad, siendo superior que el obtenido con el tratamiento de conservacion de residuos sin aplicacion de fertilizante

PurposeThe purpose of this paper is to provide an overview of the research in a project aimed at developing manufacturing techniques for integrated optical and electronic interconnect printed circuit boards (OPCB) including the motivation for this research, the progress, the achievements and the interactions between the partners.Design/methodology/approachSeveral polymer waveguide fabrication methods were developed including direct laser write, laser ablation and inkjet printing. Polymer formulations were developed to suit the fabrication methods. Computer‐aided design (CAD) tools were developed and waveguide layout design rules were established. The CAD tools were used to lay out a complex backplane interconnect pattern to meet practical demanding specifications for use in a system demonstrator.FindingsNovel polymer formulations for polyacrylate enable faster writing times for laser direct write fabrication. Control of the fabrication parameters enables inkjet printing of polysiloxane waveguides. Several different laser systems can be used to form waveguide structures by ablation. Establishment of waveguide layout design rules from experimental measurements and modelling enables successful first time layout of complex interconnection patterns.Research limitations/implicationsThe complexity and length of the waveguides in a complex backplane interconnect, beyond that achieved in this paper, is limited by the bend loss and by the propagation loss partially caused by waveguide sidewall roughness, so further research in these areas would be beneficial to give a wider range of applicability.Originality/valueThe paper gives an overview of advances in polymer formulation, fabrication methods and CAD tools, for manufacturing of complex hybrid‐integrated OPCBs.

Introduction: At high bit rates copper tracks in printed circuit boards (PCBs) suffer severe loss and pulse distortion due to radiation of electromagnetic waves, dispersion and bandwidth limitations. The loss can be overcome to some extent by transmitting higher power pulses and by changing the dielectric constant and loss tangent of the PCB substrate material. However, high power pulses consume power and can cause electro-migration which reduces the board lifetime, although the copper tracks can be surrounded by another metal to prevent this at the expense of further processing steps. The use of special board materials can be costly and some materials containing high dielectric constant crystallites can cause poor adhesion. The pulse distortion, dispersion and bandwidth limitations can be overcome to some extent by the use of pulse pre-emphasis and adaptive equalisation at further cost. Electromagnetic waves are radiated efficiently at high bit rates removing power from the track so causing loss, but more importantly they are also received efficiently by other nearby and distant copper tracks on the same PCB, or on adjacent PCBs, or PCBs and other electrical conductors outside of the system enclosure. This EMI crosstalk causes increased noise and so degrades the signal to noise ratio and the bit error rate of the copper track interconnections. Therefore, the main forces driving the development of alternative interconnect technologies are the EMI crosstalk, which becomes increasingly more serious as bit rates increase for longer and denser interconnects, and secondly the cost of overcoming the other problems that occur in copper interconnects at high bit rates. Optical fibres have replaced copper cables for long distance, backbone and submarine applications where they offer wide bandwidths for low loss, produce and receive no electromagnetic interference, and are relatively low cost. Optical interconnects are beginning to penetrate the markets at shorter distances, such as in local area networks, and as their cost is reduced, will be used within the system enclosure. The use of optics is expected to occur first where the problems for copper are most significant which is for high bit rate, dense interconnections in large area backplanes within non-conducting enclosures. Optical fibres are not the most convenient for interconnections within a system as they can only bend through a large radius of about 10 cm, otherwise light escapes from the fibre core into the cladding resulting in loss and signal corruption. Fibre connectors form a major part of the cost of the optical interconnect and a system with many fibres has many costly connectors. The fibres must be individually routed and errors in routing are time consuming to debug and correct. The fibres can be laid flat on the PCB plane and even bonded together within an epoxy layer, but this is not suited to low cost mass production. An alternative technology suitable for low cost mass production is that of multimode polymer buried channel optical waveguide interconnections within layers in the multilayer PCB formed by the same, or slightly modified, processes already available within PCB manufacturing facilities. Copper tracks are still required in such substrates to transmit power through the backplane (or motherboard), Figure 1, in order to power mezzanine (or line, or drive, or daughter) boards and copper is still a practical and low cost option at low data rates. Hence, there is a need to develop a new type of multilayer hybrid PCB in which optical waveguide interconnects are used for the highest data rates, with copper tracks for lower data rates and for power lines and earth planes. These issues have been anticipated by system design companies such as Xyratex Technology, IBM Zurich and Siemens C-Labs, microprocessor designers such as Intel and materials development companies such as Dow Corning, NTT, Rohm and Haas and Exxelis, who have instituted research in their own laboratories and in associated universities into optical waveguide interconnect technology. Leading Universities and Research Institutions such as Cambridge (CAPE), University College London (UCL), Heriot Watt University, Loughborough University, National Physical Laboratory (NPL), IMEC - Ghent University, TFCG Microsystems, Belgium, Paderborn University, Germany, Helsinki University of Technology, Espoo, Finland and ETRI, South Korea are developing novel polymer materials, developing fabrication techniques, discovering design rules for waveguide layout and carrying out precision characterisation. Optical buried channel waveguides usually have a core with an approximately square or rectangular cross section made from a high refractive index (slow speed of light) material and a cladding surrounding the core of a lower refractive index (higher speed of light). They operate by total internal reflection (TIR) in a similar way to optical fibres. The cost of waveguide connectors is minimised by choosing to use multi-mode waveguides which typically have cores of 40 - 70micron width which can tolerate more misalignment than single mode waveguides. The optical buried channel waveguides are formed on a plane by a variety of fabrication techniques which can be implemented, after slight adaptation, in PCB manufacturers. Arrays of low-cost vertical cavity surface emitting lasers (VCSELs) emitting 850 nm wavelength and arrays of photodiodes operating at 1 0 Gb/s are readily available at low-cost for use in optical transmitters and receivers. At this wavelength, polymer is a convenient low-loss material for use as the core and cladding. Polymers can be chosen or designed which can be easily processed to form waveguides at low temperatures, have low cost, and can withstand subsequent high temperature reflow soldering processes. For optical printed circuit boards to be brought into widespread use, layout tools must be made readily available which design both the copper tracks and the optical waveguides [1]. In 2006 David R. Selviah of UCL, formed a large consortium of complementary universities and companies and led a successful bid to carry out a Flagship project entitled “Integrated Optical and Electronic Interconnect PCB Manufacturing (OPCB)” in the Innovative Electronics Manufacturing Research Centre (IeMRC). The consortium companies represented a complete supply and manufacturing chain and route to market for the polymer waveguide technology including companies manufacturing PCB layout tools, computer programs for modelling the behaviour of multimode waveguides, developing and supplying low loss polymer formulations, manufacturing multilayer PCBs, supplying printer fabrication equipment together with end user system companies who require optical printed circuit boards. The following sections describe the project’s objectives, the approaches being taken and some examples of what has been achieved so far in the project with an indication of future directions.

A stable reproducible optical standard source for measuring multimode optical fiber attenuation is required as recent round robin measurements of such fibers at several international companies and national standards organizations showed significant variation when using a source having only the encircled flux in the near field emerging from it defined. The paper presents and compares the far field modal power distributions for (i) 2 km and 3 km step-index multimode Hard Plastic Cladding Fibers, HPCF, (SI-MMF) with 200 μm silica core diameter, 0.37 numerical aperture (NA) and polymer cladding, (ii) a 10 m silica graded-index multimode fiber (GI-MMF) with 50 μm core diameter and 0.2 NA, and (ii) a near field Encircled Flux Mode Convertor or “modcon”. A free space method for measuring the far field using a Lightemitting diode (LED) centered at 850 nm wavelength with 40 nm 10 dB-bandwidth and a charge-coupled device (CCD) camera is compared with a f-theta multi-element lens based far field pattern (FFP) system. Mandrels of different diameter and different numbers of turns of the fiber around them were used to achieve an equilibrium mode distribution (EMD) for the GI-MMF. The paper defines encircled angular flux (EAF) as the fraction of the total optical power radiating from a multimode optical fiber core within a certain solid angle in the far field. The paper calculates the EAF when the solid angle increases from the far field centroid.

The effective dielectric constant of the top grounded coplanar waveguide with a liquid crystal (LC) superstrate for phase shifting applications is investigated in the frequency range of 30–60 GHz. Two nematic LC mixtures, namely E7 and MDA-00-3506, are used as the superstrate. The measurements show that MDA-00-3506 offers higher values of phase shift per millimeter than its E7 counterpart. In particular, the MDA-00-3506 provides 3.14°/mm, whereas E7 gives 2.79°/mm at 60 GHz. The results of the dielectric constants from measurement and computer modeling are found to agree to within 5%. For the modeling, a comprehensive finite element package predicting the local alignment of LC molecules and effective dielectric constant at different bias voltages and frequencies are used. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1416–1418, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27564

Albeit a disproportionate rate of atrophy in the medial temporal lobe (MTA) represents a reliable marker of Alzheimer’s disease (AD) pathology, the measurement of MTA is not being widely used in daily clinical practice. This is mainly because the methods available to date are sophisticated and diffiult to implement (volumetric methods) or lack objectivity (visual rating scales). Here, we aimed to assess the reproducibility of computing the 2D-yrA-MTL and the efforts needed to start the usage of 2D-yrA-MTL. A series of 290 1.5T-MRI studies on 230 subjects in the age range of 65–85 years, including patients with AD (n = 100), MCI (n = 100) and matched controls (n = 90) were examined by experienced tracers (ET) and inexperienced tracers (IT). The IT got suffiiently trained by attending to a minimum of 3 cases before being able to perform the 2D-yrA-MTL on their own and without mistakes according to the corrections made by the ET. After training, the IT needed 5 minutes to perform the 2D-yrA-MTL on a new case. The intrarater and interrater reproducibility of 2D-yrAMTL was good. In conclusion, the 2D-yrA-MTL is a simple, objective and reproducible method that could be easily implemented in clinical practice.

The seven papers in this special issue address a selection of some of the issues concerning the liquid crystal on silicon technology, from fabrication and design to some of the applications.

In this paper a two-dimensional (2-D) dynamic model, based on a tensor formulation and solved numerically by combining finite elements and finite differences, is proposed and used for analyzing nematic liquid crystal (LC) test cells with interdigital electrodes. We compare theoretical and experimental results concerning the switching behavior, response mechanism, and viewing angle characteristics of nematic LC pixel structures which use the in-plane-switching (IPS) mode. The good agreement observed between theory and experiment in terms of electro-optical properties validates our modeling and demonstrates its potential for design optimization. We show that the proposed LC test cells, using the in-plane-switching mode, ensure switching-ON and -OFF response times of 22 and 28 ms, respectively, and excellent viewing angle characteristics.

Preliminary modeling results and the description of the modeling technique for analysis and design of a tunable meander-line microstrip phase-shifter for a novel liquid crystal-based beam steerable planar antenna operating at 60 GHz are presented. In this phase-shifter, the substrate is a nematic liquid crystal. Two three-dimensional finite-element modeling programs are implemented in order to determine first the director distribution within the liquid crystal substrate for different bias voltages and then to obtain the wave-propagation along the meander-line, leading to the characterization of the phase shifter. In an example, the results from the presented anisotropic solution is compared with those generated by a commercial software considering a dielectric channel in place of the liquid crystal below the microstrip line, with an isotropic dielectric constant representing once the switched and once the un-switched state of the liquid crystal.

Accurate, reliable and fast numerical modeling methods are required to design the optimum radial refractive index profile for single and multimode fibers to give specific dispersion characteristics prior to or even obviating costly experimental work. Such profiles include graded index and multiple concentric cladding layers. In this paper, a new numerical method is introduced which enables the derivatives of the propagation coefficient to be calculated analytically up to the third order of a single mode or multimode weakly guiding optical fiber with an arbitrary radial refractive index profile. These quantities are required to determine the group delay, 2 g , chromatic dispersion, D , and dispersion slope of the fiber. The expansion of the modal fields in terms of Laguerre-Gauss polynomials in the Galerkin method offers certain benefits. In particular, due to simplicity of the basis functions it is possible to carry out further analytical work o n the results such as repeated differentia tion of the matrix equation resulting from th e Galerkin method to define up to the third-order derivatives of the propagation coefficients with respect to wavelength. This avoids approximation errors inherent in numerical differentiation, giving better accuracy and, at the same time, significantly reduces the computation time. A computer program was developed to demonstrate the proposed method for single and multimode fibers with radially arbitrary refractive index profiles. The paper provides simulation results to validate the approach. Keywords: dispersion, dispersion slope, single-mode fibers, few-mode fibers, step-index fibers, double-clad fibers, triple-clad fibers, graded index profile, analytical dispersion evaluation, Galerkin method

This paper presents an efficient solver for the generalized eigenvalue problems of large, sparse, arbitrary real or complex matrices. This solver based on the simplified subspace iteration can efficiently find one or a group of desired eigenvalues and the respective eigenvectors. The statistics and comparison are also presented to show the performance of the sparse matrix solver. >

This paper presents a laser-based auto-stereoscopic 3D display technique and a prototype utilizing a dual projector light engine. The solution described is able to form dynamic exit pupils under the control of a multi-user head-tracker. A prototype completed recently is able to provide a glasses-free solution for a single user at a fixed position. At the end of the prototyping phase it is expected to enable a multiple user interface with an integration of the pupil tracker and the spatial light modulator.

A finite element framework is presented to combine advanced three-dimensional liquid crystal director calculations with a full-vector beam propagation analysis. This approach becomes especially valuable to analyze and design structures in which disclinations or diffraction effects play an important role. The wide applicability of the approach is illustrated in our overview from several examples including small pixel LCOS microdisplays with homeotropic alignment.

A finite element modesolver and beam propagation (BPM) algorithm are applied to the optical analysis of liquid crystal waveguides. Both approaches are used in combination with advanced liquid crystal calculations and include a full dielectric tensor in solving the Helmholtz equation to model the liquid crystal behavior properly. Simulation of the beam propagation in a waveguide with tunable liquid crystal cladding layer illustrates the coupling of a Gaussian beam to the fundamental waveguide mode obtained with the modesolver. Excellent quantitative agreement between both approaches illustrates the potential of these methods for the design of advanced devices. The high accuracy of the BPM algorithm for wide angle propagation, essential in the analysis of high index contrast waveguides, is illustrated for angles up to 40 deg.

Dielectric-lined hollow metallic waveguides provide a solution for guiding THz pulses that exhibits low losses, excellent mode quality and low dispersion. We analyzed mode structure and dispersion using THz near-field microscopy, timedomain spectroscopy and numerical methods to describe THz pulse propagation.

In this paper the current state of research in our labs on the mm-wave characterization of LCs and the application of LC in development of two devices were presented. It has been shown that the characterization of LCs can be done using the resonant and broadband methods, but each has its own advantages and disadvantages. Also shown were a LC-based reflection type phase shifter, providing a large phase shift compared to the conventional transmission line phase shifters and a long LC-based resonator with multiple tunable resonant frequencies.

An autostereoscopic 3D display based on direct-view RGB laser projection via a transparent display screen is presented. Dynamic exit pupils are formed at the target eye locations with the help of a pupil tracker.

We demonstrate tuning of the resonance wavelength of silicon-on-insulator optical ring resonators. The devices are clad with a layer of nematic liquid crystal. The electrooptic effect of the anisotropic liquid crystal allows us to change the effective index of the TE waveguide mode with an externally applied voltage. The electric field will reorient the liquid crystal director which alters the refractive index of the cladding layer. The evanescent tails of the waveguide mode feel this change. The change in effective index has a direct effect on the resonance wavelength. In our setup, the director tilts from an orientation parallel to the waveguides to an orientation perpendicular to the substrate. This way, it is the longitudinal component of the electric field of the light that experiences the largest change in refractive index. Starting from this principle, we show experimental tuning of the resonance wavelength over 0.6nm towards shorter wavelengths. Theoretical considerations and simulations with a finite element modesolver capable of handling full anisotropy confirm the experimental results and provide insights in the tuning mechanism.

An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell's equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a directional coupler based on liquid crystals and the near-field diffraction of a plane wave in a structure containing micrometer scale variations in the transverse refractive index, similar to the pixels of a spatial light modulator. (C) 2009 Optical Society of America

Design curves for insertion loss of multimode polymer waveguide 90 bends are reported as a function of bend radius for several waveguide widths. For the first time, to our knowledge, in multimode rectangular waveguides the insertion loss is resolved into its components of transition, radiation and propagation loss, in order of decreasing strength, separating them from input and output coupling loss by calibration and comparison of experimentally measured and beam propagation method ( BPM) modeled curves. We used the method of nested bends for the first time in multimode polymer waveguides to calculate the propagation loss on a small substrate without using destructive cut-back. The lowest loss of 0.74 dB occurred for a 50 mu m square cross section, Delta n=0.0296, 13.5 mm radius waveguide bend. (c) 2007 Optical Society of America.

Liquid crystals are an attractive medium for millimetre-wave band communications devices due to their large birefringence and reconfigurability. However, characterizing these materials is challenging at these frequencies. This work details simulation tools that have been developed to aid in this process, through the accurate analysis of the liquid crystal orientation and wave propagation.

Ion conductance microscopy (ICM) is a powerful new technique that allows non-contact, nano-scale imaging of the topography of living cells in physiological solutions (Hansma et al., Science 243:641-643, 1989; Korchev et al., Biophys. J. 73:653-658, 1997). ICM works by measuring the reduction of current that occurs when a nano-pipette probe, in a conducting solution, approaches a non-conducting surface, such as the cell membrane. In ICM a point is chosen in the x-y plane and the probe is lowered towards the surface. The z-position at which the probe current is reduced by a specified amount (determined by the current set-point) indicates the relative height of the sample at that location. Measuring such heights at each position as the sample is scanned in the x-y plane allows the cell topography to be determined. We have developed a finite element-based computational model that can simulate nano-scale ICM imaging for small (∼100 nm) probes. This model allows us to make a systematic study of how objects of arbitrary size and geometry appear in images obtained using a variety of current set-points and/or probes of different shapes. The implications of these simulations for producing an optimized scanning routine and the feasibility of using data from simulations to correct the recorded image so that it represents a true topography are also examined.

An overview of the £1.3 million EPSRC and company matched funded Innovative electronics Manufacturing Research Centre (IeMRC) Flagship project between 3 UK universities and 10 companies entitled "Integrated Optical and Electronic Interconnect PCB Manufacturing". The project aims to develop of optical waveguide design rules, layout software, fabrication methods compatible with commercial production, characterisation techniques and optical connector design to provide a supply chain for Polymer Multimode Optical Waveguide Printed Circuit Boards (OPCB) for 10 Gb/s board-to-board interconnections.

Purpose – To introduce the Innovative Electronics Manufacturing Research Centre Flagship Project: Integrated Optical and Electronic Interconnect PCB Manufacturing, its objectives, its consortium of three universities and ten companies and to describe the university research being carried out. This paper briefly reviews the motivation for developing novel polymer formulations, fabrication techniques, layout design rules and characterisation techniques for hybrid electronic and optical printed circuit boards (PCBs) using multimode polymer optical waveguide interconnects. Design/methodology/approach – The authors are investigating a number of different fabrication techniques which they compare with each other and with modelled calculations of waveguide components. The fabrication techniques include photolithography, laser ablation, direct laser writing, embossing, extrusion and ink jet printing. Findings – A number of design rules for polymer multimode waveguides have been found and published. Techniques for ink jetting polymer to print waveguides and laser ablation techniques have been developed. New formulations of polymer which cure faster for direct writing have also been developed. Research limitations/implications – Further work is needed to thicken the ink jet printed polymer and to investigate side wall roughness of the ablated waveguides and development of new polymer formulations for dry film. Further research is also needed on construction of prototype system demonstrators. Practical implications – The fabrication techniques being developed are designed to be transferred to industrial PCB manufacturers to enable them to make higher value optical PCBs. The design rules being discovered are being entered into commercial PCB layout software to aid designers of optical PCBs. Originality/value – The paper is of interest to PCB manufacturers who wish to upgrade their processes to be able to manufacture optical PCBs. The university research is original and some has been published as shown in the publications in the reference list.

A nematic liquid crystal spatial light modulator used as a phase-modulating device and operating in the reflective mode is analyzed using three-dimensional modeling. Two configurations, which differ in their electrode placement relative to a fixed quarter-wave plate, are considered across a range of steering directions, with the grating conformal and in some cases oblique to the pixel grid. For each steering direction the sensitivity of the diffraction orders to the polarization state of the incident wavefront is studied. Optimal alignment of the liquid crystal is suggested to reduce this sensitivity.

Modeling of nematic liquid crystal structures using the tensor method are presented for various configurations. In particular defect formation at the edges of electrodes, which depend on alignment direction have been studied, as well as droplets of cholesteric liquid crystals, where the pitch must adapt to conform to the surface alignment of the droplet and the position of the defects at the poles.

A novel and rigorous analysis of an abrput bend in a dielectric waveguide is presented, obtained by using a combination of the vector finite element method (FEM) formulation and the least squares boundary residual boundary (LSBR) method. The transmission efficiency of an optical wave through a guided-wave structure incorporating a sharp corner is investigated. After validating the newly developed numerical approach for a planar structure, results for a more realistic structure with a three-dimensional structure are also presented.

We show that the resonance wavelength of silicon-on-insulator ring resonators can be tuned when a top cladding of liquid crystal is present. In-plane strip electrodes are used to generate an electric field that reorients the liquid crystal director in the plane parallel to the chip surface. This causes the resonance wavelength to shift toward longer wavelengths. The magnitude of this shift is about 1 nm, which is twice as large as previously reported shifts. The experimental results are verified extensively with our simulation tools, where a calculation of the director orientation is combined with a fully anisotropic mode solver. From this, we get a clear view of the mechanism behind the tuning.