Journal Publications

The following is a list of publications for the members of the Soft Matter Photonics Group (includes research carried out at Oxford and elsewhere).

2020

 

Millisecond optical phase modulation using multipass configurations with liquid crystal devices Yihan Jin, Steve J. Elston, Julian A. J. Fells, Martin J. Booth, Chris Welch, Georg H. Mehl, and Stephen M. Morris Physical Review Applied 14, 024007 (2020)

We present two configurations for analog 0 to 2π optical phase modulation using liquid crystals (LCs), each of which achieve switching times that are 1 ms or less. One configuration is based on the switching behavior of a so-called nematic pi cell, and the other is based on the flexoelectro-optic effect in chiral nematic LCs when operated in the uniform lying helix geometry. Both configurations exploit a multipass optical arrangement to enhance the available optical phase range, while maintaining a fast switching speed. Moreover, these devices can be operated at or close to room temperature. Experimental data are found to be in good agreement with results predicted from theory for these multipass phase-modulation configurations.

Electrically Tunable Printed Bifocal Liquid Crystal Microlens Arrays Waqas Kamal, Jia‐De Lin, Steve J. Elston, Taimoor Ali, Alfonso A. Castrejón‐Pita, and Stephen M. Morris Advanced Materials Interfaces 7, 2000578 (2020) 

In this communication, the fabrication of electrically tunable bifocal liquid crystal (LC) microlenses using drop‐on‐demand inkjet printing is demonstrated. By treating the glass substrate with a homeotropic alignment layer, the printed droplets are found to form plano‐convex lenses with focal lengths in the range of 220–463 µm, depending upon the number of droplets deposited at each location on the substrate. The precision of the process allows for the microlenses to be deposited in between in‐plane indium tin oxide electrodes. In the presence of a high amplitude electric field, the director within the LC droplets is observed to align with the direction of the applied field, but without any accompanying distortion in the droplet profile. However, these changes in the LC director alignment are found to result in a bifocal behavior rather than a continuous change in the focal length. It is also found that there exists a range of voltages for which two focal planes are observed.

Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2π modulation  Xiuze Wang, Julian A. J. Fells, Taimoor Ali, Jia-De Lin Chris Welch, Georg H. Mehl, Timothy D. Wilkinson, Martin J. Booth, Stephen M. Morris, and Steve J. Elston AIP Advances 10, 055011 (2020)

In this paper, we demonstrate analog phase modulation in a transmissive configuration using the flexoelectro-optic effect in short-pitch chiral nematic liquid crystal (LC) devices. Two different modes are considered, both of which are shown to generate full 2π phase modulation at 1 kHz switching frequency. The first configuration that is considered consists of a half-wave plate that is placed between two flexoelectro-optic LC devices that are subjected to electric fields that are applied in phase. Second, we demonstrate that a similar phase modulation response can be observed by removing the half-wave plate and subjecting the two flexoelectro-optic LC devices to electric fields whereby the polarities are out of phase. Both configurations demonstrated herein are promising for the development of next-generation LC spatial light modulators, particularly when reflective geometries are challenging or impractical.

Electrically-tunable positioning of topological defects in liquid crystals John J. Sandford O’Neill, Patrick S. Salter, Martin J. Booth, Steve J. Elston, Stephen M. Morris Nature Communications 11, 2203 (2020

Topological defects are a consequence of broken symmetry in ordered systems and are important for understanding a wide variety of phenomena in physics. In liquid crystals (LCs), defects exist as points of discontinuous order in the vector field that describes the average orientation of the molecules in space and are crucial for explaining the fundamental behaviour and properties of these mesophases. Recently, LC defects have also been explored from the perspective of technological applications including self-assembly of nanomaterials, optical-vortex generation and in tunable plasmonic metamaterials. Here, we demonstrate the fabrication and stabilisation of electrically-tunable defects in an LC device using two-photon polymerisation and explore the dynamic behaviour of defects when confined by polymer structures laser-written in topologically discontinuous states. We anticipate that our defect fabrication technique will enable the realisation of tunable, 3D, reconfigurable LC templates towards nanoparticle self-assembly, tunable metamaterials and next-generation spatial light modulators for light-shaping.

A Thin‐Film Flexible Defect‐Mode Laser Taimoor Ali, Jia‐De Lin, Benjamin Snow, Xiuze Wang, Steve J. Elston, Stephen M. Morris Advanced Optical Materials 81901891 (2020) 

Laser emission from a flexible defect‐mode structure consisting of two photopolymerized liquid crystal thin films separated by a dye‐doped polymethylmethacrylate defect layer is demonstrated. A simple and cost‐effective film transfer technique is used to fabricate the flexible laser and the corresponding laser emission characteristics, which shows single‐mode laser emission at λ = 582 nm, with an excitation threshold of Eth = 12.3 ± 0.5 µJ cm−2 per pulse and a slope efficiency of ηs = 6.0 ± 0.3%, are presented. The polarization state of the laser emission are also presented and are compared with the findings reported in the literature. Finally, laser‐beam steering is demonstrated up to 42° by subjecting the device to a mechanically induced deformation that creates a radius of curvature of 5 mm, which is of potential interest for conformable and wearable technology platforms.

Active Metamaterials with Negative Static Electric Susceptibility Flynn Castles, Julian A. J. Fells, Dmitry Isakov, Stephen M. Morris, Andrew A. R. Watt, Patrick S. Grant Advanced Materials (2020)

Although well‐established textbook arguments suggest that static electric susceptibility χ(0) must be positive in “all bodies,” it has been pointed out that materials that are not in thermodynamic equilibrium are not necessarily subject to this restriction. Media with inverted populations of atomic and molecular energy levels have been predicted theoretically to exhibit a χ(0) < 0 state, however the systems envisioned require reduced temperature, reduced pressure, and an external pump laser to maintain the population inversion. Further, the existence of χ(0) < 0 has never been confirmed experimentally. Here, a completely different approach is taken to the question of χ(0) < 0 and a design concept to achieve “true” χ(0) < 0 is proposed based on active metamaterials with internal power sources. Two active metamaterial structures are fabricated that, despite still having their power sources implemented externally for reasons of practical convenience, provide evidence in support of the general concept. Effective values are readily achieved at room temperature and pressure and are tunable throughout the range of stability −1 < χ(0) < 0, resulting in experimentally‐determined magnitudes that are over one thousand times greater than those predicted previously. Since χ(0) < 0 is the missing electric analog of diamagnetism, this work opens the door to new technological capabilities such as stable electrostatic levitation.

Plasmonic Effects of Dual-Metal Nanoparticle Layers for High-Performance Quantum Dot Solar Cells John Hong, Byung-Sung Kim, Bo Hou, Yuljae Cho, Sang Hyo Lee, Sangyeon Pak, Stephen M. Morris, Jung Inn Sohn, and SeungNam Cha Plasmonics 1510071013 (2020).

To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films.


2019

 

Direct Epitaxial Synthesis of Selective Two-Dimensional Lateral Heterostructures Juwon Lee, Sangyeon Pak,Young-Woo Lee,Youngsin Park, A-Rang Jang, John Hong, Yuljae Cho, Bo Hou, Sanghyo Lee, Hu Young Jeong, Hyeon Suk Shin, Stephen M. Morris, SeungNam Cha, Jung Inn Sohn, Jong Min Kim ACS Nano 13, 13047-13055 (2019)

Two-dimensional (2D) heterostructured or alloyed monolayers composed of transition metal dichalcogenides (TMDCs) have recently emerged as promising materials with great potential for atomically thin electronic applications. However, fabrication of such artificial TMDC heterostructures with a sharp interface and a large crystal size still remains a challenge because of the difficulty in controlling various growth parameters simultaneously during the growth process. Here, a facile synthetic protocol designed for the production of the lateral TMDC heterostructured and alloyed monolayers is presented. A chemical vapor deposition approach combined with solution-processed precursor deposition makes it possible to accurately control the sequential introduction time and the supersaturation levels of the vaporized precursors and thus reliably and exclusively produces selective and heterogeneous epitaxial growth of TMDC monolayer crystals. In addition, TMDC core/shell heterostructured (MoS2/alloy, alloy/WS2) or alloyed (Mo1–xWxS2) monolayers are also easily obtained with precisely controlled growth parameters, such as sulfur introduction timing and growth temperature. These results represent a significant step toward the development of various 2D materials with interesting properties.

Electrochemically active binary anion compounds with tailored oxygen vacancy for energy storage system John Hong, Juwon Lee, Young-Woo Lee, Woon Bae Park, Docheon Ahn, Jong Bae Park, Sangyeon Pak, Jaeyoon Baik, Stephen M. Morris, SeungNam Cha, Kee-Sun Sohn, Jung Inn Sohn, Journal of Power Sources444, 227301 (2019)

The search for new materials that exhibit rapid Faradaic energy-storing behavior continues to be ever more important as they offer a promising alternative to battery technology because of their unrivalled ability to deliver large amounts of power along with large amounts of energy. Here, we present a reduced binary anion compound (r-BAC) as a first demonstration of redox-active materials, which are fabricated by a facile and direct activation synthetic method. The r-BAC exhibits excellent energy storage characteristics compared to non-reduced full binary anion compound (f-BAC). Based on the density functional theory (DFT) calculations and the ex-situ chemical study, it is found that the superior electrochemical performance is strongly attributed to not only the Ni cation sites (Ni2+/Ni3+ redox couple) that are energetically more activated by oxygen vacancies, but also to the additive electrochemical activity at the unsaturated sulfur sites (S4+/S6+ redox couple) in a binary anion. Thus, we expect that this study on the binary anion material and the corresponding anion-based charge transfer mechanisms may provide a new strategy for the efficient storage of charge in next-generation energy storage applications.

Dynamic response of large tilt-angle flexoelectro-optic liquid crystal modulators Julian A. J. Fells, Chris Welch, Wing C. Yip, Steve J. Elston, Martin J. Booth, Georg H. Mehl, Timothy D. Wilkinson, and Stephen M. Morris Opt. Express 27(11), 15184-15193 (2019) 

We present here the first time-resolved tilt-angle and retardance measurements for large-tilt (>45°) flexoelectro-optic liquid crystal modulators. These devices have potential for next generation fast switching (>1 kHz), 0-2π analog phase spatial light modulators (SLMs), with applications in optical beamsteering, microscopy and micromachining. The chiral nematic device used consisted of a mixture of CBC7CB and the chiral dopant R5011 in a nominally 5 µm-thick cell, aligned in the uniform lying helix mode. As the device is dynamically switched over angles of ± 54°, retardance changes of up to 0.17λ are observed. Furthermore, the time-resolved measurements reveal an asymmetry in the tilt in the optic-axis depending on the polarity of the applied electric field. The change in the optic-axis exhibits a pattern dependence, whereby it is determined by both the pulse history and the applied field. This pattern dependence results in tilt-angle errors of up to 8.8°, which could manifest as phase errors as large as 35.2° in potential SLMs. These time domain measurements may allow correction of these deterministic errors, to realize practical devices.

Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector Xiuze Wang, Julian A. J. Fells, Wing C. Yip, Taimoor Ali, Jia-de Lin, Chris Welch, Georg H. Mehl, Martin J. Booth, Timothy D. Wilkinson, Stephen M. Morris & Steve J. Elston Scientific Reports 9, 7016 (2019)

In this paper, we demonstrate a flexoelectro-optic liquid crystal phase-only device that uses a chiral nematic reflector to achieve full 2π phase modulation. This configuration is found to be very tolerant to imperfections in the chiral nematic reflector provided that the flexoelectro-optic LC layer fulfils the half-wave condition. Encouragingly, the modulation in the phase, which operates at kHz frame rates, is also accompanied by low amplitude modulation. The configuration demonstrated herein is particularly promising for the development of next-generation liquid crystal on silicon spatial light modulators.

Robust measurement of flexoelectro-optic switching with different surface alignments John J. Sandford O’Neill, Julian A. J. Fells, Chris Welch, Georg MehlWing C. Yip, Timothy D. Wilkinson, Martin J. Booth, Steve J. Elston, and Stephen M. Morris  Journal of Applied Physics 125, 093104 (2019)

The alignment of chiral nematic liquid crystals in the so-called uniform lying helix geometry allows for the observation and exploitation of the flexoelectro-optic effect. However, high-quality uniform lying helix alignment is difficult to achieve reliably, and this can potentially impact the accuracy of the measurements made on the flexoelectro-optic switching behaviour. Here, we show that, using an appropriate method, it is possible to make measurements of the flexo-electric coefficients that are not substantially influenced by the alignment quality.

Surface Functionalization-induced Photoresponse Characteristics of Monolayer MoS2 for Fast Flexible Photodetectors S. Pak, A. Jang, J. Lee, J. Hong, P. Giraud, S. Lee , Y. Cho, G. Ah, Y. Lee, H. S. Shin, S. M. Morris, S. Cha, J. I. Sohn and J. M. Kim, Nanoscale 11, 4726-4734 (2019)

Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving a fast photoresponse time in MoS2 photodetectors. In this study, we investigate the importance of surface functionalization on controlling the charge carrier densities in a MoS2 monolayer and in turn the corresponding behavior of the photoresponse in relation to the position of the Fermi-level and the energy band structure. We find that the p-doping and n-doping, which is achieved through the surface functionalization of the MoS2 monolayer, leads to devices with different photoresponse behavior. Specifically, the MoS2 devices with surface functional groups contributing to p-doping exhibited a faster response time as well as higher sensitivity compared to that observed for the MoS2 devices with surface functional groups contributing to n-doping. We attribute this difference to the degree of bending in the energy bands at the metal–semiconductor junction as a result of shifting in the Fermi-level position, which influences the optoelectronic transport properties as well as the recombination dynamics leading to a low dark and thus high detectivity and fast decay time. Based upon these findings, we have also demonstrated the broad applicability of surface functionalization by fabricating a flexible MoS2 photodetector that shows an outstanding decay time of 0.7 s, which is the fastest response time observed in flexible MoS2 detectors ever reported.

Chalcogenide Solution-Mediated Activation Protocol for Scalable and Ultrafast Synthesis of Single-Crystalline 1-D Copper Sulfide for Supercapacitor 

2018

Femtosecond fiber Bragg grating fabrication with adaptive optics aberration compensation Julian Fells, Patrick Salter, Matthew Woolley, Stephen Morris, and Martin Booth Optics Letters 43, 5993-5996 (2018)

We present fiber Bragg gratings (FBGs) fabricated using adaptive optics aberration compensation for the first time to the best of our knowledge. The FBGs are fabricated with a femtosecond laser by the point-by-point method using an air-based objective lens, removing the requirement for immersion oil or ferrules. We demonstrate a general phase correction strategy that can be used for accurate fabrication at any point in the fiber cross-section. We also demonstrate a beam-shaping approach that nullifies the aberration when focused inside a central fiber core. Both strategies give results which are in excellent agreement with coupled-mode theory. An extremely low wavelength polarization sensitivity of 4 pm is reported.

Featured in Top Downloads in Optics Letters December 2018

Consecutive Junction-Induced Efficient Charge Separation Mechanisms for High-Performance MoS2/Quantum Dot Phototransistors Sangyeon Pak, Yuljae Cho, John Hong, Juwon Lee, Sanghyo Lee, Bo Hou, Geon-Hyoung An, Young-Woo Lee, Jae Eun Jang, Hyunsik Im, Stephen M. Morris, Jung Inn Sohn, SeungNam Cha, and Jong Min Kim ACS Applied Materials & Interfaces  10 (44), 38264–38271 (2018)

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 μs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS2 channel, our experimental results reveal that the detectivity can be as large as 1 × 1011 jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures.

Flexoelectro-optic liquid crystal analog phase-only modulator with 2π range and 1 kHz switching Julian A.J. Fells, Xiuze Wang, Steve J. Elston, Chris Welch, Georg H. Mehl, Martin J. Booth, and Stephen M. Morris Optics Letters 43, 4362-4365 (2018)

We present a flexoelectro-optic liquid crystal (LC) analog phase modulator with >2π phase range at a 1 kHz switching frequency. The chiral nematic LC mixture consists of the bimesogen CBC7CB with chiral dopant R5011, aligned in the uniform lying helix mode. The mixture exhibits > +/-π∕4 rotation of the optic axis for a drive voltage of +/-21.5 V (E =4.5 V/μm). The rotation of the optic axis is converted into a phase modulation with the aid of a reflective device configuration incorporating a ∼5 μm LC cell, a polarizer, two quarter-wave plates, and a mirror. The residual amplitude modulation is found to be <23%. This flexoelectro-optic phase modulator combination has the potential to enable analog spatial light modulators with very fast frame rates suitable for a range of applications.

Read on Demand Images in Laser‐Written Polymerizable Liquid Crystal Devices Chloe C. Tartan, John J. Sandford O'Neill, Patrick S. Salter, Jure Aplinc, Martin J. Booth, Miha Ravnik, Stephen M. Morris, Steve J. Elston Advanced Optical Materials 6, 1800515 (2018)

Two‐photon laser writing is a powerful technique for creating intricate, high resolution features in polymerizable materials. Here, using a single‐step process to microfabricate polymer inclusions, the ability to generate read‐on‐demand images and identification codes in a liquid crystal (LC) device is demonstrated. These micrometer‐sized polymer features are encoded directly into LC devices using direct laser writing, which locks‐in the local molecular orientation at the moment of fabrication. By reading the devices with the same voltage amplitude that is used to write the polymer structures, features can be made to disappear as the director profile becomes homogeneous with the surrounding regions, effectively cloaking the structure for both polarized and unpolarized light. It is shown how this process can be used to create micrometer‐scale reconfigurable emoticons and quick‐response codes within a fully assembled LC device, with potential use in authenticity and identification applications.

Highlighted in Nature Photonics, read here.

Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices Xiuze Wang, Julian A. J. Fells, Chris Welch, Maria-Gabriela Tamba, Georg H. Mehl, Stephen M. Morris, Steve J. Elston Liquid Crystals 46, 408-414 (2018)

The ‘flexoelastic ratio’ is commonly used to characterise the electro-optic behaviour of chiral nematic liquid crystal (LC) devices that exhibit flexoelectro-optic switching. There has been renewed interest in this electro-optic effect of late as new LC materials and mixtures have been developed that exhibit large tilt angles, Ø, of the optic axis (Ø ≥ 45°) whilst maintaining a fast response time (< 1 ms). In this study, we compare the different flexoelastic ratios that are obtained for fixed and variable-pitch chiral nematic LCs for materials with a tilt of the optic axis as large as Ø = ± 45°. We show that for large tilt angles of the optic axis the values for the two different flexoelastic ratios measurably diverge. Of the two ratios, we propose that for large tilt-angle mixtures it is more appropriate to use the flexoelastic ratio that is derived for the case when the pitch of the helix is constrained. In addition, a simple way of determining the ‘pitch-constrained’ flexoelastic ratio is presented that involves identifying the electric field amplitude at the point for which the transmission levels are the same for both positive and negative electric field polarities.

Dynamics of pitch change in chiral azobenzene-doped liquid crystals Cheng-KaiLiua, Min-Cheng TsaiStephen M.Morris, Chian-Yu Chiua, Chii-Chang Chen, Ko-Ting Cheng Journal of Molecular Liquids, 263, 406-412 (2018)

Dynamics of pitch change in chiral azobenzene-doped liquid crystals (CAdLCs) has been investigated. Theoretically, the pitch change in CAdLCs is discontinuous. Completed behavior of the discontinuous pitch jump in a fixed thickness cell is analyzed based on the calibration term, which is a key length parameter of the gradually increasing elastic potential energy with time, according to Hooke's law. At a specific time, the energy reaches maximum value and then releases to provide a compressed/extended force to discontinuously change pitch to minimize the energy of the whole system. At other times, the compressed/extended force disturbs the uniformity of planar texture if the surface anchoring energy is weak. Discontinuous pitch jump can be observed in CAdLCs with a few turns of helix. Thus, a novel method to evaluate the pitch of CAdLCs with only two turns of the helix after UV illumination is feasible. In contrast, discontinuous pitch jump in the previous work is hard to be noticed if CAdLCs has a large number of turns of helix. The behavior of pitch change in CAdLCs on the bases of the number of turns of helix and the cell thickness will be discussed in detail.

Formation of radial aligned and uniform nematic liquid crystal droplets via drop-on-demand inkjet printing into a partially-wet polymer layer Ellis Parry, Dongjin Kim, Alfonso Castrejon-Pita, Steve J. Elston, and Stephen M. Morris Optical Materials 80, 71–76 (2018)

This paper investigates the drop-on-demand inkjet printing of a nematic liquid crystal (LC) onto a variety of substrates. Achieving both a well-defined droplet boundary and uniformity of the LC director in printed droplets can be challenging when traditional alignment surfaces are employed. Despite the increasing popularity of inkjet printing LCs, the mechanisms that are involved during the deposition process such as drop impact, wetting and spreading have received very little attention, in the way of experiments, as viable routes for promoting alignment of the resultant LC droplets. In this work, radial alignment of the director and uniformity of the droplet boundary are achieved in combination via the use of a partially-wet polymer substrate, which makes use of the forces and flow generated during droplet impact and subsequent wetting process. Our findings could have important consequences for future LC inkjet applications, including the development of smart inks, printable sensors and lasers.

Balancing Charge Carrier Transport in a Quantum Dot P–N Junction toward Hysteresis-Free High-Performance Solar Cells Yuljae Cho, Bo HouJongchul LimSanghyo LeeSangyeon PakJohn HongPaul GiraudA-Rang JangYoung-Woo LeeJuwon LeeJae Eun JangHenry J. SnaithStephen M. MorrisJung Inn SohnSeungNam Cha, and Jong Min Kim ACS Energy Lett. 3, 1036–1043 (2018)

In a quantum dot solar cell (QDSC) that has an inverted structure, the QD layers form two different junctions between the electron transport layer (ETL) and the other semiconducting QD layer. Recent work on an inverted-structure QDSC has revealed that the junction between the QD layers is the dominant junction, rather than the junction between the ETL and the QD layers, which is in contrast to the conventional wisdom. However, to date, there have been a lack of systematic studies on the role and importance of the QD heterojunction structure on the behavior of the solar cell and the resulting device performance. In this study, we have systematically controlled the structure of the QD junction to balance charge transport, which demonstrates that the position of the junction has a significant effect on the hysteresis effect, fill factor, and solar cell performance and is attributed to balanced charge transport.

Time-resolved retardance and optic-axis angle measurement system for characterization of flexoelectro-optic liquid crystal and other birefringent devices Julian A. J. Fells, Steve J. Elston, Martin J. Booth, and Stephen M. Morris Optics Express 26(5), 6126-6142 (2018)

A new polarimeter is presented which gives time-resolved measurements of both the optic-axis angle and the linear phase retardation for modulated birefringent optical devices. It is suitable for characterizing dynamic waveplate devices based on liquid crystal and other materials. It is fully automated and requires no angular alignment of the device under test. The system has an absolute angle error of < ± 0.3° and a retardance error of < ± 0.44°, with considerably better relative accuracy. The method has been tested with a chiral nematic liquid crystal device exhibiting flexoelectro-optic switching at 3 kHz in the uniform lying helix mode. These results represent the first time-resolved tilt-angle and phase retardation measurements for a liquid crystal device operating at fast switching frequencies.

Solvent-induced self-assembly of uniform lying helix alignment of the cholesteric liquid crystal phase for the flexoelectro-optic   effect  S. Bolis, C. C. Tartan, J. Beeckman, P. Kockaert, S. J. Elston and S. M. Morris  Liquid Crystals 45, 774-782 (2018) 

A uniform lying helix (ULH) alignment of cholesteric liquid crystals (LCs) is obtained using a solvent evaporation technique. The solvent evaporation method allows for the spontaneous formation of a virtually defect-free alignment, even in the absence of an external electric field. A small amount of solvent diffuses into the LC and changes its phase into isotropic state where the individual LC molecules are more mobile. As the solvent diffuses out of the LC and consequently evaporates, additional mobility provided by the solvent allows the molecules to reach the lowest energy configuration, dictated by the boundary conditions, the solvent evaporation direction and the elastic forces among the molecules. Compared to a shear-flow-induced alignment, the solvent-induced ULH exhibits a contrast ratio between the bright and dark states that is a factor of 4 times larger, due to the low number of defects in the structure. From measurements of the flexoelectro-optic effect, the difference between the splay and bend flexoelectric coefficients, , for the nematic LC E7 is found to be in agreement with the measured values reported in the literature (12.11.0 pC/m), demonstrating that the solvent self-aligning does not change the electric response of the medium, while improving its optical properties.

Field effect transistors and phototransistors based upon p-type solution-processed PbS nanowires Paul Giraud, Bo Hou, Sangyeon Pak, Jung Inn Sohn, Stephen Morris, SeungNam Cha and Jong Min Kim Nanotechnology 29, 075202 (2018)

We demonstrate the fabrication of solution processed highly crystalline p-type PbS nanowires via the oriented attachment of nanoparticles. The analysis of single nanowire field effect transistor (FET) devices revealed a hole conduction behaviour with average mobilities greater than 30 cm2/V/s, which is an order of magnitude higher than that reported to date for p-type PbS colloidal nanowires. We have investigated the response of the FETs to near-infrared light excitation and show herein that the nanowires exhibited gate-dependent photo-conductivities, enabling us to tune the device performances. The responsivity was found to be greater than 104 A W−1 together with a detectivity of 1013 Jones, which benefits from a photogating effect occurring at negative gate voltages. These encouraging detection parameters are accompanied by relatively short switching times of 15 ms at positive gate voltages, resulting from a combination of the standard photoconduction and the high crystallinity of the nanowires. Collectively, these results indicate that solution-processed PbS nanowires are promising nanomaterials for infrared photodetectors as well as p-type nanowire FETs.

2017

Drop-on-Demand Inkjet Printing of Thermally Tunable Liquid Crystal Microlenses E. Parry, S. Bolis, S. J. Elston, A. Castrejon-Pita and S. M. Morris, Advanced Engineering Materials, 1700774 (2017)

Optically Controllable Linear-Polarization Rotator Using Chiral-Azobenzene-Doped Liquid Crystals C.-K. LiuC.-Y. Chiu,S. M. MorrisM.-C. TsaiC.-C. Chen, K.-T. Cheng Materials 10(11), 1299 (2017)

Spatial fluctuations of optical solitons due to long-range correlated dielectric perturbations in liquid crystals S. Bolis, S.-P. Gorza, S. J. Elston, K. Neyts, P. Kockaert, and J. Beeckman Physical Review A 96, 031803(R), (2017)

Charge Transport Modulation of a Flexible Quantum Dot Solar Cell Using a Piezoelectric Effect  Y. Cho, P. Giraud, B. Hou, Y.-W. Lee, J. Hong, S. Lee, S. Pak, J. Lee, J. E. Jang, S. M. Morris, J. I. Sohn, S. Cha, and J. M. Kim Adv. Energy Mater.,1700809 (2017)

Strain-Mediated Interlayer Coupling Effects on the Excitonic Behaviors in an Epitaxially Grown MoS2/WS2 van der Waals Heterobilayer S. Pak, J. Lee, Y.-W. Lee, A-R. Jang, S. Ahn, K. Y. Ma, Y. Cho, J. Hong, S. Lee, H. Y. Jeong, H. Im, H. S. Shin, S. M. Morris, S. Cha, J. Sohn, and J. M. Kim Nano Letters, 17 (9), 5634–5640 (2017)

Highly stable 3D porous heterostructures with hierarchically-coordinated octahedral transition metals for enhanced performance supercapacitors J. Hong, Y.-W. Lee, D. Ahn, S. Pak, J. Lee, A-R. Jang, S. Lee, Bo Hou, Y. Cho, S. M. Morris, H. S. Shin, S. Cha, J. I. Sohn, J. M. Kim, Nano Energy, 39, 337-345 (2017)

 J. Lee, S. Pak, P. Giraud, Y-W. Lee, Y. Cho, J. Hong, A.-R. Jang, H.-S. Chung, W.-K. Hong, H.-Y. Jeong, H. S. Shin, L. G. Occhipinti, S. M. Morris, S. Cha, J. I. Sohn, and J. M. Kim
Advanced Materials 29, 1702206 (2017)


Hierarchically assembled tubular shell-core-shell heterostructure of hybrid transition metal chalcogenides for high-performance supercapacitors with ultrahigh cyclability Y.-W. LeeB.-S. KimJ. HongH. ChoiH.-S. JangB. HouS. PakJ. LeeS.-H. LeeS. M. MorrisD. WhangJ. P. HongH. S. ShinS. ChaJ. Sohn, and J. M. Kim  Nano Energy 37, 15–23 (2017)

Monolayer optical memory cells based on artificial trap-mediated charge storage and release J. Lee, S. Pak, Y.-W. Lee, Y. Cho, J. Hong, P. Giraud, H. Suk Shin, S. M. Morris, J. I. Sohn, S. Cha and J. M. Kim Nature Communications 8, 14734 (2017)

Red green blue emissive lead sulfide quantum dots: heterogeneous synthesis and applications B. Hou, Y. Cho, B.-S. Kim, D. Ahn, S. Lee, J. B. Park, Y.-W. Lee, J. Hong, H. Im, S. M. Morris, J. Sohn, S. Cha and J.-M. Kim Journal of Materials C 5, 3692-3698 (2017)

Generation of 3-dimensional polymer structures in liquid crystalline devices using direct laser writing C. C. Tartan, P. S. Salter, T. D. Wilkinson, M. J. Booth, S. M. Morris, and S. J. Elston RSC Advances 7, 507-511 (2017)  

2016

 

Solubility-Dependent NiMoO4 Nanoarchitectures: Direct Correlation between Rationally Designed Structure and Electrochemical Pseudokinetics John Hong, Young-Woo Lee, Bo Hou, Wonbae Ko, Juwon Lee, Sangyeon Pak, JinPyo Hong, Stephen M. Morris, SeungNam Cha, Jung Inn Sohn, and Jong Min Kim ACS Appl. Mater. Interfaces 8 (51), 35227–35234 (2016)

Speckle contrast reduction of laser light using a chiral nematic liquid crystal diffuser David J. Hansford, Julian A. J. Fells, Steve J. Elston, and Stephen M. Morris Applied Physics Letters 109, 261104 (2016)

Wavelength Tuning of the Photonic Band Gap of an Achiral Nematic Liquid Crystal Filled into a Chiral Polymer Scaffold S. M. Wood, J. A. J. Fells, S. J. Elston, and S. M. Morris Macromolecules 29, 8643-8652 (2016)

Enhanced charge carrier transport properties in colloidal quantum dot solar cells via organic and inorganic hybrid surface passivation John Hong, Bo Hou, Jongchul Lim, Sangyeon Pak, Byung-Sung Kim, Yuljae Cho, Juwon Lee, Young-Woo Lee, Paul Giraud, Sanghyo Lee, Jong Bae Park, Stephen M. Morris, Henry J. Snaith, Jung Inn Sohn, SeungNam Cha and Jong Min Kim Journal of Materials Chemistry A, 4, 18769-18775 (2016)            

Wavelength-tuneable laser emission from a dye-doped achiral nematic liquid crystal dispersed into a chiral polymer scaffold Simon J. Wood, Steve J. Elston, and Stephen M. Morris Molecular Crystals and Liquid Crystals 632, 89-96 (2016)

Enhanced Ferroelectric Property of P(VDF-TrFE-CTFE) Film Using Room-Temperature Crystallization for High-Performance Ferroelectric Device Applications Yuljae Cho, Docheon Ahn, Jong Bae Park, Sangyeon Pak, Sanghyo Lee, Byoung Ok Jun, John Hong, Su Yong Lee, Jae Eun Jang, Jinpyo Hong, Stephen M. Morris, Jung Inn Sohn, Seung Nam Cha, Jong Min Kim Advanced Electronic Materials 2, 1600225 (2016)

Porous nematic microfluidics for generation of umbilic defects and umbilic defect lattices Jure Aplinc, Stephen Morris, and Miha Ravnik Physical Review Fluids 1, 023303 (2016)

Localised polymer networks in chiral nematic liquid crystals for high speed photonic switching Chloe C. Tartan, Patrick. S Salter, Martin J. Booth, Stephen M. Morris & Steve J. Elston Journal of Applied Physics 119, 183106 (2016)

Wavelength-tuneable laser emission from stretchable chiral nematic liquid crystal gels via in situ photopolymerization S. M. Wood, F. Castles, S. J. Elston, and S. M. Morris, RSC Advances, 6, 31919-31924 (2016)

Stabilizing the uniform lying helix alignment in chiral nematic liquid crystals using direct laser writing Chloe C. Tartan, Patrick. S Salter, Martin J. Booth, Stephen M. Morris & Steve J. Elston, Ferroelectrics, 495, 167-173 (2016)

Structured Organic–Inorganic Perovskite toward a Distributed Feedback Laser M. Saliba, S. M. Wood, J. B. Patel, P. K. Nayak, J. Huang, J. A. Alexander-Webber, B. Wenger, S. D. Stranks, M. T. Horantner, J. Tse-Wei Wang, R. J. Nicholas, L. M. Herz, M. B. Johnston, S. M. Morris, H. J. Snaith, and M. K. Riede Advanced Materials, 28, 923-929 (2016)

 

2015

Asymmetric director structures and flexoelectricity in nematic pi-cell devices C. C. Tartan and S. J. Elston, Applied Physics Letters 107, 081902 (2015)

Polarized Phosphorescence of Isotropic and Metal-Based Clustomesogens Dispersed into Chiral Nematic Liquid Crystalline Films S. M. Wood, M. Prévôt, M. Amela-Cortes, S. Cordier, S. J. Elston, Y. Molard and S. M. Morris Advanced Optical Materials, 3, 1368-1372, (2015)

Asymmetric Director Structures and Ions in the Measurement of the Flexoelectric Sum (e1 + e3) C. C. Tartan and S. J. Elston, Molecular Crystals and Liquid Crystals, 610, 77-88 (2015)

Enhanced Amplified Spontaneous Emission in Perovskites using a Flexible Cholesteric Liquid Crystal Reflector S. D Stranks, S. M Wood, K. Wojciechowski, F. Deschler, M. Saliba, H. Khandelwal, J. B Patel, S. Elston, L. M. Herz, M. B Johnston, A. P. H. J. Schenning, M. G. Debije, M. Riede, S. M Morris, and H. J. Snaith, Nano Letters 15, 4935-4941 (2015)

Improving the stability of organosiloxane smectic A liquid crystal random lasers using redox dopants A. A. Khan, S. M. Morris, D. J. Gardiner, M. M. Qasim, T. D. Wilkinson, and H. J. Coles, Optical Materials, 42, 441-448 (2015)

Hybrid aligned nematic based measurement of the sum ( + ) of the flexoelectric coefficients C. C. Tartan and S. J. Elston, Journal of Applied Physics 117, 064107 (2015)


Optically Switchable Smart Windows with Integrated Photovoltaic Devices

H.-K. Kwon, K.-T. Lee, K. Hur, S. H. Moon, M. M. Qasim, T. D. Wilkinson, J.-Y. Han, H. Ko, I.-K. Han, B. Park, B. K. Min, B.-K. Ju, S. M. Morris, R. H. Friend, and D. H, Ko,

Advanced Energy Materials, 5, 1401437 (2015)

2014

Polarization-independent phase modulation using a blue-phase liquid crystal over silicon device R. Hyman, A. Lorenz, S. M. Morris, and T. D. Wilkinson, Applied Optics, 53, 6925 (2014)

Stretchable liquid-crystal blue-phase gels F Castles, S. M. Morris, J. M. Hung, M. M. Qasim, A. D. Wright, S. Nosheen, S. S. Choi, B. I Outram, S. J. Elston, C. Burgess, L. Hill, T. D. Wilkinson, H. J. Coles, Nature Materials, 13, 817-821(2014)

Electrical addressing of polymer-stabilized hyper-twisted chiral nematic liquid crystals with interdigitated electrodes: Experiment and model A. Lorenz, D. J. Gardiner, S. M. Morris, F. Castles, M. M. Qasim, S. S. Choi, W. S. Kim, H. J. Coles, and T. D. Wilkinson, Applied Physics Letters 104, 071102 (2014)

 

2013

 

Dielectric enhancement of chiral flexoelectro-optic switching B. I. Outram and S. J. Elston, Liquid Crystals 40, 1529 (2013)

Alignment of cholesteric liquid crystals using the macroscopic flexoelectric polarization contribution to dielectric properties B. I. Outram and S. J. Elston, Applied Physics Letters 103, 141111 (2013)

Dual-frequency bistable reflective cholesteric liquid crystal displays based on chiral-flexoelectric polarisation dispersion B. I. Outram and S. J. Elston, Journal of Applied Physics 114, 083113 (2013)

Frequency-dependent dielectric contribution of flexoelectricity allowing control of state switching in helicoidal liquid crystals B. I. Outram and S. J. Elston, Physical Review E 88, 012506 (2013)

The use of mould-templated surface structures for high-quality uniform-lying-helix liquid-crystal alignment B. I. Outram, S. J. Elston, R. Tuffin, S. Siemianowski, B. Snow, Journal of Applied Physics  113, 213111 (2013)

Spontaneous and stable uniform lying helix liquid-crystal alignment B. I. Outram and S. J. Elston, Journal of Applied Physics 113, 043103 (2013)

Adaptive holographic pumping of thin-film organic lasers, S. M. Wood, T. K. Mavrogordatos, S. M. Morris, P. J. W. Hands, F. Castles, D. J. Gardiner, K. L. Atkinson, H. J. Coles, and T. D. Wilkinson Optics Letters 38, 4483 (2013)

Optically activated shutter using a photo-tunable short-pitch chiral nematic liquid crystal S. M. Morris, M.M. Qsaim, K. T. Cheng, F. Castles, D. H. Ko, D. J. Gardiner, S. Nosheen, T. D. Wilkinson, H. J. Coles, C. Burgess, and L. Hill Applied Physics Letters 103, 101105 (2013)

A nano-patterned photonic crystal laser with a dye-doped liquid crystal D. H. Ko, S. M. Morris, A. Lorenz, F. Castles, H. Butt, D. J. Gardiner, M. M. Qasim, B. Wallikewitz, P. J. W. Hands, T. D. Wilkinson, G. Amaratunga, H. J. Coles, and R. H. Friend Applied Physics Letters 103, 051101 (2013)

Spontaneous emission from radiative chiral nematic liquid crystals at the photonic band edge: An investigation into the role of the density of photon states near resonance T. K. Mavrogordatos, S. M. Morris, S. M. Wood, H. J. Coles, and T. D. Wilkinson, Physical Review E 87, 062504 (2013)

A printable optical time-temperature integrator based on shape memory in a chiral nematic polymer network A. R. Vaccaro, D. J.D. Davies, S. M. Morris, N. Herzer, A. P.H.J. Schenning, C. W. M. Bastiaansen, Advanced Functional Materials 23, 2723 (2013)

Liquid crystalline chromophores for photonic band-edge laser devices S. M. Morris, M. M. Qasim, D. J. Gardiner, P. J. W. Hands, F. Castles, G. Tu, W. T. S. Huck, R. H. Friend, H. J. Coles, Optical Materials 35, 837 (2013)

 

2012

 

Flexoelectric and dielectric in-plane switching behaviour of Grandjean liquid-crystal structures B. I. Outram and S. J. Elston EPL, 99 37007 (2012)

Determination of flexoelectric coefficients in nematic liquid crystals using the crystal rotation method B. I. Outram and S. J. Elston Liquid Crystals 39, 149 (2012)

A novel method for measuring the difference in flexoelectric coefficients of nematic liquid crystals B. I. Outram and S. J. Elston, Solid State Phenomena, 181, 26 (2012)

Simulation of the viewing properties and optical compensation of the biaxial nematic in-plane switching mode P. W. Benzie, D. Corbett, and S. J. Elston, Applied Optics, 51, 75 (2012)

Increasing the flexoelastic ratio of liquid crystals using highly fluorinated ester-linked bimesogens  K. L. Atkinson, S. M. Morris, M. M. Qasim, F. Castles, D. J. Gardiner, P. J. W. Hands, S. S. Choi, W.-S. Kim, H. J. Coles Physical Chemistry Chemical Physics, 14, 16377 (2012)

Printed photonic arrays from self-organised chiral nematic liquid crystals, D. J. Gardiner, W.-S. Kai, S. M. Morris, P. J. W. Hands, T. D. Wilkinson, I. Hutchings, and H. J. Coles, Soft Matter, 8, 9977 (2012)

The density of photon states in dye-doped chiral nematic liquid crystal cells in the presence of losses and gain Th. K. Mavrogordatos, S. M. Morris, F. Castles, P. J. W. Hands, A. D. Ford, H. J. Coles and T. D. Wilkinson, Physical Review E 86, 011705 (2012)

Blue-phase templated fabrication of three-dimensional nanostructures for photonic applications F. Castles, F.V. Day, S.M. Morris, D.-H. Ko, D.J. Gardiner, M.M. Qasim, S. Nosheen, P.J.W. Hands, S.S. Choi, R.H. Friend, H. J. Coles Nature Materials 11, 599 (2012)

Flexoelectric coefficient measurements in the nematic liquid crystal phase of 5CB F. Castles, S.C. Green, D.J. Gardiner, S.M. Morris, H.J. Coles AIP Advances, 2 (2), 022137, (2012)

Electrically switchable random to photonic band-edge laser emission in chiral nematic liquid crystals S.M. Morris, D.J. Gardiner, P.J.W. Hands, M.M. Qasim, T.D. Wilkinson, I.H. White, H.J. Coles Applied Physics Letters 100, 071110, (2012)

Lowering the excitation threshold of a random laser using the dynamic scattering states of an organosiloxane smectic A liquid crystal S.M. Morris, D.J. Gardiner, M.M Qasim, P.J.W. Hands, T.D. Wilkinson, H.J. Coles, Journal of Applied Physics 111 (3), 033106, (2012)

Spontaneous induction of the uniform lying helix alignment in bimesogenic liquid crystals for the flexoelectro-optic effect D.J. Gardiner, S.M. Morris, P.J.W. Hands, F. Castles, M.M. Qasim, W.-S. Kim, S.S. Choi, T.D. Wilkinson, H.J. Coles Applied Physics Letters 100, 063501, (2012)

Flexoelectric and elastic coefficients of odd and even homologous bimesogens K.L. Atkinson, S.M. Morris, F. Castles, M.M. Qasim, D.J. Gardiner, H.J. Coles Physical Review E 85, 012701,  (2012)

 

2011

 

Modeling the helical flexoelectro-optic effect D. R. Corbett and S. J. Elston, Physical Review E 84, 041706 (2011)

Uniform lying helix alignment on periodic surface relief structure generated via laser scanning lithography G. Carbone, D. Corbett, S. J. Elston, E. P. Raynes, A. Jesacher, R. Simmonds, M. Booth Molecular Crystals and Liquid Crystals 544, 37 (2011)

Fast-switching phase gratings using in-plane addressed short-pitch polymer stabilized chiral nematic liquid crystals S.M. Morris, D.J. Gardiner, F. Castles, P.J.W. Hands, T.D. Wilkinson, H.J. Coles Applied Physics Letters 99, 253502 (2011)

The limits of flexoelectricity in liquid crystals F. Castles, S. M. Morris, and H. J. Coles AIP Advances, 1, 032120, (2011)

Polymer stabilized chiral nematic liquid crystals for fast switching and high contrast electro-optic devices D.J. Gardiner, S.M. Morris, F. Castles, M.M. Qasim, W.-S. Kim, S.S. Choi, H.-J. Park, I.-J. Chung, H.J. Coles Applied Physics Letters 98, 263508, (2011)

Band-edge and random lasing in paintable liquid crystal emulsions P.J.W. Hands, D.J. Gardiner, S.M. Morris, C. Mowatt, T.D. Wilkinson, H.J. Coles Applied Physics Letters 98 (14), 141102, (2011)

Paintable band-edge liquid crystal lasers D.J. Gardiner, S.M. Morris, P.J.W. Hands, C.G. Mowatt, R.T. Rutledge, T.D. Wilkinson, H.J. Coles Optics Express, 19 (3), p. 2432-2439, (2011)

 

2010

 

The effect of high voltage on the bend transition in Pi-cells C.-H. Lee, E. P. Raynes, and S. J. Elston, Applied Physics Letters 97, 153501 (2010)

High slope efficiency liquid crystal lasers C. Mowatt, S. M. Morris, T. D. Wilkinson, H. J. Coles, Applied Physics Letters 97 (25), 251109 (2010)

Fast electro-optical device based on chiral liquid crystals encapsulated in periodic polymer channels G. Carbone, P. Salter, S. J. Elston, E. P. Raynes, L. D. Sio, S. Ferjani, G. Strangi, C. Umeton, R. Bartolino Molecular Crystals and Liquid Crystals, 525, 41 (2010)

Novel nonvolatile memory with multibit storage based on a ZnO nanowire transistor J. I. Sohn, S. S. Choi, S. M. Morris, J. S. Bendall, H. J. Coles, W.-K. Hong, G. Jo, T. Lee, M. E. Welland, Nano Letters  10, 11 Pages 4316-4320 (2010)

Microscopic liquid crystal lasers H. Coles and S. Morris, Nature Photonics 4, 676-685 (2010)

Thermodynamically stable blue phases F. Castles, S. M. Morris, E. Terentjev, and H. J. Coles, Physical Review letters 104, 157801 (2010)

Ultra-fast switching flexoelectric liquid crystal display with high contrast F. Castles, S. M. Morris, D. J. Gardiner, Q. M. Malik, and H. J. Coles,  J. of SID 18, 128-133 (2010)

Comparison of the performance of chiral nematic liquid crystal lasers C. Mowatt, S. M. Morris, M. H. Song, T. D. Wilkinson, R. H. Friend, and H. J. Coles, Journal of Applied Physics 107, 043101 (2010)

S.S. Choi, S.M. Morris, W.T.S. Huck, H.J. Coles, Simultaneous red-green-blue reflection and wavelength tuning from an achiral liquid crystal and a polymer template Advanced Materials 22, 53-56, (2010)

 

2009

 

Liquid crystal director dynamics imaged using two-Photon fluorescence microscopy with remote focusing P.S. Salter, G. Carbone, E. J. Botcherby, T. Wilson, S. J. Elston, and E. P. Raynes, Physical Review Letters 103, 257803 (2009)

The influence of chirality on the difference in flexoelectric coefficients investigated in uniform lying helix, grandjean and twisted nematic structures P. S. Salter, C. Kishka, S. J. Elston, and E. P. Raynes, Liquid Crystals 36, 1355 (2009)

Alignment of the uniform lying helix structure in cholesteric liquid crystals  P. S. Salter, S. J. Elston, P. Raynes, and L. Parry-Jones, Japanese Journal of Applied Physics 48, 1013021 (2009)

Design and implementation of optical wireless communications with optically powered smart dust motes D. C. O'Brien, J. J. Liu, G. E. Faulkner, S. Sivathasan, W. W. Yuan, S. C. Member, S. J. Elston, IEEE Journal on Selected Areas in Communications 27, 1646 (2009)

Unwinding of the uniform lying helix structure in cholesteric liquid crystals next to a spatially uniform aligning surface P. S. Salter, G. Carbone, S. A. Jewell, S. J. Elston, and E. P. Raynes, Physical Review E 80, 041707 (2009) 

Analytic twist angle measurement in liquid crystal cells C. -H. Lee, P. S. Salter, E. P. Raynes, S. J. Elston, Applied Physics Letters 95, 083505 (2009)

Spontaneously chiral domains of an achiral bent-core nematic liquid crystal in a planar aligned device P. S. Salter, P. W. Benzie, R. A. Reddy, C.Tschierske, S. J. Elston, E. P. Raynes, Physical Review E 80, 031701 (2009) 

Mechanisms of flexoelectric switching in a zenithally bistable nematic device L. A. Parry-Jones, R. B. Meyer, S. J. Elston, Journal of Applied Physics 106, 014510 (2009)

Short pitch cholesteric electro-optical device based on periodic polymer structures G. Carbone, P. Salter, S. J. Elston, P. Raynes, L. De Sio, L. S. Ferjani, G. Strangi, C. Umeton, R. Bartolino, Applied Physics Letters 95, 011102 (2009)

Small twist angle measurement in homogeneously aligned liquid crystal cells C. -H. Lee, S. J. Elston, E. P. Raynes, Applied Physics Letters 94, 093507 (2009)

High contrast chiral nematic liquid crystal device using a negative dielectric material S. S. Choi, F. Castles, S. M. Morris, H. J. Coles, Applied Physics Letters 95, 193502 (2009)

Flexoelectro-optic properties of a chiral nematic liquid crystal in the standing helix configuration F. Castles, S. M. Morris, H. J. Coles Physical Review E 80 031709 (2009)

Removing the discontinuous shift in emission wavelength of a chiral nematic liquid crystal laser S.M. Morris, A.D. Ford, H.J. Coles Journal of Applied Physics 106, 023112, (2009)

Electrically tuneable liquid crystal photonic bandgaps S.S. Choi, S.M. Morris, W.T.S. Huck, H.J. Coles Advanced Materials 21, 3915-3918, (2009)

High speed liquid crystal over silicon display based on the flexoelectro-optic effect J. Chen, S.M. Morris, T.D. Wilkinson, J.P. Freeman, H.J. Coles  Optics Express, 17 (9), 7130–7137, (2009)

High-efficiency multistable switchable glazing using smectic A liquid crystals D.J. Gardiner, S.M. Morris, H.J. Coles Solar Energy Materials and Solar Cells, 93 (3), 301 (2009)

The switching properties of chiral nematic liquid crystals using electrically commanded surfaces S.S. Choi, S.M. Morris, W.T.S. Huck, H.J. Coles Soft Matter, 5, 354-362, (2009)

 

2008

 

Polychromatic liquid crystal laser arrays towards display applications S.M. Morris, P.J.W. Hands, S. Findeisen-Tandel, R.H. Cole, T.D. Wilkinson, H.J. Coles Optics Express, 16 (23), 18827-18837, (2008)

Two-dimensional liquid crystal laser array P.J.W. Hands, S.M. Morris, T.D. Wilkinson, H.J. Coles Optics Letters, 33 (5), 515-517, (2008)

 

2007

 

Wavelength tuning the photonic band gap in chiral nematic liquid crystals using electrically commanded surfaces S.S. Choi, S.M. Morris, H.J. Coles, and W.T.S. Huck  Applied Physics Letters 91, 231110 (2007)

Emission Characteristics of a homologous series of bimesogenic liquid-crystal lasers A. D. Ford, S. M. Morris, M. N. Pivnenko, C. Gillespie, and H. J. Coles, Physical Review E 76, 051703 (2007)

Reversible color switching from blue to red in a polymer stabilized chiral nematic liquid crystal Jing Chen, Stephen M. Morris, Timothy D. Wilkinson, and Harry J. Coles Applied Physics Letters 91, 121118 (2007)

The influence of surface anchoring agents on the flexoelectro-optic properties of a chiral nematic liquid crystal S. M. Morris, Y. Cho, and H. J. Coles Journal of Applied Physics 101, 114109 (2007)

Structure-flexoelastic properties of bimeogenic liquid crystals S. M. Morris, M. J. Clarke, A. E. Blatch, and H. J. Coles, Physical Review E 75, 041701 (2007)

 

2006

 

Correlations between the performance characteristics of a liquid crystal laser and the macroscopic material properties S. M. Morris, A. D. Ford, M. N. Pivnenko, O. Hadeler, and H. J. Coles Physical Review E 74, 061709 (2006)

Photonics and lasing in liquid crystals Alison D. Ford, Stephen M. Morris, and Harry J. Coles  Materials Today 9, 36 (2006)

The emission characteristics of liquid crystal lasers S. M. Morris, A. D. Ford, C. Gillespie, M. N. Pivnenko, O. Hadeler, and H. J. Coles J. Soc. Info. Display, 14, 565 (2006)

The effect of polymer concentration on stabilised large tilt-angle flexoelectro-optic switching B. J. Broughton, M. J. Clarke, S. M. Morris, A. E. Blatch, and H. J. Coles Journal of Applied Physics 99, 023511 (2006)

Strong flexoelectric coupling in bimesogenic liquid crystal mixtures H. J. Coles, M. J. Clarke, S. M. Morris, B. J. Broughton, and A. E. Blatch Journal of Applied Physics  99, 034104 (2006)

 

2005

 

Enhanced emission from liquid crystal lasers S. M. Morris, A. D. Ford, M. N. Pivnenko, and H. J. Coles Journal of Applied Physics 97, 023103 (2005)

The effects of reorientation on the emission properties of a photonic band edge liquid crystal laser S. M. Morris, A. D. Ford, M. N. Pivnenko, and H. J. Coles  J. Opt. A: Pure Appl. Op. 7, 215 (2005)

Electronic control of nonresonant random lasing from a dye-doped smectic A* liquid crystal scattering device S. M. Morris, A. D. Ford, M. N. Pivnenko, and H. J. Coles Applied Physics Letters 86, 141103 (2005)

 

Book Chapters

 

Chapter 16: Electric, Magnetic and Mechanical fields and Chiral Nematic Liquid Crystals Stephen Morris and Harry Coles, Handbook of Liquid Crystals (Vol. 3) Wiley-VCH Verlag GmbH & Co. KGaA (2014)

Chapter 15: Structures and Optical Properties of Chiral Nematic Liquid Crystals Flynn Castles and Stephen Morris, Handbook of Liquid Crystals (Vol. 3) Wiley-VCH Verlag GmbH & Co. KGaA (2014)

Flexoelectro-optic liquid crystal displays Harry Coles and Stephen Morris Handbook of visual display technology (Vol.3), pages 1681 – 1698 Editors J. Chen, W. Cranton, M. Fihn, Springer (2012)

Red-green-blue 2D tuneable liquid crystal laser devices and displays H.J. Coles, S.M. Morris, A.D. Ford, P.J.W. Hands, T.D. Wilkinson Liquid crystal microlasers (Chapter 13) Editors L.M. Blinov, R. Bartolino, Transworld Research Network (2010)