Job responsibilities
Professor Carl Brown is UCAS Admissions Tutor for undergraduate physics and astronomy courses. He is Module leader for Condensed Matter Physics (PHYS3213), Research Methods in Physics/Astronomy/Instrumentation (PHYS2161), Work Experience (PHYS22621) and Ballistics and Firearms (PHYS32711). His teaching contributions are made to Experimental Techniques (PHYS3053) and Level 3 Projects (PHYS3001).
Research, scholarly and professional interests
Current research is being carried out in the following areas of Materials Physics:
- Bistable Nematic Liquid Crystal Displays: Bistable liquid crystal modes have the ability to retain an image in the power off state and therefore have very high potential for use in low power displays for mobile phones, games and camcorders. Bistable liquid crystal device modes can be produced by the alignment of nematic liquid crystals across grooved surfaces - one such nematic device, the “ZBD Display”, was co-invented at QinetiQ by Professor Carl Brown. This device has been shown to switch via an induced polarisation called the flexoelectric polarisation. This polarisation effect is being investigated, both theoretically and experimentally, using the Freedericksz effect in the presence of mobile ionic contamination, and using a newly developed transient capacitance technique.
- Multistable Photonic Devices: The development of multi-level, multi-stable switchable phase structures is of significant importance for photonic switching since bi/multistability in optical telecommunications switches will enable (i) enhanced network security after a power outage, since the device would continue to operate and be optically transparent, and (ii) redundancy management, where semi permanent re-routing can easily be implemented. In this project, they are building on recent work where they have demonstrated the possibility of not only bistability, but multistability, by micro-structuring the sidewall in a planar aligned liquid crystal layer in order to control alignment. The use of the sidewall avoids the need for index matching with surface structures and allows for more functionality in the substrate surface, for instance so that it can be used as an active waveguide cladding.
- Optical devices based on electrowetting: These devices are promising for low power flexible displays and for optically transparent and polarisation insensitive switching in optical interconnects. In electrowetting, a liquid forms one of the conducting contacts in a substrate-insulator-liquid capacitive structure. Applying a voltage modifies the balance of surface free energies at the solid-liquid interface, causes spreading and so results in a modification of the radius of curvature in the meniscus at the liquid-air interface. In devices this principle is applied to modify the meniscus at an oil-water (rather than liquid-air) interface. Part of the current research involves the fabrication of suitable surface patterns to demonstrate polarisation independent phase grating structures using interference to produce a diffractive optical effect.
Selected publications
- Voltage-programmable liquid optical interface. Brown C V, Wells G G, Newton M I and McHale G, Nature Photonics, 2009, 3, 420.
- “Liquid Crystal Diffractive Optical Elements”, E E Kriezis and C V Brown. Chapter 8, pp 235-299, Handbook of Organic Electronics and Photonics Volume 2, Ed. H S Nalwa, American Scientific Publishers, ISBN 1588830977 (2008).
- “Multistable Liquid Crystal Waveplate”, G G Wells and C V Brown, Vol 91, Applied Physics Letters p223506 (2007).
- “Rotatable Liquid Crystal Waveplate”, G G Wells and C V Brown, Accepted for Journal of Materials Science: Materials in Electronics (2007).
- “Theoretical Analysis of the Magnetic Freedericksz Transition in the Presence of Flexoelectricity and Ionic Contamination”, A A T Smith, C V Brown and N J Mottram, Physical Review E. Vol. 75, p 041704 (2007).
- “Multistable alignment states in nematic liquid crystal filled wells”, C Tsakonas, A Davidson, C V Brown and N J Mottram, Applied Physics Letters Vol 90, p 111913 (2007).
- “Pulsed addressing of a dual frequency nematic liquid crystal”, N J Mottram and C V Brown, Physical Review E. Vol 74(3), p 031703 (2006).
- “Transient capacitance study of switching in the nematic Freedericksz geometry”, J M Hind, A A T Smith and C V Brown, Journal of Applied Physics Vol. 100 (9), p 094109 (2006).
- “Unified model of fractal conductance fluctuations for diffusive and ballistic semiconductor devices”, C A Marlow, R P Taylor, T P Martin, B C Scannell, H Linke, M S Fairbanks, G D R Hall, I Shorubalko, L Samuelson, T M Fromhold, C V Brown, B Hackens, S Faniel, C Gustin, V Bayot, X Wallart, S Bollaert and A Cappy. Physical Review B. Vol 73(19) p 195318 (2006).
- “Study of Elastic Constant Ratios in Nematic Liquid Crystals”, J F Strömer, C V Brown and E P Raynes. Applied Physics Letters Vol 88, p 051915 (2006).
- “Electric-field induced disclination migration in a Grandjean-Cano wedge”, J F Strömer, D Marenduzzo, C V Brown, J M Yeomans, and E P Raynes, Journal of Applied Physics Vol 99, p 064911 (2006).
- “Double Minimum in the Surface Stabilised Ferroelectric Liquid Crystal Switching Response”, C V Brown, J M Hind, K P Lymer and J C Jones, Applied Physics Letters Vol 85 pp 1763-1765 (2004).
- “Surface Stabilised Ferroelectric Liquid Crystal diffraction gratings with micrometer scale pitches”, C V Brown and E E Kriezis, Applied Optics Vol. 43 pp. 5287-5294 (2004). Featured on cover.
- “A Novel Method for the Measurement of the Nematic Liquid Crystal Twist Elastic Constant”, J F Strömer, C V Brown and E P Raynes, Mol. Cryst. Liq. Cryst. Vol 409 pp. 293-299 (2004).
- “Comparison of theoretical and experimental switching curves for a zenithally bistable nematic liquid crystal device”, C V Brown, L Parry-Jones, S J Elston and S J Wilkins, Mol. Cryst. Liq. Cryst. Vol 410 pp. 417/[945]-425/[953] (2004).
- “Diffraction from the two stable states in a Nematic Liquid Crystal Cell containing a mono-grating with homeotropic director alignment”, E G Edwards, S C Kitson, C J P Newton, C V Brown, E E Kriezis and S J Elston, Mol. Cryst. Liq. Cryst. Vol 410 pp. 401/[929]-408/[936] (2004).
- “Zenithal bistability in a nematic liquid crystal device with a monostable surface condition”, L Parry-Jones, S J Elston and C V Brown, Mol. Cryst. Liq. Cryst. Vol 410 pp. 427/[955]-433/[961] (2004).
- “Influence of flexoelectricity above the nematic Freedericksz transition”, C V Brown and N J Mottram, Physical Review E. Vol 68, No. 3, pp.31702-31706 (2003).
- “Calculation of the efficiency of polarisation-insensitive SSFLC diffraction gratings”, C V Brown and E E Kriezis, Applied Optics Vol. 42, No. 13, pp.2257-2263 (2003).
- “Zenithal bistability in a nematic liquid crystal device with a monostable surface condition”, L Parry-Jones, E G Edwards, S J Elston, C V Brown, Applied Physics Letters. Vol 82, pp.1476-1478 (2003).
- “A Method for Measurement of the K22 Nematic Elastic Constant”, E P Raynes, C V Brown and J F Strömer, Applied Physics Letters. Vol 82, pp.13-15 (2003).
- “X-ray structural studies of Ferroelectric Liquid Crystal Devices”, C V Brown, P E Dunn, J C Jones, S A Jenkins, and R M Richardson, Mol. Cryst. Liq. Cryst.Vol. 402, pp.55/[291]-75/[311] (2003).
- “Behaviour of a Nematic Liquid Crystal Cell Containing a Diffraction Grating”, E G Edwards, C V Brown, E E Kriezis and S J Elston, Mol. Cryst. Liq. Cryst. Vol. 400, pp.13-19 (2003).
- “Optical Diffraction from a Liquid Crystal Phase Grating”, C V Brown, E E Kriezis and S J Elston, Journal of Applied Physics. Vol 91, pp.3495-3500 (2002).
Information for prospective research students
Opportunities arise to carry out postgraduate research towards an MPhil/PhD in the areas identified above.
Further information may be obtained from the University Graduate School.
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