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Electromagnetic Materials
Led by Prof Roy Sambles FRS Join our research group
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Liquid Crystal Research
Liquid crystal displays (LCDs) now outnumber the population of the world and are a multi-billion dollar a year industry. Understanding the fundamental physics behind the operation of such structures is essential to allow the development of the next generation of such devices.
Many liquid crystals are composed of rod-shaped molecules which tend to align roughly parallel to each other. Dictating their alignment by applying a voltage across a thin layer of the liquid crystal material allows the amount of light transmitted through it to be controlled. This has been the underlying physical principle in the operation of pixels in LCDs since their invention in the 1970s. To enable us to develop this technology to meet the high speed-switching, low power consumption and miniaturized pixel sizes required for today’s market we need to be able to understand the behaviour of the liquid crystal layer on a sub-millisecond timescale with a spatial resolution on the sub-micron scale. 
The liquid crystal research in the Electromagnetic Materials Group, lead by Prof. Roy Sambles in the School of Physics at Exeter is primarily concerned with the use of optical techniques to characterise the alignment properties of a range of liquid crystals. Through the use of rigorous multilayer optics models and liquid crystal continuum theories fundamental physical and dielectric properties of these materials are determined. In the 1990’s the group pioneered the use of the “half-leaky” [1] and “fully-leaky” [2] optical guided mode technique to determine the director profile (average molecular orientation) in thin (~10 micron thick) liquid crystal layers. This technique was then developed further in the early 2000’s to allow the electrically induced director reorientation dynamics to be recorded on a sub-millisecond timescale [3]. More recently, wWork has also been undertaken to take the study of liquid crystals in the microwave [4] and THz [5] regions of the electromagnetic spectrum. More recently we have explored sign dependent switching [6], patterned surface alignment [7], surface plasmon coupling to guided modes [8] and used confocal microscopy [9] and conoscopy [10] to explore the dynamics of liquid crystal flow. Further information relating to these previous studies can be found in the publications section of this site. The research projects that are currently active in the group are as follows:
[1] F. Z. Yang, and J. R. Sambles, Journal of the Optical Society of America B-Optical Physics 10, 858 (1993). |
