Soft Matter Physics Seminar: Dr Philip Hands, University of Edinburgh

Dr Philip Hands, of the School of Engineering, University of Edinburgh, will be presenting a seminar on his research. All are welcome to attend.

Getting into a spin over liquid crystal lasers Abstract: Liquid crystals are ubiquitous in the world of modern displays, thanks to their ability to self-organise into optically anisotropic crystalline structures, whilst their molecules retain their fluidic ability to move and rotate when subject to electric fields. However, the variety of self-organising liquid crystalline mesophases, and the optical phenomena resulting from them, is much more diverse than is currently used by the displays industry, and so the development of new applications of liquid crystals remains a promising area of research.

Cholesteric (or chiral nematic) liquid crystals have the ability to self-assemble into period chiral nanostructures, with repeat patterns that have similar size to the wavelength of visible light. Such periodic nanostructured materials display colour-selective Bragg reflection (a photonic band-gap), whereby light of a specific range of frequencies is reflected from the structure. Nano-structural colour (or iridescence) also occurs in nature, in the carapaces of certain beetles, or the wings of some butterflies, but with liquid crystals we can control and manipulate the exact wavelengths that are reflected through careful control of the chirality.

With the addition of fluorescent dyes to the cholesteric, and a suitable excitation source, we can combine this reflective resonance effect with optical gain, to create a low-cost, semi-disposable, and highly customisable liquid crystal laser. Until recent years, the liquid crystal laser has remained an invention looking for a job; just as the original invention of the laser was also considered for many years. In this talk, we will explore recent developments in the field of liquid crystal lasers, discussing their unique properties, their current limitations, and their potential for future applications. In particular we look at how spinning liquid crystal laser systems can be used to significantly increase repetition rate and average power, thus opening the door to low-cost custom sources for biomedical imaging and holographic projection.

Host: Professor Helen Gleeson