NSF-EC: Tunable Mirrorless Lasing in Cholesteric Liquid Crystalline Elastomers

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Liquid crystalline elastomers are a new class of soft materials, distinguished by the coupling between orientational order and strain, whose mechanical deformations give rise to changes in the dielectric tensor. Cholesteric liquid crystal elastomers, due to their periodic structure, are photonic band-gap materials whose band structure can be altered by mechanical strain. Optically pumped cholesteric liquid crystal elastomers exhibit distributed cavity effects, stimulated emission, and, above a threshold, mirrorless lasing at the band edges. The proposed work is to study, in conjunction with EC collaborators, the response of optically pumped helical cholesteric and other periodic liquid crystalline elastomers under mechanical strain. Participating graduate and undergraduate students will gain hands-on experience using the latest research techniques in laser physics and spectroscopy studying photonic band gap elastomers. In addition to gaining fundamental insights into the processes underlying the optical response of these materials, the proposed research will lead to mechanically tunable laser sources, switchable mirrors and tunable band-gap materials.Liquid crystal elastomers are novel rubber-like materials that dramatically change their optical properties when mechanically deformed. This unique property can be used to produce exceptional properties not possible with other materials; for example, they can be used to produce mechanically tunable wavelength selective mirrors, and large area, thin film lasers. The planned research will focus on exploring and utilizing these unique properties and effects. The high-risk materials research that led to the recent discovery of tunable 'rubber band' lasers would not have been possible without public funding of basic research. The proposed work, to be performed in collaboration with European Community scientists already engaged in the study of elastomeric materials, is needed to ensure U.S. presence at the forefront of this materials science and technology area. The project will educate participating graduate and undergraduate students in the cutting-edge interdisciplinary areas of soft materials characterization, laser physics and photonics, and is expected to impact on a variety of technologies ranging from telecommunications to artificial muscles.