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

液晶弹性体是一类新型的软材料，其特点是取向序和应变之间的耦合，其力学变形引起介电张量的变化。胆甾体液晶弹性体是一种具有周期性结构的光子带隙材料，其能带结构可以通过机械应变改变。光泵浦胆甾液晶弹性体表现出分布腔效应，受激发射，并且在带边缘超过阈值时，无反光镜激光。本文的工作是与EC合作者一起研究光泵螺旋胆甾和其他周期性液晶弹性体在机械应变下的响应。参与的研究生和本科生将获得使用激光物理和光谱学研究光子带隙弹性体的最新研究技术的实践经验。除了对这些材料的光学响应过程获得基本的见解外，拟议的研究还将导致机械可调谐激光源，可切换反射镜和可调谐带隙材料。液晶弹性体是一种新型的类似橡胶的材料，当机械变形时，它的光学特性会发生巨大的变化。这种独特的性质可以用来产生其他材料不可能产生的特殊性质；例如，它们可用于制造机械可调谐波长选择镜和大面积薄膜激光器。计划的研究将集中在探索和利用这些独特的性质和效果。高风险材料的研究导致了最近可调谐“橡皮筋”激光器的发现，如果没有公共基础研究的资助，这是不可能的。拟议的工作将与已经从事弹性体材料研究的欧共体科学家合作进行，以确保美国在材料科学和技术领域的前沿地位。该项目将为参与的研究生和本科生提供软材料表征、激光物理和光子学等前沿跨学科领域的教育，并有望对从电信到人造肌肉等各种技术产生影响。

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.