Liquid-crystal optical activity for temperature sensing

Abstract

In this letter, we report a novel temperature‐sensing device based on the optical rotatory power of cholesteric liquid‐crystal films. The transducer is small and compact, compatible with lasers and fiber optics, and capable of resolving temperature differences of 0.02 °C or better. It is simpler and more precise than most liquid‐crystal techniques and does not pose the hazard that may be posed by electrical temperature sensors in certain applications. Dilute solutions of cholesteric liquid crystals in nematic solvents exhibit highly temperature‐dependent optical rotation near the isotropic phase transition temperature. We place these solutions between crossed polarizers and measure the temperature by monitoring the transmission accurately. Using a laser source, we have installed a device of this nature at the end of a bundle of fibers with encouraging results.