The application of the phase transition in nematic liquid crystals for theoptical detection of volatile organic compounds

It is demonstrated that optical transducers can take advantage from the out standing optical properties of nematic liquid crystals. The measurements po int out that the birefringence and the phase transition of a liquid crystal can be exploited for the threshold sensing. For that purpose a device cons isting of an orientated liquid crystalline film between two crossed polariz ers was used. The nematic liquid crystal was also used as a sensitive coati ng material on an integrated optical Mach-Zehnder interferometer. The calib ration experiments were carried out with volatile organic solvents and diff erent calibration curves were measured for meta-xylene and para-xylene.