Contact angle measurement on xerogel sensitive layer for optical fibre sensor

This paper deals with approach for the detection of chemical vapours based on refractive-index changes of a silica xerogel layer deposited as an optical cladding on the fibre core. The fibre is multimode fibre excited with an inclined collimated beam. The refractive-index changes are evaluated by means of changes of the output power at the end put of the fibre. The optical properties of the sensitive cladding (refractive index and absorption coefficient) can be obtained with modelisation program. The sensitivities of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS)-based xerogel layers to toluene and water are presented in the paper. The hydrophobicity of the two-xerogel layers and their surface-free energy has been determined with contact angle measurements. A correlation between optical detection results and contact angle measurements can be done.