Volatile organic compounds detection using porphyrin-based metal-cladding leaky waveguides

A novel planar optical chemical sensor based on free 5,10,15,20 meso-tetraphenylporphyrin (H2TPP) is investigated. The sensor is based on metal-cladding leaky waveguides (MCLWs), in which a thin porphyrin film acts as the guiding layer. This configuration permits a strong interaction between the optical field and the sensing film. Several devices having different thickness of the porphyrin guiding layer are investigated as sensors of ethanol vapours in air at several concentrations. Moreover, measurements were performed at two different wavelengths, showing that there is a different behaviour of the porphyrin as a function of the wavelength. The proposed sensor exhibits good sensitivity and very fast dynamic responses.