Optical fiber refractometers based on lossy mode resonances supported by TiO₂ coatings

We obtain lossy mode resonances by the coupling of light from a multimode optical waveguide to a TiO₂/PSS coating deposited with the layer-by-layer method. The resonances can be generated in a wide wavelength range from the ultraviolet to the infrared region of the optical spectrum. The transmission spectrum is monitored as a function of the number of bilayers deposited, and the experimental results agree with the theoretical predictions. Moreover, each of the resonances owns a particular sensitivity to the external refractive index. This permits us to use the sensor as a refractometer with multiplewavelength monitorization.