Tunable humidity sensor based on ITO-coated optical fiber

Here, it is presented the fabrication and characterization of a new tunable humidity sensor based on ITO-coated optical fiber. A thin nanostructurated multilayer polymeric film sensitive to humidity is deposited onto the ITO layer. The device is characterized by means of a resonance in the infrared region. Resonance wavelength variations of 600 nm have been recorded during the multilayer fabrication process. The thickness of the polymeric coating was adjusted to operate on the point of maximum variation of the resonance wavelength per refractive index unit (RIU) in order to take advantage of the high sensitivity of these resonance based devices. The precise thickness control was achieved by using the layer-by-layer (LbL) deposition technique. The quality of the device is proved experimentally with a sensitivity improvement of a factor four if the tuned optical fiber sensor is used instead of the non-tuned one.