Effect of relative humidity on the optical and waveguide properties of thin chitosan films

We have measured the optical characteristics of thin films based on various ion forms of chitosan and studied their mutual correlation. Using the spectral ellipsometry and mode spectroscopy techniques, it has been established that the optical characteristics of chitosan depend on the relative humidity $(RH)$ of the ambient medium. All samples are characterized by threshold $RH$ values, at which the optical characteristics exhibit a change. The obtained data allow chitosan to be classified as a promising sensor material with the optical properties controlled by relative humidity of the ambient medium.