Influence of humidity on refractive index of polymers for optical waveguide and its temperature dependence

Humidity dependence of the refractive index of deuterated polymethylmethacylate (d-PMMA) is examined at a wavelength of 1.3 mu m using the return loss method. The refractive index of d-PMMA increases as humidity increases at room temperature, while it decreases as humidity increases at temperatures higher than 60 degrees C. This humidity dependence was ascribed to the counterbalance between moisture sorption and swelling, Some hydrophobic polymers, such as silicone resin and fluorinated epoxy resin were affected by humidity to a lesser degree than d-PMMA. (C) 1998 American Institute of Physics.