OPTICAL WAVE-GUIDING AND MORPHOLOGY OF CHITOSAN THIN-FILMS

An investigation was made of the optical and waveguiding properties of thin Alms fabricated from solutions of chitosan-acetic acid (chitosan /HAc) and chitosan/HAc doped with rare-earth metal ions (Er+++ or Nd++). For all three films, the refractive indices were approximately 1.5 and there was nearly no absorption in the range of 300 to 2700 nm. Th e optical loss in a waveguides was less than 0.5 dB/cm. Morphological observations disclosed that all the films possessed a dense and homoge neous amorphous structure with smooth surfaces. Extrinsic scattering, especially the scattering caused by surface impurities, was the domina ting factor affecting the optical loss value. It is also interesting t o note that for all the films, doped with rare-earth metal ions or not , the morphological characteristics were alike and the optical propert ies were similar. Doping rare-earth metal ions into chitosan thin film s did not seriously influence optical waveguiding. This paper reports, we believe, the first study of chitosan films for optical application s. The experimental results demonstrate that chitosan and its derivati ves are potential candidates for optical materials. (C) 1996 John Wile y & Sons, Inc.