The Investigation of the Waveguiding Properties of Silk Fibroin from the Visible to Near-Infrared Spectrum.

Silk fibroin protein has been reinvented as a new optical material for biophotonic applications because of its optical transparency, biocompatibility, and easy fabrication process. It is used in various silk-based optical devices, which makes it desirable to investigate the optical properties of silk from diverse perspectives. This paper presents our investigation of the optical properties of silk fibroin, extracted from Bombyx mori cocoons. We have measured transmission spectra from the visible to near-infrared region and investigated waveguiding properties by the prism-coupling technique for five wavelengths (473.0, 632.8, 964.0, 1311, and 1552 nm). From the measurements, we determined the values of refractive indices. The measurements also proved waveguiding properties for all of the wavelengths. Optical scattering losses were measured by the fiber probe technique at 632.8 nm and were estimated to be 0.22 dB·cm-1 .