All-polymer silk-fibroin optical planar waveguides

Abstract

This paper presents the properties of optical planar waveguides made of silk fibroin, extracted from Bombyx mori cocoons deposited on an allyl diglycol carbonate substrate. Raman spectroscopy and Fourier-transform infrared spectroscopy were used to characterise the molecular structures of the silk fibroin layer, while the waveguiding properties were measured by the m-line spectroscopy at six wavelengths 532.0, 654.2, 846.4, 1308.2, 1549.1 and 1652.1 nm. The measurement proved that the silk fibroin layers guide light at all measured wavelengths. Optical losses were measured by scanning a fibre-optic probe at 846.4 and 1549.1 nm; they were estimated to be 0.24 dB cm−1 and 0.25 dB cm−1, respectively. Our results have proved that the Bombyx mori silk fibroin has a great potential for realization of optical waveguides for new bio-photonic devices.