Optically induced birefringence and holography in silk

In this study, we demonstrated that thin films of azobenzene-modified Bombyx mori silk showed optically induced effects similar to those found in other polymers incorporating azobenzene moieties. Optically induced anisotropy in refractive index reached 7 × 10−3 with 18 J cm−2 required to reach 50% of steady state. Holograms were formed with diffraction efficiencies reaching 2.5%. The holograms were accompanied by surface relief gratings and measurements of the mechanical properties of films with surface relief gratings showed that the raised areas were more adhesive than the lower areas. We also demonstrated the fidelity of holographic images. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011