Photonic crystal slab strain sensors: A viable tool for structural health monitoring

We discuss the possible use of photonic crystals as strain sensors. We demonstrate the feasible fabrication of a crystal having sub-micrometric polystyrene colloidal spheres in a PDMS matrix on a rubber substrate, and we demonstrate that the photonic properties change with substrate elongation according to theoretical prediction. The crystal's sensitivity to strain depends directly on interplanar spacing and on Poisson's ratio. To enhance the crystal strain resolution, we propose to fabricate photonic crystal slabs, which exhibit a high geometrical Poisson's ratio, and we investigate their mechanical behavior through non-linear Finite Element analysis and then, through an approximate optomechanical approach, the optical response.