Monolithic silicon photonic crystal slab fiber tip sensor

We demonstrate that monolithic photonic crystals (PCs) confined to the facet, or tip, of single-mode optical fibers can be designed as highly sensitive refractive index point sensors. Monolithic photonic-crystal slabs are fabricated on silicon wafers and subsequently released and micro-assembled on the tip of optical fibers. The PC slab´s reflection spectrum is modulated by the refractive index of the environment and shows sensitivity comparable to fiber Bragg gratings (FBGs). The compact sensing element is located at the tip of a fiber and hence is a highly localized sensor. The sensor is made of robust, high-temperature dielectric materials and therefore has the potential to be used for many applications including measurements in harsh environments.