Photonic-Crystal-Based Optical Fiber Bundles and Their Applications

A simple method to create two-dimensional or three-dimensional periodic nano-structures on optical fiber bundle end facets (FBEFs) is proposed and demonstrated, and periodicity of these nano-structures can be controlled. Polystyrene opal films and silica inverse opal films were fabricated on single-mode optical FBEFs by vertical self-assembly and sol-gel co-assembly methods. Optical properties of the three-dimensional photonic crystal (PC) films on FBEFs were studied by their reflection spectra, which were measured from the other end of the bundle. As a result, a good, repeatable, and reliable optical performance of the PC films, which were fabricated at low cost, was achieved, and applications of the PC films will be easy to perform by this structure, especially for sensing applications. Composite PC films on FBEFs as relative humidity sensors are demonstrated. Its reflection peak will shift 21 nm as the relative humidity changes from 12% to 76%.