Three-dimensional tunable colloidal photonic crystal self-assembled on the end face of an optical fiber

Abstract

High-quality three-dimensional nanostructure colloidal crystal-fiber structure is obtained by the modified vertical deposition method. The morphology of the colloidal crystal is examined by the scanning electron microscope, which illustrates that the (111) plane is parallel to the substrate of the fiber end face. The optical characterization of the colloidal crystal is also analyzed with an all-fiber network system. Reflection spectra show the existence of photonic band gap, which is located at 845 nm. As the liquid refractive index filled in the voids of the sample increases, the tunable wavelength of reflected light which is predicted by Bragg's equation with considering the effect of photonic band gap shows a good agreement with experimental results. Also, as the refractive index is changed because of different concentrations of solution, the colloidal photonic crystal-fiber system can also be distinguished by recording the shift of the maximum of Bragg reflection spectra.