A facile way to introduce planar defects into colloidal photonic crystals for pronounced passbands

Abstract

We demonstrate a facile method for introducing planar defects into colloidal photonic crystals. Firstly, a 2D monolayer of SiO2 microspheres (guest spheres) was fabricated at the air/water interface by compressing the individual microspheres with a surfactant into long-range hexagonal arrays. The floating monolayer, which served as our defect layer, was then transferred onto a pre-deposited colloidal crystal slab consisting of PS@SiO2 microspheres (host spheres). Subsequently, a second colloidal crystal slab of host spheres was deposited on the surface of the defect layer. In comparison to previous methods to introduce planar defects into colloidal photonic crystals, this fabrication results in pronounced passbands in the band gaps of the colloidal photonic crystals. More importantly, the FWHM of the passband in our experiment is just 16 nm, which is narrower than the previously reported results to the best of our knowledge. Furthermore, the defect modes can be engineered by changing the diameter of the guest spheres and/or transforming the host spheres from PS@SiO2 spheres to hollow SiO2 spheres by calcination. The measured defect modes in the spectra match well with the simulated results.