Optical properties of Ag nanocap decorated SiO2 opal plasmonic photonic crystals and their applications

We fabricated plasmonic-photonic crystal that consists of SiO2 nanosphere opal decorated with silver nano-caps with self-assembly methods. Optical measurements of the sample show anomalous suppression of the reflectivity in... [ view full abstract ]

We fabricated plasmonic-photonic crystal that consists of SiO₂ nanosphere opal decorated with silver nano-caps with self-assembly methods. Optical measurements of the sample show anomalous suppression of the reflectivity in the spectral range of the photonic band gap of the opal structure, which results in an inverted reflection peak in the spectrum compared to that of a bare opal structure. Our numerical simulations indicate that the coupling between the excitation of Ag-cap surface plasmon and the scattering of the incident light inside the opal lead to the suppression of the opal reflection at the photonic bandgap wavelengths. We apply such coupling to identify light diffraction from the opals surfaces as the physical mechanism responsible for the the high-order reflection peaks in the specular reflection spectra, whose origin has been long searched since their discovery.