Hybrid metallic photonic crystals with higher-order coupling processes

Hybrid metallic photonic crystals (MPCs) combine the orderly arranged grating structures and the disordered gold nanostructures, where the gratings are fabricated by interference lithography on a layer of waveguide and the isolated gold nanoislands arranged randomly in the grating grooves are produced using solution-processible gold nanoparticles. Strong coupling between multiple higher-order resonance modes of the waveguide grating structures and particle plasmon resonance of the isolated gold nanoislands has been observed in the visible spectral range. This technique actually realizes fabrication of the waveguide grating structures and the plasmonic gold nanostructures separately. In this way, the plasmonic resonance of the gold nanostructures is not determined by the dimensions of the grating lines anymore. Thus, the grating structures can be fabricated easily with a period of microns, whereas the size of the gold nanostructures can be controlled flexibly by changing the colloidal concentration and the annealing temperature. Large grating period leads to higher-order coupled modes in the visible. This contributes to the “family” of the MPC fabrication techniques and lowers significantly the rigorous requirements on fabrication method of the large-area nanoscale MPCs.