Distance, shape and arrangement pattern dependence of the extinction spectra for hole arrays in a silver film

摘要

The extinction spectra of hole arrays in a silver film are investigated with discrete dipole approximation method. The influences of distances between holes to the extinction spectra are explored; the effects of shapes and sizes of holes on the extinction spectra are also probed. For holes of the same areas, simulations show that the holes with square and rectangular shapes exhibit more efficient couplings compared with the circular ones. The increased aspect ratios (length/width) of rectangular holes perpendicular to the polarization direction strengthen their couplings. The influences of hole distances to the extinction spectra are examined. In the simulations, the lattice areas of hole arrays are first kept to be a constant (400×400 nm~2), and then allowed to be changed with one fixed edge length of the rectangular lattice arrays. The calculations indicate that the extinction resonance wavelengths are more sensitive to the hole spacings along the polarization direction. The distance variations perpendicular to the polarization direction only alter the strengths of the coupling between holes and show little impact to the resonance wavelengths.