Interdisk spacing effect on resonant properties of Ge disk lattices on Si substrates

The light reflection properties of Ge disk lattices on Si substrates are studied as a function of the disk height and the gap width between disks. The interdisk spacing effect is observed even at such large gap widths as 500 nm. The gap width decrease leads to the appearance of the reflection minimum in the short wavelength region relative to one originated from the magnetic and electric dipole resonances in individual Ge disks, thereby essentially widening the antireflection properties. This minimum becomes significantly deeper at small gap widths. The observed behavior is associated with the features of the resonant fields around closely spaced disks according to numerical simulation data. The result shows the importance of using structures with geometrical parameters providing the short-wavelength minimum. This can essentially enhance their other resonant properties, which are widely used for applications, in particular, based on collective lattice resonances.