Fabrication-induced disorder in structures for nanophotonics

摘要

We investigated the influence of nanoscale technological imperfections to the macroscopic behavior of ordered composite structures for photonic applications. A connection between the deviations from the designed geometry on nanoscopic level and macroscopic behavior was established using amplitude and frequency noise as the primary figures of merit. We calculated the influence of nanoscale deviations by transfer matrix technique, while surface roughness was taken into account by using the effective medium theory. As an example we considered our nonuniform silicon/silica ID photonic bandgap structures fabricated by rf sputtering, which contained defect layers with spatially varying thickness. The cross-sections and surface morphology of the samples were analyzed by scanning electron microscopy and atomic force microscopy while spectral transmission was measured by FTIR spectrometry. It was established that thickness deviations of 5-7 nm caused scattering losses of 20-40%, while lattice parameter change of 70 nm resulted in spectral transmission shift of about 70 nm. The approach is applicable to other mesoscopic and subwavelength structures, including those with higher dimensional (2D and 3D) geometries and could be used as a means for fast assessment of optical nanodevice fabrication systems.