title: Shape-dependent light scattering properties of subwavelength silicon nanoblocks.
abstract: We explore the shape-dependent light scattering properties of silicon (Si) nanoblocks and their physical origin. These high-refractive-index nanostructures are easily fabricated using planar fabrication technologies and support strong, leaky-mode resonances that enable light manipulation beyond the optical diffraction limit. Dark-field microscopy and a numerical modal analysis show that the nanoblocks can be viewed as truncated Si waveguides, and the waveguide dispersion strongly controls the resonant properties. This explains why the lowest-order transverse magnetic (TM01) mode resonance can be widely tuned over the entire visible wavelength range depending on the nanoblock length, whereas the wavelength-scale TM11 mode resonance does not change greatly. For sufficiently short lengths, the TM01 and TM11 modes can be made to spectrally overlap, and a substantial scattering efficiency, which is defined as the ratio of the scattering cross section to the physical cross section of the nanoblock, of ∼9.95, approaching the theoretical lowest-order single-channel scattering limit, is achievable. Control over the subwavelength-scale leaky-mode resonance allows Si nanoblocks to generate vivid structural color, manipulate forward and backward scattering, and act as excellent photonic artificial atoms for metasurfaces.
authors: Department of Physics and Institute for the NanoCentury, KAIST , Daejeon 305-701, Republic of Korea.
authors: Ho-Seok
authors: HS
authors: Ee
authors: Ju-Hyung
authors: JH
authors: Kang
authors: Mark L
authors: ML
authors: Brongersma
authors: Min-Kyo
authors: MK
authors: Seo
keywords: Silicon nanoblock; leaky-mode resonance; resonant scattering; scattering cross section; structural color