Coupling between localized resonance and excitation of surface waves in metal hole arrays

We investigate the transition of the dominant resonant transmission mechanism from localized resonance to excitation of surface waves and vice versa in metal hole arrays. The transition occurs continuously with a change in the length of the rectangular holes. We also study the effect of the incident-beam diameter and surface condition on the transmission spectrum. Our experimental results show the important differences between the two mechanisms. They also confirm the theoretical prediction of Bravo-Abad [Phys. Rev. B 76, 241102(R) (2007)].ArticlePHYSICAL REVIEW B. 79(15):153405 (2009)journal articl

Effect of dielectric thin films on reflection properties of metal hole arrays

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in APPLIED PHYSICS LETTERS. 96(2):021106 (2010) and may be found at https://doi.org/10.1063/1.3292024 .We study the effect of a dielectric film attached to the surface of a metal hole array (MHA) on the reflection spectrum in the terahertz (THz) region. The frequency of the reflection dip, attributed to the excitation of surface waves in the vicinity of the MHA surface, shifts to lower frequencies with increasing dielectric film thickness. This resonant characteristic of MHAs can be applied to highly sensitive THz sensing for samples attached to the MHA surface. We also investigate the dependence of the reflection spectrum on the MHA's thickness and the side to which the dielectric film is attached.ArticleAPPLIED PHYSICS LETTERS. 96(2):021106 (2010)journal articl

Inelastic Neutron Scattering Study of Ferroelectric Phase Transition in Lithium Heptagermanate (Li(2)Ge(7)O(15))

Phonon dispersions in ferroelectric lithium heptagermanate Li(2)Ge(7)O(15) (LGO) were measured by inelastic neutron scattering in the vicinity of the transition temperature T(C) = 283.5 K. The (300) reflections show more pronounced temperature dependence than the (500) reflections. The energy of a peak corresponding to the Brillouin zone-center phonon, around 0.5 meV at 297.0 K, decreases as the temperature decreases. Then, this inelastic component disappears into the central component at 288.0 K, just above T(C). The present phonon shows the typical soft mode feature and shows good accordance with the B(1u) mode observed by hyper-Raman and FTIR measurements. It is confirmed that the ferroelectric phase transition in LGO is associated with the soft optical phonon at the zone center. Moreover, elastic diffuse scattering is observed below 0.1 meV. This implies that there exists a critical phenomenon at energies below than 0.1 meV.ArticleFERROELECTRICS. 412(0):45-51 (2011)journal articl