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

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

Controlling extraordinary transmission characteristics of metal hole arrays with spoof surface plasmons

We experimentally controlled the spectral characteristics of the extraordinary transmissions observed in metal hole arrays by analogy with spoof surface plasmon-polaritons (spoof SPPs), We constructed doubly periodic metal hole arrays. The larger and smaller periodic holes are for inducing extraordinary transmissions and modifying the spoof SPPs characteristics, respectively. Introducing the smaller holes that surround the larger hole arrays can modify the dispersion curve of the surface waves excited on a structured metal surface analogous to the spoof SPP model, and consequently, the extraordinary transmission peak will show a redshift. (C) 2012 American Institute of Physics. [https://doi.org/10.1063/1.3689784]ArticleAPPLIED PHYSICS LETTERS. 100(8):081112 (2012)journal articl

Terahertz absorption spectra of L-, D-, and DL-alanine and their application to determination of enantiometric composition

Absorption spectra of polycrystalline L-, D-, and DL-alanine have been measured by the terahertz time domain spectroscopy (THz-TDS)in the frequency range from 10 to 90 cm−1 at room temperature. We observed several absorption bands, which have the large difference between enantiomers (L- and D-alanine)and the racemic compound (DL-alanine)in their peak frequencies. This obvious difference shows that the THz absorption bands are strikingly sensitive to the crystal structures. This result indicates that the THz-TDS can be used for distinguishing between the enantiomers and the racemic compound. We propose and demonstrate a method to determine the enantiometric composition of amino acids from the THz absorption spectra

Hidden Symmetry Protection and Topology in Surface Maxwell Waves

Since the latter half of the 20th century, the use of metal in optics has become a promising plasmonics field for controlling light at a deep subwavelength scale. Surface plasmon polaritons localized on metal surfaces are crucial in plasmonics. However, despite the long history of plasmonics, the underlying mechanism producing the surface waves is not fully understood. This study unveils the hidden symmetry protection that ensures the existence of degenerated electric zero modes. These zero modes are identified as physical origins of surface plasmon polaritons, and similar zero modes can be directly excited at a temporal boundary. In real space, the zero modes possess vector-field rotation related to surface impedance. Focusing on the surface impedance, we prove the bulk-edge correspondence, which guarantees the existence of surface plasmon polaritons even with nonuniformity. Lastly, we extract the underlying physics in the topological transition between metal and dielectric material using a minimal circuit model with duality. The transition is considered the crossover between electric and magnetic zero modes.Comment: 26 pages, 19 figures, minor correction

Dependence of emission of terahertz radiation on geometrical parameters of dipole photoconductive antennas

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(21):211104 (2010) and may be found at https://doi.org/10.1063/1.3436724 .The dependence of the emission spectrum of terahertz (THz) radiation on the geometrical parameters of the dipole antenna, and the relationship between these parameters and the temporal characteristics of the transient current that generate THz radiation, is reported. The emission intensity and the peak frequency strongly depend on these geometrical parameters. This dependence varies significantly with changes in the temporal characteristics of the transient current. We have also found that the emission efficiency can be increased by increasing the aspect ratio for the dipole.ArticleAPPLIED PHYSICS LETTERS. 96(21):211104 (2010)journal articl