We present symmetric and asymmetric couplings within a pair of split-ring resonators (SRRs). The former shows a single transmittance dip, following the equivalent circuit model; yet, the latter introduces an additional transmittance peak, stemming from an asymmetrically coupled resonance (ACR) between the subradiant and superradiant modes. The mechanism of such induced transparency is elucidated well by the suppression of induced currents within the SRR element with a lower quality factor. Finally, the excitation of ACR is further associated with remarkable confinement of electromagnetic field, providing a compelling sensing performance based on its excellent sensitivity and figure of merit.

Asymmetric coupling between subradiant and superradiant plasmonic resonances and its enhanced sensing performance.

We study analytically and numerically the far-field extraordinary optical transmission (EOT) through double-layer metallic grating structures patterned with subwavelength hole arrays. In addition to EOT phenomena due to the well-known surface plasmon polaritons (SPPs) on the outer surfaces such as those on a single layer hole array, further EOT peaks are observed. The separation between the metallic layers is small enough to allow SPPs propagating through the inner interfaces to couple and form an internal SPP, with a different dispersion relation from the outer one and so giving rise to EOT peaks at different frequencies. We propose a relatively simple model to predict the frequencies of those EOT peaks. Internal SPPs show certain unique properties different from the external SPPs: they can give rise to a magnetic response and a negative effective permeability, and the transmission of their EOT peaks increases when no direct line of sight is allowed through the structure. All these findings may be utilized in wavelength tuning of extraordinary optical transmission in subwavelength optics.

Role of surface plasmon polaritons on optical transmission through double layer metallic hole arrays

A new type of absorber, a four-tined fish-spear-like resonator (FFR), constructed by the two-photon polymerization process, is reported. An absorbance of more than 90% is experimentally realized and the resonance occurs in the space between the tines. Since a continuous layer of metallic thin film covers the structure, it is perfectly thermo- and electroconductive, which is the mostly desired feature for many applications.

Structured metal film as a perfect absorber.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-000304.pdf

Structured Metal Film as Perfect Absorber

In this work, Ba(Zr0.25Ti0.75)O3 ceramic was prepared by solid-state reaction. This material was characterized by x-ray diffraction and Fourier transform Raman spectroscopy. The temperature dependent dielectric properties were investigated in the frequency range from 1 kHz to 1 MHz. The dielectric measurements indicated a diffuse phase transition. The broadening of the dielectric permittivity in the frequency range as well as its shifting at higher temperatures indicated a relaxor-like behaviour for this material. The diffusivity and the relaxation strength were estimated using the modified Curie–Weiss law. The optical properties were analysed by ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements at room temperature. The UV–vis spectrum indicated that the Ba(Zr0.25Ti0.75)O3 ceramic has an optical band gap of 2.98 eV. A blue PL emission was observed for this compound when excited with 350 nm wavelength. The polarity as well as the PL property of this material was attributed to the presence of polar [TiO6] distorted clusters into a globally cubic matrix. (Some figures in this article are in colour only in the electronic version)

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Optical and dielectric relaxor behaviour of Ba(Zr 0.25 Ti 0.75 )O 3 ceramic explained by means of distorted clusters

Optical magnetic response from parallel plate metamaterials

Infrared optical properties of Ba(Zr0.20Ti0.80)O3 and Ba(Zr0.30Ti0.70)O3 thin films prepared by sol–gel method

92%Pb(Mg1∕3Nb2∕3)O3–8%PbTiO3 (PMNT) thin films have been prepared on Pt∕Ti∕SiO2∕Si substrate with a LaNiO3 (LNO) buffer layer and on sapphire substrate by a chemical solution deposition method, respectively. X-ray diffraction analysis shows that the PMNT thin films on Pt∕Ti∕SiO2∕Si substrate are polycrystalline with (110)-preferential orientation. Pt∕PMNT∕Pt capacitors have been fabricated and show a ferroelectric character with a spontaneous polarization (Ps) of 25.2μC∕cm2 and a remanent polarization (Pr) of 6.56μC∕cm2. The dielectric constant (er) and the dissipation factor (tanδ) at 1 kHz are 680 and 0.014, respectively. The band-gap energy of the PMNT thin films on the sapphire substrate was found to be about 4.03 eV by the optical transmission spectra measurement. The optical constants (n, k) of the PMNT thin films in the wavelength range of 2.5–12.6 μm were obtained by infrared spectroscopic ellipsometry measurement.

Electrical and optical properties of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 thin films prepared by chemical solution deposition

Using infrared spectroscopic ellipsometry, the dielectric functions of (111) oriented Bi2Ti2O7 thin films with pyrochlore structure prepared on Pt∕Ti∕SiO2∕Si substrate were determined in the temperature range of 20–70 °C. It is demonstrated that there is a phase transition that appears near 40 °C in terms of static effective charge as a function of temperature calculated from the infrared spectroscopic ellipsometric data of Bi2Ti2O7 thin films. It suggests that the static effective charge is related to the structural distortion, which can facilitate the polarization of Bi2Ti2O7. Accordingly, ferroelectricity in Bi2Ti2O7 is proved by analyzing the infrared dielectric function.

Study of the ferroelectricity in Bi2Ti2O7 by infrared spectroscopic ellipsometry

The infrared dielectric constants of the perovskite BaTiO3 are obtained by infrared spectroscopic ellipsometry in the temperature range of 20–150°C. Apparent temperature-dependent distribution of the spectral weight variation is observed for complex dielectric function. Both high frequency dielectric function and bound electrical charge show the temperature dependence from the tetragonal to the cubic phase transition. The bound electrical charge appears to be composed of a hopping component and a temperature-dependent one for BaTiO3 with first-order transitions.

Jianqiang Xue

Papers

Optical magnetic response from parallel plate metamaterials

Infrared optical properties of Ba(Zr0.20Ti0.80)O3 and Ba(Zr0.30Ti0.70)O3 thin films prepared by sol–gel method

Electrical and optical properties of Pb(Mg1∕3Nb2∕3)O3–PbTiO3 thin films prepared by chemical solution deposition

Study of the ferroelectricity in Bi2Ti2O7 by infrared spectroscopic ellipsometry

Temperature dependence of BaTiO3 infrared dielectric properties