A periodic array of InSb spheres on a substrate is numerically analyzed at terahertz frequencies. The incident field is shown to be coupled to the substrate due to the guided-mode resonance. The effect of the background refractive index on the transmission characteristics is investigated for sensor applications.

A grating consisting of a periodic array of InSb-coated dielectric cylinders on a substrate is analyzed at THz frequencies using the frequency-dependent finite-difference time-domain method based on the trapezoidal recursive convolution technique. The transmission characteristics of an infinite periodic array are investigated not only at normal incidence but also at oblique incidence. The incident field is shown to be coupled to the substrate due to the guided-mode resonance (GMR), indicating the practical application of a grating coupler. For the sensor application, the frequency shift of the transmission dip is investigated with attention to the variation of the background refractive index. It is found that the shift of the dip involving the surface plasmon resonance is almost ten times as large as that of the dip only from the GMR. We finally analyze a finite periodic array of the cylinders. The field radiation from the array is discussed, when the field propagates through the substrate. It is shown that the radiation direction can be controlled with the frequency of the propagating field.

Photophysical properties of water-soluble porphyrin were studied in aqueous solutions with/without DNA and in DNA solid films. Ultrathin films were prepared from aqueous DNA solutions by a spin-coating method on glass or on gold nanoparticles (AuNPs). Remarkable enhancement of phosphorescence was observed for porphyrin immobilized in DNA films spin-coated on AuNPs, which was attributed to the electric field enhancement and the increased radiative rate by localized surface plasmon resonance of AuNPs.

In this work, we report the in situ growth of gold nanoparticles (AuNPs) for the improvement of a transmission surface plasmon resonance (T-SPR) sensor to detect human immunoglobulin G (IgG). Human IgG was immobilized on an activated self-assembled monolayer of 11-mercaptoundecanoic on a gold-coated grating substrate. The T-SPR system was also used to monitor the construction of sensor chips as well as the binding of IgG and anti-IgG conjugated with AuNPs. After specific adsorption with IgG, the T-SPR signal was further enhanced by the in situ growth of AuNPs bound with anti-IgG. Using AuNP conjugation and in situ growth of bound AuNPs, the sensitivity of the IgG immunosensor was improved by two orders of magnitude compared with that without conjugated AuNPs.

Two plasmonic band-bass filters are analyzed: one is a grating-type filter and the other is a slit-type filter. The former shows a band-pass characteristic with a high transmission for a two-dimensional structure, while the latter exhibits a high transmission even for a three-dimensional structure with a thin metal layer.

The optical properties of arrays of nanoholes and nanoslits in Al films were investigated both numerically and experimentally. The choice of Al was based on its low cost and ease of processing, in addition to the fact that it has a higher plasma frequency than gold or silver, leading to lower optical losses at wavelengths of 400 to 500nm.

A quartz-crystal-microbalance (QCM) and surface-plasmon-resonance (SPR) hybrid sensor was prepared, and the depositions of polymer electrolytes layer-by-layer (LbL) films were observed in situ. The estimated thicknesses obtained from the QCM method were different from those obtained from the SPR method. This was estimated to be caused by film swelling and water contained in the film.

The fabrication of a grating structure formed by a solid-state electrolyte layer on a dye-TiO$_{2}$ film by the nanoimprinting technique using a polydimethylsiloxane (PDMS) stamp and its application in photoelectric conversion devices are described. The PDMS grating pattern is imprinted from blu-ray disc recordable. A silver electrode was deposited on the patterned solid-state electrolyte layers. Surface plasmon resonance (SPR) excitation was observed in the fabricated solar cells by irradiation with white light. The photoelectric conversion properties were measured to study the effect of the two types of SPR excitations, i.e., the propagating surface plasmon on the Ag grating surface and the localized surface plasmon from the Au nanoparticles on TiO$_{2}$.

The main purpose of this paper is to apply the boundary integral equation (BIE) method to the analysis of spoof localized surface plasmons (spoof LSPs) excited in a perfectly conducting cylinder with longitudinal corrugations. Frequency domain BIE schemes based on electric field integral equation (EFIE), magnetic field integral equation (MFIE) and combined field integral equation (CFIE) formulations are used to solve two-dimensional electromagnetic (EM) problems of scattering from the cylinder illuminated by a transverse electric plane wave. In this approach effects of spoof LSPs are included in the secondary surface current and charge densities resulting from the interaction between the plane wave and the cylinder. Numerical results obtained with the BIE schemes are validated by comparison with that of a recently proposed modal solution based on the metamaterial approximation.

We report enhanced photocurrent properties of dye/Au-loaded titanium dioxide (TiO2) films on Au gratings. Au-loaded TiO2 nanopowders were first synthesized by a modified sol-gel method and then prepared by the impregnation method. We also fabricated dye-sensitized solar cells, which were composed of Au grating/Au-TiO2/TMPyP-SCC LbL (20 bilayers)/electrolyte/ITO substrates. Short-circuit photo-current measurements showed that Au-loaded TiO2 with grating-coupled surface plasmon excitation can enhance the short-circuit photocurrentof the fabricated cells.

We investigated optical transmission characteristics of aluminum thin films with periodic hole arrays in sub-wavelength. We divided white light into several color spectra using a color filter based on the surface plasmon resonance (SPR) utilizing aluminum showing high plasma frequency. By optimizing a hole-array period, hole shape, polarization and index difference of two surface, transmittance of 30% and full-width at half-maximum of around 100 nm were achieved.

This paper reviews our recent activities on nanophotonics based on a photonic crystal (PC)/quantum dot (QD)-combined structure for an all-optical device and a metal/semiconductor composite structure using surface plasmon (SP) and negative refractive index material (NIM). The former structure contributes to an ultrafast signal processing component by virtue of new PC design and QD selective-area-growth technologies, while the latter provides a new RGB color filter with a high precision and optical beam-steering device with a wide steering angle.

In this review, we introduce a variety of surface sensitive techniques for the study of organic thin films, and applications to organic devices. These studies include surface plasmon emission light, organic thin film transistors, combination of quartz crystal microbalance and optical waveguide spectroscopy, evaluation of alignment of liquid crystal molecules at surfaces, and biosensor applications.

A half-cylindrical BK-7 prism/dielectric film with a grating/Ag film/fluorescent polymer film structure was prepared, and its surface plasmon (SP) excitation property was investigated. It was confirmed experimentally that SP excitations are possible in this structure by using prism and grating couplings. The SP excitation property depended on the direction of the grating vector. Furthermore, intense photoluminescence was observed when the SPs were simultaneously excited at the Ag/polymer interface by prism coupling and at the Cytop/Ag interface by grating coupling.

This paper proposes a novel metamaterial structure, which equivalently indicates negative permittivity, for the purpose of applying it to a near-field imaging and/or diagnostics of electromagnetic properties by using a surface plasmon in microwave frequency range. The proposed structure consists of a conducting wire lattice with conducting spheres embedded at the mid-point of the wire. It is shown that a spatial dispersion of the wire lattice can be reduced significantly by the sphere. It is also shown that this structure can successfully be applied to an excitation of the surface plasmon in the microwave frequency range by adequately cutting into a thin slab.

In this report, we demonstrate electrocatalytic oxidation properties of ascorbic acid at poly(3,4-ethylenedioxythiophene) (PEDOT) thin films in view of their potential application for bio-sensing devices. PEDOT thin films were deposited on gold thin films by electropolymerization of EDOT monomer in acetonitrile solvent. In-situ electrochemical-surface plasmon resonance spectroscopy (EC-SPR) was used to detect both electrochemical and optical signals upon an injection of ascorbic acid.

Attenuated total reflection (ATR) property utilizing surface plasmon (SP) excitation was investigated for BK-7 prism/MgF2/Ag film/fluorescent organic dye film structure. In the structure, it is expected that SPs are excited at MgF2/Ag and Ag/dye film interfaces by Otto and Kretschmann configurations, respectively. In the experimental ATR curve, reflection dips for the SP excitations at the interfaces could be detected. Furthermore, SP emission lights were observed by irradiation of Ar ion laser beam from the dye film side. The SP emission light curve with two peaks was observed and it was also considered that the peaks corresponded to the SP excitation of Otto and Kretschmann configurations. The SP emission light spectra indicated the excited fluorescent dyes induced the SP emission lights. Intense emission light of Otto configuration was observed in this sample.

In this study, attenuated total reflection (ATR) utilizing surface plasmon (SP) excitation and SP emission lights were observed for the adsorption of polystyrene (PS) spheres and a water-soluble polymer. The PS spheres contained fluorescent dyes and exhibited red fluorescence. The ATR properties indicated film deposition with increasing number of adsorption cycles. The SP emission light induced by the fluorescent dye in the spheres was also measured, and an increase in the peak intensity, as well as an angle shift, was observed. Furthermore, the SP emission light spectra were investigated at various emission angles. The dispersion relation obtained from the SP emission light almost corresponded to that obtained from the ATR curves.

LSI on-chip optical interconnections are discussed from the viewpoint of a comparison between optical and electrical interconnections. Based on a practical prediction of our optical device development, optical interconnects will have an advantage over electrical interconnects within a chip that has an interconnect length less than about 10 mm at the hp32-22 nm technology node. Fundamental optical devices and components used in interconnections have also been introduced that are small enough to be placed on top of a Si LSI and that can be fabricated using methods compatible with CMOS processes. A SiON waveguide showed a low propagation loss around 0.3 dB/cm at a wavelength of 850 nm, and excellent branching characteristics were achieved for MMI (multimode interference) branch structures. A Si nano-photodiode showed highly enhanced speed and efficiency with a surface plasmon antenna. By combining our Si nano-photonic devices with the advanced TIA-less optical clock distribution circuits, clock distribution above 10 GHz can be achieved with a small footprint on an LSI chip.

Excitation of plasmons on the surface of a metal grating placed in planar or conical mounting is investigated in detail. Most of the results of numerical computations are compared with experimental data. When a TM wave illuminates a metal grating, total or partial absorption of incident light occurs at angles of incidence at which the plasmon surface waves are excited. In planar mounting the absorption is generally strong and nearly total absorption is observed. While in conical mounting, it is not so strong as that in the planar mounting case and a considerable amount of incident power is reflected. This, however, is accompanied by enhanced TM-TE mode conversion and the greater part of the reflected wave is in the TE polarization. The reciprocal of the TM-wave efficiency, hence, is a practical measure in finding the angles of incidence at which the plasmons are excited. Because the angles are sensitive functions of the refractive index of a material over the grating surface, this phenomenon can be used as an index sensor.