Determining the Optical Geometry of a Gold Semi-Shell under the Kretschmann Configuration

Dielectric nanoparticles coated with metals (half-shell or semi-shell structures) have attracted attention as potential composite plasmonic nanomaterials with large optical anisotropy and absorption cross-sections. Structures approximately 100 nm in size can excite plasmons in the visible and near-infrared ranges, highlighting their distinct optical properties. This study employed metal semi-shell structures (metal: gold, dielectric: silica) in the Kretschmann configuration to experimentally and numerically demonstrate the optical determination of single-structure orientations through a finite-difference time-domain method. Gold semi-shell structures were fabricated through deposition and etching. These structures were removed from their substrate in ultrapure water and randomly dropped onto a thin gold substrate. In the single structure, we experimentally observed changes in the scattering light spectrum based on the optical geometry of the gold semi-shell at wavelengths ranging from 530 to 700 nm. The obtained results closely resembled those of a simulation and confirmed the presence of eigenmodes in the orientation through electric field analysis. These observations allow for the cost-effective and rapid determination of the orientations of numerous structures that are approximately 100 nm in size, solely through optical methods. This technique is a valuable development for measurement applications in nanostructure orientation control and functionality enhancement.


Experimental confirmation of self-imaging effect between guided light and surface plasmon polaritons in hybrid plasmonic waveguides

We fabricated a hybrid plasmonic device using self-imaging effect between guided light and surface plasmon polaritons in the hybrid plasmonic waveguide. The hybrid plasmonic device was fabricated by evaporating gold on the part of the silicon waveguide. Self-imaging was generated at the gold-covered section in the waveguide. Self-imaging of guided light and surface plasmon polaritons in hybrid plasmonic waveguides affect the output intensity of the hybrid plasmonic waveguide. The length of the hybrid plasmonic waveguide changes self-imaging conditions. We confirmed that the output intensity was affected by the length of the hybrid plasmonic waveguide. These findings contribute to the development of hybrid plasmonic devices and potentially improve integration density of hybrid photonic integrated circuits.


Ultralow-frequency ultranarrow-bandwidth coherent terahertz imaging for nondestructive testing of mortar material

Nondestructive testing of concrete materials is essential in civil engineering to maintain social infrastructure such as buildings or bridges. In this study, we constructed an ultralow-frequency, ultranarrow-bandwidth, coherent terahertz (THz) imaging system based on THz time-domain spectroscopy (THz-TDS). Based on its ultralow-frequency-localized THz wave and coherent detection, the present system achieved a wide dynamic range of THz power over 100 dB at 0.046 THz, which is appropriate to measure the mortar material. The achieved dynamic range of the THz power was 59 dB larger than that of a commercialized THz-TDS system and 49 dB larger than that of an ultralow-frequency noncoherent THz imaging system equipped with a high-power electric THz source. Ultimately, the proposed system could visualize the inner structure of a mortar sample with a thickness of 10 mm, and the present system can investigate a mortar sample with a thickness of over 130 mm. The proposed method is an attractive tool for non-destructive testing of thick concrete structures characterized by non-invasiveness and non-contact remoteness.


Comparison of hot carrier generation between self-assembled gold and silver nanoparticle arrays tailored to the same hybrid plasmon resonance


Optical Characteristics of Nano Space of Silver Nanowire on a Silver Mirror


銀ナノワイヤと銀薄膜との微小空間における光学特性，

IEEJ Transactions on Sensors and Micromachines

電気学会論文誌E (センサ・マイクロマシン部門誌)


Hydrophobic assembly of gold nanoparticles into plasmonic oligomers with Langmuir Blodgett film


Refractive index sensing at one wavelength via an active plasmonic device


MEMS plasmonic switch with stripe plasmonic waveguide


Optical Properties of Low-Loss Ag Films and Nanostructures on Transparent Substrates

We demonstrate the fabrication of a low-loss single-crystalline Ag nanostructure deposited on transparent substrates. Our approach is based on an epitaxial growth technique in which a NaCl(001) substrate is used. The NaCl substrate is dissolved in water to allow the Ag film to be transferred onto the desired substrates. Focused ion beam milling is subsequently employed to pattern a nanoarray structure consisting of 200 nanorods. The epitaxial Ag films with nanoarray structures grown in the study exhibited very flat and smooth surfaces having excellent crystallinity and local misorientation of less than 1°. Further, spectroscopic ellipsometry measurements indicated that the imaginary part of the dielectric constant of the single-crystalline film was smaller than that of a conventional polycrystalline film. Moreover, we used the three-dimensional finite-difference time-domain method to analyze the plasmonic properties of the nanoarray structure by considering the actual processed structure. Characteristically, when the SiO substrate was etched by ion beam milling to a depth of 30 nm, the spectrum showed a spectral shape 20% sharper than that of the substrate with no etching (depth: 0 nm). The plasmonic performance of the single-crystalline Ag nanostructure was largely determined by its structural precision and the dielectric properties of the metal.


Blocking Hot Electron Emission by SiO2 Coating Plasmonic Nanostructures


アスパラガスの半促成長期どり栽培における光判別による擬葉内クロロフィルa含量の推定と地上部刈り込み時期の判定，


Fabrication of single-crystalline plasmonic nanostructures on transparent and flexible amorphous substrates

A new experimental technique is developed for producing a high-performance single-crystalline Ag nanostructure on transparent and flexible amorphous substrates for use in plasmonic sensors and circuit components. This technique is based on the epitaxial growth of Ag on a (001)-oriented single-crystalline NaCl substrate, which is subsequently dissolved in ultrapure water to allow the Ag film to be transferred onto a wide range of different substrates. Focused ion beam milling is then used to create an Ag nanoarray structure consisting of 200 cuboid nanoparticles with a side length of 160 nm and sharp, precise edges. This array exhibits a strong signal and a sharp peak in plasmonic properties and Raman intensity when compared with a polycrystalline Ag nanoarray.


Effects of End of Day Lighting after Night Chilling Treatment on Growth and Development of Lettuce


FBGを用いた超音波振動の音圧の測定，

FBGを用いた超音波振動の音圧の測定，


Effect of Post-Annealing in Nitrogen Gas on the Microstructure of ZnO Thin Films Prepared Using Atmospheric Pressure Cold Plasma


Advanced fabrication of single-crystalline silver nanopillar on SiO2 substrate


Electrically driven plasmon chip: Active plasmon lenses in visible


Optical characteristics of rounded silver nanoprisms


Fabrication of silver thin film for single-crystalline nanopillar: effects of thickness and grain size

Applied Physics. A, Materials Science & Processing


Electrically controlled infrared optical transmission and reflection through metallic grating using NEMS technology


NEMS技術を利用した可変プラズモンデバイスの開発

NEMS技術を利用した可変プラズモンデバイスの開発

IEEJ Transactions on Sensors and Micromachines

電気学会論文誌E (センサ・マイクロマシン部門誌)


近赤外LED光による食品中の混入異物検出装置の開発

近赤外LED光による食品中の混入異物検出装置の開発


Self-imaging confirmed in plasmonic channel waveguides at visible wavelengths


Effect of End-of-day Light Irradiation using LED Light Sources on the Growth of Lettuce under a High Temperature


Characteristics of nano-plasmonic resonators with a gap structure


Electrically driven plasmon chip: Active plasmon filter

We have developed an electrically driven plasmon chip, i.e., an active plasmon filter, consisting of a metallic subwavelength grating modulated by a nano-electro-mechanical system (NEMS) type actuator. The device shifts the plasmon resonance wavelength and the transmittance when an electrical signal is applied. The fabricated filter shows resonance wavelength shifts of 60nm with a bias voltage of less than 10 V. A rigorous numerical calculation confirms the origin of the surface plasmon resonance and qualitatively explains the effect. Such NEMS optical devices offer rapid voltage-controlled plasmonic tuning of 20 MHz, opening up applications in agile sensing and nanoscale object trapping using actively tailored optical hot spots.


Fabrication of a Transparent Anti-stain Thin Film Using an Atmospheric Pressure Cold Plasma Deposition System


Characteristics of Double-Plasmonic-Racetrack Resonator to Increase Quality Factor


Fabrication of Transparent Antifouling Thin Films with Fractal Structure by Atmospheric Pressure Cold Plasma Deposition

Antifouling surface with both superhydrophobicity and oil-repellency has been fabricated on glass substrate by forming fractal microstructure(s). The fractal microstructure was constituted by transparent silica particles of 100 nm diameter and transparent zinc-oxide columns grown on silica particles by atmospheric pressure cold plasma deposition. The sample surface was coated with a chemically adsorbed monomolecular layer. We found that one sample has the superhydrophobic ability with a water droplet contact angle of more than 150°, while another sample has a high transmittance of more than 85% in a wavelength range from 400 to 800 nm.


Fabrication of Al doped ZnO films using atmospheric pressure cold plasma


WGMを介した光周波数信号伝達の検討

WGMを介した光周波数信号伝達の検討

電子情報通信学会技術研究報告


Electrical and Optical Properties of GaNAs/GaAs MQW p-i-n Junction

Transactions of the Materials Research Society of Japan


Experimental demonstration of plasmonic racetrack resonators with a trench structure


蛍光による生葉に含まれるビタミンB2の非破壊検出

蛍光による生葉に含まれるビタミンB2の非破壊検出


Analysis of optical frequency signal transmission through whispering gallery mode


Optical system for monitoring the internal image of foods and the human body


Design of Plasmonic Racetrack Resonators with a Trench Structure

The authors present a plasmonic racetrack resonator with a trench structure. The depth of the structure and the length of the racetrack straightaways both significantly influence the characteristics of the plasmonic racetrack resonator. The optimum depth of the structure and length of the straightaways have been numerically evaluated by the finite-difference time-domain method. The quality factor of the plasmonic racetrack resonator is 38. As compared to the output intensity of a plasmonic ring resonator with a trench structure, the output intensity of the proposed plasmonic racetrack resonator is greater by one order of magnitude.


Numerical optimization for the plasmonic Raman sensor including periodic hole arrays and tapering directions


Optical frequency signal detection through surface plasmon polaritons


Compact slot-in-type optical correlator for retrieving shape, colour, and texture


Numerical optimization of periodic hole arrays for plasmonic Raman sensor

Progress in Biomedical Optics and Imaging - Proceedings of SPIE


The optical characteristics of planar bilayered metallic prisms

Applied Physics. A, Materials Science & Processing


A Structure for Coupling Whispering Gallery Mode with Surface Plasmons

Journal of Nonlinear Optical Physics & Materials


表面プラズモンを用いた金属中の自由電子励起による光検出

表面プラズモンを用いた金属中の自由電子励起による光検出

電子情報通信学会技術研究報告(機構デバイス)

電子情報通信学会技術研究報告(機構デバイス)


Fabrication of Organic Spin-on-Glass Microring Resonator with a Narrow Gap between a Microring Resonator and a Waveguide Using Nanoimprint Lithography

A microring resonator with a narrow gap between a waveguide and a microring resonator has been fabricated by using nanoimprint lithography. An organic spin-on-glass has been used as the material for the microring resonator. The outer diameter of the microring resonator is 20 m and the coupling gap between the straight waveguide and the microring resonator is 40 nm. The filtering characteristics of the microring resonator have been evaluated using a metal halide lamp. The free spectral range is 3.9 nm and the $Q$-factor is 310. The structure of the microring resonator with a narrow gap can be used as a fundamental component of optical devices.

Japanese Journal of Applied Physics, Part 1 (Regular Papers & Short Notes)


周期ナノフォーカシングアレイの作製と最適構造に関する検討

周期ナノフォーカシングアレイの作製と最適構造に関する検討

電子情報通信学会技術研究報告(レーザー・量子エレクトロニクス)

電子情報通信学会技術研究報告(レーザー・量子エレクトロニクス)


Light detection enhanced by surface Plasmon resonance in metal film


Detailed observation of optical intensity and frequency signal transmission in random metal-dielectric film


The Plasmonic Raman Sensor Using Periodic Nanofocusing Arrays


PLASMONIC RACETRACK RESONATOR FOR APPLICATION TO PHOTONIC INTEGRATED CIRCUITS AT SUB-WAVELENGTH


Nonlinear trimer resonators for compact ultra-fast switching

We propose and numerically verify a scheme for compact optical modulation which can enable complex directional switching of signals in integrated micro-optical circuits within hundreds of femtoseconds. The scheme is based on a trimer comprised of two identical silica whispering gallery mode (WGM) microresonators spaced by a central non-linear WGM resonator. The non-linear resonator is in the form of a silica cylinder with a thin coating of an ultrafast Kerr nonlinear material (a J-aggregate of cyanine dye). Using a two-dimensional finite-difference time-domain method and realistic material and structural parameters, we investigated the near-field coupling from a waveguide to the trimer and the subsequent switching process. In our scheme the sandwiched central control resonator has a resonant frequency that is mismatched to that of the input and output resonators. Therefore the optical energy is coupled from the waveguide into only the primary resonator in linear operation. However, for control light intensities of more than approximately 10(-2) W/microm the effective index and hence eigenfrequency of the central resonator can be shifted to match that of its neighbors and hence the optical energy can be redirected.


Linear and Nonlinear Optical Phenomena of Metallic Nanoparticles

IEEE Journal of Selected Topics in Quantum Electronics


Characteristics of light intensity enhancement of a silver nanoprism with rounded corners


Electric field enhancement effect of nano gap of silver prism


Fabrication and Optical Evaluation of Silica Microsphere Coated with J-Aggregates

We have fabricated a micrometer-sized nonlinear optical resonator consisting of a silica microsphere coated with J-aggregates of 1,1'-diethyl-2,2'-cyanine iodide in a thin silica film by a sol-gel process. The sphere diameter was 4.5 µm and the film thickness was estimated to be approximately 100 nm by scanning electron microscopy. The coating on the sphere was characterized by the fluorescence of the J-aggregates and the detection of whispering gallery modes (WGM) in the fluorescence spectrum. The optical evaluation of the sphere was performed in the attenuated-total-reflection configuration. We confirmed that the resonances in the scattering spectrum were due to WGMs, on the basis of a comparison of the experimentally obtained peak positions for coated and noncoated spheres, to those obtained using Mie's theory. The positions of the scattering peaks and the values of the full-width at half-maximum in the scattering spectrum for the coated sphere differ from those of the noncoated sphere.


Self-modulation of scattering intensity from a silica sphere coated with a sol-gel film doped with J-aggregates


Two-dimensionally localized modes of a nanoscale gap plasmon waveguide

We report numerical analysis and experimental observation of two dimensionally localized plasmonic modes guided by a nanogap in a thin metal film. Dispersion, dissipation, and field structure of these modes are analyzed using the finite-difference time-domain algorithm. The experimental observation is conducted by the end-fire excitation of the proposed gap plasmon waveguides and detection of the generated modes using their edge scattering and charge coupled device camera imaging. Physical interpretation of the obtained results is presented and origins of the described modes are discussed.