This paper describes the recent trend of the surface-plasmon technology for photo-detectors. Surface plasmons create strong near-field on a metal surface thereby reducing the size of the photodetectors. One of the merits for such small detectors is their extremely small electric capacitance. A possible effect of the small capacitance is to bring about the high efficiency of the photo detector circuit at very high frequency. Small photodiodes for on-chip optical interconnection and data communication are reviewed as an example of such applications. A near-field probe for sub-wavelength THz imaging is also discussed.
A plasmonic metamaterial is an artificially designed quasi material that consists of nanometer-scale metal structures. By engineering such a material, we can create unprecedented optical materials whose permeability is changed from unity. In this review paper, recent topics on metamaterials, such as optical metamaterials, plasmonic electromagnetically induced transparency, refractive index control for the realization of high index materials, and novel laser fabrication techniques for three-dimensional metamaterials are introduced.
The state of the art of plasmonic lasers is described. The mechanism of the plasmonic band gap laser, which is our proposed plasmonic laser, is explained. The losses associated with the propagation of surface plasmons and ways to reduce them are also described.
A plasmonic waveguide is a metal optical waveguide that utilizes surface plasmon polaritons propagating at a metal-dielectric interface. The optical beam radius can be reduced to the nanometer order beyond the diffraction limit of light by utilizing a negative dielectric instead of a dielectric. We describe recent progress of our study about metal nano slab waveguides and future perspectives.
Recent developments in Surface Enhanced Raman scattering (SERS) towards single-molecule sensitivity and nanometer spatial resolution are reviewed. Particular focus is placed on detailed mechanism and fabrication methods of metal nanostructures to achieve single-molecule sensitivity. Also a gap mode plasmon relevant to transition metal with relatively large damping, and bio-medical application of SERS are reported.
This article describes recent progress of surface plasmon related techniques for bio-application. The first part is concerning propagating surface plasmon resonance (SPR), where we discuss the complication of nano to micron scale inhomogeneous materials for characterization by the interfacial waves. The second part is concerning crystalline sheets composed of metallic nanoparticles (‘plasmonic nanosheet’). This nano-thickness sheet exhibits a unique optical property originating from the two dimensionally coupled localized SPR. The concept to use the plasmonic nanosheet for new biosensing devices is introduced.
We have demonstrated thermal emission of linearly polarized and narrow-band mid-infrared waves from sub-wavelength gratings of narrow and deep rectangular cavities engraved on a Au surface. 100-nm-wide and 1000-nm-deep, high-aspect-ratio trenches were accurately manufactured by inversion from master molds. Quarter-wave resonance of surface plasmons in the cavities exhibits a Lorentzian emission peak centered at 2.5—5.5 μm. The maximum emittance reaches 0.90, and the peak width Δλ/λ is as narrow as 0.13—0.23. Furthermore, we have demonstrated that orthogonally polarized two-color infrared waves can be emitted from a single Au surface by integrating orthogonal gratings with different dimensions. The integrated emitters were applied to non-dispersive infrared analysis for determining the concentration of a specific chemical compound in liquids.
Femtosecond laser excited two-photon photoemission electron microscopy facilitates the studies on optical properties and dynamics of surface plasmon polariton (SPP) wave packets beyond the diffraction limit. In this article we review our recent work on imaging of SPP wave packets excited by an obliquely incident 10 fs laser pulse at a single slit fabricated in a thin silver film. We image the forward propagating polarization beat that is formed by the interference of the excitation laser light and the SPP wave packet fields. By systematically varying the slit width from sub- to multiple-wavelength scale, we observe modulated increase of the beat intensity, which is phenomenologically accounted for by the enhanced light-SPP coupling efficiency. By using a time-resolved pump-probe technique, we also show the temporal evolution of SPP wave packet that is imaged as the delay-time dependent displacements in space of the beat pattern.
A new matching method using Akaike's Information Criterion (AIC) is proposed to make one wide observation area of a specimen in high resolution from multiple images of Transmission Electron Microscope (TEM), where the TEM images are assumed to be due to Poisson distribution. This method is applicable to TEM images having large noises and then to specimens composed of light elements, which worsen the signal-to-noise (S/N) ratio. We applied this method to real TEM images of a glutamine synthetase as a demonstration and obtained satisfactory results quickly. A statistical method to evaluate optimum binning widths using AIC is also proposed to obtain better images. This method was applied to the real TEM images of silicon single crystal and found to prevent from highlighting the contrast of noises and from negatively affecting the results of image processing, implying that this new statistical method using AIC is a suitable approach for analyses of TEM images.