Estimation of the Number of Quantum Dots Immobilized on an Ultra-flat Au Surface.

Quantum dots (QDs) were immobilized on an ultra-flat Au surface by using amide binding between the carboxyl groups on the QDs and the amino groups of the self-assembled monolayer on the surface. The number density of the QDs estimated by atomic force microscopy (AFM) agreed with the quantity of QDs estimated by X-ray photoelectron spectroscopy and fluorescence microscopy. QDs were also immobilized on dot patterns fabricated by e-beam lithography.

Photon Counting System for High-Sensitivity Detection of Bioluminescence at Optical Fiber End.

The technique of photon counting is widely used for various fields and also applicable to a high-sensitivity detection of luminescence. Thanks to recent development of single photon detectors with avalanche photodiodes (APDs), the photon counting system with an optical fiber has become powerful for a detection of bioluminescence at an optical fiber end, because it allows us to fully use the merits of compactness, simple operation, highly quantum efficiency of the APD detectors. This optical fiber-based system also has a possibility of improving the sensitivity to a local detection of Adenosine triphosphate (ATP) by high-sensitivity detection of the bioluminescence.

Radiation pattern of plasmonic nano-antennas in a homogeneous medium.

Radiation patterns from plasmonic nano-antennas formed on a glass substrate were investigated using index-matching oils. It was confirmed that the pattern from single nano-antennas for various cases of index-mismatching between the substrate and the oil is explained well by the patterns of infinitesimal electric dipoles. We found that for an angular resolution of 2°, the index mismatch must be smaller than 0.

THz wave propagation in two-dimensional metallic photonic crystal with mechanically tunable photonic-bands.

Transmission and dispersion relation of THz waves in two-dimensional photonic crystal (PC) composed of metal rods are studied by using finite-difference time-domain simulation and THz time-domain spectroscopy measurement. The PC is embedded in a parallel metal plate waveguide with an air gap between the PC and one of the plates. The photonic-band-gap well-defined at small air gap narrows systematically with opening the air gap and disappears when the air gap is 2 ~ 3 times the rod height, where the two-dimensional nature of PC is destroyed.

Mechanical active control of surface plasmon properties.

We present a multilayer device which allows the control of Surface Plasmon (SP) propagation properties (propagation length and extension). A simple modification on an inner air gap thickness strongly affects SP propagation mode due to coupling with Parallel-Plate (PP) mode.