Tomohiko Kanie

Fiber-optic coupler based refractive index sensor and its application to biosensing

A simple and highly sensitive biosensor based on a fiber-optic coupler is developed. The change of refractive index due to biomolecular interaction on the surface of the coupler can be detected as the change of the transmission power. The sensitivity of the sensor is evaluated to be a noise level equivalent to a refractive index variation of 4×10−6. The binding of streptavidin is detected to be concentration dependent over a range of 0.5–2μg∕ml, by immobilizing biotin on the coupler surface via aminosilan treatment. This sensor allows the construction of a low-cost, portable, and label-free biosensing system.

Novel multichannel tunable chromatic dispersion compensator based on MEMS and diffraction grating

Using microelectromechanical systems and diffraction grating technologies, a novel tunable chromatic dispersion compensator for multichannel wavelength-division-multiplexing signals was developed. Independent channel-by-channel dispersion tuning with flat top loss spectra was experimentally confirmed.

Reduction mechanism of surface oxide in aluminum alloy powders containing magnesium studied by x-ray photoelectron spectroscopy using synchrotron radiation

We investigated the reduction mechanism of surface oxide on aluminum alloy powders containing magnesium, by x-ray photoelectron spectroscopy using synchrotron radiation (SR-XPS). The reduction is the initial reaction in a new aluminum nitridation method developed by one of the authors. In heating the powders to 823 K, magnesium soluted in the powders moves from the inner region to the surface at temperatures below 573 K, and finally, above 773 K, the magnesium reduces the aluminum oxide of powder surfaces by chemical reaction, which breaks the surface oxide films, and metallic aluminum appears on the topmost surface of the powders. These results suggest that the SR-XPS system is very useful for dynamic chemical reaction analysis of the surface via in situ measurement.

High-throughput assay of nitric oxide metabolites in human plasma without deproteinization by lab-on-a-chip electrophoresis using a zwitterionic additive

In order to develop a high-throughput assay for nitric oxide metabolites, nitrite (NO2-) and nitrate (NO3-), in biological fluids, we have investigated the simultaneous determination of them using an electrophoretic lab-on-a-chip (microchip capillary electrophoresis, MCE) technique. In this study, in order to establish an MCE assay process without deproteinization, the addition of a zwitterionic additive into the running buffer to reduce the adsorption of protein onto the surface of channel was investigated. Initially, some zwitterionic additives were investigated by making a comparison of relative standard deviations (RSDs) of the migration times for NO2(-) and NO3(-) on capillary electrophoresis. From the results of our comparison of the RSD values, 2% (w/w) N-cyclohexyl-2-aminoethanesulfonic acid (CHES) was selected. As a result of the application of the running buffer with CHES to the MCE process, the complete separation of NO2(-) and NO3(-) in human plasma without deproteinization was achieved within 1 min. Since the RSD values of the positions of the peaks were less than 2.3%, beneficial reduction effects on MCE were suggested. When we used an internal standard method in order to correct the injection volume, the RSDs of the peak heights and areas were less than 10%, and the correlation coefficients of spiked calibration curves ranging from 0 to 350 microM were 0.999 and 0.997 for NO2(-) and NO3(-), respectively. The limits of detection (S/N=3) were 53 microM for NO2(-) and 41 microM for NO3(-). Moreover, the correlation coefficients in excess of 0.99 between the MCE method and a conventional Griess method were achieved for both NO2(-) and NO3(-). Consequently, the possibility of establishing a high-throughput assay process was obtained by utilizing 2% (w/w) CHES to reduce protein adsorption.

A highly dense MEMS optical switch array integrated with planar lightwave circuit

We propose a novel MEMS 2/spl times/2 optical switch array integrated with a Planar Lightwave Circuit (PLC) for application to Optical Add Drop Multiplexing (OADM) in Wavelength Division Multiplexed (WDM) transmission systems. This switch array consists of two chips connected together by flip chip bonding. One is the MEMS device which has 16 channel latched silicon actuators with micro-mirrors, and the other is a PLC which has a 16 channel 2 /spl times/ 2 cross type waveguide array. In order to achieve highly dense integration, the MEMS actuator has a long beam cantilever arranged with a 500 /spl mu/m period.

Novel multichannel tunable chromatic dispersion compensator based on MEMS & diffraction grating

Using MEMS and diffraction grating technologies, a novel tunable chromatic dispersion compensator for multichannel WDM signals was developed. Independent channel-by-channel dispersion tuning with flat top loss spectra was experimentally confirmed.

Fiber-Optic Coupler Biosensor

A simple and highly-sensitive biosensor based on a fiber-optic coupler is developed. The change of refractive index in the evanescent field on the fused region of a fiber-optic coupler shifts the transmission spectrum and thus changes the power splitting ratio at a fixed wavelength. Therefore, the biomolecular interaction on the surface of a coupler can be detected as the change of transmission power. The sensitivity of the coupler sensor is evaluated to be a noise level equivalent to a refractive index variation of 4x10-6. The binding of streptavidin is detected to be concentration dependent over a range of 0.5 to 2 mug/ml, by immobilizing biotin on the coupler surface via aminosilan treatment. This coupler sensor based on the standard fiber-optic component allows the construction of a low-cost, portable, and label-free biosensing system, which is suitable for use in field applications such as point of care (POC) diagnosis, environmental monitoring, and food safety testing.

Ultra-compact multichannel optical components based on PLC technologies

We propose multichannel based on PLC and MEMS technologies. 12 channel optical switch arrays and VOA arrays have been successfully developed by integrating 2/spl times/2 cross type and MEMS micro-mirrors connected together by flip chip bonding.

X-ray-written optical waveguides in germanosilicate glasses

We irradiated 3% GeO/sub 2/-97% SiO/sub 2/ glasses with 1-5 keV X-rays from a synchrotron radiation source. The samples were prepared by vapor-phase axial deposition and polished to a 0.2-mm thickness. We show the induced UV-VUV absorption in the sample after irradiation. The spectrum was obtained by subtracting the spectrum of the sample before irradiation from that after irradiation.