Reseach 2007-2010

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Improvement of the spatial resolution in three dimensions beyond the diffraction limit of light by saturated excitation in confocal fluorescence microscopy

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Individual viruses and other nano-entities could be imaged in colour in the far field

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Screen-printed field electron emitter using purification-free and length-controlled CNTs

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Optical polarizer made of single-wall CNTs

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Localized Surface Plasmon Resonance Nanochip- Multiple Label-Free Detection of Antigen-Antibody Reaction

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Fluorescence imaging of biomolecules in living cells by time-resolved long-lived luminescence microscopy

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Nanosized polymer wires fabricated by two-photon fabrication

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Sensitive Detection of Carbon Monoxide Using Platinum-Decorated Single-Walled Carbon Nanotubes

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Highly luminescent ZnS-AgInS2 solid solution nanoparticles

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gold - silver alloy nanoparticles exhibiting composition-sensitive surface plasmon resonance

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Laser action of high-Q cavity fabricated in Cholesteric liquid crystals (pseudo-photonic bandgap materials)

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Nanofocusing of 2D optical beam: a gateway to nano-optical IC

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Simple structure luminogenic lanthanide probes that detect protease activities

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Generation of polarization entangled twin-photon beams using a Type-II QPM waveguide NLO device
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High spatial selectivity and resolution of SERS imaging for observation of biomolecules involved in cellular events in situ with gold nanoparticles
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Snapshots of energy density of the field: (the left) T-branch without a mesa, (the right) T-branch with a mesa

Transmissivity through a T-branch of metal gap optical waveguide can be improved (more than four times) by introducing thin metal barrier into dielectric gap
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SEM images of silver nanocubes that were synthesized (a) with 8 mL/min oxygen flow and (b) without oxygen flow.

The shape of silver nanocrystals is conveniently controlled by injection of oxygen gas during the polyol reduction of silver ions and SERS activities of the synthesized nanocrystals are examined.
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MFM images and schematic illustrations of micro-fabricated test devices; one of the “NAND” operations

Magnetic logic devices composed of 4 elliptical permalloy dots perform both the NAND and NOR logic operations.
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(a) FDTD Model representing the Ag-coated oxidized Si probe that consists of Si, SiO2, and Ag layers. (b) Calculated near-field spectra of the Ag-coated oxidized Si probes with different SiO2 thicknesses.

(top) TEM images of the Si probes for after 30 s oxidization, (bottom)SEM images of Ag-coated oxidized probe

We present a novel technique to tune the plasmon resonance of metal-coated silicon tips in the whole visible region without altering the tips original sharpness. The technique involves modification of the refractive index of silicon probe by thermal oxidization. Lowering the refractive index of silicon tip coated with metal shift the plasmon resonance of the metallic layer to shorter wavelength. Numerical simulation using FDTD agrees well with the empirical results. This novel technique is very useful in tip-enhanced Raman spectroscopy studies of various materials because plasmon resonance can tuned to a specific Raman excitation wavelength.

Controlling the plasmon resonance wavelength in metal-coated probe using refractive index modification
Atsushi Taguchi, Norihiko Hayazawa, Yuika Saito, Hidekazu Ishitobi, Alvarado Tarun, and Satoshi Kawata

Optics Express, Vol. 17, Issue 8, pp. 6509-6518 (2009)



Scattering spectra of (a) Ag-coated oxidized Si probe and (b) Ag-coated non-oxidized Si probe. Inset shows a spectrum of the halogen lamp used for the illumination.





It is demonstrated that a pressure-assisted tip-enhanced Raman technique could image an isolated single-walled carbon nanotube and a two-dimensional adenine nanocrystal at a spatial resolution of 4 nm.

Pressure-assisted tip-enhanced Raman imaging at a resolution of a few nanometres
Taka-aki Yano, Prabhat Verma, Yuika Saito, Taro Ichimura and 
Satoshi Kawata

NATURE PHOTONICS | VOL 3 | AUGUST 2009 |


The sinusoidal oscillation of the tip and the synchronized opening of the time gate for laser illumination are illustrated.

(a) Raman spectra of an isolated SWNT at four different indicated tip-sample distances. (b) A plot of integrated Raman intensity of the G-band versus the tip-sample distance d. The solid curve represents a profile obtained from FDTD simulation.

For 1D scan of an isolated SWNT along a direction perpendicular to its axis, the TERS intensity increases when the tip is exactly above the SWNT, depicting a spatial resolution of 3 nm.

We realized near-field Raman microscopy with an accuracy of better than a few angstroms. The tip-sample distance is precisely controlled by our newly developed time-gated illumination technique. We have profiled the spatial decay of evanescent light on an isolated carbon nanotube. We also investigated extremely short-ranged chemical and mechanical interactions between the metal on the tip apex and the molecules of an adenine sample, which are observable only within the subnanometric vicinity of the tip. Present result shows strong promise for super high resolution in optical microscopy based on this technique.

Subnanometric near-field Raman investigation in the vicinity of a metallic nanostructure
Ichimura T, Fujii S, Verma P, Yano T, Inouye Y, Kawata S

Physical Review Letters, 102, 186101 (2009)



Raman and TERS measurements showed evidences of  simultaneous occurrence of polymerization and depolymerization of C60 encapsulated inside single-walled carbon nanotube (en-C60)
during the laser irradiation: the unique movement of C60
molecules inside SWNT generates frictional heat, which results in the scission of polymeric bonds between neighboring C60 molecules, resulting in a dynamic coexistence of polymers 
and monomers, never completely polymerized like the 
nonencapsulated bulk-C60 molecules.

Temporally dynamic photopolymerization of C60 molecules encapsulated in single-walled carbon nanotubes
Yuika Saito, Mitsuhiro Honda, Yoshikiyo Moriguchi and 
Prabhat Verma

PHYSICAL REVIEW B 81, 245416 (2010)


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