Seiji Toyoda

Bio: Seiji Toyoda is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Optical coherence tomography & Optical switch. The author has an hindex of 19, co-authored 122 publications receiving 1110 citations.

Room-temperature near-ultraviolet electroluminescence from a linear silicon chain

Abstract: Single-layer light emitting diodes (LEDs) were fabricated using poly[bis(p-butylphenyl)silane] as the emissive layer. An efficient and stable electroluminescence with a maximum at 407 nm was observed at room temperature under a forward electric field greater than 6×105 V/cm. The coincidence of electroluminescence with photoluminescence suggests the origin of the electroluminescence in an excited silicon chain segment. The high external quantum efficiency (0.1% photons/electron), narrow emission (full width at half maximum=15 nm), improved operating stability, and good solubility in organic solvents provide the possibility of using polysilanes for ultraviolet LEDs.

New Beam Scanning Model for High-Speed Operation Using KTa1-xNbxO3 Crystals

Abstract: We propose a new beam scanning model that is applicable to electrooptic materials with electron traps. With this model, we can achieve both high-speed operation and wide-angle scanning, because the operating speed is limited not by the electron mobility but by the frequency limit of the electrooptic effect of the materials. The voltage dependence of the scanning angle at 100 kHz using a KTa1-xNbxO3 crystal is consistent with the property predicted by the proposed model.

Thermo-optic devices

Abstract: In a digital thermo-optic switch and an optical ADM filter of the present invention, functional components such as a splitter and a grating structure part formed in the course of an optical circuit as a component are composed of silicone materials which are superior in heat resistance, reduced loss, and low birefringence, thereby achieving sufficiently practical thermal stability, low loss at 1.55 to 1.58 μm band, wavelength selectivity, and cost reduction.

Low-Driving-Voltage Electro-Optic Modulator With Novel KTa1-xNbxO3 Crystal Waveguides

Abstract: We have successfully demonstrated a low-driving-voltage electro-optic (EO) modulator using newly developed KTa1-xNbxO3 (KTN) buried waveguides We prepared high-quality and large KTN crystals The crystals exhibited a large quadratic EO coefficient of 48×10-15 m2/V2 at 155 µm The KTN crystals also exhibited a very large linear EO effect, for example 600 pm/V at a biased potential of 60 V/mm, which is twenty times larger than the r33 of LiNbO3 The waveguide layers for the core and cladding were formed by liquid phase epitaxy techniques on the KTN crystals The propagation loss was less than 05 dB/cm and the polarization dependent loss was less than 01 dB/cm The EO modulators had a low Vπ of <25 V (40-V biased potential, l=6 mm) and a fast response of 3 GHz

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

Abstract: Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

Measurement of intraocular distances by backscattering spectral interferometry

Abstract: The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

Chiral Architectures from Macromolecular Building Blocks

Abstract: The chiral architectures from macromolecular building blocks were discussed. The conformational dynamics of the helicity and their effect on the (photo)physical properties of the polymers and the induction of helicity in the polymer chain were elaborated. The influence of kinetics on the macromolecular secondary structure and the use of multiple interactions in the hierarchical organization of macromolecules to well-defined supramolecular assemblied were also examined.