Search

We design a temporary optical coupler to obtain high injection and extraction efficiencies while keeping the bending loss low with the aim of realizing optical cable re-routing without service interruption. The temporary optical coupler injects/extracts signal lights into/from a fiber by using fiber bending. The extraction efficiency is improved by using a double-clad fiber or a graded-index fiber for light injection and extraction while the injection efficiency is maintained compared with that of a conventional temporary optical coupler that uses a single-mode fiber. This improvement enables us to realize an optical cable re-routing operation support system that requires no service interruption.

We design a temporary optical coupler that extracts 1.25-Gbps optical signals for traffic monitoring. The temporary optical coupler employs a fiber bending technique that uses a receiving fiber to receive leaked signal light from a bent fiber. We optimize the bending condition and the receiving fiber to obtain a high extraction efficiency while keeping the bending loss below 2 dB. We also measure the bit error rates for the 1.25-Gbps signals and reveal that our temporary optical coupler extracts the 1.25-Gbps optical signals without any deterioration in signal quality. Finally, we confirm experimentally that we achieved traffic monitoring using a traffic monitoring system and our temporary optical coupler in a fiber-to-the-home access network system based on a gigabit Ethernet passive optical network.

We propose a switching equipment that employs a bent fiber and its application for changing optical cables in an access network. This equipment reduces the length of the interruption in the transmission between an optical line terminal and an optical network unit during construction work. We designed the equipment with communication light injection and detection technology.

We propose a novel test light injection tool for fiber identification below an optical splitter in a passive optical network. This tool makes it easy to input a test light into a bent fiber with a lateral light injection technique. We designed a high precision alignment technique to improve the test light injection efficiency and confirmed that the proposed tool can be used for fiber identification below an optical splitter.

We achieve a temporary optical coupler that injects/extracts light into/from a fiber with high efficiency by using fiber bending. We demonstrate experimentally that extraction efficiency is improved by using a double-clad fiber.

Background: Patients with orthostatic hypotension have pathologic hemodynamics related to changes in body posture. A new cephalic laser blood flowmeter that can be worn on the tragus to investigate the hemodynamics upon rising from a sitting or squatting posture was developed. Methods and Results: The relationship between cephalic hemodynamics and cerebral ischemic symptoms in 63 subjects in a sitting, squatting, and standing positions using the new device was evaluated. Transient decrease in blood pressure within 15 s after rising to an erect position possibly causes dizziness, syncope, and fall. Subjects exhibiting dizziness upon standing showed a significant decrease in the cephalic blood flow (CBF) and indirect beat-to-beat systolic blood pressure, as monitored by the Finometer, and a significant correlation was observed between the drop ratio (drop value on rising/mean value in the squatting position) of CBF and that of systolic blood pressure. Conclusions: This new wearable CBF-meter is potentially useful for estimating cephalic hemodynamics and objectively diagnosing cerebral ischemic symptoms of subjects in a standing posture. (Circ J 2009; 73: 1950-1955)

A vacuum ultra-violet beamline for in situ angle-resolved photoemission spectroscopy of MBE-grown high-Tc superconductors at low temperature has been constructed at beamline ABL-6B of the normal-conducting ring in the synchrotron radiation facility of the NTT Atsugi R&D Center. The constant-deviation-angle varied-line-spacing plane grating monochromator covers the energy range of 20–200 eV by using two gratings. A photon flux of the order of 1011s−1 with a resolving power of 2000 or more was achieved in the whole energy range. The endstation is equipped with an angle-resolved photoelectron spectrometer, an rf-stimulated He discharge lamp, a custom-designed sample manipulator for low-temperature measurements and a loadlock system for in situ measurements. Total energy resolution of about 13 meV has been obtained for the photoemission spectrum of the Au Fermi edge, in spite of the bending-magnet light source of a second-generation synchrotron radiation ring.

This paper describes a Fourier transform (FT) near-infrared spectrometer that uses an integrated prism scanning interferometer whose optical paths are stabilized by corner cubes. A combination of corner cubes and a retroreflection mirror, which is sometimes used in the conventional interferometer for FT spectrometers, is adopted and adapted to the integrated prism scanning interferometer through a special design. Without any degradation of spectroscopic properties, the optical path in the interferometer is highly stabilized and the moving distance of the stage is halved. These advantages provide a robust and portable FT spectrometer for field use.

This paper describes an integrated prism-scanning interferometer that consists of a sliding triangular prism with two mirror surfaces attached to a fixed triangular prism beamsplitter. This design eliminates the effect of ambient air and simplifies the alignment. It also halves the stage moving distance because the optical path difference is doubled as a result of both mirrors moving while the sliding prism is scanning. The volume of the interferometer is 2 cm3. We tested the basic operation. The resolution of 0.14 nm and the accuracy of 0.012 nm are obtained at the wavelength of 1525 nm. This interferometer is a significant step towards the realization of a field-use spectrometer based on Fourier transform spectroscopy.

A grazing incidence varied line spacing plane grating monochromator (VLS-PGM) has been designed and installed at the Photon Factory bending magnet beamline, BL-1C. The monochromator is designed to cover 20 to 250 eV with a high resolving power as well as a high photon flux and intended for a high-resolution angle-resolved photoemission study of quantum nano-structures. The resolving power of the beamline is observed to be more than 16,000 at around 65 eV and exceeds 10,000 at all the covered energy ranges of the monochromator with photon flux over 10 9 photons/s which shows that this monochromator reaches the expected design goals.

The electronic structures and the work functions of pristine and Cs-intercalated single-walled carbon nanotube bundles were investigated by C 1 s and valence band photoemission spectroscopy. The C 1 s spectrum of the pristine material showed a Doniach–Sunjic type asymmetry, indicating the existence of metallic tubes. The work function of the pristine bundles was found to be 4.8 eV, which is about 0.2 eV larger than that of graphite. A drastic decrease of the work function to about 2.0 eV was observed in the Cs-intercalated sample. The Cs intercalation also caused a nearly two-order increase in the spectral intensity at the Fermi level.

Ga 3d two-hole states were observed from GaAs(111)A-(2×2), (001)-c(4×4), (001)-(2×4), and (110)-(1×1) surfaces using Ga 3p→4s resonant photoemission spectroscopy. The Slater integrals F 2 and F 4 of the Ga 3d orbitals were determined to be 14.4 and 6.0 from the relative energy positions of multiplet terms 1 G, 1 D, and 3 F. Surface components of the two-hole states were observed in the spectra of the (111)A-(2×2), (001)-(2×4) and (110)-(1×1) surfaces involving Ga atoms at the surface. The intensities of the surface components of the two-hole states were found to be considerably smaller than those of the d 9 states. This is ascribed to the reduced absorption probability of the 3p electrons at the surface caused by surface relaxation.

A method for fabricating a microstructure with a high aspect ratio has been developed. It uses a combination of fluorinated polyimide and silicone-based positive photoresist, which reduces the number of process steps and the turn-around time. This fabrication method is applicable to optical micromachines and IC probes.

The Ga 3 d two-hole states were observed from GaAs(001)-c(4×4), -2×4, and (110)-1×1 surfaces using resonant photoemission spectroscopy. Multiplet terms 1 G , 1 D , and 3 F were clearly distinguished at the photon energy around the 3 p absorption threshold. The surface components of the two-hole states were observed in the spectra of the (001)-2×4 and (110)-1×1 surfaces having Ga atoms at the surfaces. The curve-fitting analysis revealed that the intensities of the surface component of the two-hole states were considerably smaller than those of the d 9 states. This is ascribed to the reduced absorption probabilities of the 3 p electrons at the surfaces caused by the surface relaxation.

We have developed a submicron-area high energy resolution photoelectron spectroscopy system equipped with a multilayer-coated Schwarzschild objective for forming a soft x-ray microbeam. We show the photoelectron microspectroscopy results of the cross section of a semiconductor double heterostructure sample, namely an epitaxial film [InP (50 nm thick)/ In0.53Ga0.47As (2.3 μm thick)/InP (100) substrate] grown by metalorganic chemical vapor deposition. The core-level photoelectron spectra were obtained from the cross section of the cleaved sample. The As 3d, Ga 3d, and In 4d peaks were observed in the In0.53Ga0.47As region. In the InP region, the As 3d and Ga 3d peaks were not observed, and only the In 4d peak was. This result corresponds to the structure observed by cross-sectional scanning electron microscopy. Moreover, we observed an irradiation effect that was caused by the microbeam. These results suggest that this photoelectron microspectroscopy system is a powerful tool for studying chemical and electronic states of submicron-area surfaces.

We fabricated a Schwarzschild X-ray objective which has the maximum X-ray transmittance of 9% at the wavelength of 14.1nm and evaluated an X-ray microbeam formed by the objective. We measured the knife-edge response of the microbeam and performed a fitting calculation of the response, using the point-spread function for the objective. It was found that the beam diameter of the microbeam was 45nm. In this paper, details of these experiments and the application of the microbeam will be discussed.

As a step toward a field-use spectrometer based on Fourier-transform spectroscopy, we have developed a prism-scanning interferometer. It consists of a sliding triangular prism with two mirror surfaces attached to a fixed triangular-prism beam splitter. This design eliminates the effect of ambient air and simplifies alignment, which can otherwise be time consuming. It also halves the stage-moving distance, because the optical path difference is doubled, since both mirrors move while the sliding prism is scanning. We have tested the basic operation of the prototype and found that the spectral resolution and the wavelength scale agree well with our simple calculation.

The design and performance of a 24 m high-resolution spherical grating monochromator (H-SGM) for the undulator beamline (BL-16B) at the Photon Factory are described. With three interchangeable gratings of 400, 900 and 2000 lines mm−1, the H-SGM is designed to cover the photon energy range 40–600 eV. With a resolving power of approximately 2000 in the photon energy range 40–530 eV, more than 1011 photons s−1 have been measured. The best resolutions obtained so far, at a substantially lower photon flux, are greater than 10 000 at 250 eV and 8000 at 400 eV

The valence band and $\mathrm{C}1s$ photoemission spectra were measured from the tips and the sidewalls of multiwalled carbon nantoubes grown on Si substrates. The results show an overall spectral shift to the higher-binding-energy side, a larger density of states at the Fermi level, and a lower work function at the tips. These results can be explained by assuming that the Fermi level is slightly shifted upward and located inside the conduction band at the tips. We suggest that the electronic structure at the tips is considerably affected by defects.

Photoemission spectra were measured from the tips and the sidewalls of multi-walled carbon nanotubes grown on Si substrates. The results show that the Fermi level is located slightly inside the conduction band at the tips. We suggest that the Fermi level pinning is due to a large defect density at the tips of the multi-walled carbon nanotubes.

A vacuum ultraviolet beamline with a grazing-incidence constant-deviation-angle monochromator, equipped with a varied-line-spacing plane grating, has been designed for a bending-magnet light source. This type of monochromator has become very popular because of its high resolution, high throughput, simple scanning mechanism and fixed exit slit. To improve the energy resolution for a wide spectral range, Yan & Yagishita [(1995), KEK Report 95-9. KEK, Tsukuba, Ibaraki 305, Japan] proposed eliminating the defocus aberration at two specific energies in the spectral range, and their monochromator successfully achieved higher energy resolution by using an undulator light source. The possibility of applying this method to a bending-magnet beamline was examined and it was found that high performance can be achieved even using a bending-magnet light source with wide emittance. Performance evaluation relating to energy resolution, photon flux and spot size are reported.

we grew compound semiconductor nanocrystals on passivated Si surfaces, which were characterized by photoelectron spectroscopy and RHEED (reflection high energy electron diffraction). The Ga-deposited Si(111) surface with a 1x1 RHEED pattern was significantly converted into GaSb nanocrystals by Sb beam irradiation at 500 degrees C. In order to grow better quality GaSb nanocrystals, Se-terminated Si surfaces were employed, and about 20 nm uniform GaSb nanocrystals were grown, whose crystallinity of good quality was verified by cross-sectional TEM. For InAs nanocrystals, hydrogen-terminated Si surfaces are suitable for growth at as low substrate temperature as 300 degrees C.

Surface modification of EuBa2Cu3O7- y (EBCO) thin films induced by an electron cyclotron resonance (ECR) oxygen ion beam treatment has been studied using X-ray and synchrotron-radiation photoelectron spectroscopy (XPS and SRPES). The in situ characterization has been performed during the course of 50 eV ECR oxygen treatment for 30 min. Time-dependent analysis shows that the contaminant carbon layer on the surface region can be removed at the initial stage of the treatment (2+ after 30 min treatment. It is found that room-temperature treatment using ECR oxygen can alter the contaminated, oxygen-depleted surface to a clean, well-oxygenated surface. The present results suggest that ECR treatment which can modify the surfaces in a well-defined manner would be a feasible technique for surface cleaning of high-temperature superconductors.

Photoelectron spectroscopy was performed on EuBa2Cu3O y thin films before and after immersion into de-ionized pure water to clarify the water immersion effect on copper oxide superconductors during water rinsing in device fabrication. The surface Ba compounds were found to drastically decrease, while a short (5 minutes) water immersion of epitaxial-quality thin films barely affected bulk EuBa2Cu3O y .

The throughput of a Schwarzschild objective using undulator synchrotron radiation was measured. Conventionally, the throughput was estimated from the squared reflectivity of one multilayer mirror and from the obstruction ratio. However, we evaluated the transmission ratio from the input and output photon flux using a precisely calibrated monochromatic beam from an undulator light source. It was found that the objective has a maximum throughput of 8.5% at a wavelength of 13.9 nm.

A submicrometre-area photoelectron spectroscopy system that uses a multi-layer-coated Schwarzschild objective as the soft X-ray microbeam optics has been developed. The system is located at an undulator beamline (BL-16U) at the Photon Factory in the High Energy Accelerator Research Organization. By knife-edge measurement, the microbeam size was estimated to be 160 nm at the sample position using a 25–75% criterion. Photoelectron spectral measurements revealed that the Fermi edge width was 0.12 eV, which means that the instrumental resolution was 0.05 eV, after removing the natural broadening of the Fermi edge at room temperature. This system offers both high energy resolution and high spatial resolution.