bluuebunny/crossref_metadata_2025 huggingface dataset:
Compatible Objective Lens for Blu-ray Disc and Degital Versatile Disc Using Diffractive Optical Element and Phase-Step Element which Corrects both Chromatic and Spherical Aberrations
Authors: Komma Yoshiaki , Tanaka Yasuhiro , Mizuno Sadao
Published: February 2005

A compatible lens with a diffractive optical element that overcomes differences in disk thickness and longitudinal chromatic aberration and phase steps that eliminate chromatic spherical aberrations are proposed. Both blue and red parallel incident rays can be converged on both disks; therefore, the servo and readout signals can be detected by a single common photodetector. A compatible optical head, which can write Blu-ray Discs (BDs) and degital versatile discs (DVDs) with only one objective lens assembly and one photodetector, can be achieved. We show the convergence of the blue and red parallel incident rays and signal readout using the compatible objective lens.
Mechanical Filter on Actuator for System Stability of 9.5 mm Drive
Authors: Song Byung Youn , Lee Dong Ju , Kang Hyung Joo , Cho Won Ik , Ryoo Byung Ryul , Seong Pyong Yong , Lee Kyung Ho , Park No Cheol , Park Young Pil
Published: February 2005

We propose a redesign method for modal parameters to depress the second resonance peak of an ultraslim optical pickup actuator. With the addition of the countermode near the second resonance frequency, we can achieve the gain margin, which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.
Microminiaturized Aspherical Single Lens with Numerical Aperture of 0.9 for Blue Laser Diode
Authors: Miura Takahiro , Yamada Masahiro , Aoki Sunao , Kanazawa Takakiyo , Urakawa Yoshiyuki , Watanabe Hidetoshi , Watanabe Tetsu
Published: February 2005

A single lens with an effective diameter of 0.3 mm and a high numerical aperture (NA) of 0.9 for a blue laser diode has been developed. The current wavefront aberration of the lens is approximately equal to that of a conventional high-NA lens. The optical flying head with a mold process lens (MPL) can be respectively designed so that the disk-tilt margin may become wide for each cover layer thickness of the disk (compact disk, digital versatile disk, etc.).
Polarization-Free Blu-ray Disc/Digital Versatile Disc Compatible Optical Pick-up
Authors: Saito Ryo , Ito Fumihiko , Yokochi Yoshinari , Saito Toshiya , Ohira Takuji , Sato Hidetoshi , Itonaga Makoto
Published: February 2005

We have developed Blu-ray disc (BD)/digital versatile disc (DVD) compatible technology employing a polarization-free wavefront correction element. The polarization-free wavefront correction elements have high diffraction efficiencies for both BD and DVD. Also, this element has a large decentering tolerance for the objective lens. The effectiveness of this element was confirmed by examining wavefront aberrations for DVD and readout signal waveforms for both BD and DVD.
High-Speed Tracking Method Using Zero Phase Error Tracking-Feed-Forward (ZPET-FF) Control for High-Data-Transfer-Rate Optical Disk Drives
Authors: Koide Daiichi , Yanagisawa Hitoshi , Tokumaru Haruki , Nakamura Shoichi , Ohishi Kiyoshi , Inomata Koichi , Miyazaki Toshimasa
Published: February 2005

We describe the effectiveness of feed-forward control using the zero phase error tracking method (ZPET-FF control) of the tracking servo for high-data-transfer-rate optical disk drives, as we are developing an optical disk system to replace the conventional professional videotape recorder for recording high-definition television signals for news gathering or producing broadcast contents. The optical disk system requires a high-data-transfer-rate of more than 200 Mbps and large recording capacity. Therefore, fast and precise track-following control is indispensable. Here, we compare the characteristics of ZPET-FF control with those of conventional feedback control or repetitive control. Experimental results show that ZPET-FF control is more precise than feedback control, and the residual tracking error level is achieved with a tolerance of 10 nm at a linear velocity of 26 m/s in the experimental setup using a blue-violet laser optical head and high-density media. The feasibility of achieving precise ZPET-FF control at 15000 rpm is also presented.
Noise-Predictive Viterbi Detector with Pattern-Dependent Distortion Canceller for High-Density Optical Recording
Authors: Itoh Akira , Hiura Tomoyuki , Ino Hiroyuki , Kobayashi Shoei
Published: February 2005

We propose noise-predictive maximum-likelihood (NPML) detection with a pattern-dependent distortion canceller (PDDC) to cancel nonlinear distortion. NPML detection and NPML/PDDC detection were applied to a Blu-ray disc with a capacity of 27 Gbytes. The detection performance was investigated. And the results are reported. Both the NPML detector and the NPML/PDDC detector lower bit error rate (BER), and improve the radial-tilt margin and spherical-aberration margin. Only the NPML/PDDC detector could improve tangential-tilt margin, however.
Data-to-Wobble Cross Talk Cancellation in Optical Disc Systems
Authors: Yin Bin , Padiy Alexander , Schep Kees
Published: February 2005

In this paper, a signal processing method for removing the data-to-wobble cross talk is presented. First, various causes of the leakage from the data signal to the wobble channel are analyzed. Then a general method for using a finite impulse response (FIR) filter to cancel this leakage is proposed, which is realized electronically and adaptively, and thus is cheap and robust. Instead of a full-fledged filter, a simple structure with only one adaptable gain is suggested, specifically aimed at tackling the cross talk caused by the light path astigmatism, which is considered to be the main cause of the data leakage to the push-pull channel. This simplification results in a very cost-effective solution. Finally, the experimental results show that the cross talk cancellation significantly improves the carrier-to-noise ratio (CNR) of the wobble signal, thereby leading to more reliable wobble detection.
Signal-to-Noise Ratio in a Partial-Response Maximum-Likelihood Detection
Authors: Ohkubo Shuichi , Ogawa Masatsugu , Nakano Masaki , Honma Hiromi , Iwanaga Toshiaki
Published: February 2005

In this paper we describe a derivation of general expression of signal-to-noise ratio (SNR) in a partial-response maximum-likelihood (PRML) detection system. Because of media noise, as well as difference of transfer function between target PR and the actual channel, the noise at the Viterbi detector is no longer white but colored. The conventional expression of SNR is not appropriate for evaluating signal quality for the colored noise. We have shown how to calculate the variance of the colored noise in the PRML system. The derived SNR can be easily calculated using hardware and is very useful for evaluating signal quality under high-density recording conditions where jitter cannot be accurately measured. We have confirmed that the bit error rate (bER) predicted by the SNR correlates well with the actual bER, regardless of bit density.
Three-Dimensional Optical Storage with Photosensitive Fluorescent Material
Authors: Chen Chien-Wen , Li Ming Chia , Liao Wen-Yih , Hu Andrew Teh
Published: February 2005

We propose a three-dimensional optical storage medium in which a confocal laser-scanning microscopy is applied for multilayer fluorescence readout. The contrast of signal intensity for inside and outside of the pit can reach 71%.
Super Resolution Read Only Memory Disc Using Super-Resolution Near-Field Structure Technology
Authors: Yoon Duseop , Kim Jooho , Kim Hyunki , Hwang Inoh , Park Insik , Shin Dongho , Park Yunchang , Tominaga Junji
Published: February 2005

Super resolution near-field structure (super-RENS) technology is one of the promising technologies for a sub-terabyte optical storage of around 200 GB capacity. We confirmed the possibility of super-RENS read only memory (ROM) media with multilayer structure using the combination of the PtO
x
, AgInSbTe, ZnS-SiO2 films. The carrier to noise ratio (CNR) and readout cyclability was measured for the super-RENS ROM disc in both the red laser and the blue laser systems.
Holographic Recording on Azo-benzene Functionalized Polymer Film
Authors: Itoh Masahide , Harada Kenji , Kamemaru Shun-ichi , Yatagai Toyohiko
Published: February 2005

Surface relief holograms are fabricated by irradiation of laser intensity pattern on the azo-benzene functionalized polymer films. The diffraction efficiency and the surface relief depth depend on the writing energy and the polarization of the laser beam. This structure is very stable at temperatures below the glass transition temperature T
g. The relief depth increases approximately ten times with the electric field by corona discharge at the temperature near T
g even if there is no recording laser light. On the other hand, the surface relief disappears keeping the film temperature near T
g, neither recording laser beam nor external electric field. Using this material as a holographic memory, we demonstrate some memory modes, such as write-once, erase, rewritable, overwrite and data holding, under the combination of recording laser beam, external electric field and film temperature.
Write-Once Disk with BiFeO Thin Films for Multilevel Optical Recording
Authors: Sasa Noboru , Hayashi Yoshitaka , Fujii Toshishige , Otaka Kawori , Watada Atsuyuki , Kamezaki Hisamitsu , Komoda Hirotaka
Published: February 2005

We found out that small marks are formed without large deformation and intersymbol interference (ISI) on a BiFeO thin film. Therefore, a BiFeO write-once disk is suitable for multilevel optical recording. We confirmed that our write-once disk realizes a recording capacity of 23 GB using a laser diode with a 405 nm wavelength and a 0.65 numerical aperture objective lens.
High-Density Recording on Air-Stabilized Flexible Optical Disk
Authors: Onagi Nobuaki , Aman Yasutomo , Murata Shozo , Uchida Keisuke
Published: February 2005

We have developed an optical disk system constructed from a flexible disk and an air stabilizer. The key feature of the system is an extremely small axial runout that has been reduced by 5 microns as a result of the aerodynamic effect of the stabilizer. We experimentally demonstrated that the system can achieve an axial runout of less than 5 microns and enables a recording signal at a density of 0.13 µm/bit.
Novel Route for the Preparation of Nanosized NiFe2O4 Powders
Authors: Silva Marlon N. B. , Duque José G. dos S. , Gouveia Daniel X. , Paiva José A. C. de , Macedo Marcelo A.
Published: February 2005

Nanosized NiFe2O4 powders were prepared by a novel sol-gel route. The powders calcined at 1200°C and quenched to liquid nitrogen temperature showed a mixed spinel phase, with a saturation magnetization of 49 emu/g, crystallite size of 67 nm and hyperfine magnetic field B
1 = 520 kOe, B
2 = 484 kOe and A = 488 kOe.
Optical-Pulse-Injection-Induced 40 GHz Photonic Frequency Multiplication in Erbium-Doped Fiber Laser
Authors: Lin Gong-Ru , Lin Gong-Cheng , Wu Jung-Rung
Published: February 2005

The generation of a 40 GHz regeneratively amplified and frequency-multiplied optical pulse train from an erbium-doped fiber ring laser is demonstrated. This is achieved by seeding a 1 GHz gain-switched Fabry–Perot laser diode and detuning its repetition frequency to coincide with the harmonic resonant cavity mode. The peak power of frequency-multiplied erbium-doped fiber lasers (EDFL) pulses increases from 80 mW to 230 mW as the modulation level of the Fabry–Perot laser diode (FPLD) increases from 18 dBm to 30 dBm. The pulsewidth and peak power are 10 ps and 5 mW at a repetition rate of 40 GHz. The EDFL longitudinal mode frequency fluctuation is within ±2.5 kHz during 2 h. The frequency-multiplied EDFL pulses exhibit relatively low phase noises of -95 dBc/Hz and -120 dBc/Hz at offset frequencies of 10 kHz and 1 MHz, respectively. The associated timing jitter of the EDFL pulses exponentially increases from 0.6 ps to beyond 5.8 ps as the frequency multiplication order increases from 1 to 40.
Adaptive Pulse Compression of Femtosecond Laser Pulses Using a Low-Loss Pulse Shaper
Authors: Hong Kyung-Han , Nam Chang Hee
Published: February 2005

A simple low-loss pulse shaper, employing a micromachined deformable mirror and a Brewster-cut prism, is demonstrated for the adaptive compression of femtosecond laser pulses. Using this pulse shaper, we compress a positively chirped 84 fs pulse down to 23 fs and compensate for the high-order phase distortion of a sub-10-fs laser pulse. The transmission efficiency of the pulse shaper reaches 93% with dielectric mirrors and 85% with gold-coated mirrors, designed for broad spectrum application.
Observation of X-ray Topographs Using Borrmann Effect in the Bragg Case
Authors: Fukamachi Tomoe , Negishi Riichirou , Zhou Shengming , Yoshizawa Masami , Matsumoto Isao , Kawamura Takaaki
Published: February 2005

By tuning X-ray energy from synchrotron radiation, the plane wave topographs from a Ge crystal in the Bragg case are recorded at an energy for which the real part of the atomic scattering factor is zero and the imaginary part is approximately equal to zero. At the former energy the high reflectivity is obtained due to the Borrmann effect, and at the latter energy it is obtained due to the extinction effect. In diffraction topography, the defect contrasts at these two energies are almost the same. Differences exist in that some deeper defects can be seen at the former energy. This indicates that we can determine the depth of a defect by changing the resonance condition. In transmission topography the images of defects, the contrasts of which are the reverse of those in diffraction topography, are observed at the latter energy, but no such defect images are observed at the former energy.
Effects of MgO-Doping on Electrical Properties and Microstructure of BaTiO3
Authors: Jeong Jaill , Han Young Ho
Published: February 2005

Degradation behaviors of Mg-doped BaTiO3 have been studied in terms of oxygen vacancy concentration and microstructural development. Mg-doped BaTiO3 powders were precisely synthesized by the Pechini method. As MgO content was increased to 1.0 mol%, Curie points moved to lower temperatures and dielectric constants decreased. The specimens doped with MgO showed higher leakage currents under the continuously applied dc field at a high temperature (100°C) during the aging process, compared with the undoped BaTiO3. With low levels of MgO (<1.0 mol%), the microstructure is similar to that of undoped BaTiO3, whereas a significant reduction in grain size was observed with higher levels (>2.0 mol%).
Dielectric and Piezoelectric Properties in the BiScO3–PbTiO3–PbO·SnO2 Ternary System
Authors: Song Tae-Ho , Eitel Richard E. , Shrout Thomas R. , Randall Clive A.
Published: February 2005

The effect of Sn substitution on the dielectric and piezoelectric properties of BiScO3–PbTiO3 was investigated in the ternary system, (1-x){(1-y)BiScO3–yPbO·SnO2}–xPbTiO3 (x=0.43–0.63, y=0.25–0.75). The ferroelectric phase transition temperature near morphotropic phase boundary (MPB) decreased with increasing Sn content from 450°C (x, y=0.64, 0) down to ∼250°C for the composition with x, y=0.46, 0.75. Piezoelectric activity (d
33=460–465 and k
p=0.54) in Sn-substituted MPBs remained at similar levels to the pure 0.46BiScO3–0.64PbTiO3 MPB, with Sn content of up to y=0.5. However, further Sn-additions lead to decreased electromechanical performance and the formation of secondary phases such as SnO2. Broad temperature dependence of the permittivity near the ferroelectric phase transition was assessed by a diffuseness parameter δ, which generally decreased with firing temperature in the range of 1050–1250°C. The temperature of the permittivity maximum (T
max) increased with measuring frequency, a characteristic consistent with relaxor ferroelectric materials.
Microstructure Characterization and Phase Transformation Kinetic Study of Mechanosynthesized Non-Stoichiometric CdFe2O4 by Rietveld's Analysis
Authors: Bid Srinjoy , Pradhan Swapan Kumar
Published: February 2005

Nanocrystalline non-stoichiometric cadmium ferrite (CdFe2O4) has been synthesized by high-energy ball milling the mixture (1:1 mol%) of CdO and α-Fe2O3 at room temperature. Formation of nanocrystalline CdFe2O4 as normal spinel structures has been noticed after ball milling the mixture for different durations. The structural and microstructural evolution of CdFe2O4 caused by milling is investigated by X-ray powder diffraction. The relative phase abundances, particle sizes, r.m.s strains, lattice parameter changes of different phases have been estimated employing Rietveld powder structure refinement analysis of XRD data. Particle size and amount (wt%) of CdO reduce very fast in comparison to α-Fe2O3 and a significant amount of nanocrystalline CdFe2O4 is formed within 5 h ball milling of CdO+α-Fe2O3 powder mixture. It appears that solid state diffusion of nanocrystalline CdO and α-Fe2O3 particles results in formation of nanocrystalline CdFe2O4 spinel. A significant amount of α-Fe2O3 did not take part in ferrite formation within 25 h of milling time and even after post annealing the 5 h milled samples at different temperatures (up to 1273 K) for different durations, ∼13 wt% of α-Fe2O3 remained as an excess phase. It indicates that the ferrite prepared by ball milling is a non-stoichiometric Cd-riched phase. However the ferrite phase content increases considerably when the 5 h milled sample is annealed at different elevated temperatures for different durations.
Experimental Determination of Mechanical Properties of Electroformed Ni–Fe Microstructures
Authors: Cheng Chao-Min , Ho Mon-Shu
Published: February 2005

In this study, the mechanical properties of nanocrystalline Ni–Fe alloy are evaluated at various current densities in the electroforming process. The results indicate that the finer grain size of Ni–Fe alloy leads to the enhancement of its hardness, which is above 9 GPa, and the elastic modulus is approximately 316 GPa obtained by controlling current density. A finer grain size of Ni–Fe alloy can induce the formation of dense Ni–Fe alloy and improve the mechanical properties of Ni–Fe microstructures.
Piezoelectricity and Visible Light Emission in Superlattice Silica Films with Tetravalent Metal Dopants
Authors: Noge Satoru , Shiroishi Makoto , Uno Takehiko
Published: February 2005

Piezoelectricity was produced in superlattice silica films with tetravalent metal dopants by poling. Poling treatment in germanium-doped silica (Ge:SiO2) glass films raises their optical nonlinearity and producers, among other things, the Pockels effect. We generated piezoelectricity in poled Ge:SiO2 glass thin films. Tetravalent-metal-doped SiO2 (M4+:SiO2) films were prepared on Si substrates by RF magnetron sputtering. We used germanium, titanium, and tin as doping materials. The piezoelectricity of the films was compared with that of quartz. The piezoelectricity of the same order of magnitude as that of quartz was observed in the M4+:SiO2 films. However, less than a week later, piezoelectricity disappeared almost completely in all the samples. To prevent piezoelectricity from disappearing, we attempted to pin the doping ions. We developed a pinning technique based on the structure of a Ge:SiO2–Ti:SiO2–Sn:SiO2 superlattice. This superlattice structure was very effective in preventing piezoelectricity from disappearing. Furthermore, broadband visible light emission was observed in the proposed superlattice film.
Scattering Patterns and Energy Distribution of Scattered Electrons under Field Emission Conditions of Scanning Tunneling Microscopy
Authors: Mizuno Seigi , Fukuda Jun , Iwanaga Masayuki , Tochihara Hiroshi
Published: February 2005

A low-energy electron diffraction (LEED) apparatus using field emissions from scanning tunneling microscope (STM) tips has been developed. The apparatus was designed to detect scattered electrons toward the surface normal direction using the tip shield and the extractor. The kinetic energies of the scattered electrons were measured. There were two bright regions. One consisted of inelastically scattered electrons, while the other mainly consisted of elastically scattered electrons. The behavior of the latter region was consistent with our simple calculations. This result supports the possibility that the LEED uses field emissions from STM tips. The specific diffraction patterns of surface structures have not yet been obtained. The features of the apparatus are discussed.
Sheath Model for Dual-Frequency Capacitively Coupled Plasmas
Authors: Denpoh Kazuki , Wakayama Go , Nanbu Kenichi
Published: February 2005

Lieberman's radio-frequency (RF) sheath theory is extended to dual-frequency capacitively coupled plasmas. The extended RF sheath theory describes the nonlinear motion of the sheath, for example, the very high frequency (VHF) component of plasma potential varies during the low frequency (LF) cycle and shrinks at the phase such that the lower electrode potential becomes closer to the plasma potential. The theory also describes the plasma potential having a variety of frequency components due to the interaction between VHF and LF. Then the plasma potential and the sheath thickness described in the extended RF sheath theory are incorporated into the Particle-in-Cell, Monte-Carlo-Collision (PIC-MCC) sheath model. The plasma potential, the sheath thickness, and the energy distribution functions of electrons and ions impinging on the biased electrode obtained using the PIC-MCC sheath model correlate well with the results from the one-dimensional PIC-MCC plasma model.
Ratio of Transverse Diffusion Coefficient to Mobility of Electrons in High-Pressure Xenon
Authors: Kobayashi Shingo , Hasebe Nobuyuki , Igarashi Tsutomu , Miyachi Takashi , Miyajima Mitsuhiro , Okada Hiroyuki , Doke Tadayoshi , Shibamura Eido , Dmitrenko Valery V. , Vlasik Konstantin F.
Published: February 2005

We constructed a parallel plate drift chamber for measuring the ratio of the transverse diffusion coefficient D
t to the mobility µ of electrons multiplied by the elementary charge e, e
D
t/µ, which is called the transverse characteristic energy, in high-pressure xenon gas. The characteristic energies of electrons in Xe were obtained at a high pressure of 1.0 MPa and the reduced electric field, E/N, from 0.77 to 7.7 ×10-18 V·cm2, where E denotes an electric field and N the number density of Xe atoms. At the same E/N, our results agreed well with the data at pressures from 107 to 193 kPa previously obtained by Koizumi et al. [J. Phys. B 19 (1986) 2331]. The characteristic energies of electrons in Xe were found to be constant as a function of E/N from a low pressure to 1.0 MPa.
Optical Deflection Technique for Investigation of Laser-Induced Oscillating Bubble on Metal Surface
Authors: Xu Rong-Qing , Chen Xiao , Shen Zhong-Hua , Lu Jian , Ni Xiao-Wu
Published: February 2005

The oscillation of a laser-generated single cavitation bubble on a metal surface is investigated by a fiber-optic diagnostic technique based on an optical beam deflection (OBD). The sequence of waveforms induced by the bubble pulsation is obtained with respect to detection distance. The maximum and minimum bubble radii for each oscillation cycle are determined from the experimental results. Furthermore, by tracking the arrival time of a bubble wall during its expanding and collapsing stages, the temporal development of a cavitation bubble on the metal surface is obtained.
Cooling of Microspot by Microdroplets
Authors: Chou Fu-Chu , Gong Shih-Chin , Chung Cheng-Ru , Wang Ming-Wen , Chang Chi-Yuan
Published: February 2005

In this work, we explored a novel technique using microdroplets to cool hot microspots in advanced microelectronic devices. A hot floating membrane 150 µm ×150 µm is used both as a hot microspot and a thermal microsensor in the experiment. Microdroplet of pure water is ejected from the inkjet head onto the hot microspot. The evaporation time of a microdroplet decreased with increasing microspot temperature, and the temperature decrease due to microdroplet cooling increased with increasing microspot temperature. The microspot temperature can be maintained constant without flooding with cooling liquid when microdroplets are ejected continuously at an optimal frequency.
A Versatile X-Ray Topographic Camera with Elastic Translation
Authors: Hönnicke Marcelo Goncalves , Mazzaro Irineu , Cusatis Cesar , Etgens Victor Hugo
Published: February 2005

A versatile X-ray topographic Lang camera was developed and tested. A simple and easy-to-build elastic system driven by a stepping motor is used to avoid expensive and sophisticated bearings normally required for highly precise translation. After initial and permanent corrections for repetitive angular deviation (yaw), the angular stability was 10 µrad for a 30 mm translation during a 16 h run. Topographical images taken with this camera show that it is a reliable and thermomechanically stable apparatus.
Surface Response Methodology for Write Strategy Optimisation in Optical Drives
Authors: Langereis Geert
Published: February 2005

A method for optimising write strategies in optical drives is proposed which is rigid and gives additional information on the reliability of the calculated results. In addition, the mathematical tool is used to examine the typical differences in write strategies with respect to parameter variations. As a test platform, digital versatile discs of the recordable type (DVD+R) are used at a speed of 8×. A comparison is made between the “castle” strategy and the blocked “thermally balanced” strategy. The differences are verified on three different discs. It appears that the write strategy determines the interdependence between write strategy parameters, while the disc brands differ in the optimum settings of the parameter. The presented method and experiments once more show the power of mathematical tools for understanding and applying physical processes.
Scattering of Electromagnetic Waves from Linearly Moving Perfect Surface Using Relativistic Boundary Conditions
Authors: Ho Mingtsu
Published: February 2005

The objective of this study is to demonstrate the one-dimensional numerical simulation results of the electromagnetic waves scattered from constantly moving perfect electric conductors using characteristic-based algorithm. In the model, the perfect surfaces are moving at a constant speed, either advancing toward or receding from the incident waves. The computed scattered electric field intensities are illustrated as functions of time. The predicted double-Doppler shifts are found to be in fairly good agreement with the theoretical values.
A Superconducting Quantum Interference Device Detection Coil Design with Enhanced Sensitivity for Deep Brain Activation
Authors: Takenaka Makoto , Tamura Itsuro , Fujimaki Norio , Miyauchi Satoru
Published: February 2005

We propose a new combination coil system to be used in magnetoencephalography (MEG). This system is capable of detecting magnetic signals produced by brain activation located in deep regions (40 mm to 60 mm beneath the head skin) while minimizing brain noises that arise from shallow regions (10 mm to 30 mm beneath the head skin). The system has two coils at each measurement location around the head, a magnetometer coil and a second-order gradiometer coil, which have different dependences of magnetic sensitivity to the distance between the coils and brain activation sources. The magnetic signals detected by one coil multiplied by a weighting coefficient is subtracted from those detected by the other coil so that the magnetic sensitivity for the combination coil is more enhanced for deep sources than for shallow ones. We designed a practical configuration of the combination coil system by optimizing the weight and the base line length of the gradiometer. We improved the signal-to-noise ratio for typical source and noise depths by sixteen times in comparison with a conventional magnetometer coil. By optimizing parameters, we obtained magnetic sensitivity that was 3.6 times higher on average for deep brain signal sources than for shallow brain noise sources.
A Dielectric Biosensor Using the Capacitance Change with AC Frequency Integrated on Glass Substrates
Authors: Hong Jongin , Yoon Dae Sung , Park Myung-Il , Choi Jongwan , Kim Tae Song , Im Geunbae , Kim Sanghyo , Pak Y. Eugene , No Kwangsoo
Published: February 2005

Glass-based microchannel chips were fabricated using photolithographic technology, and Pt thin-film microelectrodes as dielectric biosensors were integrated on them. From capacitance-frequency measurements at various interelectrode distances and ionic concentrations, a significant difference between deionized (DI) water and tris-ethylenediaminetetraacetic acid (EDTA) (TE) buffer was observed in the low-frequency region. Although the capacitance (C
M) of the DI water decreased as the interelectrode distance increased, that of the TE buffer was similar up to a frequency of 100 Hz, after which it was spilt in the same manner as the DI water above 100 Hz. As the ionic concentration increased, the C
M of the TE buffer increased and the slope in the low frequency region changed from -0.875 to -0.425. The point where the slope changed shifted towards the frequency increase. These observations were clarified from the viewpoint of interfacial phenomena, such as the electrical double layer and Faradaic reactions, the dielectric constant related to conductivity, and the capacitance inversely proportional to the interelectrode distance. The addition of deoxyribonucleic acid (DNA) molecules (10 ng/µl) increased the capacitance and dielectric loss in the TE buffer at low frequency. It is feasible to use dielectric properties for the rapid and direct detection of biomolecules, particularly DNA molecules, without using labels or indicators.
Interferometric X-Ray Imaging of Breast Cancer Specimens at 51 keV X-Ray Energy
Authors: Takeda Tohoru , Wu Jin , Tsuchiya Yoshinori , Yoneyama Akio , Lwin Thet Thet , Aiyoshi Yuji , Zeniya Tsutomu , Hyodo Kazuyuki , Ueno Ei
Published: February 2005

The feasibility of the interferometric X-ray imaging technique is examined for revealing the features of breast cancer specimens. The interferometric X-ray imaging system consisted of an asymmetrically cut silicon crystal, a monolithic X-ray interferometer, a phase-shifter, an object cell, and an X-ray CCD camera. Ten 10-mm-thick formalin-fixed breast cancer specimens were imaged at 51 keV, and these images were compared with absorption-contrast X-ray images obtained at 18 keV monochromatic synchrotron X-ray. The interferometric X-ray images clearly depicted the essential features of the breast cancer such as microcalcification down to a size of 0.036 mm, spiculation, and detailed inner soft tissue structures closely matched with histopathological morphology, while the absorption-contrast X-ray images obtained using nearly the same X-ray dose only resolved microcalcification down to a size of 0.108 mm and spiculation. The interferometric X-ray imaging technique can be considered to be an innovative technique for the early and accurate diagnosis of breast cancer using an extremely low X-ray dose.
In Situ Study of Fe/ITO Catalysts for Carbon Nanocoil Growth By X-Ray Diffraction Analysis
Authors: Nishimura Kenji , Pan Lujun , Nakayama Yoshikazu
Published: February 2005

We have investigated the structural change of catalysts of iron-coated indium–tin–oxide films during the chemical vapor deposition (CVD) of carbon tubule nanocoils by in situ measurement of X-ray diffraction. It was found that heating the catalysts to a CVD temperature of 700°C in He atmosphere induces the oxidation of iron and forms nanoparticles with a diameter of several tens of nanometers, containing nanocrystals of indium oxide and iron oxide. At the initial stage of CVD using acetylene, the catalyst particles start to be deoxidized and then absorb carbon atoms to form crystalline iron–indium–tin–carbide compounds. The carbon nanocoils are grown from these compounds.
Structure Analyses of Artificial Methane Hydrate Sediments by Microfocus X-ray Computed Tomography
Authors: Jin Shigeki , Takeya Satoshi , Hayashi Junko , Nagao Jiro , Kamata Yasushi , Ebinuma Takao , Narita Hideo
Published: February 2005

The structure of natural gas hydrate sediments was characterized by microfocus X-ray computed tomography (CT). The obtained two-dimensional (2-D) and three-dimensional (3-D) images clearly showed the spatial distribution of the free-gas spaces, sand particles, and hydrates or ices. The estimated porosity from the X-ray CT data was consistent with the value that was obtained from the sample mass and volume. These results indicate that microfocus X-ray CT can be very useful for researching natural samples of hydrate sediments.
Progress in Fabrication and Modeling of Microstructured Optical Fibers
Authors: Fini John , Bise Ryan
Published: February 2005

We discuss recent advancements made in the fabrication and theoretical modeling of microstructured optical fibers and highlight opportunities for these fibers for low-loss transmission, nonlinear applications, and sensing.
Design of a Super-Paraboloidal Solid Immersion Mirror for Near-Field Recording
Authors: Kim Young-Sik , Lee Seung-Jae , Kim Young-Joo , Park No-Cheol , Park Young-Pil
Published: February 2005

We design a superparaboloidal solid immersion mirror (SP-SIM) using a tilt paraboloidal mirror and total internal reflection for application to the optical flying head for near-field recording. The design parameters are optimized in terms of the symmetric beam intensity on the high-numerical-aperture focusing system. Since the SP-SIM has two functions, namely, as an objective lens and a folding mirror, the height and weight of the optical flying head can be reduced.
Narrow Band-Pass Transmission Filter Consisting of Two Fiber Bragg Gratings with Different Periods
Authors: Yabe Yusuke , Yamada Yuto , Komatsu Shinichi
Published: February 2005

We developed a narrow band-pass transmission filter by connecting in series two fiber Bragg gratings (FBGs) with slightly different periods. The filter was fabricated by writing two FBGs directly onto the core of a single optical fiber. The center wavelengths of the element FBGs are 1549.71 nm and 1550.05 nm, their bandwidths are 0.36 nm and 0.42 nm, and their reflectances are 99.8% and 99.9%, respectively. The measured bandwidth (full width at half maximum, FWHM) of the fabricated band-pass filter is 0.052 nm, and the maximum transmittance is -12.5 dB. In order to reduce the transmission loss, we adjusted the period difference between the two element FBGs by temperature control, and achieved a maximum transmittance of -0.3 dB although the bandwidth slightly increased up to 0.092 nm. To obtain the narrower bandwidth of the transmission peak, we fabricated a series-type FBG filter using FBGs with higher reflectance, whose measured band-pass bandwidth was as narrow as 0.033 nm.
Control of Group Delay and Chromatic Dispersion in Tunable Hollow Waveguide with Highly Reflective Mirrors
Authors: Sakurai Yasuki , Koyama Fumio
Published: February 2005

We propose the control of group delay and chromatic dispersion in a hollow waveguide with a variable air core and highly reflective mirrors. Both group delay and chromatic dispersion in a hollow optical waveguide increase markedly with decreasing air core. A wide tunability of group velocity and chromatic dispersion is predicted by reducing the air core to nearly half of wavelength. We discuss the potential applications of the proposed hollow waveguide for compact photonic integrated circuits including tunable optical delay lines, interferometers, chromatic dispersion compensators and dispersion slope compensators.
Plastic Microlens Arrays by Deep Lithography with Protons: Fabrication and Characterization
Authors: Ottevaere Heidi , Volckaerts Bart , Vervaeke Michael , Vynck Pedro , Hermanne Alex , Thienpont Hugo
Published: February 2005

In this paper, we present the state-of-the-art of deep lithography with protons (DLP), a technology that we have adopted and optimized to rapidly prototype three-dimensional micro optical components and high-aspect-ratio micro mechanical structures in poly(methyl methacrylate). In particular, we focus on the fabrication of individual plastic refractive microlenses featuring a wide range of numerical apertures, diameters and pitches and on their 2-dimensional arrays. We provide a detailed description of the microlens fabrication technique and its calibration procedure. We highlight the quantitative geometrical and optical characteristics of these DLP microlenses and we demonstrate the reproducibility of their fabrication process. We also illustrate the prototyping flexibility of DLP by fabricating arrays featuring microlenses with different sags, pitches and diameters. As a conclusion, we analyze and discuss the strengths and weaknesses of this technology.
Fabrication Method of Double-Microlens Array Using Self-Alignment Technology
Authors: Kitamura Kazuya , Okada Kuniaki , Fujita Noboru , Nagasaka Yukiko , Ueda Minoru , Sekimoto Yoshihiro , Kurata Yukio
Published: February 2005

A fabrication method for double-microlens arrays with self-alignment technology (SAT) is proposed. To satisfy the tolerance of the alignment of a two-layer-lens array, we developed a new fabrication method without an alignment process. Using SAT, we achieved a brightness increase of 30% compared with the conventional single-layer microlens array.
Low-Driving-Voltage Electro-Optic Modulator With Novel KTa1-xNbxO3 Crystal Waveguides
Authors: Toyoda Seiji , Fujiura Kazuo , Sasaura Masahiro , Enbutsu Koji , Tate Akiyuki , Shimokozono Makoto , Fushimi Hiroshi , Imai Tadayuki , Manabe Katsue , Matsuura Tohru , Kurihara Takashi
Published: February 2005

We have successfully demonstrated a low-driving-voltage electro-optic (EO) modulator using newly developed KTa1-x
Nb
x
O3 (KTN) buried waveguides. We prepared high-quality and large KTN crystals. The crystals exhibited a large quadratic EO coefficient of 4.8×10-15 m2/V2 at 1.55 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 r
33 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 0.5 dB/cm and the polarization dependent loss was less than 0.1 dB/cm. The EO modulators had a low V
π of <2.5 V (4.0-V biased potential, l=6 mm) and a fast response of 3 GHz.
Optical Method for Personal Identification Based on Recognition of Three-Dimensional Objects
Authors: Kobayashi Junjiro , Komatsu Shinichi
Published: February 2005

We propose an optical method of personal identification utilizing three-dimensional information about a portable object, for which we choose a seal in the present study. The three-dimensional information about the seal, i.e., its engraved design and engraved depth, is recorded with a charge-coupled device (CCD) camera as a two-dimensional oblique projection. For identification, a target projection is compared with a reference projection on the basis of the joint transform correlation (JTC). In order to enhance the detail of the projections for better discrimination, we adopt the modified JTC in which, instead of employing the power spectra of the target and reference projections, their logarithms are used. The feasibility of the proposed method is examined by computer simulation as well as by optical experimentation, and satisfactory results are obtained.
Synthesis of Novel P-Type Nanocrystalline Si Prepared from SiH2Cl2 and SiCl4 for Window Layer of Thin Film Si Solar Cell
Authors: Ikeda Yoshie , Ito Tetsuji , Li Yali , Yamazaki Michiaki , Hasegawa Yasuhiro , Shirai Hajime
Published: February 2005

A novel p-type hydrogenated chlorinated nanocrystalline silicon (nc-Si:H:(Cl)) film was fabricated from chlorinated materials, i.e., SiH2Cl2 and SiCl4,by rf plasma-enhanced chemical vapor deposition. These p-type nc-Si:H:(Cl) films showed high conductivities of 10–50 S/cm under 3000–5000 ppm B2H6-mixing concentrations with lower optical absorption in the visible region, while maintaining a high film crystallinity. No marked darkening of the ZnO:Al layer was observed after deposition of the p-type nc-Si:H:(Cl) layer fabricated from SiH2Cl2 and SiCl4 compared to the p-type Si:H film fabricated from SiH4. The origin of the low optical absorption in p-type nc-Si:H:(Cl) is demonstrated along with the performance of a p–i–n structure amorphous silicon solar cell.
A New Surface Modification Method to Prevent the Release-Stiction of Micromechanical Structures during HF Vapor-Phase Etching
Authors: Yang Woo Seok , Kang Sung Weon , Lee Jaewoo , Jung Sung Hae , Kim Yoon Tae
Published: February 2005

A novel release process without stiction problem is a major concern in surface micromachining technology to fabricate microelectromechanical systems (MEMS) devices. HF vapor-phase etching (VPE) has been focused as a promising dry process to remove sacrificial SiO2 layer, but still has limitation due to water condensation. We have first demonstrated the effectiveness of a new surface modification method using strongly hydrophilic materials (i.e., Ti, Al2O3) in preventing the release-stiction during HF VPE process. The role of hydrophilic surface layer is proposed to suppress the water bridging causing a attractive capillary force between micromechanical and stationary structures.
Bottom Coverage of Cu Deposit for 200-nm-Class Circular Vias with High Aspect Ratios Investigated by Magnetron Sputtering Activated Using Superconducting Bulk Magnet
Authors: Hazama Hirofumi , Matsuda Takashi , Mizutani Uichiro , Ikuta Hiroshi , Yanagi Yousuke , Itoh Yoshitaka , Sakurai Kazuo , Sekiguchi Atsushi , Imai Atsuo
Published: February 2005

We have investigated the bottom coverage effect of circular vias with different aspect ratios patterned on Si substrates by depositing Cu using a magnetron sputtering apparatus equipped with a superconducting bulk magnet. The superconducting SmBa2Cu3O7-δ bulk of 60 mm diameter was magnetized up to 4.5 T at 52 K and cooled to 40 K in a refrigerator. It served as a permanent magnet producing magnetic fields about 10 times as strong as that obtained from a conventional Nd–Fe–B permanent magnet, resulting in a marked enhancement in plasma density on the Cu target. Indeed, the present magnetron sputtering apparatus was capable of sputtering under Ar gas pressures of at least 3.33 ×10-3 Pa with a throw distance D
st of 300 mm when a Cu target of 150 mm diameter was employed. Practical sputtering was possible under 2.66 ×10-2 Pa even when D
st was extended to 500 mm. Under this condition, a uniform Cu film with a bottom coverage of 58% was successfully deposited at the bottom of a circular via of 250 nm diameter and 1.15 µm depth with an aspect ratio of 4.6 within a circle of 120 mm diameter on the substrate.
Improved Confinement of Neon Plasma Inside a High-Critical Temperature Superconducting Tube: A Theoretical Approach
Authors: Agop Maricel , Chicos Liliana-Elena , Buzea Calin , Matsuzawa Hidenori , Alexandroaie Dumitru
Published: February 2005

A mathematical model, aiming at the improved confinement of neon plasma inside a high-T
c superconducting tube, is given. It is shown that the presence of the superconducting tube modifies the decay time of the plasma by means of the characteristic length of diffusion for generating a double-layer structure.
Spectrum Analysis of Lightwaves Generated by Multilongitudinal Mode Laser Diode Using Sum Frequency Generation Theory under Quasi-Phase Matching Condition
Authors: Chen Qiang , Takagi Takeshi , Matsuura Hiroshi
Published: February 2005

We investigate spectral characteristics of light waves generated by broadband fundamental light waves using the sum frequency generation theory. First, we divide the fundamental light waves into N sections as wavelength domains, and assume that all lights waves couple with each other, and the interaction can be described by SFG theory. The generated light waves can be considered as the sum of all SFG light waves. Next, due to the effect of cointeraction of N fundamental light waves with atomic matter, two compensating functions are introduced into parameters of power flow and phase mismatching in SFG calculation. As a result, we obtain excellent agreement of calculated and measured spectra.
Temperature Dependence of Threshold Currents of 1.55 µm p-Substrate Buried Crescent Laser Diodes
Authors: Kakimoto Shouichi
Published: February 2005

We have fabricated 1.55 µm p-substrate buried crescent (PBC) laser diodes (LDs) and measured light output power versus current characteristics at various temperatures. The called characteristic temperature, T
0, is 78 K in the temperature range of 20–80°C. Above a critical temperature, T
c, of 80°C, T
0 becomes lower than 54 K. We have also calculated the T
0 of the 1.55 µm PBC LDs using our model, in which the temperature dependence of gain, and the carrier density dependence of the intervalence band absorption and carrier lifetime are taken into account. The calculated T
0 is 95 K which nearly agrees with that measured in the temperature range of 20–80°C. Therefore, our model explains well the experimental results.
Lasing in Cholesteric Liquid Crystals Doped with Oligothiophene Derivatives
Authors: Amemiya Kazuhiro , Shin Ki-Chul , Takanishi Yoichi , Ishikawa Ken , Azumi Reiko , Takezoe Hideo
Published: February 2005

Lasing behavior has been studied in cholesteric liquid crystals (CLCs) doped with three oligothiophene (OT) derivatives such as α,α'-dimethylquaterthiophene (DMQtT) as laser dyes. CLCs spontaneously form a distributed feedback cavity, in which OT molecules are highly oriented parallel to the local director of CLCs with an order parameter of about 0.65, as studied by polarized emission spectra. Lasing occurs at only the low-energy edge of the photonic bandgap above a threshold input power of about 4.6 mJ/cm2/pulse in a DMQtT-doped CLC cell by pulsed (4 ns duration and 10 Hz repetition) excitation. This lasing emission mode selection is attributed to the high order parameter of OT molecules.
Coherent Control of Exciton in a Single Quantum Dot Using High-Resolution Michelson Interferometer
Authors: Okada Takumi , Komori Kazuhiro , Goshima Keishiro , Yamauchi Shohgo , Morohashi Isao , Sugaya Takeyoshi , Yamazaki Osamu , Ogura Mutsuo , Hattori Toshiaki
Published: February 2005

We developed a high-resolution Michelson interferometer with a He–Ne two-frequency laser positioning system, and measured the coherent carrier dynamics of a single InAs self-assembled quantum dot (SAQD) using a micro-spectroscopy system. The phase-locked double pulses were stabilized, with the maximum deviation being below 10 nm during the long measurement time of 1 h. Using this system, coherent control of an exciton in an InAs SAQD with very fine phase stabilization was demonstrated. The dephasing time of the single quantum dots was 9.5 ps which is close to that estimated from the homogeneous linewidth in the photoluminescence excitation (PLE) spectrum.