Hitachi, Ltd.

Hitachi Cable, Inc.

Tsuneo Suganuma

Toshio Katsuyama

Hiroyoshi Matsumura

Iwao Matsuyama

Shin Satoh

Kenzo Susa

Norio Ohta

Koji Ishida

Kazuyuki Nagatsuma

Hiroyuki Suzuki

Yutaka Sugita

Naoki Kodama

Gyozo Toda

Mamoru Sugie

Toshiki P Tanaka

Seiichi Onoda

Masao Sumi

Harukazu Miyamoto

Shigeru Nakamura

Hirofumi Sukeda

Toshimitsu Kaku

Yuzuru Hosoe

Yoshihiro Shiroishi

Masaaki Hayashi

Fumiyoshi Kirino

Masahiro Ojima

Takeshi Nakao

Katsuyuki Imoto

Makoto Sano

Yoshinori Miyamura

Takashi Toyooka

Masahiko Takahashi

Toshio Niihara

Heigo Ishihara

Sadao Hishiyama

Norikazu Tsumita

Katsuo Abe

Katsuki Miyauchi

Yasutaro Uesaka

Hidehito Obayashi

Tokuho Takagaki

Takaaki Shirakura

Tetsu Oi

Hajime Fukke

Keikichi Ando

Shojiro Kawakami

Masayuki Katsumoto

Katsuyoshi Chiba

Naoto Endo

Shigeo Nishida

Yasuo Tsukuda

Takao Yonekawa

Yoshio Gobara

A magnetic recording medium and magnetic recording apparatus which can provide a high output level and a low noise level are disclosed. A magnetic recording medium includes a multilayer structure of magnetic alloy thin films containing Co, and at least one paramagnetic intermediate region or oxygen-rich region disposed between the magnetic layers. The intermediate region reduces the magnetic interaction between the magnetic layers without the degradation of crystallinity of the magnetic layers. As a result, a magnetic recording medium having such a structure shows low noise performance and a high recording density.

Magnetic recording medium and magnetic recording apparatus

A magnetic field of a polarity corresponding to information to be recorded is applied while a recording spot having a high energy is irradiated to a magneto-optical recording medium to record domains representing the information along a track. The recorded domains are read out by a reproducing spot having a lower energy than the recording spot and a high resolution power along the track. A recording head has an optical system for irradiating the recording spot having the high energy to the magneto-optical recording medium and a magnetic head for applying a magnetic field having a polarity thereof switched in accordance with the information to be recorded, to an irradiation area of the recording spot, a reproducing head has an optical system for irradiating the reproducing spot having the low energy by a laser beam having a wavelength of no larger than 600 nm and a magneto-optical signal detector for detecting a displacement of a polarization plane of a reflected light of the reproducing spot to read out the recording domains. The magneto-optical recording medium is made of a recording film having a multi-layer structure of alternate lamination of metal layers and dielectric layers.

Magneto-optical recording and reproducing method, magneto-optical memory

A method for magnetic orientation of a magnetic recording medium using Meissner effect of a superconductor and a system therefor and a magnetic recording medium produced thereby. The magnetic particles of plate hexagonal barium ferrite in the magnetic coating are allowed to orient in the longitudinal direction thereof so that a magnetic recording medium having a magnetic orientation in such direction with the magnetic particles can be obtained.

Method for magnetic orientation of magnetic recording medium using

An optical fiber having an intense polarization plane maintenability is constructed of an optical waveguide having a circular core and a circular cladding, a jacket formed on the outer circumference of the optical waveguide and having an elliptical outer circumference, and a supporting portion formed on the jacket. In order to fabricate the above-specified optical fiber, a preformed rod therefor is prepared by forming the inner wall of an silica glass tube with the jacket and the optical waveguide made of such materials as satisfy a relationship of c.sub.2 /a.gtoreq.200/(100-.gamma.)-1, wherein: letter .gamma. stands for the ellipticity of the outer circumference of the aforementioned jacket; letter c.sub.2 stands for the minor axis of an ellipse; and letter a stands for the radius of the circular optical waveguide, and by subsequently collapsing the aforementioned silica glass tube while having its internal pressure made lower than the atmospheric pressure by 1 to 20 mmH.sub.2 O.

Polarization plane maintaining optical fiber fabricating method

A magnetic recording medium comprises a non-magnetic substrate and a thin magnetic film, the thin magnetic film being composed mainly of Co, Ni and at least one of Zr and Hf, and a concentration of Zr, Hf or Zr and Hf as contained in the thin magnetic film being 0.1 to 30% by atom on the basis of the total of Co and Ni, and has a considerably higher corrosion resistance than that of the conventional magnetic recording medium having a thin Co-Ni magnetic film.

Magnetic recording medium

A measuring instrument of magnetic field utilizing Faraday rotation is disclosed in which a medium exhibiting Faraday rotation includes at least one thin magnetic garnet film magnetized in a propagation direction of light and having a composition expressed by a general formula R.sub.3-x Q.sub.x (Fe.sub.5-y M.sub.y)O.sub.12 (where R indicates at least one element selected from a group consisting of Y, La, Lu, Ca, Sm and Bi, Q indicates at least one element selected from a group consisting of Gd, Eu, Er, Tm, Tb, Yb, Ho and Dy, M is at least one element selected from a group consisting of Ga, Al, Ge, Si, Sc, Mn, In, V and Cr, the value of x lies in a range expressed by a formula 0.1.ltoreq.x.ltoreq.3.0, and the value of y lies in a range expressed by a formula 0.ltoreq.y.ltoreq.5.0). According to this instrument, stable measured values are obtained independently of temperature variation.

Temperature-compensated magnetic field measuring instrument

In a magnetic-field measuring apparatus having a Faraday rotation property, a medium having the Faraday rotation property includes at least one magnetic garnet thin film having a composition represented by a general formula of R.sub.3 (Fe.sub.5-x M.sub.x)O.sub.12 (where R is at least one element selected from a group consisting of La, Sm, Lu, Ca and Bi, or at least two elements selected from the group with Y being added thereto, M is at least one element selected from a group consisting of Ga, Ge, Al, Si, Sc, In and Cr, and a range of x is 0.ltoreq.x.ltoreq.1.5), and magnetized in a direction of light transmission, whereby an overall temperature characteristic of a ratio (4.pi.Ms/Ho) of a saturation flux density 4.pi.Ms to a collapse field Ho of a strip domain of the thin film is improved. The magnetic-field measuring apparatus offers a stable measurement of magnetic-field irrespective of a temperature change.

Optical magnetic-field measuring apparatus having improved temperature

An electric-field measuring apparatus utilizing electrooptic effect for measuring the intensity of an electric DC field includes a material exhibiting both electrooptic effect and photoelectric effect or both a material exhibiting the electrooptic effect and a material exhibiting the photoelectric effect which material or materials are irradiated with a continuous light ray of a wavelength capable of inducing the electrooptic effect and an intermittently interrupted light ray of a wavelength capable of inducing the photoelectric effect.

Optical D.C. electric-field measuring apparatus with optic sensing means

A method of producing a preform for a single-polarization optical fiber wherein a glass rod to become a core or a glass rod to become a clad is inserted into a quartz tube which has on its inner wall surface a glass thin film to become a clad layer, a glass thin film to become a jacket layer or glass films to become a jacket layer and a clad layer, and wherein under a state under which the internal pressure of the quartz tube is reduced, the quartz tube is heated to become solid, whereby at least one of the clad and the jacket of the optical fiber preform becomes elliptic in cross section.

Method of producing optical fiber preform

In an optical gyroscope comprising a coil of an optical fiber having opposite ends on which linearly polarized input light beams are incident and from which output light beams are derived which create an interference pattern to be detected, the optical fiber has orthogonal principal axes along which the light beams propagate at a large propagation constant difference. The application of the linearly polarized input light beams to the opposite ends of the optical fiber coil is such that the polarization plane of the linearly polarized light beam coincides with the same principal axis on the opposite ends. Thus, polarization characteristics of the output light beam from the optical fiber coil becomes time invariant and the light paths for the two light beams coincide with each other. In particular, in order to minimize the influence of external disturbances, the optical fiber has a structure defined by

Optical gyroscope with large propagation constant difference

A glass layer is formed inside a silica glass tube and another glass layer having a refractive index higher than that of the abovementioned glass layer is formed on said glass layer. After these glass layers are formed, one end of the glass tube is collapsed. While the internal pressure of the glass tube is being reduced below the atmospheric pressure, the glass tube is caused to collapse by heating, thereby yielding a preform for an optical fiber. The optical fiber produced from this preform has the difference in the refractive indices of the two orthogonal major axes of at least 1.6.times.10.sup.-4 and maintains the linear polarization plane.

Optical fiber and method of producing the same

Optical glass is produced by heating a porous gel to a high temperature to partly sinter it, heating it in a chlorine-containing atmosphere to subject it to hydroxyl group removal treatment, and then further heating it to sinter it. The optical glass produced by this process does not rise in bubbles even when heated.

Process for producing optical glass

A single-mode-transmission optical fiber comprises a core of a radius a having an arbitrary (non constant) refractive index distribution n(r) in the radial direction r, the index distribution being expressed by n.sup.2 (r)=n.sub.1.sup.2 {1-2.DELTA..sub.o f(r)}, and a cladding having a constant refractive index n.sub.2, the radius a of the core being: ##EQU1## In these expressions, n.sub.1 denotes a maximum refractive index of the core, .lambda. denotes a transmission light wavelength, ##EQU2## and a normalized frequency V is expressed by ##EQU3## Y is a solution Y in the case where X and Y are solutions of simultaneous equations: ##EQU4## of a function which is expressed by: ##EQU5##

Single-mode-transmission optical fiber and a method of manufacturing the

Disclosed is a lithium oxide based amorphous material having a composition included in a region defined by lines connecting points A, B, C and D in the composition diagram of the ternary system of Li.sub.2 O.SiO.sub.2.P.sub.2 O.sub.5 shown in FIG. 1 of the accompanying drawings. This amorphous material can be formed by performing sputtering by using as a target a mixture of a lithium silicate/lithium phosphate composition and LiO.sub.2. This amorphous material is excellent in the ionic conductivity.

Lithium oxide based amorphous material and process for preparation

A method for producing optical glass, which comprises charging a mixed solution capable of forming a high-silica-content gel by hydrolysis reaction into a vessel, the inner wall face of which is composed of a material unwettable to the mixed solution, such as a fluorocarbon resin or silicone resin, causing gelation of the mixed solution in the vessel, drying the obtained gel, and heating and sintering the obtained dry gel. When electrodes are placed in the mixed solution at the gelation step and an electric voltage is applied, the time required for formation of the gel is shortened. Furthermore, at the gel-drying step, if the amount of materials evaporated from the gel is detected or the weight of the gel is measured, the detected amount of the evaporated materials or the change of the weight of the gel is fed back to a factor regulating the drying speed, such as the drying temperature to control the drying speed to an appropriate level.

Method for producing optical glass

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Tokorozawa, Japan

Tsuneo Suganuma