Fdk Corporation

Other

Hiromitsu Umezawa

Hirotaka Kawai

Hidenori Nakada

Tsugio Tokumasu

Toshiyasu Suzuki

Masaharu Hoshikawa

Nobuhiro Fukushima

Mikio Kitaoka

Isao Kojima

Yuji Goto

Takashi Kato

Teruhisa Sahashi

Hidenori Nakata

Tomokazu Imura

Youichi Suzuki

Toshihiko Watanabe

Shinzo Fujii

Yoichi Suzuki

Akitoshi Mesaki

Hiroshi Rikukawa

Katsuhiro Iwasaki

Chiharu Nishida

A magneto-optical device is provided with a non-magnetic substrate, a magneto-optical crystal embedded in recessed portions formed in the surface of the non-magnetic substrate at positions where pixels are to be located, and a partitioning wall monolithic with the non-magnetic substrate and magnetically separating the magneto-optical crystal from each other at the position of a gap between the pixels, wherein the entire surface of the magneto-optical device is flattened. A method for manufacturing a magneto-optical device includes a digging down step, executed at positions where pixels are to be located, of digging down into the surface of a non-magnetic substrate in advance at the positions where the pixels are to be formed, so that a gap portion located between the pixels and around the dug areas remains to form a partitioning wall, a magnetic film forming step of forming a film made of a magneto-optical crystal over substantially the entire surface of the non-magnetic substrate, and a surface flattening step of performing flattening by removing a protruded portion formed by the magnetic film that has grown on the gap portion.

Magneto-optical device and manufacturing method thereof

An optical attenuator with increased dynamic range and reduced temperature-dependence over the dynamic range. The optical attenuator has a Faraday rotational angle variable device which applies an external magnetic field to light polarized by a garnet crystal, and a polarizer and an analyzer disposed at the front and rear of the optical axis of the device. There is an angle x formed between the plane of polarization of the light incident to the garnet crystal and the magnetic field orthogonal to the optical axis, where an angle y is formed between the polarizer and the analyzer, and the angle x is set to satisfy {(&#x2212;z/2)+90&#xd7;n}&#x2212;12&#x3c;x&#x3c;{(&#x2212;z/2)+90&#xd7;n}+12 (n=0, 1, 2 or 3), where z=y&#xb1;90; z is the angle of rotation of the plane of polarization caused by the Faraday rotational angle variable device.

Optical attenuator

It is possible to reduce the size of a magneto-optical device, increase the speed of optical control, simplify power supply structure and its control, and maintain a Faraday rotation angle in an arbitrary state even after shut-off of the excitation current. The magneto-optical device includes a magnetic yoke () made of a high-permeability magnetic material, the magnetic yoke including a tabular portion () and four pillar portions () protruding from one side of the tabular portion (), a coil () wound on each of the pillar portions, and a magneto-optical element () arranged in an open-magnetic-circuit region surrounded by the end portions of the four pillar portions. A magnetic field obtained by a coil is applied to the magneto-optical element.

Magneto-optical device

A polarized-light separating/combining element is obtained which can suppress deviation in a direction of rays (angular error), reduce beam coupling loss and improve extinction ratio. Size reduction and loss lowering is achieved for an optical device (optical circulator or optical switch), to enable manufacture at a low cost and with ease. A polarized-light separating/combining element has a transparent member having flat surfaces parallel with each other on which both parallel surfaces, polarized-light separating/combining films are formed respectively, wherein both polarized-light separating/combining films are faced to air. By using the polarized-light separating/combining element, various kinds of optical devices (optical circulators or optical switches) can be formed. Particularly, it is effective for realizing a low crosstalk characteristic in a matrix optical switch.

Polarization separating/synthesizing element and optical device using it

There is provided a Faraday rotation angle varying device in which external magnetic fields are applied from at least two directions to a garnet single crystal having a Faraday effect and a synthesized magnetic field is varied so that Faraday rotation angle of light which transmits through the garnet single crystal is controlled. The device has a base film of garnet single crystal having a rotation angle varied in accordance with variation of a synthesized magnetic field, and a compensating film of a garnet single crystal having a constant Faraday rotation angle. The base film has a wavelength coefficient sign and the compensating film has a wavelength coefficient sign which is different from that of the base film, so that a wavelength variation component of the Faraday rotation angle of the base film is reduced by the compensating film. For example, a fixed magnetic field parallel to a light direction is applied by permanent magnets and a variable magnetic field is applied by an electromagnet.

Faraday rotation angle varying device

Disclosed is a Faraday rotator capable of reducing the temperature dependence on a Faraday rotation angle, thereby enhancing the temperature characteristic, particularly, in a service environment in which the magnetization direction is variable, and an optical device using the Faraday rotator. The Faraday rotator includes a Faraday element which rotates the polarization plane of polarized light rays passing through the Faraday element when an external magnetic field is applied to the Faraday element. In this Faraday rotator, assuming that an angle between a magnetization direction of the Faraday element and a light ray direction is taken as &agr;, the amount of the temperature-dependent change in Faraday rotation angle is reduced by applying the external magnetic field in a direction in which a first amount of the change in Faraday rotation angle due to the temperature dependence on the angle &agr; and a second amount of the change in Faraday rotation angle due to the temperature dependence on the Faraday effect satisfy a relationship in which the sign of the first amount is plus or minus, the sign of the second amount is minus or plus, and the absolute value of one of the first and second amounts is less than twice the absolute value of the other amount, more preferably, substantially equal to the absolute value of the other amount.

Faraday rotator

A Faraday rotation angle varying apparatus for controlling a Faraday rotation angle of a light beam passing through a garnet single crystal having a Faraday effect by applying external magnetic fields to the garnet single crystal in two or more of directions and varying a synthetic magnetic field synthesized from the external magnetic fields is disclosed. According to an aspect of the present invention, the garnet single crystal has the (111) plane polished and the light beam is allowed to pass through the garnet single crystal along the &lt;111&gt; direction of the garnet single crystal perpendicular to the (111) plane. A displacement path of a synthetic vector of the external magnetic fields is within a fan-shaped range (peripheral lines of the fan-shape inclusive) of a stereographic projection chart of the garnet single crystal with the (111) plane taken as the center of the chart. The fan-shaped range is surrounded by two lines connecting a point indicating the (111) plane positioned at the center of the stereographic projection chart to two positions apart 10.degree. rightward and leftward from a point indicating one of crystal planes equivalent to the (110) plane positioned on the outermost peripheral circle of the stereographic projection chart.

Faraday rotation angle varying apparatus

Disclosed is a magneto-optical element material composed of a magnetic garnet single crystal which is small in temperature dependency of a Faraday rotation angle, capable of being formed into a film by the LPE, and significantly small in wavelength dependency of a Faraday rotation angle in a specific composition region defined by. The magneto-optical element material is composed of a magnetic garnet single crystal expressed by a composition formula of R.sub.3-x Bi.sub.x Fe.sub.5-v-w-y Ma.sub.v Mb.sub.w Co.sub.y O.sub.12 where R indicates a rare earth element including yttrium, Ma is a trivalent cationic element, and Mb is a tetravalent cationic element; and x, y, v and w satisfy relationships of 0.6.ltoreq.x.ltoreq.1.9, 0.01.ltoreq.y.ltoreq.0.47, 260y-88x+45.ltoreq.0, 500y-30x+37.ltoreq.0, 0.ltoreq.v.ltoreq.1.0, and 0.ltoreq.w.ltoreq.0.35. The material satisfying the following relationships of 0.01.ltoreq.y.ltoreq.0.28 and 800y-130x+45.ltoreq.0 specifically shows improvement in a wavelength dependency of a Faraday rotation angle. Further disclosed is a Faraday element formed by superimposing an A film on a B film for broadening a usable wavelength band region using difference in wavelength dependency of a Faraday rotation coefficient between both the films A and B. The A film is made, by the LPE, from a Bi-substitution type rare earth-iron garnet single crystal not containing Co and the B film is made, by the LPE, from a rare earth-iron garnet single crystal containing Co.

Magneto-optical element material and Faraday element using the same

Disclosed is a material for a magneto-optical element, which is made of magnetic garnet single crystals being wide in a band width in a 1310 nm band and thereby being capable of coping with the wavelength multiplex communication at the wavelength band, and a Faraday rotator using the same. The material for a magneto-optical element is made of a magnetic garnet having a composition formula expressed by R.sub.3-y-x Sm.sub.y Bi.sub.x Fe.sub.5 O.sub.12, where R is one kind of rare earth elements including yttrium (Y), and 'x' and 'y' are constants defined by 0.3.ltoreq.x.ltoreq.1.9 and 0.4.ltoreq.y.ltoreq.2.7, the magnetic garnet being formed on a non-magnetic substrate by liquid-phase epitaxial growth. R is preferably one of Y, La, Sm and Lu. The Faraday rotator, which is used in a wavelength range of from 1250 to 1370 nm, is formed by superposing a film A made of LPE magnetic garnet single crystals expressed by a composition formula of R1.sub.3-x Bi.sub.x Fe.sub.5-z Z.sub.z O.sub.12, to a film B made of LPE magnetic garnet single crystals expressed by a composition formula of R2.sub.3-y Sm.sub.y Fe.sub.5 O.sub.12, where R1 is one of Al, In of rare earth elements including Y; Z is one of Al, In and Ga; R2 is one kind of rare earth elements including Bi and Y; and 'x', 'y' and 'z' are constants defined by 0.3.ltoreq.x.ltoreq.1.9, 0.5.ltoreq.y.ltoreq.3 and 0.ltoreq.z.ltoreq.0.5.

Material for magneto-optical element and faraday rotator using the same

A material made of magnetic garnet single crystals has excellent characteristics particularly in a wavelength band of from 950 to 1070 nm, which is usable for a wavelength 980 nm for pumping light of erbium doped fiber amplifier, and for a wavelength of 1017 nm for pumping light of an praseodymium doped fiber amplifier. One example of the material is made of magnetic garnet single crystals expressed by a composition formula of Nd.sub.3-x Bi.sub.x Fe.sub.5 O.sub.12 (0.5.ltoreq.x.ltoreq.1.9), the single crystals being formed by liquid-phase epitaxial growth on a non-magnetic garnet substrate having a lattice constant &lt;a&gt; specified in the range of 12.61 .ANG..ltoreq.a.ltoreq.12.63 .ANG.. The material is suitably used for a magneto-optical element having a wavelength band from 950 to 1070 nm. The non-magnetic garnet substrate can be made of a material having a composition formula expressed by Gd.sub.3-y Nd.sub.y Sc.sub.2 Ga.sub.3 O.sub.12 (1.0.ltoreq.y.ltoreq.1.4).

Magneto-optical element material formed of magnetic garnet single

A polarization plane switch comprising a Faraday rotator made of an iron-containing garnet single-crystal film and magnetic field applying devices capable of reversing a magnetic field to be applied to the Faraday rotator. The polarization plane switch has a structure in which magnetization of part of the Faraday rotator is unsaturated and that of the remaining portion of it is saturated when a magnetic field is applied to the Faraday rotator by the magnetic field applying device, and a light beam passes through the magnetically saturated portion almost vertically to the film surface. As the above Faraday rotator, it is the most preferable to use a Faraday rotator made of Bi-substituted iron garnet single crystal formed by liquid-phase epitaxy and having a compensation temperature, and thermally treated under the top condition at a temperature between 1,120.degree. and 1,180.degree. C. for 7 hours or less.

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Minato-ku, Japan

Hiromitsu Umezawa