JP2005249893A - Ring type faraday rotation device - Google Patents

Ring type faraday rotation device Download PDF

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JP2005249893A
JP2005249893A JP2004056891A JP2004056891A JP2005249893A JP 2005249893 A JP2005249893 A JP 2005249893A JP 2004056891 A JP2004056891 A JP 2004056891A JP 2004056891 A JP2004056891 A JP 2004056891A JP 2005249893 A JP2005249893 A JP 2005249893A
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magnetic
faraday rotation
magneto
optical element
magnetic field
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Akitoshi Mesaki
明年 目崎
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FDK Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a ring type Faraday rotation device wherein response characteristics for switching polarization surfaces are improved and a magnetic yoke can be miniaturized and which can be easily controlled. <P>SOLUTION: The ring type Faraday rotation device is provided with the substantially ring type magnetic yoke 10 consisting of a high magnetic permeability material, a plurality of coils 12 wound on the magnetic yoke and a magneto-optical element 14 positioned in a nearly center part of the magnetic yoke. A coil current is controlled so that the direction of a magnetic flux passing through one side half of the magnetic yoke and the direction of a magnetic flux passing through the other half are always reverse to each other and a synthesized magnetic field thereof is made to pass through the magneto-optical element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、光スイッチなどに用いるファラデー回転デバイスに関し、更に詳しく述べると、リング型の磁気ヨークを用い、その片側半分を通る磁束の向きと反対側半分を通る磁束の向きが常に逆となるようにコイル電流を制御し、それらの合成磁界が磁気光学素子を通るようにしたリング型ファラデー回転デバイスに関するものである。   The present invention relates to a Faraday rotation device used for an optical switch or the like. More specifically, a ring-type magnetic yoke is used so that the direction of the magnetic flux passing through one half of the magnetic yoke is always opposite to the direction of the magnetic flux passing through the opposite half. The present invention relates to a ring type Faraday rotation device in which the coil current is controlled so that the combined magnetic field passes through the magneto-optical element.

光通信システムあるいは光計測システムなどでは、光路を制御するために光スイッチが組み込まれている。光スイッチは、一般に、第1の偏光子と、磁気光学素子と、第2の偏光子とを、光軸に沿ってその順序で配置し、電磁石によって前記磁気光学素子に可変磁界を印加する構成である。磁気光学素子はファラデー効果を有し、磁界中の磁気光学素子を光が透過するときに、その磁界の方向が光軸と平行の成分を有する場合、偏光面が回転する。その偏光面の回転角は、磁界の強さや向きによって変化する。そこで、磁気光学素子を用いて偏光面の方向を制御することで、光のスイッチング(光のオン−オフや光路の切り替え)を行わせることができる。   In an optical communication system or an optical measurement system, an optical switch is incorporated to control an optical path. In general, an optical switch has a configuration in which a first polarizer, a magneto-optical element, and a second polarizer are arranged in that order along an optical axis, and a variable magnetic field is applied to the magneto-optical element by an electromagnet. It is. The magneto-optical element has a Faraday effect. When light passes through the magneto-optical element in a magnetic field, the plane of polarization rotates when the direction of the magnetic field has a component parallel to the optical axis. The rotation angle of the plane of polarization changes depending on the strength and direction of the magnetic field. Thus, by controlling the direction of the plane of polarization using a magneto-optical element, light switching (light on-off or light path switching) can be performed.

このようなファラデー回転デバイスは、通常、C型(環状の一部が開いている形状)の磁気ヨークにコイルを巻装した構造の電磁石を用い、C型磁気ヨークの開いている部分に磁気光学素子を挿入し、コイルに通電することによって該磁気光学素子に所望の磁界を印加する構造である。ここで磁気ヨークには半硬質磁性材料が用いられており、そのためコイルに電流を流し磁気光学素子に磁界を印加すると、コイル電流を遮断した後でも半硬質磁気特性によって磁気ヨークは磁力を保持し、磁気光学素子に磁界を印加し続けるような磁気回路が採用されている。   Such a Faraday rotation device normally uses an electromagnet having a structure in which a coil is wound around a C-shaped (annular part-open shape) magnetic yoke, and a magneto-optical device is used in the open part of the C-type magnetic yoke. In this structure, a desired magnetic field is applied to the magneto-optical element by inserting the element and energizing the coil. Here, a semi-hard magnetic material is used for the magnetic yoke. Therefore, when a current is applied to the coil and a magnetic field is applied to the magneto-optical element, the magnetic yoke retains the magnetic force due to the semi-hard magnetic characteristics even after the coil current is cut off. A magnetic circuit that continuously applies a magnetic field to the magneto-optical element is employed.

しかし、このような構成では、コイル電流を遮断した後でもファラデー回転が起こる磁界を磁気光学素子に印加し続けるため、磁気ヨークが大型化する。また、半硬質磁性材料を用いているため、磁界の向きが反転して必要なファラデー回転角が得られる磁界の強さが発生するまでに時間がかかる(応答特性が悪い)欠点もあった。   However, in such a configuration, since the magnetic field in which Faraday rotation occurs even after the coil current is interrupted is continuously applied to the magneto-optical element, the magnetic yoke is increased in size. In addition, since a semi-hard magnetic material is used, there is a drawback that it takes time (the response characteristics are poor) until the magnetic field strength is generated to reverse the direction of the magnetic field and obtain the required Faraday rotation angle.

応答特性を改善するため、磁気光学素子を不飽和で動作させる技術もあるが(特許文献1参照)、制御が難しい問題がある。
特開平7−306390号公報
In order to improve response characteristics, there is a technique for operating the magneto-optical element in an unsaturated state (see Patent Document 1), but there is a problem that control is difficult.
JP-A-7-306390

本発明が解決しようとする課題は、従来技術では磁気ヨークが大型化する点、応答特性が悪い(磁界の向きの反転に時間がかかる)点、制御が難しい点、などである。   The problems to be solved by the present invention are that the magnetic yoke is enlarged in the prior art, the response characteristics are poor (it takes time to reverse the direction of the magnetic field), and the control is difficult.

本発明は、実質的にリング型の高透磁率磁性材料からなる磁気ヨークと、該磁気ヨークに巻装した複数のコイルと、磁気ヨークのほぼ中央に位置する磁気光学素子とを具備し、磁気ヨークの片側半分を通る磁束の向きと反対側半分を通る磁束の向きが常に逆となるようにコイル電流を制御し、それらの合成磁界が磁気光学素子を通るようにしたことを特徴とするリング型ファラデー回転デバイスである。   The present invention includes a magnetic yoke substantially made of a ring-type high-permeability magnetic material, a plurality of coils wound around the magnetic yoke, and a magneto-optical element positioned substantially at the center of the magnetic yoke. A ring characterized in that the coil current is controlled so that the direction of the magnetic flux passing through one half of the yoke and the direction of the magnetic flux passing through the opposite half are always opposite so that their combined magnetic field passes through the magneto-optical element. Type Faraday rotation device.

例えば、2個のU型コアを、それらの脚部の先端面同士が衝合するように配置し、各U型コアの両脚部にそれぞれコイルを巻装する構造が好ましい。全てのコイルを共通の電源に接続し、コイルに流れる電流の向きを正逆2方向に切り替えることにより、ファラデー回転方向を正逆2方向に切り替えることができる。電源としては、可変電圧源あるいは可変電流源を使用し、各コイルは並列もしくは直列に接続する。   For example, a structure in which two U-shaped cores are arranged so that the end surfaces of their leg portions abut each other, and a coil is wound around each leg portion of each U-shaped core is preferable. By connecting all the coils to a common power source and switching the direction of the current flowing in the coils between two forward and reverse directions, the Faraday rotation direction can be switched between two forward and reverse directions. As the power source, a variable voltage source or a variable current source is used, and the coils are connected in parallel or in series.

磁界の向きが磁気光学素子に入射される光の光軸と平行の時の磁気光学素子のファラデー回転角をθf0、必要なファラデー回転角をθf としたとき、光軸に対する合成磁界の向きθc を、
θc=cos-1(θf /θf0
となるように設定する。
When the direction of the magnetic field of the Faraday rotation angle theta f0 of the magneto-optical element when the parallel to the optical axis of the light incident on the magneto-optical element, and a Faraday rotation angle required theta f, the direction of the combined magnetic field with respect to the optical axis θ c
θc = cos −1f / θ f0 )
Set to be.

本発明に係るリング型ファラデー回転デバイスは、光スイッチにおけるファラデー回転子として利用できる。本発明では、半硬質磁性材料ではなく、高透磁率磁性材料(軟磁性材料)からなる磁気ヨークを用いているため、小型化、高速化できる。特に、磁気ヨークの片側半分を通る磁束の向きと反対側半分を通る磁束の向きが常に逆となるようにコイル電流を制御しているため、磁界の反発力が利用でき、磁界の向きの切り替えが高速化し、スイッチング速度の速い光スイッチが実現できる。また磁気光学素子は、磁気飽和させた状態で使用するので、制御は容易である。   The ring type Faraday rotation device according to the present invention can be used as a Faraday rotator in an optical switch. In the present invention, since a magnetic yoke made of a high magnetic permeability magnetic material (soft magnetic material) is used instead of a semi-hard magnetic material, the size and speed can be increased. In particular, since the coil current is controlled so that the direction of the magnetic flux passing through one half of the magnetic yoke and the direction of the magnetic flux passing through the opposite half are always opposite, the repulsive force of the magnetic field can be used, and the switching of the magnetic field direction Therefore, an optical switch with a high switching speed can be realized. Further, since the magneto-optical element is used in a magnetically saturated state, the control is easy.

本発明に係るリング型ファラデー回転デバイスは、図1に示すように、実質的にリング型の磁気ヨーク10と、該磁気ヨーク10に巻装した複数のコイル12と、リング型の磁気ヨーク12のほぼ中央に設置した磁気光学素子14とを具備している。磁気ヨーク10は高透磁率磁性材料(軟磁性材料)からなり、ここでは口の字型(四角リング型)の形状である。その磁気ヨーク10の左右の柱状部の上下に間隔を空けて合計4個のコイル12を巻装する。そして、磁気ヨーク10の上側半分を通る磁束の向きと下側半分を通る磁束の向きが常に逆となるようにコイル電流を制御する。それらによる合成磁界が磁気光学素子14を通るように構成する。   As shown in FIG. 1, a ring type Faraday rotation device according to the present invention includes a substantially ring type magnetic yoke 10, a plurality of coils 12 wound around the magnetic yoke 10, and a ring type magnetic yoke 12. And a magneto-optical element 14 installed at substantially the center. The magnetic yoke 10 is made of a high-permeability magnetic material (soft magnetic material), and here has a mouth shape (square ring type). A total of four coils 12 are wound at intervals above and below the left and right columnar portions of the magnetic yoke 10. Then, the coil current is controlled so that the direction of the magnetic flux passing through the upper half of the magnetic yoke 10 and the direction of the magnetic flux passing through the lower half are always opposite. The combined magnetic field is configured to pass through the magneto-optical element 14.

つまり、同じ柱状部に巻装したコイル同士は逆向きの磁界が生じるように通電され、左右の柱状部の磁気光学素子を介して対向する位置関係にあるコイル(上側のコイル同士、あるいは下側のコイル同士)は、一方は上向きに、他方は下向きに磁界が生じるようにする。これによって、両柱状部の中央に磁極が現れ、一方の柱状部の中央から他方の柱状部の中央へ向かう磁界が生じる。この磁界は、磁気ヨークの上側半分による磁界と下側半分による磁界が加わった合成磁界である。この合成磁界が、磁気光学素子に印加されることになる。   That is, the coils wound around the same columnar part are energized so that opposite magnetic fields are generated, and the coils in the positional relationship facing each other via the magneto-optical elements of the left and right columnar parts (upper coils or lower coils) The coils are arranged so that one side is upward and the other side is downward. As a result, a magnetic pole appears at the center of both columnar portions, and a magnetic field is generated from the center of one columnar portion toward the center of the other columnar portion. This magnetic field is a combined magnetic field in which the magnetic field by the upper half of the magnetic yoke and the magnetic field by the lower half are added. This combined magnetic field is applied to the magneto-optical element.

本発明では、図1のBに示すように、合成磁界の向きは、光軸に対して平行でも垂直でもなく、ある角度θc をもつように傾ける。磁界の向きが磁気光学素子10に入射される光の光軸と平行の時の磁気光学素子のファラデー回転角をθf0、必要なファラデー回転角をθf としたとき、光軸に対する合成磁界の向きθc を、
θc =cos-1(θf /θf0
となるように設定する。例えば、θf0が90度の磁気光学素子を使用し、45度のファラデー回転角θf を得ようとする場合、θc を60度に設定すればよい。必要なファラデー回転角θf を得るためには、θf0従って磁気光学素子の長さを調整てもよいし、θc を調整してもよい。
In the present invention, as shown in FIG. 1B, the direction of the combined magnetic field is not parallel or perpendicular to the optical axis, but is inclined to have a certain angle θ c . When the direction of the magnetic field is parallel to the optical axis of the light incident on the magneto-optical element 10, the Faraday rotation angle of the magneto-optical element is θ f0 , and the necessary Faraday rotation angle is θ f . Orientation θ c
θ c = cos −1f / θ f0 )
Set to be. For example, when a magneto-optical element having θ f0 of 90 degrees is used to obtain a Faraday rotation angle θ f of 45 degrees, θ c may be set to 60 degrees. In order to obtain the necessary Faraday rotation angle θ f , the length of the magneto-optical element may be adjusted according to θ f0 , or θ c may be adjusted.

4個のコイルは同時に電流の向きを切り替えることになるため、図2のAに示すように並列に、あるいは図2のBに示すように直列に結線して(コイルをa〜dで示す)、共通の正負電源(双方向に通電可能な電源)20,22に接続する。並列に接続すれば低電圧駆動が可能であるし、直列に接続すれば低電流駆動が可能である。また4個のコイルを2個ずつ直並列に接続してもよいし、並直列に接続してもよい。   Since the directions of the currents of the four coils are switched simultaneously, they are connected in parallel as shown in FIG. 2A or in series as shown in B of FIG. 2 (the coils are indicated by a to d). Are connected to common positive and negative power sources (power sources that can be energized in both directions) 20 and 22. Low voltage drive is possible if connected in parallel, and low current drive is possible if connected in series. Further, two of the four coils may be connected in series or parallel, or may be connected in parallel.

コイルへの通電電流の向きによって、例えば図3のA1に示すように、左側柱状部中央から右側柱状部中央に向かって(図3のA2では左上から右下方向に)合成磁界が生じるようにでき、コイルへの通電電流の向きを反転すると、図3のB1に示すように、右側柱状部中央から左側柱状部中央に向かって(図3のB2では右下から左上方向に)合成磁界が生じるようにできる。A2の状態では、光の入射方向に対して逆方向の磁界成分が磁気光学素子に印加され、B2の状態では、光の入射方向に対して同方向の磁界成分が磁気光学素子に印加される。従って、入射光の偏光面は、磁気光学素子14でコイル電流の向きに応じて丁度同じ角度だけ時計回りあるいは反時計回りに回転することになる。また、磁気光学素子を磁気飽和の状態で使用するため、磁界の制御は容易である。   Depending on the direction of the energization current to the coil, for example, as shown by A1 in FIG. 3, a combined magnetic field is generated from the center of the left columnar portion toward the center of the right columnar portion (from the upper left to the lower right in A2 in FIG. 3). When the direction of the energization current to the coil is reversed, the composite magnetic field is generated from the center of the right columnar portion toward the center of the left columnar portion (in the direction of lower right to upper left in B2 of FIG. 3), as indicated by B1 in FIG. Can occur. In the state A2, a magnetic field component in a direction opposite to the light incident direction is applied to the magneto-optical element, and in a state B2, a magnetic field component in the same direction as the light incident direction is applied to the magneto-optical element. . Therefore, the polarization plane of the incident light is rotated clockwise or counterclockwise by exactly the same angle according to the direction of the coil current in the magneto-optical element 14. Further, since the magneto-optical element is used in a magnetic saturation state, the magnetic field can be easily controlled.

図1に示すような構造のファラデー回転デバイスの製造手順の一例を図4に示す。NiCuZn系フェライト等の高透磁率磁性材料からなるU型コア30を用意する(図4のA参照)。U型コア30は、常法に従い、プレス成形で所望の形状に成形し、焼成することで得られる。勿論、切削などで加工してもよい。このU型コア30の両脚部に、予め作製しておいた空芯コイル32をそれぞれ挿入し、接着剤などで固定する(図4のB参照)。この場合、空芯コイルの線材をエナメル被覆の線材とすれば、脚部に挿入後、エチルアルコール等の有機溶剤を塗布することでエナメルが溶けてコイルを脚部に固着することもできる。   An example of the manufacturing procedure of the Faraday rotation device having the structure as shown in FIG. 1 is shown in FIG. A U-shaped core 30 made of a high permeability magnetic material such as NiCuZn ferrite is prepared (see A in FIG. 4). The U-shaped core 30 can be obtained by molding into a desired shape by press molding and firing according to a conventional method. Of course, you may process by cutting etc. Air core coils 32 prepared in advance are inserted into both legs of the U-shaped core 30 and fixed with an adhesive or the like (see B in FIG. 4). In this case, if the wire of the air-core coil is enameled, the enamel can be melted by applying an organic solvent such as ethyl alcohol after being inserted into the leg, and the coil can be fixed to the leg.

このようなコイル付きU型コアを、2個、それらの脚部の先端面同士が衝合するように組み合わせ、接着剤などで固定する(図4のC参照)。また、非磁性ステージ34にサポート36を介して磁気光学素子38を固定し(図4のC参照)、各脚部の先端部分で囲まれた中央領域に磁気光学素子38が位置するように、前記ステージ34をU型コア30に接着剤などにより固定する(図4のD参照)。その場合、磁気光学素子38とU型コア30が所定の角度関係となるように、サポート36に角度を持たせるなどの対策を施すことが好ましい。磁気光学素子32としては、例えばビスマス置換希土類鉄ガーネット単結晶を用いる。この単結晶は、LPE(液相エピタキシャル)法により育成できる。その他、YIG(イットリウム鉄ガーネット)単結晶等でもよい。   Two such U-shaped cores with coils are combined so that the end surfaces of their leg portions abut each other, and are fixed with an adhesive or the like (see C in FIG. 4). In addition, the magneto-optical element 38 is fixed to the non-magnetic stage 34 via the support 36 (see C in FIG. 4), and the magneto-optical element 38 is positioned in the central region surrounded by the tip portions of the legs. The stage 34 is fixed to the U-shaped core 30 with an adhesive or the like (see D in FIG. 4). In that case, it is preferable to take measures such as providing the support 36 with an angle so that the magneto-optical element 38 and the U-shaped core 30 have a predetermined angular relationship. As the magneto-optical element 32, for example, a bismuth-substituted rare earth iron garnet single crystal is used. This single crystal can be grown by the LPE (liquid phase epitaxial) method. In addition, YIG (yttrium iron garnet) single crystal may be used.

そして、突き合わせた脚部同士に巻装したコイル同士は逆向きの磁界が発生し、同じU型コアの両脚部に巻装したコイルは同じ向きの磁束が生じるように(両脚部の先端に異なる磁極が現れるように)電流を流す。これによって、上側のU型コアと下側のU型コアには逆向きの磁束が生じ、衝合部分に磁極が現れる。従って、一方の衝合部分から他方の衝合部分に向かう合成磁界が生じ、この合成磁界が間に設置されている磁気光学素子に印加される。コイル電流が全て逆向きになると、磁気光学素子に印加される合成磁界の向きは反転する。   The coils wound around the butted legs generate a reverse magnetic field, and the coils wound around both legs of the same U-shaped core generate a magnetic flux in the same direction (different at the tips of the legs. Current is passed so that the magnetic pole appears. As a result, opposite magnetic fluxes are generated in the upper U-shaped core and the lower U-shaped core, and magnetic poles appear at the abutting portions. Accordingly, a combined magnetic field is generated from one abutting portion toward the other abutting portion, and this combined magnetic field is applied to the magneto-optical element disposed therebetween. When all the coil currents are reversed, the direction of the combined magnetic field applied to the magneto-optical element is reversed.

ここで光軸に対する合成磁界の向きθc を、
θc =cos-1(θf /θf0
となるように設定する。但し、
θf0:磁界の向きが磁気光学素子に入射される光の光軸と平行の時の磁気光学素子のファラデー回転角
θf :必要なファラデー回転角
である。例えば、θf0が90度の磁気光学素子を使用し、合成磁界の向きθc を60度に設定すれば、θf が45度のファラデー回転デバイスが得られる。コイルへの通電電流の向きを切り替えることで、透過する光の偏光面を±45度に切り替えることができる。
Here, the direction θ c of the combined magnetic field with respect to the optical axis is
θ c = cos −1f / θ f0 )
Set to be. However,
θ f0 : Faraday rotation angle of the magneto-optical element when the direction of the magnetic field is parallel to the optical axis of the light incident on the magneto-optical element θ f : A necessary Faraday rotation angle. For example, if a magneto-optical element having θ f0 of 90 degrees is used and the direction of the combined magnetic field θ c is set to 60 degrees, a Faraday rotation device having θ f of 45 degrees can be obtained. By switching the direction of the energization current to the coil, the polarization plane of the transmitted light can be switched ± 45 degrees.

光スイッチの構成例を図5に示す。レンズ40と、偏光子42と、上記の構造のファラデー回転デバイス44と、検光子46と、レンズ48を、その順序で光軸に沿って配列する。光ファイバなどからの入射光は、偏光子42を通り、ファラデー回転デバイス44で偏光面が回転し、検光子46に達する。例えば、偏光面が+45度回転した時に検光子46を通過するような組み合わせにすると、偏光面が−45度回転した時は検光子46で遮光される。従って、コイル電流の向きを正逆切り替えることによって、光の透過のオン−オフを制御することができる。   A configuration example of the optical switch is shown in FIG. The lens 40, the polarizer 42, the Faraday rotation device 44 having the above structure, the analyzer 46, and the lens 48 are arranged along the optical axis in that order. Incident light from an optical fiber or the like passes through the polarizer 42, and the polarization plane is rotated by the Faraday rotation device 44 to reach the analyzer 46. For example, when the polarization plane is rotated by +45 degrees, the analyzer 46 is shielded when the polarization plane is rotated by −45 degrees. Therefore, on / off of light transmission can be controlled by switching the direction of the coil current between forward and reverse.

このような測定系について応答特性を測定した結果の一例を図6に示す。図6は、ステップ状の入力電圧に対する応答特性であり、出力光を光電変換して出力電圧として求めたものである。本発明のファラデー回転デバイスによって応答時定数(63%到達に要する時間)16μ秒の高速応答特性能が得られた。なお90%到達に要する時間は33μ秒であった。   An example of the result of measuring the response characteristics for such a measurement system is shown in FIG. FIG. 6 shows response characteristics with respect to a step-like input voltage, which is obtained as an output voltage by photoelectrically converting the output light. With the Faraday rotation device of the present invention, a high-speed response characteristic with a response time constant (time required to reach 63%) of 16 μsec was obtained. The time required to reach 90% was 33 μsec.

なお、本発明において「実質的にリング型の磁気ヨーク」とは、磁路がほぼループ状になっている形状を意味し、必ずしも四角形である必要はない。完全な一体構造であってもよいし、上記実施例のような分割構造であってもよい。磁気ギャップが存在していてもよい。コイルの数や位置は適宜変更してもよい。   In the present invention, “substantially ring-type magnetic yoke” means a shape in which the magnetic path is substantially in a loop shape, and does not necessarily have to be a quadrangle. It may be a completely integrated structure, or may be a divided structure as in the above embodiment. There may be a magnetic gap. The number and position of the coils may be changed as appropriate.

本発明に係るファラデー回転デバイスの説明図。Explanatory drawing of the Faraday rotation device which concerns on this invention. コイル結線の説明図。Explanatory drawing of coil connection. ファラデー回転デバイスの動作説明図。Operation | movement explanatory drawing of a Faraday rotation device. ファラデー回転デバイスの構造説明図。Structure explanatory drawing of a Faraday rotation device. 光スイッチの構成例を示す説明図。Explanatory drawing which shows the structural example of an optical switch. 応答特性を示すグラフ。The graph which shows a response characteristic.

符号の説明Explanation of symbols

10 磁気ヨーク
12 コイル
14 磁気光学素子
10 Magnetic yoke 12 Coil 14 Magneto-optical element

Claims (4)

実質的にリング型の高透磁率磁性材料からなる磁気ヨークと、該磁気ヨークに巻装した複数のコイルと、磁気ヨークのほぼ中央に位置する磁気光学素子とを具備し、磁気ヨークの片側半分を通る磁束の向きと反対側半分を通る磁束の向きが常に逆となるようにコイル電流を制御し、それらの合成磁界が磁気光学素子を通るようにしたことを特徴とするリング型ファラデー回転デバイス。   A magnetic yoke substantially made of a ring-type high-permeability magnetic material, a plurality of coils wound around the magnetic yoke, and a magneto-optical element positioned substantially at the center of the magnetic yoke. Ring type Faraday rotation device characterized in that the coil current is controlled so that the direction of the magnetic flux passing through the opposite half and the direction of the magnetic flux passing through the opposite half are always reversed so that their combined magnetic field passes through the magneto-optical element. . 磁気ヨークは、2個のU型コアを、それらの脚部の先端面同士が衝合するように配置した構造をなし、各U型コアの両脚部にそれぞれコイルが巻装されている請求項1記載のリング型ファラデー回転デバイス。   The magnetic yoke has a structure in which two U-shaped cores are arranged so that tip surfaces of their leg portions abut each other, and a coil is wound around each leg portion of each U-shaped core. The ring-type Faraday rotation device according to 1. 全てのコイルを共通の電源に接続し、コイルに流れる電流の向きを正逆2方向に切り替えることにより、ファラデー回転方向を正逆2方向に切り替える請求項1又は2記載のリング型ファラデー回転デバイス。   The ring type Faraday rotation device according to claim 1 or 2, wherein all the coils are connected to a common power source, and the direction of the current flowing in the coils is switched between two forward and reverse directions, thereby switching the Faraday rotation direction between two forward and reverse directions. 磁界の向きが磁気光学素子に入射される光の光軸と平行の時の磁気光学素子のファラデー回転角をθf0、必要なファラデー回転角をθfとしたとき、光軸に対する合成磁界の向きθcを、
θc =cos-1(θf /θf0
となるように設定する請求項3記載のリング型ファラデー回転デバイス。
When the direction of the magnetic field is parallel to the optical axis of the light incident on the magneto-optical element, when the Faraday rotation angle of the magneto-optical element is θf0 and the necessary Faraday rotation angle is θf, the direction θc of the combined magnetic field with respect to the optical axis is ,
θ c = cos −1f / θ f0 )
The ring-type Faraday rotation device according to claim 3, which is set to be
JP2004056891A 2004-03-01 2004-03-01 Ring type faraday rotation device Pending JP2005249893A (en)

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