JP2985022B2 - Magneto-optical element and optical isolator - Google Patents
Magneto-optical element and optical isolatorInfo
- Publication number
- JP2985022B2 JP2985022B2 JP3081199A JP8119991A JP2985022B2 JP 2985022 B2 JP2985022 B2 JP 2985022B2 JP 3081199 A JP3081199 A JP 3081199A JP 8119991 A JP8119991 A JP 8119991A JP 2985022 B2 JP2985022 B2 JP 2985022B2
- Authority
- JP
- Japan
- Prior art keywords
- plane
- crystal
- extinction
- optical
- magneto
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Crystals, And After-Treatments Of Crystals (AREA)
Description
【0001】[0001]
【産業上の利用分野】本発明は短波長(0.6〜0.8
μm 帯)光アイソレータのファラデー回転子に用いられ
る磁気光学素子及びそれを用いた光アイソレータに関す
る。The present invention relates to a short wavelength (0.6 to 0.8)
The present invention relates to a magneto-optical element used for a Faraday rotator of an optical isolator and an optical isolator using the same.
【0002】[0002]
【従来の技術】短波長(0.6〜0.8μm 帯)半導体
レーザ等を光源として用いる光通信,光計測,光磁気デ
ィスクシステム等において戻り光雑音除去のための光ア
イソレータの使用が提案されている。光アイソレータ
は,ファラデー回転子を偏向子及検光子で軸方向に挟み
込んだ構成を有し,そのファラデー回転子材料として半
磁性半導体Cd1-x Mnx Te(0<x≦1)の使用が
検討されている。2. Description of the Related Art It has been proposed to use an optical isolator for removing return optical noise in optical communication, optical measurement, magneto-optical disk systems and the like using a short wavelength (0.6 to 0.8 .mu.m band) semiconductor laser or the like as a light source. ing. Optical isolator has a structure sandwiching axially Faraday rotator with deflectors及検photons, the use of semi-magnetic semiconductor Cd 1-x Mn x Te ( 0 <x ≦ 1) as a Faraday rotator material Are being considered.
【0003】[0003]
【発明が解決しようとする課題】一般に,Cd1-x Mn
x Te(0<x≦0.7)単結晶は,ブリッジマン法に
より液相から凝固させて作製するが,双晶欠陥が発生す
ることが知られている。この双晶欠陥を持つ結晶をファ
ラデー回転子として用いた場合,充分な消光特性が得ら
れないという問題が生じた。この双晶欠陥の発生はこの
物質の相変態に帰因するとされ,高温相である六方晶か
ら低温相の立方晶に相転移する際に,双晶欠陥が発生す
ると説明されている。最近,Teを溶媒として融点を相
変態温度以下に設定することにより直接立方晶で結晶成
長を行なわせるTHM法(Travelling Heater Method)
が提案され,双晶欠陥のない結晶育成が可能となった。
しかし,現状ではTHM法はブリッジマン法に比べ成長
速度が1/10以下となり,また大型の単結晶が作製す
ることが困難であるとの理由からコスト高で,量産レベ
ルには到っていない状況であった。Generally, Cd 1-x Mn
An xTe (0 <x ≦ 0.7) single crystal is produced by solidification from a liquid phase by the Bridgman method, but it is known that twin defects are generated. When a crystal having such twin defects is used as a Faraday rotator, a problem arises in that sufficient quenching characteristics cannot be obtained. The generation of this twin defect is attributed to the phase transformation of the substance, and it is described that a twin defect is generated at the time of a phase transition from a hexagonal crystal, which is a high-temperature phase, to a cubic crystal, which is a low-temperature phase. Recently, the THM method (Travelling Heater Method), in which the cubic crystal is grown directly by setting the melting point below the phase transformation temperature using Te as a solvent.
Has been proposed, and it has become possible to grow crystals without twin defects.
However, at present, the THM method has a growth rate of 1/10 or less of that of the Bridgman method, and is expensive and has not reached mass production level because it is difficult to produce a large single crystal. It was a situation.
【0004】そこで本発明の技術的課題は,生産性に優
れたブリッジマン法により作製したCd1-x Mnx Te
結晶で実用上充分な消光特性を持つファラデー回転子材
料及びそれを用いた光アイソレータを提供することにあ
る。[0004] Therefore the technical problem of the present invention was made by better Bridgman method in productivity Cd 1-x Mn x Te
It is an object of the present invention to provide a Faraday rotator material that is crystallized and has practically sufficient extinction characteristics, and an optical isolator using the same.
【0005】[0005]
【課題を解決するための手段】Cd1-x Mnx Te結晶
のベルデ定数は光を入射させる結晶面の方位に依存しな
いことから,従来は,任意の面でファラデー回転子を構
成していた。ところが,この結晶に発生する双晶欠陥
は,双晶面が[111]方向に垂直に積み重なった規則
的な構造を有している。本発明者は結晶の消光特性が結
晶方位に依存することを実験的に見い出し,本発明をな
すに至ったものである。Since the Verdet constant of the problem-solving means for the] Cd 1-x Mn x Te crystal does not depend on the orientation of the crystal plane through which light enters, conventionally constituted the Faraday rotator in any plane . However, the twin defects generated in the crystal have a regular structure in which twin planes are stacked perpendicular to the [111] direction. The present inventors have experimentally found that the extinction characteristic of a crystal depends on the crystal orientation, and have accomplished the present invention.
【0006】本発明によれば,ブリッジマン法により育
成した(Cd1-xMnx Te(0.1≦x≦0.7)単
結晶の双晶面に垂直な壁開面である{110}面に垂直
にレーザ光を入射させるように構成したことを特徴とす
る磁気光学素子が得られる。さらに,本発明によれば,
前記磁気光学素子の{110}面内の最大消光方位を消
光軸とし,前記消光軸に対し,偏光子あるいは検光子の
偏光方向を22.5度傾斜させて設定したことを特徴と
する光アイソレータが得られ,双晶欠陥を持つ結晶で実
用上充分な消光特性を確保できるものである。According to the present invention, a vertical wall open surface in twin planes of the grown (Cd 1-x Mn x Te (0.1 ≦ x ≦ 0.7) single crystal by the Bridgman method {110 According to the present invention, there is provided a magneto-optical element characterized in that a laser beam is made to be incident perpendicularly to the} plane.
An optical isolator characterized in that a maximum extinction azimuth in a {110} plane of the magneto-optical element is defined as an extinction axis, and a polarization direction of a polarizer or an analyzer is inclined by 22.5 degrees with respect to the extinction axis. Is obtained, and a quenching characteristic sufficient for practical use can be ensured with a crystal having twin defects.
【0007】[0007]
【実施例】以下に,本発明の実施例について図面を参照
して説明する。図1に示したように直線偏光1を結晶面
2に垂直に入射させ,偏光方位角θを変え,磁場を印加
しない状態で消光比を測定した。消光比I[dB:デシベ
ル]はI=−10loy10 (消光時の透過光の強度/入射
光の強度)で定義される。その結果は図2に示したよう
になる。Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, linear polarization 1 was perpendicularly incident on the crystal plane 2, the polarization azimuth θ was changed, and the extinction ratio was measured without applying a magnetic field. The extinction ratio I [dB: decibel] is defined by I = −10 loy10 (intensity of transmitted light at the time of extinction / intensity of incident light). The result is as shown in FIG.
【0008】図2において,θが90°周期で,消光比
が変動している。変動の大きさは,曲線21で示される
双晶面に垂直や劈開面である{110}面で最も大き
く,この{110}面及び双晶面である{111}面を
除く任意面(曲線23)では変動は最小になるが消光比
のピーク値は小さくなる。消光比が最大になる消光軸は
{111}面(曲線22)及び{110}面内に存在す
る。すなわち本来光学的に等方な結晶に双晶欠陥の影響
で複屈折を生じている。高い消光比を得るには{11
1}又は{110}面の消光軸を使用すればよいが,光
アイソレータのファラデー回転子の場合戻り光の偏光ベ
クトルは45度回転するため,消光軸から±22.5度
の領域を通過させることになる。この点においては結晶
の{111}面を使用するのが最も有利である。しかし
ブリッジマン法による結晶は<110>方向に成長する
ため,育成した結晶インゴットは図3(a)の斜視図及
び(b)の側面図で示すような方位を持つので{11
1}面の加工は{110}面に比べて以下,のよう
な欠点を持つ。尚,図3(a)及び(b)において,
{111}面の切り出しはインゴットを成長面に対して
垂直に行い,{110}面は成長面に平行に輪切りにす
ることを示す。{110}面は壁開面であるため方位
出しの必要がないが{111}面は方位出しが必要であ
る。高濃度(x>0.5)の結晶に有効なエッチング液
は現状では知られておらず方位出しは容易ではない。
図3(b)のように{111}面の切断33は,結晶イ
ンゴットを成長面に対して垂直に切断するため,同じ大
きさのウエハーが切り出せない。また壁開がウエハーに
垂直に起こるので,切断及び研磨工程での破損による歩
留り低下が起こりやすい。一方図(b)の{110}面
の切断34の場合はインゴットを輪切りにするため同じ
径のウエハーが切り出せる。またウエハーの壁開も生じ
ないので切断及び研磨工程での歩留りは高い。従って
{110}面は量産に関しては{111}面よりも有利
であり,{110}面でも実用上充分な消光特性が得ら
れる。In FIG. 2, the extinction ratio fluctuates with a period of θ of 90 °. The magnitude of the fluctuation is largest in the {110} plane which is perpendicular to the twin plane or the cleavage plane shown by the curve 21, and is an arbitrary plane except for the {110} plane and the {111} plane which is the twin plane (curve 21). In 23), the fluctuation is minimized, but the peak value of the extinction ratio is reduced. The extinction axis at which the extinction ratio is maximized exists in the {111} plane (curve 22) and the {110} plane. That is, birefringence is caused in the originally optically isotropic crystal by the influence of twin defects. $ 11 to get high extinction ratio
The extinction axis of the {1} or {110} plane may be used. However, in the case of a Faraday rotator of an optical isolator, the polarization vector of the return light is rotated by 45 degrees, so that the light passes through the area of ± 22.5 degrees from the extinction axis Will be. In this regard, it is most advantageous to use the {111} plane of the crystal. However, since the crystal by the Bridgman method grows in the <110> direction, the grown crystal ingot has the orientation shown in the perspective view of FIG. 3A and the side view of FIG.
The processing of the {1} plane has the following disadvantages compared to the {110} plane. In FIGS. 3A and 3B,
The cutting of the {111} plane indicates that the ingot is to be made perpendicular to the growth plane, and the {110} plane is to be sliced in parallel to the growth plane. Since the {110} plane is an open wall, it is not necessary to determine the orientation. However, the {111} plane requires the orientation. At present, an etching solution effective for a crystal having a high concentration (x> 0.5) is not known, and it is not easy to determine the orientation.
As shown in FIG. 3 (b), the cutting 33 of the {111} plane cuts the crystal ingot perpendicular to the growth plane, so that a wafer of the same size cannot be cut out. Further, since the wall is opened perpendicular to the wafer, the yield is likely to be reduced due to breakage in the cutting and polishing steps. On the other hand, in the case of the cutting of the {110} plane in FIG. 9B, a wafer having the same diameter can be cut out to cut the ingot. Further, since the wall of the wafer is not opened, the yield in the cutting and polishing steps is high. Therefore, the {110} plane is more advantageous than the {111} plane for mass production, and practically sufficient extinction characteristics can be obtained even with the {110} plane.
【0009】次に本発明を実施例による磁気光学素子の
製造の具体例を説明する。ブリッジマン法により組成C
d1-x Mnx Te(x=0.2,0.5)の単結晶を育
成した。これらの結晶は<111>方向に約10μm 間
隔で双晶面の重なった構造を有していた。双晶面に平行
な{111}面,それに垂直な壁開面である{110}
面,及びそれら以外の任意の面でそれぞれ切り出し,光
学研磨後反射防止膜を蒸着し2000ガウスの磁場を印
加し,ファラデー回転角45度を有するファラデー回転
子を構成した。x=0.5のものは波長633nm,x=
0.2のものは780nmのファラデー回転子とした。
{111}面,{110}面のファラデー回転子に対し
て検光子の偏光方向を結晶の消光軸から22.5度,6
7.5度,任意角度傾けて配置し,比較した。22.5
度の場合は45度のファラデー回転を起こす偏向ベクト
ルは主軸から22.5度以内にあり,67.5度の場合
は偏向ベクトルは主軸から22.5度〜45度にあるよ
うに設定した。また,任意面のファラデー回転子に対し
ては検光子の偏光方向を最大の消光比が得られる任意に
配置した。このような構成のファラデー回転子について
消光比を測定した結果を表1及び表2に示した。表1に
おいて,表1は組成x=0.2の結晶を用いた場合の波
長780nmでの消光比を示し,表2は組成x=0.5の
結晶を用いた場合の波長633nmでの消光比を示す。表
1及び表2で示すように,{110}面で検光子の偏光
方向を消光軸から22.5度傾けたファラデー回転子の
場合,消光比は実用上必要なレベル40dBを満足してい
る。Next, a specific example of manufacturing a magneto-optical element according to an embodiment of the present invention will be described. Composition C by Bridgman method
and growing a single crystal of d 1-x Mn x Te ( x = 0.2,0.5). These crystals had a structure in which twin planes overlapped at about 10 μm intervals in the <111> direction. {111} plane parallel to the twin plane and {110} which is a wall open plane perpendicular to the {111} plane
A Faraday rotator having a Faraday rotation angle of 45 degrees was formed by cutting out a surface and an arbitrary surface other than the above, applying an antireflection film after optical polishing and applying a magnetic field of 2000 Gauss. When x = 0.5, the wavelength is 633 nm, x =
The one with 0.2 was a 780 nm Faraday rotator.
With respect to the Faraday rotators of the {111} plane and the {110} plane, the polarization direction of the analyzer is set at 22.5 degrees from the extinction axis of the crystal, and 6 degrees.
Arranged at an arbitrary angle of 7.5 degrees for comparison. 22.5
In the case of degrees, the deflection vector causing a 45 degree Faraday rotation is set within 22.5 degrees from the main axis, and in the case of 67.5 degrees, the deflection vector is set so as to be between 22.5 degrees and 45 degrees from the main axis. Further, for the Faraday rotator on an arbitrary surface, the polarization direction of the analyzer is arbitrarily arranged so as to obtain the maximum extinction ratio. Tables 1 and 2 show the results of measuring the extinction ratio of the Faraday rotator having such a configuration. In Table 1, Table 1 shows the extinction ratio at a wavelength of 780 nm when using a crystal having a composition x = 0.2, and Table 2 shows the extinction at a wavelength 633 nm when using a crystal having a composition x = 0.5. Shows the ratio. As shown in Tables 1 and 2, in the case of a Faraday rotator in which the polarization direction of the analyzer is tilted by 22.5 degrees from the extinction axis on the {110} plane, the extinction ratio satisfies a practically necessary level of 40 dB. .
【0010】[0010]
【表1】 [Table 1]
【0011】[0011]
【表2】 [Table 2]
【0012】[0012]
【発明の効果】以上述べたごとく本発明によれば,良好
な消光特性を有する光アイソレータ用ファラデー回転子
材料及びそれを用いた光アイソレータを低コストで提供
することができる。As described above, according to the present invention, a Faraday rotator material for an optical isolator having good extinction characteristics and an optical isolator using the same can be provided at low cost.
【図1】本発明の実施例に係る磁気光学素子の消光比の
測定方法を示している。FIG. 1 shows a method for measuring an extinction ratio of a magneto-optical element according to an embodiment of the present invention.
【図2】本発明の実施例に係る磁気光学素子の偏光方位
依存性を示す図である。FIG. 2 is a diagram showing the polarization azimuth dependence of a magneto-optical element according to an example of the present invention.
【図3】(a)はブリッジマン法により育成した結晶イ
ンゴットの方位を示す斜視図である。 (b)は(a)の結晶インゴットの側面図で,切断方向
を示している。FIG. 3A is a perspective view showing the orientation of a crystal ingot grown by the Bridgman method. (B) is a side view of the crystal ingot of (a), showing a cutting direction.
1 入射光 2 光学面 3 偏光方向 4 出射光 10 Cd1-X MnX Te 21 {110}面の曲線 22 {111}面の曲線 23 任意面の曲線1 the incident light 2 optical surface 3 the polarization direction 4 the emitted light 10 Cd 1-X Mn curve of X Te 21 {110} plane curve 23 any surface curve 22 {111} plane of the
フロントページの続き (58)調査した分野(Int.Cl.6,DB名) G02F 1/09 - 1/095 C30B 29/52 G02B 27/28 CA(STN) JICSTファイル(JOIS)Continuation of the front page (58) Field surveyed (Int. Cl. 6 , DB name) G02F 1/09-1/095 C30B 29/52 G02B 27/28 CA (STN) JICST file (JOIS)
Claims (2)
して用いられるブリッジマン法で作製したカドミウム・
マンガン・テルルCd1-x Mnx Te(0.1≦x≦
0.7)単結晶からなる磁気光学素子であって,前記単
結晶は前記入射光に対する入射面が{110}面である
ことを特徴とする磁気光学素子。Cadmium produced by the Bridgman method used for incident light in a wavelength band of 0.6 to 0.8 μm.
Manganese telluride Cd 1-x Mn x Te ( 0.1 ≦ x ≦
0.7) A magneto-optical element made of a single crystal, wherein the single crystal has a {110} plane as an incident surface for the incident light.
内の最大消光方位を消光軸とし,前記消光軸に対し,偏
光子あるいは検光子の偏光方向を22.5度傾斜させて
設定したことを特徴とする光アイソレータ。2. The extinction axis is defined as the maximum extinction azimuth in the {110} plane of the magneto-optical element according to claim 1, and the polarization direction of a polarizer or an analyzer is inclined by 22.5 degrees with respect to the extinction axis. An optical isolator characterized by:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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JP3081199A JP2985022B2 (en) | 1991-03-22 | 1991-03-22 | Magneto-optical element and optical isolator |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3081199A JP2985022B2 (en) | 1991-03-22 | 1991-03-22 | Magneto-optical element and optical isolator |
Publications (2)
Publication Number | Publication Date |
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JPH04294320A JPH04294320A (en) | 1992-10-19 |
JP2985022B2 true JP2985022B2 (en) | 1999-11-29 |
Family
ID=13739806
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JP3081199A Expired - Fee Related JP2985022B2 (en) | 1991-03-22 | 1991-03-22 | Magneto-optical element and optical isolator |
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JP (1) | JP2985022B2 (en) |
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-
1991
- 1991-03-22 JP JP3081199A patent/JP2985022B2/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
日本応用磁気学会誌 Vol.12 No.2 pp.187−192(1988) |
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JPH04294320A (en) | 1992-10-19 |
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