JP4428387B2 - Paramagnetic garnet single crystal and magneto-optical device for magneto-optical devices - Google Patents

Paramagnetic garnet single crystal and magneto-optical device for magneto-optical devices Download PDF

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JP4428387B2
JP4428387B2 JP2006531288A JP2006531288A JP4428387B2 JP 4428387 B2 JP4428387 B2 JP 4428387B2 JP 2006531288 A JP2006531288 A JP 2006531288A JP 2006531288 A JP2006531288 A JP 2006531288A JP 4428387 B2 JP4428387 B2 JP 4428387B2
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幹生 下方
雄徳 関島
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Murata Manufacturing Co Ltd
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Description

本発明は、例えば光アイソレータなどの磁気光学デバイスを構成するのに用いられる磁気光学デバイス用単結晶に関し、より詳細には、テルビウム・アルミニウム系の磁気光学デバイス用常磁性ガーネット単結晶及び該常磁性ガーネット単結晶を用いた磁気光学デバイスに関する。   The present invention relates to a single crystal for a magneto-optical device used to constitute a magneto-optical device such as an optical isolator, and more particularly, to a paramagnetic garnet single crystal for a terbium-aluminum-based magneto-optical device and the paramagnetic The present invention relates to a magneto-optical device using a garnet single crystal.

近年、光通信技術の進展に伴い、光と磁気との相互作用を利用した磁気光学デバイスが注目されている。中でも、光アイソレータは、例えば光源から発した光が途中の光学系で反射されて光源に戻る現象を防止することを可能とするため注目されている。光アイソレータは、上記のような作用を有するため、例えば光源としてのレーザーと光学部品との間に配置されている。   2. Description of the Related Art In recent years, with the progress of optical communication technology, a magneto-optical device using an interaction between light and magnetism has attracted attention. Among them, the optical isolator is attracting attention because it can prevent, for example, a phenomenon in which light emitted from a light source is reflected by an intermediate optical system and returns to the light source. Since the optical isolator has the above operation, it is disposed, for example, between a laser as a light source and an optical component.

光アイソレータは、ファラデー回転子と、ファラデー回転子の光入射側に配置された偏光子と、ファラデー回転子の光出射側に配置された検光子とを有する。光アイソレータは、ファラデー回転子に光の進行方向に平行に磁界を加えた状態で、光がファラデー回転子に入射されると、ファラデー回転子の中で偏光面が回転するという性質、すなわちファラデー効果を利用している。より具体的には、入射光の内、偏光子と同じ偏光面を持つ光が偏光子を通過して、ファラデー回転子に進入する。この光は、ファラデー回転子の中で光の進行方向に対して、例えば＋４５度回転され、出射される。   The optical isolator includes a Faraday rotator, a polarizer disposed on the light incident side of the Faraday rotator, and an analyzer disposed on the light emitting side of the Faraday rotator. The optical isolator has the property that when the light is incident on the Faraday rotator with a magnetic field applied to the Faraday rotator in parallel to the light traveling direction, the polarization plane rotates in the Faraday rotator, that is, the Faraday effect. Is used. More specifically, light having the same polarization plane as the polarizer in the incident light passes through the polarizer and enters the Faraday rotator. This light is rotated by, for example, +45 degrees with respect to the traveling direction of the light in the Faraday rotator and emitted.

これに対して、入射方向と逆方向からファラデー回転子に入射する、いわゆる戻り光は、先ず検光子を通過する。ここでは、検光子と同じ偏光面を持つ成分の光のみが検光子を通過し、ファラデー回転子に入射することなる。そして、ファラデー回転子の中で、戻り光の偏光面は、さらに＋４５度回転されるため、偏光子と＋９０度、すなわち直角の偏光面を有する光となる。従って、戻り光が偏光子を通過することはない。   On the other hand, so-called return light incident on the Faraday rotator from the direction opposite to the incident direction first passes through the analyzer. Here, only light having a component having the same polarization plane as the analyzer passes through the analyzer and enters the Faraday rotator. In the Faraday rotator, the polarization plane of the return light is further rotated by +45 degrees, so that the light has a polarization plane of +90 degrees, that is, a right angle with the polarizer. Therefore, the return light does not pass through the polarizer.

上記のような光アイソレータの、ファラデー回転子として用いられる材料では、ファラデー効果が大きく、かつ光透過率が高いことが求められる。このような材料の一例としてのテルビウム・アルミニウム系常磁性ガーネット単結晶の製造方法が下記の特許文献１に開示されている。   A material used as a Faraday rotator of the optical isolator as described above is required to have a large Faraday effect and a high light transmittance. A method for producing a terbium-aluminum-based paramagnetic garnet single crystal as an example of such a material is disclosed in Patent Document 1 below.

特許文献１に記載の製造方法では、先ず原料棒と種結晶とを用意する。次に、レーザー光を照射して、原料棒と種結晶とを溶融接合する。しかる後、溶融接合部分から原料棒側へレーザー光照射領域を移動させる。このような製造方法により、テルビウム・アルミニウム系常磁性ガーネット単結晶（以下、ＴＡＧ単結晶と略す）を得ることができるとされている。   In the manufacturing method described in Patent Document 1, first, a raw material rod and a seed crystal are prepared. Next, a laser beam is irradiated to melt and bond the raw material rod and the seed crystal. Thereafter, the laser beam irradiation region is moved from the melt-bonded portion to the raw material rod side. It is said that a terbium-aluminum paramagnetic garnet single crystal (hereinafter abbreviated as TAG single crystal) can be obtained by such a manufacturing method.

また、下記の特許文献２には、ファラデー回転子用ガーネット結晶体として、組成式（Ｔｂ1-(a+b+c+d)ＬｎaＢｉbＭ1 cＥｕd）3（Ｆｅ1-eＭ2 e）5Ｏ12で表わされるガーネット結晶体を用いた光アイソレータが開示されている。なお、上記式においてＬｎは、ＴｂとＥｕとを除く希土類元素及びＹから選択される元素であり、Ｍ1は、Ｃａ、Ｍｇ、Ｓｒから選択される元素であり、Ｍ2はＡｌ、Ｇａ、Ｓｃ、Ｉｎ、Ｔｉ、Ｓｉ、Ｇｅから選択される元素である。また、ａは０〜０．５、ｂは０．３〜０．６、ｃは０〜０．０２、ｄは０〜０．３、ｅは０．０１〜０．３の範囲の数字とされている。Patent Document 2 below, for the Faraday rotator garnet crystal, composition formula (Tb 1- (a + b + c + d) Ln a Bi b M 1 c Eu d) 3 (Fe 1-e An optical isolator using a garnet crystal represented by M 2 e ) 5 O 12 is disclosed. In the above formula, Ln is an element selected from rare earth elements and Y excluding Tb and Eu, M 1 is an element selected from Ca, Mg, and Sr, and M 2 is Al, Ga, It is an element selected from Sc, In, Ti, Si, and Ge. A is 0 to 0.5, b is 0.3 to 0.6, c is 0 to 0.02, d is 0 to 0.3, and e is a number in the range of 0.01 to 0.3. Has been.

特許文献２に記載の光アイソレータでは、上記のように、Ｆｅを必須成分とするＹＩＧ系強磁性ガーネット単結晶を用いることにより、消光比の温度依存性や光挿入損失を低減することができるとされている。
特開２００４−１３１３６９号公報 特開２００１−１０８９５２号公報 In the optical isolator described in Patent Document 2, as described above, it is possible to reduce the temperature dependence of the extinction ratio and the optical insertion loss by using a YIG ferromagnetic garnet single crystal containing Fe as an essential component. Has been.
JP 2004-131369 A JP 2001-108952 A

特許文献１に記載の製造方法により得られたＴＡＧ単結晶は、常磁性体の単位長さ及び単位磁界当たりのファラデー回転角の大きさを示すヴェルデ定数が他の常磁性材料に比べて非常に大きいという利点を有する。しかしながら、この製造方法により得られたＴＡＧ単結晶では、直線偏光がファラデー回転子を通過する際の楕円化の指標である消光比が２２ｄＢ程度と小さかった。従って、光アイソレータなどの光デバイスに上記ＴＡＧ単結晶を用いた場合、光アイソレータ全体の消光比、すなわちアイソレーションを高めることができなかった。   The TAG single crystal obtained by the manufacturing method described in Patent Document 1 has a Verde constant indicating the unit length of the paramagnetic material and the Faraday rotation angle per unit magnetic field much higher than that of other paramagnetic materials. Has the advantage of being large. However, in the TAG single crystal obtained by this manufacturing method, the extinction ratio, which is an index of ovalization when linearly polarized light passes through the Faraday rotator, was as small as about 22 dB. Therefore, when the TAG single crystal is used for an optical device such as an optical isolator, the extinction ratio, that is, the isolation of the entire optical isolator cannot be increased.

また、特許文献１に記載の製造方法では、レーザー光を照射し、原料棒を溶融させて結晶を育成するに際し、融帯に空気等の気体が混入してボイドが生じたり、クラックが生じたりすることがあった。そのため、ＴＡＧ単結晶の歩留りが悪く、工業的に十分な品質のＴＡＧ単結晶を安定に提供することが困難であった。   Further, in the manufacturing method described in Patent Document 1, when a crystal is grown by irradiating a laser beam and melting a raw material rod, a gas such as air is mixed into the melt zone, and a void is generated or a crack is generated. There was something to do. Therefore, the yield of TAG single crystals is poor, and it has been difficult to stably provide TAG single crystals of industrially sufficient quality.

他方、特許文献２に記載のＦｅを必須成分とするＹＩＧ系強磁性ガーネット単結晶では、４００〜８００ｎｍ程度の可視光領域における透過率が実質的にゼロであるため、可視光領域において磁気光学デバイスとして使用することはできなかった。   On the other hand, in the YIG type ferromagnetic garnet single crystal having Fe as an essential component described in Patent Document 2, the transmittance in the visible light region of about 400 to 800 nm is substantially zero. Could not be used as.

本発明は、上述した従来技術の現状に鑑み、特に可視光領域において消光比が高く、従って消光比に優れた磁気光学デバイスを提供することを可能とし、かつ製造に際しての歩留りを高め得る磁気光学デバイス用常磁性ガーネット単結晶、並びに該磁気光学デバイス用常磁性ガーネット単結晶を用いた磁気光学デバイスを提供することにある。
本発明は、Ｔｂ3Ａｌ5Ｏ12にＭｇが添加された構造を有する常磁性ガーネット単結晶であって、Ｔｂ3Ａｌ5Ｏ12１００重量部に対し、ＭｇをＭｇＯに換算して０．００１〜０．０１５重量部の範囲で含むことを特徴とする。The present invention is a magneto-optical device that can provide a magneto-optical device that has a high extinction ratio in the visible light region, and thus has an excellent extinction ratio, and can increase the yield in manufacturing, in view of the above-described state of the prior art. The object is to provide a paramagnetic garnet single crystal for devices and a magneto-optical device using the paramagnetic garnet single crystal for magneto-optical devices.
The present invention relates to a paramagnetic garnet single crystal having a Tb 3 Al 5 O 12 Mg is added to the structure, with respect to Tb 3 Al 5 O 12 100 parts by weight, in terms of Mg to MgO 0.001 It is characterized by containing in the range of ~ 0.015 part by weight.

なお、本発明はＴｂ3Ａｌ5Ｏ12としているが、ＴｂとＡｌとを主成分として含み、かつ常磁性ガーネット構造を有するものであればよい。すなわち、Ｔｂ，Ａｌ及びＯの割合は、ガーネット構造であればモル比で３：５：１２の割合から若干ずれてもよく、Ｔｂ3Ａｌ5Ｏ12に限定されるものではない。また、本発明の常磁性ガーネット単結晶は、Ｆｅを実質的に含まないガーネット単結晶であることを付記しておく。In the present invention, Tb 3 Al 5 O 12 is used, but any material that contains Tb and Al as main components and has a paramagnetic garnet structure may be used. That is, the ratio of Tb, Al, and O may be slightly deviated from the ratio of 3: 5: 12 in terms of molar ratio as long as it is a garnet structure, and is not limited to Tb 3 Al 5 O 12 . It should be noted that the paramagnetic garnet single crystal of the present invention is a garnet single crystal substantially free of Fe.

本発明の磁気光学デバイスは、第１または第２の発明に係る磁気光学デバイス用常磁性ガーネット単結晶を用いて構成されていることを特徴とする。   A magneto-optical device according to the present invention is characterized by using a paramagnetic garnet single crystal for a magneto-optical device according to the first or second invention.

本発明に係る磁気光学デバイスのある特定の局面では、上記磁気光学デバイス用常磁性ガーネット単結晶がファラデー回転子として用いられており、該ファラデー回転子の光路の前方に配置された偏光子と、後方に配置された検光子とをさらに備え、それによって光アイソレータが構成されている。   In a specific aspect of the magneto-optical device according to the present invention, the paramagnetic garnet single crystal for the magneto-optical device is used as a Faraday rotator, a polarizer disposed in front of the optical path of the Faraday rotator, And an analyzer disposed at the rear, thereby forming an optical isolator.

本発明に係る磁気光学デバイス用常磁性ガーネット単結晶は、Ｔｂ3Ａｌ5Ｏ12にＭｇが添加された構造を有する常磁性ガーネット単結晶であって、Ｔｂ3Ａｌ5Ｏ12１００重量部に対し、ＭｇをＭｇＯに換算して０．００１〜０．０１５重量部の割合で含むことを特徴とする。The present invention paramagnetic garnet single crystal for a magnetic-optical device according to the is a paramagnetic garnet single crystal having a Tb 3 Al 5 O 12 Mg is added to the structure, Tb 3 Al 5 O 12 100 parts by weight of , Mg is converted to MgO and contained in a proportion of 0.001 to 0.015 parts by weight.

本発明に係る磁気光学デバイス用常磁性ガーネット単結晶は、Ｍｇが、上記特定の割合で含有されていることを特徴とする、テルビウム・アルミニウム系常磁性ガーネット単結晶である。そして、本発明に係る磁気光学デバイス用常磁性ガーネット単結晶では、上記テルビウムサイトまたはアルミニウムサイトにＭｇが上記特定の割合で含有されているため、後述の実験例から明らかなように、フローティングゾーン法により上記単結晶を育成した際に、クラックが生じ難く、従って生産性を高めることができる。加えて、得られた単結晶では、透過損失が少なく、かつ可視光領域において大きな消光比を得ることができる。   The paramagnetic garnet single crystal for a magneto-optical device according to the present invention is a terbium-aluminum-based paramagnetic garnet single crystal characterized in that Mg is contained in the specific ratio. And, in the paramagnetic garnet single crystal for a magneto-optical device according to the present invention, Mg is contained in the terbium site or aluminum site in the above-mentioned specific proportion, so that as will be apparent from the experimental examples described later, the floating zone method Thus, when the single crystal is grown, cracks hardly occur, and thus productivity can be improved. In addition, the obtained single crystal has a small transmission loss and a large extinction ratio in the visible light region.

なお、ＭｇをＭｇＯに換算して０．００１〜０．０１５重量部の割合で含有させるには、単結晶の育成に際し、Ｍｇを添加することにより行われる。この場合、Ｔｂ3Ａｌ5Ｏ12を１００重量部に対し、ＭｇをＭｇＯに換算して０．０１〜０．１５重量部の割合で添加すれば、得られた単結晶においてＭｇの含有割合がＭｇＯに換算して０．００１〜０．０１５重量部の割合となる。すなわち、単結晶の育成に際し、添加されたＭｇの全てが得られた単結晶中に含有されるわけではない。従って、後述の実験例では、出発原料における添加量と、得られた単結晶におけるＭｇの含有割合は異なっている。
上記のように、Ｍｇの添加により、単結晶の育成に際してのクラックの発生率が低くなり、かつ消光比が十分な大きさとされ得る理由は明らかではないが、以下のように考えられる。In addition, in order to make Mg contain in the ratio of 0.001-0.015 weight part converted into MgO, it is performed by adding Mg in the case of the growth of a single crystal. In this case, if Mg is converted into MgO at a ratio of 0.01 to 0.15 parts by weight with respect to 100 parts by weight of Tb 3 Al 5 O 12 , the content ratio of Mg in the obtained single crystal is It becomes a ratio of 0.001 to 0.015 parts by weight in terms of MgO. That is, when the single crystal is grown, not all of the added Mg is contained in the obtained single crystal. Therefore, in the experimental examples described later, the amount added in the starting material is different from the Mg content in the obtained single crystal.
As described above, the reason why the addition of Mg reduces the occurrence rate of cracks during single crystal growth and the extinction ratio can be made sufficiently large is not clear, but is considered as follows.

すなわち、単結晶育成時の溶融帯がＭｇの添加割合を上記特定の割合とすることにより、粘性が適度に制御されて、対流が生じ、温度勾配が急峻な場合であっても、育成結晶に歪みが生じ難いためと考えられる。そのため、育成時または育成後に、クラックが生じ難く、それによって歩留りも高められていると考えられる。   That is, when the melting zone during single crystal growth is the Mg addition ratio specified above, the viscosity is appropriately controlled, convection occurs, and even if the temperature gradient is steep, This is probably because distortion is difficult to occur. For this reason, it is considered that cracks hardly occur at the time of or after the growth, and that the yield is also increased.

本発明に係る磁気光学デバイスは、本発明に従って得られ、上記のように十分な消光比を有する磁気光学デバイス用常磁性ガーネット単結晶を用いて構成されているため、消光比に優れた磁気光学デバイスを提供することができる。特に、上記磁気光学デバイス用常磁性ガーネット単結晶がファラデー回転子として用いられており、該ファラデー回転子の前後に偏光子及び検光子が配置されており、光アイソレータが構成されている場合には、本発明に従って可視光領域において十分な大きさの消光比を有する光アイソレータを安価に提供することが可能となる。   The magneto-optical device according to the present invention is obtained using the paramagnetic garnet single crystal for a magneto-optical device obtained according to the present invention and having a sufficient extinction ratio as described above. A device can be provided. In particular, when the paramagnetic garnet single crystal for the magneto-optical device is used as a Faraday rotator, a polarizer and an analyzer are arranged before and after the Faraday rotator, and an optical isolator is configured. According to the present invention, an optical isolator having a sufficiently large extinction ratio in the visible light region can be provided at low cost.

図１は、本発明の磁気光学デバイス用常磁性ガーネット単結晶を育成する装置の要部を示す斜視図である。FIG. 1 is a perspective view showing a main part of an apparatus for growing a paramagnetic garnet single crystal for a magneto-optical device according to the present invention. 図２は、本発明の磁気光学デバイス用常磁性ガーネット単結晶を得るための装置の略図的平面図である。FIG. 2 is a schematic plan view of an apparatus for obtaining a paramagnetic garnet single crystal for a magneto-optical device according to the present invention. 図３は、本発明の磁気光学デバイス用常磁性ガーネット単結晶を製造する装置の要部を説明するための略図的平面図である。FIG. 3 is a schematic plan view for explaining the main part of the apparatus for producing a paramagnetic garnet single crystal for a magneto-optical device according to the present invention. 図４は、実験例１で得られた実施例の磁気光学デバイス用常磁性ガーネット単結晶の結晶性を示す図である。FIG. 4 is a diagram showing the crystallinity of the paramagnetic garnet single crystal for the magneto-optical device of Example obtained in Experimental Example 1. 図５は、実験例２で作製された光アイソレータの模式的平面断面図である。FIG. 5 is a schematic plan sectional view of the optical isolator manufactured in Experimental Example 2. 図６は、図５に示した光アイソレータの図５のｘ４−ｘ４線に沿う断面図である。6 is a cross-sectional view of the optical isolator shown in FIG. 5 taken along line x4-x4 in FIG. 図７は、本発明が適用される光アイソレータの変形例の要部を示す模式的平面断面図である。FIG. 7 is a schematic plan sectional view showing the main part of a modification of the optical isolator to which the present invention is applied. 図８は、図７のｘ１−ｘ１線に沿う断面図である。FIG. 8 is a cross-sectional view taken along line x1-x1 of FIG. 図９は、本発明が適用される光アイソレータの他の変形例の要部を示す模式的平面断面図である。FIG. 9 is a schematic plan sectional view showing the main part of another modification of the optical isolator to which the present invention is applied. 図１０は、図７のｘ２−ｘ２線に沿う断面図である。10 is a cross-sectional view taken along line x2-x2 of FIG. 図１１は、本発明が適用される光アイソレータのさらに他の変形例の要部を示す模式的平面断面図である。FIG. 11 is a schematic plan sectional view showing a main part of still another modification of the optical isolator to which the present invention is applied. 図１２は、図７のｘ３−ｘ３線に沿う断面図である。12 is a cross-sectional view taken along line x3-x3 in FIG.

符号の説明Explanation of symbols

１…レーザーＦＺ装置
２…シャフト
２ａ…上シャフト
２ｂ…下シャフト
４ａ…レンズ
５…レーザー発振器
６…ミラー
７ａ〜７ｄ…ハロゲンランプ
３１…光アイソレータ
３２…ファラデー回転子
３３…第１の磁石
３３ａ…貫通孔
３４…第２の磁石
３４ａ…貫通孔
３６…偏光子
３７…検光子
４１…光アイソレータ
４３…第１の磁石
４３ａ…貫通孔
４４…第２磁石
４４ａ…貫通孔
４５…軟磁性体層
４６…軟磁性体層
５１…光アイソレータ
５３…第１の磁石
５３ａ…貫通孔
５４…第２の磁石
５４ａ…貫通孔
５５，５６…軟磁性体層
６１…光アイソレータ
６３…第１の磁石
６３ａ…第１の磁石の貫通孔
６３ｂ，６３ｃ…磁石半体
６４…第２の磁石
６４ａ…第２の磁石の貫通孔
６４ｂ，６４ｃ…磁石半体
６５…軟磁性体層
６６…軟磁性体層
Ｐ…光軸DESCRIPTION OF SYMBOLS 1 ... Laser FZ apparatus 2 ... Shaft 2a ... Upper shaft 2b ... Lower shaft 4a ... Lens 5 ... Laser oscillator 6 ... Mirror 7a-7d ... Halogen lamp 31 ... Optical isolator 32 ... Faraday rotator 33 ... 1st magnet 33a ... Through Hole 34 ... second magnet 34a ... through hole 36 ... polarizer 37 ... analyzer 41 ... optical isolator 43 ... first magnet 43a ... through hole 44 ... second magnet 44a ... through hole 45 ... soft magnetic layer 46 ... Soft magnetic layer 51 ... Optical isolator 53 ... First magnet 53a ... Through hole 54 ... Second magnet 54a ... Through hole 55, 56 ... Soft magnetic layer 61 ... Optical isolator 63 ... First magnet 63a ... First Through-holes 63b, 63c of the second magnet 64 ... second magnet 64a ... through-holes 64b, 64c of the second magnet 65 ... soft magnetic layer 66 ... Soft magnetic layer P ... Optical axis

以下、図面を参照しつつ、本発明の具体的な実施形態を及び実施例を挙げることにより本発明に明らかにする。   Hereinafter, specific embodiments of the present invention and examples will be described with reference to the drawings.

（実験例１）
まず、出発原料として、純度９９．９重量％のＴｂ4Ｏ7、純度９９．９重量％のＡｌ2Ｏ3と、純度９９．９重量％のＭｇＯ及び純度９９．９重量％のＣａＣＯ3とを用意し、ＴｂとＡｌとが、モル比で３：５となるように、かつＭｇがＭｇＯに換算し、ＣａをＣａＣＯ3に換算して下記の表１に示す割合となるように、これらを秤量し、表１の試料番号１〜８の原料組成物を用意した。なお、下記の表１におけるＭｇ添加量（重量部）、及びＣａ含有量（重量部）は、それぞれ、Ｔｂ3Ａｌ5Ｏ12を１００重量部としたときに、該１００重量部に対するＭｇやＣａのＭｇＯまたはＣａＯに換算した重量割合を示す。また、後述の結晶中Ｍｇ量、すなわち結晶中のＭｇ含有量についても、Ｔｂ3Ａｌ5Ｏ12を１００重量部とした際の、ＭｇのＭｇＯに換算した重量割合である。(Experimental example 1)
First, as starting materials, Tb 4 O 7 having a purity of 99.9 wt%, Al 2 O 3 having a purity of 99.9 wt%, MgO having a purity of 99.9 wt%, and CaCO 3 having a purity of 99.9 wt% These are prepared so that the molar ratio of Tb and Al is 3: 5, Mg is converted to MgO, Ca is converted to CaCO 3 and the ratio shown in Table 1 below is obtained. The raw material compositions of sample numbers 1 to 8 in Table 1 were prepared. In addition, Mg addition amount (parts by weight) and Ca content (parts by weight) in Table 1 below are respectively Mg and Ca with respect to 100 parts by weight when Tb 3 Al 5 O 12 is 100 parts by weight. The weight ratio in terms of MgO or CaO is shown. Further, the amount of Mg in the crystal, which will be described later, that is, the Mg content in the crystal, is also a weight ratio converted to MgO of Mg when Tb 3 Al 5 O 12 is 100 parts by weight.

次に、上記原料組成物に、純水を加え、玉石とともに約２４時間湿式混合し、混合された粉末を、脱水し、乾燥した。乾燥された混合粉末を目開き５００μｍの粗さのメッシュに通し、粒度を調整し、しかる後、電気炉を用いて１２００℃の温度で２時間仮焼した。   Next, pure water was added to the raw material composition and wet mixed with cobblestone for about 24 hours, and the mixed powder was dehydrated and dried. The dried mixed powder was passed through a mesh having a mesh size of 500 μm to adjust the particle size, and then calcined at a temperature of 1200 ° C. for 2 hours using an electric furnace.

得られた仮焼粉末を粉砕した後、有機バインダ及び溶剤を加え、玉石とともに数時間湿式混合した。このようにして、スラリー状の混合物を得た。得られた混合物を生成機を用い、円柱状に成形した。得られた円柱状成形体を、１６００℃で２時間焼成し、直径１ｍｍ×長さ４０ｍｍの円柱状のＴＡＧ多結晶体を得た。得られたＴＡＧ多結晶体の密度は８０％であった。なお、この密度はアルキメデス法により求めた値である。   After the obtained calcined powder was pulverized, an organic binder and a solvent were added, and wet-mixed with cobblestone for several hours. In this way, a slurry-like mixture was obtained. The obtained mixture was formed into a cylindrical shape using a generator. The obtained cylindrical shaped body was fired at 1600 ° C. for 2 hours to obtain a cylindrical TAG polycrystal having a diameter of 1 mm × length of 40 mm. The density of the obtained TAG polycrystal was 80%. This density is a value obtained by the Archimedes method.

次に、上記のようにして得られた試料番号１〜８の各ＴＡＧ多結晶体を用い、以下の要領で単結晶を製造した。   Next, single crystals were produced in the following manner using the TAG polycrystals of sample numbers 1 to 8 obtained as described above.

本実験例では、図１〜図３に示すレーザーＦＺ（Ｆｌｏａｔｉｎｇ Ｚｏｎｅ）装置を用いた。図１に示すように、レーザーＦＺ装置１は、上シャフト２ａと、上シャフト２ａの下端から下方に隔てられて配置された下シャフト２ｂとを有する。上シャフト２ａ及び下シャフト２ｂは、石英製チャンバー３内で上下方向に移動可能とされている。チャンバー３は、上シャフト２ａの下端と下シャフト２ｂの上端との間の結晶を育成するための融帯Ｘの雰囲気調整を可能とするために設けられている。また、チャンバー３は放熱板をも兼ねている。   In this experimental example, a laser FZ (Floating Zone) apparatus shown in FIGS. 1 to 3 was used. As shown in FIG. 1, the laser FZ apparatus 1 includes an upper shaft 2 a and a lower shaft 2 b that is arranged to be spaced downward from the lower end of the upper shaft 2 a. The upper shaft 2 a and the lower shaft 2 b are movable in the vertical direction within the quartz chamber 3. The chamber 3 is provided to enable adjustment of the atmosphere of the bandage X for growing crystals between the lower end of the upper shaft 2a and the upper end of the lower shaft 2b. The chamber 3 also serves as a heat sink.

他方、図１に示すように、チャンバー３の対向する側面には、それぞれ窓が設けられている。この各窓部に、レンズ４ａ，４ｂが取り付けられている。図３に略図的正面図で示すように、レンズ４ａ，４ｂには、レーザー発振器５から照射されたレーザー光がミラー６を介して導かれるように構成されている。すなわち、レーザー光は、レンズ４ａ，４ｂを通り、融帯Ｘに照射される。   On the other hand, as shown in FIG. 1, windows are provided on opposite side surfaces of the chamber 3. Lenses 4a and 4b are attached to the windows. As shown in a schematic front view in FIG. 3, the laser light emitted from the laser oscillator 5 is guided to the lenses 4 a and 4 b through the mirror 6. That is, the laser beam passes through the lenses 4a and 4b and is irradiated to the bandage X.

なお、図１及び図３では、レンズ４ａ，４ｂを示したが、図２に略図的平面図で示すように、実際には、レンズ４ａ，４ｂに加えて、レンズ４ｃ，４ｄも配置されている。すなわち、融帯の側方の４方向からレーザー光が照射されるように構成した。   Although FIGS. 1 and 3 show the lenses 4a and 4b, as shown in a schematic plan view in FIG. 2, the lenses 4c and 4d are actually arranged in addition to the lenses 4a and 4b. Yes. That is, the laser beam was irradiated from four directions on the side of the band.

他方、図２に示すように、上記チャンバー３の周囲には、他の熱源として、４個のハロゲンランプ７ａ〜７ｄも配置し、ハロゲンランプによる過熱と、上記レーザー光の照射による加熱を併用した。   On the other hand, as shown in FIG. 2, four halogen lamps 7a to 7d are also arranged around the chamber 3 as other heat sources, and both overheating by the halogen lamp and heating by the laser light irradiation are used in combination. .

より具体的には、上記上シャフト２ａの下端に治具を用いて上記のようにして作製された円柱状のＴＡＧ結晶体８を垂下させた。他方、下シャフト２ｂの上端に、ＴＡＧ単結晶からなる種結晶９を配置した。   More specifically, the columnar TAG crystal 8 produced as described above was suspended from the lower end of the upper shaft 2a using a jig. On the other hand, a seed crystal 9 made of a TAG single crystal was disposed at the upper end of the lower shaft 2b.

次に、チャンバー３内の雰囲気を大気中雰囲気とし、レーザー発振器５及びハロゲンランプ７ａ〜７ｄにより加熱した。この場合、レーザー発振器５によるレーザー光を、上シャフト２ａの下端に配置されたＴＡＧ多結晶体８の下端を溶融させ、溶融させた部分に、下シャフト２ｂの上端に配置された種結晶９の端部を接合させた。   Next, the atmosphere in the chamber 3 was changed to an air atmosphere, and the chamber 3 was heated by the laser oscillator 5 and the halogen lamps 7a to 7d. In this case, the laser light from the laser oscillator 5 is melted at the lower end of the TAG polycrystal body 8 disposed at the lower end of the upper shaft 2a, and the seed crystal 9 disposed at the upper end of the lower shaft 2b is melted at the melted portion. The ends were joined.

続けて、ＴＡＧ多結晶体８と種結晶９との溶融接合部に、レーザー光を照射し、融帯Ｘを形成した。なお、レーザー発振器５から上記ＴＡＧ多結晶体８及び種結晶９が保持されている部分までの距離は約５ｃｍとした。   Subsequently, the fusion bonded portion between the TAG polycrystal 8 and the seed crystal 9 was irradiated with a laser beam to form a melt zone X. The distance from the laser oscillator 5 to the portion where the TAG polycrystal 8 and the seed crystal 9 are held was about 5 cm.

また、上記レーザー発振器５としては、波長が１０．６μｍのレーザービームが出射可能な炭酸ガスレーザー発振器を用い、出力は９０〜１００Ｗとした。続いて、直径２．７ｍｍ及び長さ４０ｍｍの単結晶が得られるように、窒素雰囲気中において、シャフト２ａ，２ｂを軸方向に３ｍｍ／時間以下の速度で下方に移動させた。これによって、レーザー光の照射領域は、溶融接合部から上記ＴＡＧ多結晶体８側に移動していき、融帯Ｘの内、種結晶９側に位置する融液が冷却され、固化された。すなわち、固化部分が徐々に上方に延び、単結晶を製造することができた。   As the laser oscillator 5, a carbon dioxide laser oscillator capable of emitting a laser beam having a wavelength of 10.6 μm was used, and the output was set to 90 to 100 W. Subsequently, the shafts 2a and 2b were moved downward in the axial direction at a speed of 3 mm / hour or less in a nitrogen atmosphere so that a single crystal having a diameter of 2.7 mm and a length of 40 mm was obtained. As a result, the laser light irradiation region moved from the melt-bonded portion toward the TAG polycrystal 8 and the melt located on the seed crystal 9 side in the melt zone X was cooled and solidified. That is, the solidified portion gradually extended upward, and a single crystal could be manufactured.

上記要領で、試料番号１〜８のＴＡＧ多結晶体を用い、それぞれ複数回単結晶の製造を行った。そして、得られた単結晶を長さ６ｍｍに切断し両端面を研磨し、評価サンプルを得た。得られた単結晶を塩酸にて溶解した後、ＩＣＰ−ＡＥＳ（誘導結合プラズマ発光分光分析）法にて結晶中のＭｇ量を定量分析した。その結果、原料棒で添加されていたＭｇの内の約０．１０の量が結晶中に含有されていることが判明した。   In the above manner, single crystals were produced a plurality of times using TAG polycrystals of sample numbers 1 to 8, respectively. And the obtained single crystal was cut | disconnected to length 6mm, both end surfaces were grind | polished, and the evaluation sample was obtained. After the obtained single crystal was dissolved in hydrochloric acid, the amount of Mg in the crystal was quantitatively analyzed by ICP-AES (inductively coupled plasma emission spectroscopy) method. As a result, it was found that about 0.10 of Mg added by the raw material rod was contained in the crystal.

上記単結晶製造に際してのクラック発生率を下記の表１に示す。クラックの発生率については、試料番号１〜８の各ＴＡＧ多結晶体を用いてそれぞれ４回結晶を育成した。そして、４回の育成において、クラックが発生した回数の割合を求め、クラック発生率とした。なお、クラックの発生の有無については、得られた育成結晶を横断面方向に切断し、切断面を研磨し、目視によりクラックの有無を観察した。   Table 1 below shows the crack generation rate during the production of the single crystal. About the incidence rate of a crack, the crystal was grown 4 times, respectively using each TAG polycrystal of sample numbers 1-8. And the ratio of the frequency | count that the crack generate | occur | produced in 4 times of cultivation was calculated | required, and it was set as the crack generation rate. In addition, about the presence or absence of generation | occurrence | production of a crack, the obtained grown crystal was cut | disconnected in the cross-sectional direction, the cut surface was grind | polished, and the presence or absence of the crack was observed visually.

また、上記のようにして得た評価サンプルとしての光学評価として、透過損失及び消光比を以下の要領で測定した。   Moreover, as an optical evaluation as an evaluation sample obtained as described above, a transmission loss and an extinction ratio were measured as follows.

光学特性評価装置（Ｎｅｏａｒｋｓ社製、品番：ＢＨ−Ｍ８００ＳＦ）にて、評価サンプルとしての単結晶の光透過率を測定した。次に、得られた評価サンプルとしての単結晶の入射面及び出射面の外側に、それぞれ、偏光子及び検光子を配置した。偏光子及び検光子としては、メレスグリオ社製方解石からなるグラントムソン偏光子（消光比は５０ｄＢ）を用いた。そして、６３３ｎｍの波長のレーザー光を上記偏光子側から照射し、偏光子において直線偏光とした後、評価サンプルとしての単結晶に入射させ、検光子の偏光面を入射光に対して０°、９０°、１８０°及び２７０°と回転させることにより、それぞれ検光子から出射された光を測定した。単結晶評価サンプルが配置されておらず、光を単に透過させた場合の透過光強度をＩ0、検光子方位で本来消光するはずの消光位置における
光の強度をＩ02、単結晶評価サンプルを配置し、サンプルに光を透過させて、検光子を回転させたときの透過光強度の最大値をＩ1、最小値をＩ2とし、以下の式により透過損失及び消光比を求めた。The optical transmittance of a single crystal as an evaluation sample was measured with an optical property evaluation apparatus (manufactured by Neoarks, product number: BH-M800SF). Next, a polarizer and an analyzer were arranged on the outside of the entrance surface and exit surface of the single crystal as the obtained evaluation sample, respectively. As the polarizer and analyzer, a Glan-Thompson polarizer (extinction ratio: 50 dB) made of calcite manufactured by Melles Griot was used. Then, after irradiating a laser beam having a wavelength of 633 nm from the above-mentioned polarizer side and making it linearly polarized light in the polarizer, it is incident on a single crystal as an evaluation sample, and the polarization plane of the analyzer is 0 ° with respect to the incident light. The light emitted from the analyzer was measured by rotating at 90 °, 180 °, and 270 °, respectively. No single crystal evaluation sample is placed, the transmitted light intensity when light is simply transmitted is I 0 , the light intensity at the extinction position that should originally be extinguished in the analyzer orientation is I 02 , and the single crystal evaluation sample is arrangement, and sample by transmitting light, a maximum value of the transmitted light intensity when the analyzer is rotated I 1, the minimum value and I 2, was determined transmission loss and the extinction ratio by the following equation.

透過損失＝１０×ｌｏｇ〔Ｉ0／Ｉ1〕
消光比＝１０×ｌｏｇ〔Ｉ0／（Ｉ2−Ｉ02）〕
なお、下記の表１における試料番号８は、ＴｂとＡｌとをモル比で３：５となるように、Ｔｂ酸化物粉末及びＡｌ酸化物粉末を秤量し、さらにＴｂ3Ａｌ5Ｏ12１００重量部に対し、ＣａがＣａＯに換算して０．０５重量部含有されるようにＣａＯ粉末を混合してなる出発原料を用いることを除いては、試料番号１〜７と同様にして得られた多結晶体を用いた例である。Transmission loss = 10 × log [I 0 / I 1 ]
Extinction ratio = 10 × log [I 0 / (I 2 −I 02 )]
In Sample No. 8 in Table 1 below, Tb oxide powder and Al oxide powder were weighed so that the molar ratio of Tb and Al was 3: 5, and Tb 3 Al 5 O 12 100 wt. It was obtained in the same manner as Sample Nos. 1 to 7 except that a starting material obtained by mixing CaO powder so that Ca was contained in an amount of 0.05 parts by weight in terms of CaO with respect to parts was used. This is an example using a polycrystal.

また、代表的な例として、表１に示す試料番号４のＴＡＧ多結晶体から得られた評価サンプル単結晶の結晶性を評価した。この結晶性の評価に際しては、得られた単結晶の断面を研磨加工し、Ｐｈｉｌｉｐｓ社製、Ｘ’ｐｒｔを用い、４結晶ロッキングカーブ法により反射強度の測定を行った。結果を図４に示す。図４から明らかなように、試料番号４で得られた評価サンプル単結晶では、結晶性が高く、ＴＡＧ単結晶の（４４４）反射の半値幅は、１７／ａｒｃ秒であった。比較のために、試料番号１で得られた評価サンプルについても同様にして結晶性を評価したところ、（４４４）反射の半値幅は２７／ａｒｃ秒であった。従ってＭｇの含有により、得られる単結晶の結晶性が効果的に高められることがわかる。   As a representative example, the crystallinity of an evaluation sample single crystal obtained from the TAG polycrystal of sample number 4 shown in Table 1 was evaluated. In the evaluation of the crystallinity, the cross section of the obtained single crystal was polished, and the reflection intensity was measured by a four-crystal rocking curve method using Philips' X'prt. The results are shown in FIG. As is clear from FIG. 4, the evaluation sample single crystal obtained with the sample number 4 has high crystallinity, and the half-width of (444) reflection of the TAG single crystal was 17 / arc seconds. For comparison, the crystallinity of the evaluation sample obtained with the sample number 1 was also evaluated in the same manner. As a result, the half width of (444) reflection was 27 / arc seconds. Therefore, it can be seen that the inclusion of Mg effectively enhances the crystallinity of the resulting single crystal.

Figure 0004428387
Figure 0004428387

表１から明らかなように、試料番号１，２では、Ｍｇの添加割合が０．００５重量部以下であるため、すなわちＭｇの含有割合が０．０００５重量部以下であるため、Ｍｇの添加による効果が十分でなく、従ってクラック発生率が７５％及び３３．３％と高かった。また、消光比についても、試料番号１，２では１８ｄＢと低かった。   As is clear from Table 1, in Sample Nos. 1 and 2, since the Mg addition ratio is 0.005 parts by weight or less, that is, the Mg content is 0.0005 parts by weight or less, The effect was not sufficient, and therefore the crack generation rate was as high as 75% and 33.3%. Further, the extinction ratio was as low as 18 dB in the sample numbers 1 and 2.

他方、Ｍｇの添加割合がＭｇＯに換算して０．５重量部である、すなわちＭｇの含有割合がＭｇＯに換算して０．０５重量部である試料番号７の多結晶体を用いた場合には、育成結晶の一部がＴｂＡｌＯ3相となり、Ｔｂ3Ａｌ5Ｏ3相と、ＴｂＡｌＯ3相との間にクラックが生じた。そして、クラックが生じた部分を避けて得られた評価用サンプルにおける光学特性評価においても、透過損失は０．９ｄＢと高く、消光比は２６ｄＢと低かった。On the other hand, when the polycrystalline body of sample number 7 in which the addition ratio of Mg is 0.5 parts by weight in terms of MgO, that is, the content ratio of Mg is 0.05 parts by weight in terms of MgO is used. is part of the growing crystal becomes TbAlO 3 phases, cracking occurred and Tb 3 Al 5 O 3 phase, between the TbAlO 3 phase. Also in the optical characteristic evaluation in the evaluation sample obtained by avoiding the cracked portion, the transmission loss was as high as 0.9 dB and the extinction ratio was as low as 26 dB.

これに対して、試料番号３〜６では、ＭｇがＭｇＯに換算して０．０１〜０．１５重量部の割合で添加されているため、すなわち、ＭｇがＭｇＯに換算して単結晶中に０．００１〜０．０１５重量部の割合で含有されているため、消光比が３２ｄＢ以上と比較的に高められていることがわかる。また、クラックの発生も皆無であり、従って歩留りを効果的に高め得ることがわかる。   On the other hand, in Sample Nos. 3 to 6, Mg is added at a ratio of 0.01 to 0.15 parts by weight in terms of MgO, that is, Mg is converted to MgO in the single crystal. Since it is contained at a ratio of 0.001 to 0.015 parts by weight, it can be seen that the extinction ratio is relatively increased to 32 dB or more. In addition, it can be seen that there is no occurrence of cracks, and therefore the yield can be effectively increased.

これは、Ｍｇの添加割合がＭｇＯに換算して０．０１重量部以下では、すなわち、Ｍｇの結晶中の含有割合がＭｇＯに換算して０．００１重量部以下では、単結晶育成時に、融帯の粘性が高く、得られた育成結晶に歪みが生じているためと考えられる。また、Ｍｇの添加量がＭｇＯに換算して０．５重量部よりも多い場合には、Ｔｂの価数がＴｂ4+からＴｂ3+に変化し易くなり、ＴｂＡｌＯ3などの異相が生じるためと考えられる。This is because, when the Mg addition ratio is 0.01 parts by weight or less in terms of MgO, that is, when the Mg content in the crystal is 0.001 parts by weight or less in terms of MgO, melting occurs during single crystal growth. This is probably because the band has a high viscosity, and the resulting grown crystal is distorted. Further, when the amount of Mg added is more than 0.5 parts by weight in terms of MgO, the valence of Tb tends to change from Tb 4+ to Tb 3+ , and a different phase such as TbAlO 3 is generated. it is conceivable that.

また、試料番号８では、Ｍｇに代えて、Ｃａを０．０５重量部の割合で添加したが、クラックの発生は防止することができたものの、得られた単結晶の消光比は１８ｄＢと低く、透過損失が１．２と高いことがわかった。従って、メカニズムは不明であるが、同じ２価の金属であるＣａを添加しても、Ｍｇを添加した場合のような効果は得られないことがわかる。すなわち、表１の結果から明らかなように、Ｍｇを上記特定の割合で添加すれば、クラックの発生を抑制しつつ、可視光領域における消光比を効果的に高め得るという、予測され得ない効果の得られることがわかる。   In Sample No. 8, Ca was added in a proportion of 0.05 parts by weight instead of Mg. Although the occurrence of cracks could be prevented, the extinction ratio of the obtained single crystal was as low as 18 dB. The transmission loss was found to be as high as 1.2. Therefore, although the mechanism is unknown, it can be seen that even when Ca, which is the same divalent metal, is added, the effect as in the case of adding Mg cannot be obtained. That is, as is apparent from the results in Table 1, if Mg is added at the above specific ratio, an unexpected effect that the extinction ratio in the visible light region can be effectively increased while suppressing the occurrence of cracks. It can be seen that

なお、上記実験例では、種結晶９としてＴＡＧ単結晶を用いたが、種結晶は、ＴＡＧ多結晶体であってもよい。   In the above experimental example, a TAG single crystal is used as the seed crystal 9, but the seed crystal may be a TAG polycrystal.

さらに、Ｍｇは、原料棒であるＴＡＧ多結晶中にＭｇＯを添加させておくことにより添加されていたが、他の方法で添加されてもよい。例えば、原料棒であるＴＡＧ多結晶にＭｇを含む液体を塗布したり、Ｍｇを含む溶液中に原料棒であるＴＡＧ多結晶を浸漬することにより添加されてもよい。   Further, Mg has been added by adding MgO to the TAG polycrystal as a raw material rod, but it may be added by other methods. For example, it may be added by applying a liquid containing Mg to a TAG polycrystal as a raw material rod, or immersing the TAG polycrystal as a raw material rod in a solution containing Mg.

また、ＭｇＯ粉末を用いて原料中に添加する方法に限らず、ＭｇＣＯ3やＭｇＣｌ2、Ｍｇアルコキシドなどの他のＭｇ化合物を用いてもよい。In addition, the MgO powder is not limited to the method of adding to the raw material, and other Mg compounds such as MgCO 3 , MgCl 2 , and Mg alkoxide may be used.

本発明においては、原料として用いられる多結晶においてＭｇがＴＡＧに添加されていることが必要であるが、ＴＡＧ自体の組成は、Ｔｂ3Ａｌ5Ｏ12に限らず、Ｔｂ及びＡｌの一部が希土類元素により置換されていてもよい。希土類元素としては、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍなどを挙げることができ、特に限定されない。このように、Ｔｂ及び／またはＡｌの一部が希土類元素で置換されていたとしても、Ｍｇを上記特定の割合で添加することにより、ＴｂＡｌＯ3からなる異相の形成を抑制することができ、かつ消光比を効果的に高めることができる。また、原料に多結晶体を用いる場合、多結晶の製造過程で、原料や粉砕時に用いる玉石や容器、焼結用のサヤ等からＺｒ、Ｃａ、Ｓｉ、Ｂｉ、Ｈｆ等が若干混入することがある。In the present invention, it is necessary that Mg is added to the TAG in the polycrystal used as a raw material, but the composition of the TAG itself is not limited to Tb 3 Al 5 O 12 , and a part of Tb and Al is included. It may be substituted with a rare earth element. Examples of rare earth elements include Dy, Ho, Er, Tm, and the like, and are not particularly limited. Thus, even if a part of Tb and / or Al is substituted with a rare earth element, the addition of Mg at the specific ratio can suppress the formation of a heterogeneous phase composed of TbAlO 3 , and The extinction ratio can be effectively increased. In addition, when a polycrystalline material is used as a raw material, Zr, Ca, Si, Bi, Hf, etc. may be mixed slightly from the raw material, cobblestones and containers used during pulverization, a sheath for sintering, and the like. is there.

（実験例２）
次に、本発明に係る磁気光学デバイス用ガーネット単結晶を用いた光アイソレータについての実験例を説明する。本実験例では、図５及び図６に示す本発明の磁気光学デバイスの一実施形態としての光アイソレータ３１を作製した。(Experimental example 2)
Next, an experimental example of an optical isolator using a garnet single crystal for a magneto-optical device according to the present invention will be described. In this experimental example, an optical isolator 31 as one embodiment of the magneto-optical device of the present invention shown in FIGS. 5 and 6 was produced.

光アイソレータ３１では、図５に示す矢印Ｐ方向に光が入射される。ここでは、光路に実験例１で得た単結晶からなるファラデー回転子３２が配置されている。ファラデー回転子３２の直径は２７ｍｍ、長さは４０ｍｍとした。   In the optical isolator 31, light enters in the direction of arrow P shown in FIG. Here, the Faraday rotator 32 made of a single crystal obtained in Experimental Example 1 is disposed in the optical path. The Faraday rotator 32 had a diameter of 27 mm and a length of 40 mm.

他方、ファラデー回転子３２の一端は、第１の磁石３３に、他端は第２の磁石３４内に挿入されている。すなわち、第１の磁石３３は、図６に示すように、光軸Ｐと直交する方向の断面が正六角形であり、中央に貫通孔３３ａを有する。この断面六角形であり、貫通孔３３ａを有する形状は、具体的には、厚みの薄い略三角柱形状のネオジウム鉄ホウ素磁石を６個を接着剤等で接合することにより構成されている。   On the other hand, one end of the Faraday rotator 32 is inserted into the first magnet 33 and the other end is inserted into the second magnet 34. That is, as shown in FIG. 6, the first magnet 33 has a regular hexagonal cross section in the direction orthogonal to the optical axis P, and has a through hole 33a in the center. The shape having the hexagonal cross section and having the through-hole 33a is specifically configured by joining six neodymium iron boron magnets having a thin and substantially triangular prism shape with an adhesive or the like.

同様に、第２の磁石３４も、略三角柱形状の６個のネオジウム鉄ホウ素磁石を接合することにより構成されており、第２の磁石３４も、第１の磁石３３と同様に中央に直径３ｍｍの貫通孔３４ａを有する。ファラデー回転子３２は、上記貫通孔３３ａに一端が、他端が３４ａに、それぞれ１ｍｍの深さで挿入されて固定されている。   Similarly, the second magnet 34 is configured by joining six neodymium iron boron magnets having a substantially triangular prism shape, and the second magnet 34 has a diameter of 3 mm at the center in the same manner as the first magnet 33. Through-hole 34a. The Faraday rotator 32 is inserted and fixed at a depth of 1 mm into the through hole 33a and one end to the other end 34a.

上記正六角形の寸法は一辺が１０．４ｍｍとされており、第１の磁石３３の光軸Ｐの方向に沿う寸法は５．５ｍｍとされている。第２の磁石３４についても第１の磁石３３と同じ寸法とされている。   The dimension of the regular hexagon is 10.4 mm on one side, and the dimension along the direction of the optical axis P of the first magnet 33 is 5.5 mm. The second magnet 34 has the same dimensions as the first magnet 33.

他方、第１の磁石３３により印加される磁界の方向は、図５に示す通りであり、すなわち第１の磁石３３では、磁界の方向は外周側から貫通孔３３ａ側に向かう方向である。逆に、第２の磁石３４においては、磁界の方向は貫通孔３４ａから放射状に外側に延びる方向となる。そして、第１の磁石３３，第２の磁石３４の外周面に軟磁性体層３８を設けることで、略三角形柱形状の６個のネオジウム鉄ホウ素磁石を接合し、かつ、第１の磁石３３、第２の磁石３４及びファラデー回転子３２を一体化した。なお、軟磁性体材料としては、Ｎｉ−Ｆｅ合金（比透過磁率３０００）を用いた。図５に示す矢印Ｍは、磁界の方向を示す。   On the other hand, the direction of the magnetic field applied by the first magnet 33 is as shown in FIG. 5, that is, in the first magnet 33, the direction of the magnetic field is the direction from the outer peripheral side toward the through hole 33a. Conversely, in the second magnet 34, the direction of the magnetic field is a direction extending radially outward from the through hole 34a. Then, by providing the soft magnetic layer 38 on the outer peripheral surfaces of the first magnet 33 and the second magnet 34, six neodymium iron boron magnets having a substantially triangular prism shape are joined, and the first magnet 33. The second magnet 34 and the Faraday rotator 32 are integrated. As the soft magnetic material, a Ni-Fe alloy (specific permeability 3000) was used. An arrow M shown in FIG. 5 indicates the direction of the magnetic field.

光アイソレータ３１では、上記ファラデー回転子３２の光入射側に偏光子３６が、出射側に検光子３７が配置されている。偏光子３６及び検光子３７としては、厚みが１０ｍｍの立方晶方解石からなるものを用いた。この偏光子３６及び検光子３７の消光比は５０ｄＢであった。   In the optical isolator 31, a polarizer 36 is disposed on the light incident side of the Faraday rotator 32, and an analyzer 37 is disposed on the exit side. As the polarizer 36 and the analyzer 37, those made of cubic calcite having a thickness of 10 mm were used. The extinction ratio of the polarizer 36 and the analyzer 37 was 50 dB.

上記のようにして構成された光アイソレータ３１に半導体レーザー発振器を用いて６３３ｎｍの波長のレーザー光を入射し、透過損失及びアイソレーションを測定した。透過損失及びアイソレーションの測定は、評価サンプルとしての単結晶に入射させ、検光子の偏光面を入射光に対して４５°、１３５°、２２５°、３１５°と回転させた以外は、実験例１における単結晶の透過損失及び消光比と同様にして測定した。なお、アイソレーションは消光比と同様にして提示される値であり、ファラデー回転子３２、偏光子３６及び検光子３７を含む光アイソレータ全体としての消光比をアイソレーションとした。
結果を下記の表２に示す。Laser light having a wavelength of 633 nm was incident on the optical isolator 31 configured as described above using a semiconductor laser oscillator, and transmission loss and isolation were measured. The measurement of transmission loss and isolation is an experimental example except that it is made incident on a single crystal as an evaluation sample and the plane of polarization of the analyzer is rotated at 45 °, 135 °, 225 °, and 315 ° with respect to the incident light. 1 was measured in the same manner as the transmission loss and extinction ratio of the single crystal. The isolation is a value presented in the same manner as the extinction ratio, and the extinction ratio of the entire optical isolator including the Faraday rotator 32, the polarizer 36, and the analyzer 37 is defined as isolation.
The results are shown in Table 2 below.

Figure 0004428387
Figure 0004428387

表２から明らかなように、実験例１から得られた試料番号３〜６の評価サンプルを用いた場合、実験例１の場合と同様に透過損失が低く、かつ消光比が高いため、アイソレーションが３０ｄＢ以上と高い光アイソレータを提供することができた。   As is clear from Table 2, when the evaluation samples of sample numbers 3 to 6 obtained from Experimental Example 1 are used, the transmission loss is low and the extinction ratio is high as in Experimental Example 1, so that isolation is achieved. Was able to provide an optical isolator having a high value of 30 dB or more.

これに対して、試料番号１，２や試料番号７の評価サンプルから得られたファラデー回転子を用いた場合には、光アイソレータのアイソレーションは２４ｄＢ以下と低かった。   On the other hand, when the Faraday rotator obtained from the evaluation samples of sample numbers 1 and 2 and sample number 7 was used, the isolation of the optical isolator was as low as 24 dB or less.

従って、実験例２からも明らかなように、実験例１で得た本発明の範囲に入る単結晶を用いて光アイソレータを構成すれば、アイソレーション特性、すなわち消光比に優れた光アイソレータを提供し得ることがわかる。   Therefore, as is clear from Experimental Example 2, if an optical isolator is formed using the single crystal that falls within the scope of the present invention obtained in Experimental Example 1, an optical isolator having an excellent isolation characteristic, that is, an extinction ratio is provided. You can see that

なお、図５及び図６は、本発明が適用される磁気光学デバイスの一例としての光アイソレータを説明したが、本発明の磁気光学用デバイスは、図５及び図６に示した構造を有するものに限定されない。   5 and 6 illustrate the optical isolator as an example of the magneto-optical device to which the present invention is applied. However, the magneto-optical device of the present invention has the structure shown in FIGS. It is not limited to.

本発明が適用される磁気光学デバイスの変形例を、図７〜図１２を参照して説明する。   A modification of the magneto-optical device to which the present invention is applied will be described with reference to FIGS.

図７及び図８は、本発明が適用される光アイソレータの要部を示す平面図及びｘ１−ｘ１線に沿う断面図である。本変形例の光アイソレータ４１は、図５及び図６に示した第１，第２の磁石３３，３４に代えて、円柱状の第１，第２の磁石４３，４４を用いたこと、並びに第１，第２の磁石の貫通孔の内周面及び第１，第２の磁石の外周面に軟磁性体物層４５，４６が設けられていることを除いては、同様に構成されている。   7 and 8 are a plan view and a cross-sectional view taken along line x1-x1 showing the main part of the optical isolator to which the present invention is applied. The optical isolator 41 of this modification uses cylindrical first and second magnets 43 and 44 instead of the first and second magnets 33 and 34 shown in FIGS. The structure is the same except that the soft magnetic material layers 45 and 46 are provided on the inner peripheral surfaces of the through holes of the first and second magnets and the outer peripheral surfaces of the first and second magnets. Yes.

すなわち、第１の磁石４３，４４は、いずれも中央に円形の貫通孔４３ａ，４４ａを有し、該貫通孔４３ａ，４４ａの内周面に軟磁性体層４５が設けられている。他方、円柱状の第１，第２の磁石４３，４４の外周面には、同様にＮｉとＦｅとからなる軟磁性体層４６が設けられている。   That is, the first magnets 43 and 44 both have circular through holes 43a and 44a in the center, and the soft magnetic layer 45 is provided on the inner peripheral surfaces of the through holes 43a and 44a. On the other hand, a soft magnetic layer 46 made of Ni and Fe is similarly provided on the outer peripheral surfaces of the columnar first and second magnets 43 and 44.

また、図７及び図８では、図示を省略しているが、図５に示した光アイソレータ３１を同様に、上記光軸Ｐに沿って、第１の磁石３３の前段には偏光子が、第２の磁石４４の後段には検光子が配置される。   Although not shown in FIGS. 7 and 8, similarly to the optical isolator 31 shown in FIG. 5, a polarizer is disposed in front of the first magnet 33 along the optical axis P. An analyzer is disposed downstream of the second magnet 44.

光アイソレータ４１のように、第１，第２の磁石は一体の円柱状の形状とされていてもよい。また、上記のように、貫通孔の内周面及び第１，第２の磁石の外周面に軟磁性体層４５，４６を設けてもよい。   Like the optical isolator 41, the first and second magnets may be formed into an integral cylindrical shape. Further, as described above, the soft magnetic layers 45 and 46 may be provided on the inner peripheral surface of the through hole and the outer peripheral surfaces of the first and second magnets.

また、図５及び図６に示した光アイソレータ１においても、第１，第２の磁石３３，３４の貫通孔３３ａ，３４ａの内周面に、同様に軟磁性体層を設けてもよい。軟磁性体層としてはＮｉ−Ｆｅ合金、Ｆｅ−Ｓｉ合金、Ｆｅ単体などを用いることができる。また、貫通孔は円形だけでなく多角形でもよい。   Also in the optical isolator 1 shown in FIGS. 5 and 6, a soft magnetic layer may be similarly provided on the inner peripheral surfaces of the through holes 33 a and 34 a of the first and second magnets 33 and 34. As the soft magnetic layer, a Ni—Fe alloy, a Fe—Si alloy, a simple substance of Fe, or the like can be used. The through hole may be not only circular but also polygonal.

図９及び図１０は、本発明が適用される光アイソレータの要部のさらに他の変形例を示す平面図及び図９のｘ２−ｘ２線に沿う断面図である。本変形例の光アイソレータ５１では、第１の磁石５３及び第２の磁石５４が、光軸Ｐと直交する方向の断面形状が正方形とされている。このように、第１，第２の磁石５３，５４の光軸Ｐと直交する方向の形状は、六角形や円形に限らず、正方形とされてもよい。   9 and 10 are a plan view showing still another modification of the main part of the optical isolator to which the present invention is applied and a cross-sectional view taken along the line x2-x2 of FIG. In the optical isolator 51 of this modification, the first magnet 53 and the second magnet 54 have a square cross-sectional shape in the direction orthogonal to the optical axis P. Thus, the shape of the first and second magnets 53 and 54 in the direction orthogonal to the optical axis P is not limited to a hexagon or a circle, but may be a square.

さらに、第１，第２の磁石５３，５４は、それぞれ、略三角柱状の４個の永久磁石を接続することにより構成されている。   Further, each of the first and second magnets 53 and 54 is configured by connecting four permanent magnets having a substantially triangular prism shape.

本変形例においても、貫通孔５３ａ，５４ａの内周面及び第１，第２の磁石５３，５４の外周面に軟磁性体層５５，５６が形成されている。   Also in this modification, soft magnetic layers 55 and 56 are formed on the inner peripheral surfaces of the through holes 53a and 54a and the outer peripheral surfaces of the first and second magnets 53 and 54.

図１１及び図１２は、光アイソレータのさらに別の変形例を示す平面断面図及び図１１のｘ３−ｘ３に沿う断面図である。   11 and 12 are a plan sectional view showing still another modified example of the optical isolator and a sectional view taken along x3-x3 in FIG.

本変形例の光アイソレータ６１では、第１の磁石６３は、図１２に示すように、磁石半体６３ｂ，６３ｃを、軟磁性体層６５を介して接合されている。そして、中央に、貫通孔６３ａが設けられており、ファラデー回転子の一端が挿入されている。第２の磁石６４についても、一対の磁石半体を軟磁性体層を介して接合し、中央に貫通孔６４ａを設けた構造を有し、ファラデー回転子３２の他端が挿入されている。そして、第１，第２の磁石６３，６４の一対の外側面に軟磁性体層６６が形成されている。   In the optical isolator 61 of this modification, as shown in FIG. 12, the first magnet 63 is formed by joining magnet halves 63 b and 63 c via a soft magnetic layer 65. A through hole 63a is provided at the center, and one end of the Faraday rotator is inserted. The second magnet 64 also has a structure in which a pair of magnet halves are joined via a soft magnetic layer and a through hole 64a is provided at the center, and the other end of the Faraday rotator 32 is inserted. A soft magnetic layer 66 is formed on the pair of outer surfaces of the first and second magnets 63 and 64.

このように、第１，第２の磁石６３，６４は、複数の永久磁石を軟磁性体層を用いて接合することによりそれぞれ形成されていてもよい。なお、図７〜図１２において、軟磁性体は必ずしも設けなくてもよい。もっとも、図７〜図１２に示した位置（永久磁石の外側面）に軟磁性体を設けることにより、ファラデー回転子に印加される磁場の強さが強くなるため、好ましい。   As described above, the first and second magnets 63 and 64 may be formed by joining a plurality of permanent magnets using the soft magnetic layer. 7 to 12, the soft magnetic material is not necessarily provided. However, it is preferable to provide a soft magnetic material at the position shown in FIGS. 7 to 12 (the outer surface of the permanent magnet) because the strength of the magnetic field applied to the Faraday rotator is increased.

なお、本発明が適用される磁気光学デバイスは、上述してきた光アイソレータに限定されるものではない。すなわち、例えば導波路型光アイソレータにも本発明に係る磁気光学デバイス用常磁性ガーネット単結晶を用いることができる。また、本発明に係る磁気光学デバイス用常磁性ガーネット単結晶の良好なファラデー回転効果及び消光比を利用し得る様々な光学デバイスに本発明を適用することができる。   The magneto-optical device to which the present invention is applied is not limited to the optical isolator described above. That is, for example, the paramagnetic garnet single crystal for a magneto-optical device according to the present invention can be used for a waveguide type optical isolator. Further, the present invention can be applied to various optical devices that can utilize the good Faraday rotation effect and extinction ratio of the paramagnetic garnet single crystal for magneto-optical devices according to the present invention.

Claims (3)

Ｔｂ3Ａｌ5Ｏ12にＭｇが添加された構造を有する常磁性ガーネット単結晶であって、Ｔｂ3Ａｌ5Ｏ12１００重量部に対し、ＭｇをＭｇＯに換算して０．００１〜０．０１５重量部の範囲で含むことを特徴とする、磁気光学デバイス用常磁性ガーネット単結晶。A paramagnetic garnet single crystal having a structure in which Mg is added to Tb 3 Al 5 O 12, and 0.001 to 0.015 in terms of Mg in terms of MgO with respect to 100 parts by weight of Tb 3 Al 5 O 12. A paramagnetic garnet single crystal for a magneto-optical device, characterized in that it is contained in the range of parts by weight. 請求項１に記載の磁気光学デバイス用常磁性ガーネット単結晶を用いて構成されている、磁気光学デバイス。  A magneto-optical device, comprising the paramagnetic garnet single crystal for magneto-optical devices according to claim 1. 前記磁気光学デバイス用常磁性ガーネット単結晶がファラデー回転子として用いられており、該ファラデー回転子の光路の前方に配置された偏光子と、後方に配置された検光子とをさらに備え、それによって光アイソレータが構成されている、請求項２に記載の磁気光学デバイス。  The paramagnetic garnet single crystal for the magneto-optical device is used as a Faraday rotator, and further comprises a polarizer disposed in front of the optical path of the Faraday rotator, and an analyzer disposed behind. The magneto-optical device according to claim 2, wherein an optical isolator is configured.
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