JP2006098561A

JP2006098561A - Optical isolator

Info

Publication number: JP2006098561A
Application number: JP2004282801A
Authority: JP
Inventors: Yukiko Furukata; 由紀子古堅; Tetsuya Suga; 哲也菅
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2004-09-28
Filing date: 2004-09-28
Publication date: 2006-04-13

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems of an optical isolator, in which an optical element falls off or cracks, joint strength degrades, and optical characteristics deteriorate. <P>SOLUTION: In the optical isolator where magnets and the optical element including a Faraday rotor and polarizers are integrated on the top surface of a flat mounting substrate via an adhesive, level differences for disposing the optical element on part of the top face of the mounting substrate are formed, and the area where the adhesive joins to the optical element on the mounting substrate and the area where the adhesive joins to the magnet on the mounting substrate are separated by the level difference. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、光源から出射された光を各種光学素子や光ファイバに導入した際に生じる戻り光を除去するために用いられる光アイソレータに関するものである。 The present invention relates to an optical isolator used for removing return light generated when light emitted from a light source is introduced into various optical elements and optical fibers.

光通信用モジュール等において、レーザ光源等の光源から出射した光は、各種光学素子や光ファイバに入射されるが、入射光の一部は各種光学素子や光ファイバの端面や内部で反射されたり散乱されたりする。この反射や散乱した光の一部は、戻り光として光源に戻ろうとするが、この戻り光を防止するために光アイソレータが用いられる。 In an optical communication module or the like, light emitted from a light source such as a laser light source is incident on various optical elements or optical fibers, but a part of the incident light is reflected on the end surfaces or inside of the various optical elements or optical fibers. It is scattered. A part of the reflected or scattered light tries to return to the light source as return light, and an optical isolator is used to prevent the return light.

従来、この種の光アイソレータは、２枚の偏光子の間に平板状のファラデー回転子を設置し、これら３つの部品を筒状の磁石内に各部品ホルダを介して収納することにより構成されていた。通常、ファラデー回転子は飽和磁界内において所定の波長をもつ光の偏光面を４５°回転する厚みに調整され、また２つの偏光子はそれぞれの透過偏光方向が４５°回転方向にずれるように回転調整されて構成されている。 Conventionally, this type of optical isolator is configured by installing a flat Faraday rotator between two polarizers, and storing these three components in a cylindrical magnet via respective component holders. It was. Normally, the Faraday rotator is adjusted to a thickness that rotates the polarization plane of light having a predetermined wavelength in the saturation magnetic field by 45 °, and the two polarizers rotate so that their transmission polarization directions are shifted by 45 ° in the rotation direction. Coordinated and configured.

このような構成の光アイソレータは、ファラデー回転子と２つの偏光子が別部品で各素子にホルダが必要であり、そのため部品点数が多くなり組立工数が多くなるばかりか、各部品間の光学上の調整作業が煩雑で、コスト高を招いていた。また、小型化が難しく、さらに、光源モジュールに組み込む際に、光アイソレータの偏波面の調整が必要となり実装が煩雑であった。 The optical isolator having such a configuration requires a Faraday rotator and two polarizers as separate parts and a holder for each element, which increases the number of parts and the number of assembling steps. The adjustment work is complicated and incurs high costs. In addition, it is difficult to reduce the size, and further, it is necessary to adjust the polarization plane of the optical isolator when it is incorporated in the light source module, and the mounting is complicated.

このため、ファラデー回転子と偏光子の各光学素子と、直方体の磁石を、平板状の実装基板に設置した光アイソレータも提案されている。 For this reason, an optical isolator in which optical elements of a Faraday rotator and a polarizer and a cuboid magnet are installed on a flat mounting board has been proposed.

特許文献１には図４に示す従来の小型化された光アイソレータ１５が示されており、以下にその構成について説明する。 Patent Document 1 shows a conventional miniaturized optical isolator 15 shown in FIG. 4, and the configuration thereof will be described below.

光アイソレータ１５はファラデー回転子１６、偏光子１７、１８の各光学素子と、直方体の磁石１９が、平板状の実装基板２０上に配置した構造を有している。ここで偏光子１７、１８は透過する光の一方向の偏波成分を吸収し、その偏波成分に直交する偏波成分を透過する機能を有し、また、ファラデー回転子１６は飽和磁界強度において所定波長の光の偏波面を約４５度回転する機能を有する。また２つの偏光子１７、１８は、それぞれの基板２０に接する面を基準面とし、この基準面に対し透過偏波方向が０度および４５度となるように切り出されている。
特開平１０−２２７９９６号 The optical isolator 15 has a structure in which optical elements of a Faraday rotator 16 and polarizers 17 and 18 and a cuboid magnet 19 are arranged on a flat mounting board 20. Here, the polarizers 17 and 18 have a function of absorbing a polarization component in one direction of transmitted light and transmitting a polarization component orthogonal to the polarization component, and the Faraday rotator 16 has a saturation magnetic field strength. 1 has a function of rotating the polarization plane of light of a predetermined wavelength by about 45 degrees. The two polarizers 17 and 18 are cut out so that the plane contacting the respective substrates 20 is a reference plane, and the transmitted polarization directions are 0 degrees and 45 degrees with respect to the reference plane.
JP-A-10-227996

しかしながら図４の特許文献１に示すように、ファラデー回転子１６、偏光子１７、１８の各光学素子と、直方体の磁石１９が、平板状の実装基板２０上に配置した光アイソレータ１５においては、これら各光学素子２１と平板状の実装基板２０、あるいは磁石１９と平板状の実装基板２０との接合方法の記載がなく、その接合方法によっては光学素子の脱落、クラック接合強度の低下、光学特性の劣化が発生するという問題がある。 However, as shown in Patent Document 1 of FIG. 4, in the optical isolator 15 in which the optical elements of the Faraday rotator 16 and the polarizers 17 and 18 and the rectangular magnet 19 are arranged on a flat mounting board 20, There is no description of the bonding method between each of the optical elements 21 and the flat mounting substrate 20 or between the magnet 19 and the flat mounting substrate 20, and depending on the bonding method, the optical element may drop off, the crack bonding strength may decrease, and the optical characteristics. There is a problem that the deterioration occurs.

具体的には、単一の実装基板２０の表面という狭小領域に光学素子２１と磁石１９を固定する構造のため、特に高温で溶融固着する接合剤を使用する場合は、磁石１９の熱膨張係数が光学素子２１に対して大きいため、隣接する光学素子２１に影響し、引っ張りの応力を発生させることが一つの原因である。 Specifically, since the optical element 21 and the magnet 19 are fixed to a narrow area of the surface of the single mounting substrate 20, the thermal expansion coefficient of the magnet 19 is particularly large when a bonding agent that is melted and fixed at a high temperature is used. Is large with respect to the optical element 21, which affects one of the adjacent optical elements 21 and generates a tensile stress.

本発明は、上記問題点に鑑みてなされたものであり、ファラデー回転子及び偏光子を含む光学素子と磁石とが、互いに対向する様に、平板状の実装基板上面に配置されるとともに、実装基板上面に光学素子及び磁石が接合剤を介して一体化されている光アイソレータにおいて、前記接合剤が実装基板上面の一部に上記光学素子を配置する段差を形成するとともに、該段差により、前記接合剤が実装基板上で光学素子と接合する領域と磁石と接合する領域とに分離されていることを特徴とする。 The present invention has been made in view of the above problems, and an optical element including a Faraday rotator and a polarizer and a magnet are disposed on the upper surface of a flat mounting substrate so as to face each other, and mounted. In the optical isolator in which the optical element and the magnet are integrated on the upper surface of the substrate via the bonding agent, the bonding agent forms a step for arranging the optical element on a part of the upper surface of the mounting substrate. The bonding agent is separated into a region bonded to the optical element and a region bonded to the magnet on the mounting substrate.

前記接合剤として低融点ガラスが用いられるとともに、光学素子と実装基板を接合する低融点ガラスは、前記ファラデー回転子と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以下の熱膨張係数を有することを特徴とする。 A low-melting glass is used as the bonding agent, and the low-melting glass for bonding the optical element and the mounting substrate is equal to or smaller than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting substrate. It is characterized by having.

前前記接合剤として低融点ガラスが用いられるとともに、前記磁石と実装基板を接合する低融点ガラスは、前記磁石と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以下の熱膨張係数を有することを特徴とする。 A low-melting glass is used as the bonding agent before, and the low-melting glass for bonding the magnet and the mounting substrate has a thermal expansion coefficient equal to or lower than the smaller one of the thermal expansion coefficients of the magnet and the mounting substrate. It is characterized by having.

前記接合剤として半田が用いられるとともに、光学素子と実装基板を接合する半田は、前記ファラデー回転子と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以上の熱膨張係数を有することを特徴とする。 Solder is used as the bonding agent, and the solder for bonding the optical element and the mounting board has a thermal expansion coefficient equal to or higher than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting board. Features.

前記接合剤として半田が用いられるとともに、前記磁石と実装基板を接合する半田は、前記磁石と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以上の熱膨張係数を有することを特徴とする。 Solder is used as the bonding agent, and the solder for bonding the magnet and the mounting board has a thermal expansion coefficient equal to or greater than the smaller one of the thermal expansion coefficients of the magnet and the mounting board. To do.

本発明の構成によれば、磁石と光学素子を実装基板に高温にて溶融、接合する接合剤を用いて接合する構成の光アイソレータにおいて、実装基板に段差を設けることで、磁石を接合する接合剤と光学素子をする接合剤は互いに接触しない構成となり、光学素子への応力を十分に緩和することができ、光学素子の特性劣化、クラック、脱落の課題を解決することができる。 According to the configuration of the present invention, in an optical isolator having a configuration in which a magnet and an optical element are bonded to a mounting substrate using a bonding agent that melts and bonds at a high temperature, the bonding is performed by providing a step on the mounting substrate. The bonding agent that makes the agent and the optical element does not come into contact with each other, the stress to the optical element can be sufficiently relaxed, and the problems of characteristic deterioration, cracking, and dropping off of the optical element can be solved.

以下、図面を用いて本発明の実施例を説明する。 Embodiments of the present invention will be described below with reference to the drawings.

図１は、本発明の光アイソレータの実施形態を示す斜視図である。 FIG. 1 is a perspective view showing an embodiment of an optical isolator according to the present invention.

図に示すように、本発明の光アイソレータ１０は、段差９が設けられた実装基板６と、偏光子３、ファラデー回転子２、偏光子４からなる光学素子１と、磁石７とから成り、磁石７は接合剤５ａを介して実装基板６と接合され、光学素子１は接合剤５ｂを介して実装基板６の段部９上に接合されている。ここで、光学素子１と磁石７は段部９の段差側面に対向して配置される。 As shown in the figure, the optical isolator 10 of the present invention includes a mounting substrate 6 provided with a step 9, an optical element 1 including a polarizer 3, a Faraday rotator 2, and a polarizer 4, and a magnet 7. The magnet 7 is bonded to the mounting substrate 6 via the bonding agent 5a, and the optical element 1 is bonded to the step portion 9 of the mounting substrate 6 via the bonding agent 5b. Here, the optical element 1 and the magnet 7 are arranged to face the step side surface of the step portion 9.

実装基板６の材質として光アイソレータ１０を半導体レーザモジュールに実装する実装方法によって選択され、例えば、ＹＡＧ溶接で半導体レーザモジュールのサブマウントに固定される場合は、ステンレス、コバール、パーマロイ等の金属が選択され、また、ハンダによる実装の場合は、前記金属、あるいはセラミック、ガラス等の材料が用いられ実装面にたとえばＣｒ下地でＡｕメッキを施こしているものが選択される。実装基板６の表面に形成する段差９の高さは、接合剤５ａ、５ｂが完全に分離できる程度の高さであればよく、段差９の側面に磁石７を当接させて接合させることができるので、磁石７の配置、特に磁石７同士のＸ断面における間隔をほぼ設計値どおりに配置固定できる。磁石７同士の間隔は、ファラデー回転子２へ与える磁界強度に大きく影響し、その間隔が設計値より大きくなるとファラデー回転子への磁界強度が弱くなり、アイソレータの特性劣化につながる。従って、段差９の側面に磁石７を当接させて接合させることは、アイソレータの特性安定化、歩留まり向上の点で有効である。なお、段差９の側面に磁石９を当接して配置する場合、磁石９を接合する接合剤５ｂが磁石９の底面及び側面にも接合させると接合強度が高くなり、また、２個の磁石７を両側から挟むようにハンドリングするアイソレータの固定、保持を行う場合、段差９がハンドリングの力を受け止めるため、その製品強度も強くなる。 The material of the mounting substrate 6 is selected by a mounting method in which the optical isolator 10 is mounted on the semiconductor laser module. For example, when it is fixed to the submount of the semiconductor laser module by YAG welding, a metal such as stainless steel, Kovar, or permalloy is selected. In the case of mounting by solder, a material such as the metal, ceramic, glass or the like is used, and the mounting surface is plated with, for example, Cr as a base. The height of the step 9 formed on the surface of the mounting substrate 6 may be high enough to allow the bonding agents 5a and 5b to be completely separated, and the magnet 7 is brought into contact with the side surface of the step 9 to be bonded. Therefore, the arrangement of the magnets 7, particularly the distance between the X-sections of the magnets 7 can be arranged and fixed almost as designed. The distance between the magnets 7 greatly affects the magnetic field strength applied to the Faraday rotator 2. If the distance is larger than the design value, the magnetic field strength to the Faraday rotator becomes weak, leading to deterioration of the isolator characteristics. Accordingly, it is effective to bring the magnet 7 into contact with the side surface of the step 9 so as to stabilize the isolator characteristics and improve the yield. When the magnet 9 is disposed in contact with the side surface of the step 9, the bonding strength is increased when the bonding agent 5 b for bonding the magnet 9 is also bonded to the bottom surface and the side surface of the magnet 9. When the isolator that is handled so as to be sandwiched from both sides is fixed and held, the step 9 receives the handling force, so that the strength of the product is also increased.

光学素子１は、平板状の偏光子３、ファラデー回転子２、偏光子４からなり、これら光学素子１の底面は実装基板６の段部９上に精度良く接合剤５ｂを介して接合されている。 The optical element 1 includes a plate-shaped polarizer 3, a Faraday rotator 2, and a polarizer 4. The bottom surface of these optical elements 1 is bonded to the stepped portion 9 of the mounting substrate 6 with a bonding agent 5b with high accuracy. Yes.

接合剤５ａ、５ｂには低融点ガラスが用いられ、それらは同一の材料かあるいは異なる組成材料でもよく、ガラス材であるＳｉＯ２に他の金属酸化物、例えば酸化鉛や酸化リンや酸化亜鉛を混ぜ合わせ、その融点を低くなるように調整したもので、溶剤とともにクリーム状にしたものを、実装基板６上にあらかじめ塗布し、仮焼成により溶剤をとばしておくか、あるいは実装基板６の上面の５ａ、５ｂの領域とほぼ同じ大きさの平板状に形成したプリフォームがもちいられる。このように実装基板６上に形成された低融点ガラス５ｂと光学素子１、低融点ガラス５ａと磁石７をそれぞれ密着させたまま３００〜４２０度の高温炉で数秒から数分間焼成することで接合することができる。 Low melting glass is used for the bonding agents 5a and 5b, which may be the same material or different composition materials, and other metal oxides such as lead oxide, phosphorus oxide and zinc oxide are mixed with the glass material SiO2. In addition, it is adjusted so as to lower its melting point, and is applied in a cream form together with a solvent to the mounting substrate 6 in advance, and the solvent is removed by temporary baking, or 5a on the upper surface of the mounting substrate 6 A preform formed in a flat plate shape approximately the same size as the region 5b is used. The low melting point glass 5b and the optical element 1, and the low melting point glass 5a and the magnet 7 thus formed on the mounting substrate 6 are bonded to each other by firing in a high temperature furnace of 300 to 420 degrees for several seconds to several minutes. can do.

次に光アイソレータ１０の光学素子１とこれらの構成について説明する。 Next, the optical element 1 of the optical isolator 10 and the configuration thereof will be described.

偏光子３の透過偏波方向は、実装基板６の底面と平行な１辺（これを基準辺と呼ぶ）に対し平行な方向に設定されており、他方の偏光子４の透過偏波方向は、その基準辺に対して４５度の方向に設定されている。また、実装基板６の段部９の上面は底面と略平行に加工されており、実装基板６の段部９の上面と偏光子３と偏光子４の基準辺と略一致させ、固定することにより、偏光子３と偏光子４の透過偏波方向は回転調整することなく、互いに４５度ずれた状態となり、ファラデー回転子２のファラデー回転角が略４５度の場合、最良の挿入損失特性とアイソレーション特性を得ることができる。 The transmission polarization direction of the polarizer 3 is set in a direction parallel to one side parallel to the bottom surface of the mounting substrate 6 (referred to as a reference side), and the transmission polarization direction of the other polarizer 4 is The angle is set to 45 degrees with respect to the reference side. The top surface of the step portion 9 of the mounting substrate 6 is processed substantially parallel to the bottom surface, and the upper surface of the step portion 9 of the mounting substrate 6 and the reference sides of the polarizer 3 and the polarizer 4 are substantially aligned and fixed. Thus, the transmission polarization directions of the polarizer 3 and the polarizer 4 are shifted from each other by 45 degrees without rotating adjustment, and when the Faraday rotation angle of the Faraday rotator 2 is approximately 45 degrees, the best insertion loss characteristic is obtained. Isolation characteristics can be obtained.

偏光子３、４は、入射する光の１方向の偏光成分を吸収する機能を有する吸収型偏光子、あるいは入射する光の１方向の偏光成分を分離または合成する複屈折性偏光子で構成される。吸収型偏光子は例えば楕円体形の金属粒子がガラス内に分散された構造の偏光ガラスからなる。この偏光ガラスは長く延伸された金属粒子をガラス自身の中に一方向に配列させることにより偏光特性を持たせたガラスであり、金属粒子の延伸方向に垂直な偏波面を持つ光が透過し、平行な偏波面を持つ光は吸収される。例えば楕円体形の金属粒子がガラス内に分散された構造の偏光ガラスからなる。この偏光ガラスは長く延伸された金属粒子をガラス自身の中に一方向に配列させることにより偏光特性を持たせたガラスであり、金属粒子の延伸方向に垂直な偏波面を持つ光が透過し、平行な偏波面を持つ光は吸収される。 The polarizers 3 and 4 are configured by an absorption polarizer having a function of absorbing a unidirectional polarization component of incident light, or a birefringent polarizer that separates or synthesizes a unidirectional polarization component of incident light. The The absorptive polarizer is made of, for example, polarizing glass having a structure in which ellipsoidal metal particles are dispersed in glass. This polarizing glass is a glass having polarization characteristics by arranging long stretched metal particles in one direction in the glass itself, light having a polarization plane perpendicular to the stretch direction of the metal particles is transmitted, Light with a parallel polarization plane is absorbed. For example, it is made of polarizing glass having a structure in which ellipsoidal metal particles are dispersed in glass. This polarizing glass is a glass having polarization characteristics by arranging long stretched metal particles in one direction in the glass itself, light having a polarization plane perpendicular to the stretch direction of the metal particles is transmitted, Light with a parallel polarization plane is absorbed.

ファラデー回転子２は常温において入射した光の偏波方向が４５度回転する厚みに調整されている。また、光アイソレータ１０に高いアイソレーションが要求される場合は、ファラデー回転子２の偏波回転角度４５＋α度に対し、偏光子３と偏光子４の回転ズレを４５−α度に精密に調整する必要があり、光を逆方向から（偏光子４側から）入射し、透過してくる光が最も小さくなるように偏光子２を回転調整する方法がある。そこであらかじめ偏光子３と偏光子４の透過偏波方向を４５−α度ずらして切り出し、例えば偏光子４の透過偏波方向を基準辺に対して４５−α度とすることも可能である。また、ファラデー回転子の偏波回転角の精度±αは光アイソレータの特性上、１度程度とすることが望ましく、また実装基板６の上面に精度良く設置する。 The Faraday rotator 2 is adjusted to have a thickness at which the polarization direction of light incident at room temperature rotates 45 degrees. When high isolation is required for the optical isolator 10, the rotational deviation between the polarizer 3 and the polarizer 4 is precisely adjusted to 45−α degrees with respect to the polarization rotation angle 45 + α degrees of the Faraday rotator 2. There is a method in which light is incident from the opposite direction (from the side of the polarizer 4), and the polarizer 2 is rotationally adjusted so that the transmitted light is minimized. Therefore, the transmission polarization directions of the polarizer 3 and the polarizer 4 can be cut out by shifting by 45-α degrees in advance, and for example, the transmission polarization direction of the polarizer 4 can be set to 45-α degrees with respect to the reference side. In addition, the accuracy ± α of the polarization rotation angle of the Faraday rotator is desirably about 1 degree due to the characteristics of the optical isolator, and is installed on the upper surface of the mounting substrate 6 with high accuracy.

ファラデー回転子２は、例えば、ビスマス置換ガーネット結晶等で、その厚みは所定の波長をもつ入射光線の偏光面が４５度回転する様に設定する。一般に、偏波面を回転させるためには、入射光線の光軸Ｌ方向に十分な磁界を印可することが必要であり、磁石７はファラデー回転子２の両脇に配置されている。 The Faraday rotator 2 is, for example, a bismuth-substituted garnet crystal, and the thickness thereof is set so that the polarization plane of incident light having a predetermined wavelength rotates 45 degrees. In general, in order to rotate the polarization plane, it is necessary to apply a sufficient magnetic field in the direction of the optical axis L of the incident light, and the magnets 7 are arranged on both sides of the Faraday rotator 2.

磁石７の材料としては、例えばサマリウムコバルトからなる材料が適している。磁石７は光学素子１の両側に配置されており、磁石７には、ファラデー回転子２を通過する光軸方向の磁力線が最大になるような向きに磁極が配置されており、ファラデー回転子２が所定の波長をもつ入射光線の偏光面を４５度回転させるだけの磁界強度以上（飽和磁界強度）を有する。また、磁石の形状はこれに限ることもなく、ファラデー回転子に所定の磁界強度を満足すれば、１個でも良く、その形状も限定されない。 As a material of the magnet 7, for example, a material made of samarium cobalt is suitable. The magnets 7 are arranged on both sides of the optical element 1, and the magnetic poles are arranged in the magnet 7 in such a direction that the magnetic field lines passing through the Faraday rotator 2 are maximized. Has a magnetic field intensity (saturation magnetic field intensity) equal to or greater than a 45 degree rotation of the polarization plane of incident light having a predetermined wavelength. Further, the shape of the magnet is not limited to this, and may be one as long as the Faraday rotator satisfies a predetermined magnetic field strength, and the shape is not limited.

ここで、ファラデー回転子２の熱膨張係数は約１０×１０−６／℃であり、偏光ガラスの熱膨張係数は約６．５×１０−６／℃であり、また磁石７の熱膨張係数は約１３×１０−６／℃であり、これらの熱膨張係数の異なる部材を共通の実装基板６に堅固に実装し、かつ所望の光学特性を得るために本発明は考え出されたものである。すなわち、本発明の構成は実装基板６に形成する接合剤５ａと５ｂが、段部９の効果により互いに接触していないため、磁石７による引っ張り応力が光学素子１、特にファラデー回転子２にかかることなく、良好な特性を示すこと発明した。 Here, the thermal expansion coefficient of the Faraday rotator 2 is about 10 × 10 −6 / ° C., the thermal expansion coefficient of the polarizing glass is about 6.5 × 10 −6 / ° C., and the thermal expansion coefficient of the magnet 7. Is about 13 × 10 −6 / ° C. The present invention has been conceived in order to firmly mount these members having different thermal expansion coefficients on the common mounting substrate 6 and obtain desired optical characteristics. is there. That is, in the configuration of the present invention, since the bonding agents 5a and 5b formed on the mounting substrate 6 are not in contact with each other due to the effect of the step portion 9, the tensile stress due to the magnet 7 is applied to the optical element 1, particularly the Faraday rotator 2. It was invented that it shows good characteristics without.

ここで、より強固な接合状態を得るためには、最適な熱膨張係数を有する低融点ガラスを用いる方がよい。ファラデー回転子２及び接合剤５に生じる応力は、接合剤５を介した磁石７による引っ張りだけではなく、接合剤５自身の熱収縮も原因となり得る。低融点ガラスを用いる場合は、この材料特性として引っ張り応力に弱く、引っ張り応力がかかった状態ではガラスの破断が発生し接合強度の劣化につながるため、接合する部材同士の内、一番熱膨張係数が小さい部材にあわせるか、それ以下の熱膨張係数を有する低融点ガラスを介在することが接合強度の点から望ましい。そのため、ファラデー回転子２と実装基板６の接合には、ファラデー回転子２と実装基板６のいずれか熱膨張係数が小さい方と同じかそれ以下の熱膨張係数を有する接合剤低融点ガラスを介在することが望ましい。これは後述の通り、光アイソレータの特性を左右するファラデー回転子への残留応力の点からも好ましい。また、磁石７と実装基板６の接合には、磁石７と実装基板６のいずれか熱膨張係数が小さい方と同じかそれ以下の熱膨張係数を有する低融点ガラスを介在することが望ましい。このように選択した結果、接合剤５ａと接合剤５ｂで異なる材料配合の低融点ガラスを用いてもよい。 Here, in order to obtain a stronger bonding state, it is better to use a low-melting glass having an optimum thermal expansion coefficient. The stress generated in the Faraday rotator 2 and the bonding agent 5 can be caused not only by pulling by the magnet 7 via the bonding agent 5 but also by thermal contraction of the bonding agent 5 itself. When using low-melting-point glass, the material properties are weak against tensile stress, and when tensile stress is applied, the glass breaks and leads to deterioration of joint strength. It is desirable from the viewpoint of bonding strength that a low melting point glass having a thermal expansion coefficient equal to or smaller than that of a member having a low thermal expansion coefficient is interposed. Therefore, the Faraday rotator 2 and the mounting substrate 6 are joined with a low melting point glass having a thermal expansion coefficient equal to or lower than that of the Faraday rotator 2 or the mounting substrate 6 that has a smaller thermal expansion coefficient. It is desirable to do. As will be described later, this is also preferable from the viewpoint of residual stress on the Faraday rotator that affects the characteristics of the optical isolator. In addition, it is desirable to interpose a low-melting glass having a thermal expansion coefficient equal to or lower than the smaller one of the magnet 7 and the mounting board 6 in the bonding of the magnet 7 and the mounting board 6. As a result of such selection, low melting point glass having different material composition may be used for the bonding agent 5a and the bonding agent 5b.

図２は本発明の効果について説明した断面図である。 FIG. 2 is a sectional view for explaining the effect of the present invention.

図２は本発明と従来の光アイソレータの熱応力のかかり方を説明する図であり、（ａ）はＹ−Ｙ線断面であり、接合剤５０が実装基板２０の全面に形成され、磁石１９とファラデー回転子１５が共に接合剤５０により固着されている様子を示し、（ｂ）は図１のＸ−Ｘ線断面図であり、接合剤５ａ、５ｂが実装基板６の段部９の効果により、互いに接触せずに別領域に形成され、磁石７が接合剤５ａによって、光学素子１が接合剤５ｂにより固着されている様子を示す。なお、ガラスは引っ張り応力に対して弱いので、接合相手との応力が許容範囲を超えないように熱膨張係数や固着温度を最適に設定した状態での様子である。 2A and 2B are views for explaining how the thermal stress is applied to the present invention and the conventional optical isolator. FIG. 2A is a cross-sectional view taken along the line YY, and the bonding agent 50 is formed on the entire surface of the mounting substrate 20. And FIG. 5B is a sectional view taken along the line XX of FIG. 1, and the bonding agents 5 a and 5 b are the effects of the step portion 9 of the mounting substrate 6. Thus, the magnetic elements 7 are formed in different regions without being in contact with each other, and the optical element 1 is fixed by the bonding agent 5a and the optical element 1 by the bonding agent 5b. Since glass is weak against tensile stress, the thermal expansion coefficient and the fixing temperature are optimally set so that the stress with the bonding partner does not exceed the allowable range.

物体は温度の上昇により膨張し、温度の降下により収縮する。温度１℃の変化によって生じる単位長さあたりの収縮量を熱膨張係数といい、これをαで表す。各接合部における応力は、接合剤５０、５ａ、５ｂの固着温度（ほぼガラス転移温度Ｔｇと等しい）付近で発生し始め、ここから温度が下がるほど各残留応力は大きくなる。図中の矢印は各部材が温度降下時に収縮する方向を示している。 The object expands with increasing temperature and contracts with decreasing temperature. The amount of shrinkage per unit length caused by a change in temperature of 1 ° C. is called a thermal expansion coefficient, and this is represented by α. The stress at each joint starts to occur near the fixing temperature (approximately equal to the glass transition temperature Tg) of the bonding agents 50, 5a, and 5b, and the residual stress increases as the temperature decreases from here. The arrows in the figure indicate the direction in which each member contracts when the temperature drops.

また、光学素子１の内、ファラデー回転子２はその残留応力、特に引っ張り応力により、その消光比が大幅に低下することがわかっている。ファラデー回転子２の消光比とは、入射した直線偏波の光のうち、どれだけの光が直線偏波を保持したまま回転するかをパワーの比で表したものである。 Further, it has been found that the extinction ratio of the Faraday rotator 2 among the optical elements 1 is greatly reduced by the residual stress, particularly the tensile stress. The extinction ratio of the Faraday rotator 2 is a ratio of power indicating how much of the incident linearly polarized light rotates while maintaining the linearly polarized light.

以上の考察から、図２（ａ）の構成では、熱膨張係数が大きい磁石１９が接合剤５０の固着温度から常温への温度降下に伴い大きく収縮し、図中の矢印Ｆの方向に接合剤５０を介してファラデー回転子１６を引っ張るため、ファラデー回転子１６の消光比の低下や、低融点ガラス５０にクラック発生という問題が生じる。これに対し本発明の図２（ｂ）では段差９により接合剤５ａと５ｂが分離しているため、磁石７の収縮に伴う影響をファラデー回転子２が受けにくい構成となっているために、ファラデー回転子２の特性低下や接合剤５のクラックが発生しにくくなる。 From the above consideration, in the configuration of FIG. 2A, the magnet 19 having a large coefficient of thermal expansion contracts greatly with a temperature drop from the fixing temperature of the bonding agent 50 to room temperature, and the bonding agent in the direction of arrow F in the figure. Since the Faraday rotator 16 is pulled through 50, there arises a problem that the extinction ratio of the Faraday rotator 16 is lowered and cracks are generated in the low melting point glass 50. On the other hand, in FIG. 2B of the present invention, since the bonding agents 5a and 5b are separated by the step 9, the Faraday rotator 2 is not easily affected by the contraction of the magnet 7, The characteristic degradation of the Faraday rotator 2 and cracks in the bonding agent 5 are less likely to occur.

本発明は接合剤５ａ、５ｂとして低融点ガラスを用いた場合について説明したが、本発明の段部の効果はこれに限ることはなく、常温より高い温度で硬化する接合剤、たとえば熱硬化型の樹脂接着剤や、半田、ロウ材による接合についても同様の効果を得ることができる。特に本実施例で説明した低融点ガラス５を接合剤として用いた場合、光学素子２、３、４のメッキ等の前処理は不要であり工数の削減が実現する、または、樹脂による接合に比較して非常に堅固な固定が実現し、高温高湿化での特性劣化がなくなり、信頼性の高い光アイソレータが実現する、等の効果が期待される。 Although this invention demonstrated the case where low melting glass was used as joining agent 5a, 5b, the effect of the step part of this invention is not restricted to this, Joining agent hardened | cured at temperature higher than normal temperature, for example, thermosetting type The same effect can be obtained for bonding with a resin adhesive, solder, or brazing material. In particular, when the low melting point glass 5 described in the present embodiment is used as a bonding agent, pretreatment such as plating of the optical elements 2, 3, and 4 is unnecessary, and the number of man-hours can be reduced, or compared with bonding by resin. As a result, it is possible to achieve an effect such as realizing a very firm fixation, eliminating characteristic deterioration due to high temperature and high humidity, and realizing a highly reliable optical isolator.

ここで接合剤として半田を用いる場合は、より強固な接合状態を得るために、最適な熱膨張を有する半田を用いる方がよい。 Here, when solder is used as the bonding agent, it is better to use solder having optimum thermal expansion in order to obtain a stronger bonding state.

即ち、従来のファラデー回転子１６及び接合剤５０に生じる応力は、接合剤５０を介した磁石１９による引っ張りだけではなく、ファラデー回転子１６および接合剤５０自身の熱収縮も原因となり得る。これに対して本発明では、段差９により磁石７による引っ張りを抑制したので、半田を接合剤として用いる場合は、ファラデー回転子２より熱膨張係数が大きい半田を介在することが接合強度の点から望ましい。この理由は、ファラデー回転子２より熱膨張係数が小さい半田を用いた場合には、材料特性としてファラデー回転子２に比べて引っ張り応力に強く、引っ張り応力がかかった状態でも半田の破断が発生することはないが、逆にファラデー回転子２へは引っ張り応力に弱く、ひどい場合にはファラデー回転子２に破断が発生する原因となるからである。 That is, the stress generated in the conventional Faraday rotator 16 and the bonding agent 50 can be caused not only by the tension by the magnet 19 through the bonding agent 50 but also by thermal contraction of the Faraday rotator 16 and the bonding agent 50 itself. On the other hand, in the present invention, since the pulling by the magnet 7 is suppressed by the step 9, when solder is used as a bonding agent, a solder having a larger thermal expansion coefficient than the Faraday rotator 2 is interposed from the viewpoint of bonding strength. desirable. The reason for this is that when a solder having a smaller thermal expansion coefficient than that of the Faraday rotator 2 is used, the material characteristics are stronger than the Faraday rotator 2, and the solder breaks even when the tensile stress is applied. However, the Faraday rotator 2 is weak against tensile stress, and in the worst case, the Faraday rotator 2 may be broken.

これは、光アイソレータの特性を左右するファラデー回転子への残留応力の点からも好ましい。また、磁石７と実装基板６の接合には、同様の理由により、磁石７より熱膨張係数が大きい半田を介在することが望ましい。このように選択した結果、接合剤５ａと接合剤５ｂで異なる材料配合の半田を用いることが最も好ましい。 This is also preferable from the viewpoint of the residual stress on the Faraday rotator that affects the characteristics of the optical isolator. In addition, for the same reason, it is desirable that solder having a larger thermal expansion coefficient than that of the magnet 7 be interposed in the bonding between the magnet 7 and the mounting substrate 6. As a result of such selection, it is most preferable to use solders having different material blends for the bonding agent 5a and the bonding agent 5b.

以上説明したように、本発明の構成によれば、磁石７と光学素子１を共通の実装基板６に高温にて溶融、接合する接合剤５ａ、５ｂを用いて接合する構成の光アイソレータにおいて、磁石７を接合剤５ａで、光学素子１を接合剤５ｂで接合し、接合剤５ａと接合剤５ｂとは互いに確実に接触しない段差９を用いた構成とすることで、光学素子１への応力を緩和することができ、光学素子１の特性劣化、クラック、脱落の課題を解決することができる。 As described above, according to the configuration of the present invention, in the optical isolator configured to bond the magnet 7 and the optical element 1 to the common mounting substrate 6 using the bonding agents 5a and 5b that are melted and bonded at a high temperature. By joining the magnet 7 with the bonding agent 5a and the optical element 1 with the bonding agent 5b, and using the step 9 in which the bonding agent 5a and the bonding agent 5b do not reliably contact each other, the stress applied to the optical element 1 Can be mitigated, and the problems of characteristic deterioration, cracks, and dropout of the optical element 1 can be solved.

本発明の実施例として図２（ａ）に示した従来の実装基板を用いた光アイソレータＡと、図２（ｂ）に示した本発明の光アイソレータＢを試作し、その特性について比較した。 As an example of the present invention, an optical isolator A using the conventional mounting substrate shown in FIG. 2 (a) and an optical isolator B of the present invention shown in FIG. 2 (b) were prototyped and their characteristics were compared.

各部品と構成について以下に説明する。 Each component and configuration will be described below.

偏光子は、コーニング社製のポーラコア（製品名）を用い、サイズは１ｍｍ角で厚み０．２ｍｍのものを使用し、実装基板との実装辺を基準辺とし、入射側の偏光子は基準辺に平行な偏波方向を透過し、出射側の偏光子は基準辺に対して４５度の偏波方向を透過するように設定した。なお、偏光子の熱膨張係数は６．５×１０−６／℃のものを用いた。 The polarizer is a polar core (product name) manufactured by Corning, and the size is 1 mm square and the thickness is 0.2 mm. The mounting side with the mounting board is the reference side, and the polarizer on the incident side is the reference side. The output side polarizer is set to transmit a polarization direction of 45 degrees with respect to the reference side. The polarizer had a thermal expansion coefficient of 6.5 × 10 −6 / ° C.

ファラデー回転子はビスマス置換ガーネットを用い、サイズは１ｍｍ角で厚み０．５ｍｍ、飽和磁界強度中における偏波回転角は４５度であった。なお、ファラデー回転子の熱膨張係数は１０×１０−６／℃のものを用いた。 The Faraday rotator was a bismuth-substituted garnet, the size was 1 mm square, the thickness was 0.5 mm, and the polarization rotation angle in the saturation magnetic field strength was 45 degrees. In addition, the thermal expansion coefficient of the Faraday rotator was 10 × 10 −6 / ° C.

いずれも波長１．５５μｍの光に対して動作する素子であり、偏光子、ファラデー回転子の両面には対空気（ｎ＝１）の反射防止膜が施されている。 Both are elements that operate with respect to light having a wavelength of 1.55 μm, and antireflection films for air (n = 1) are applied to both surfaces of the polarizer and the Faraday rotator.

光アイソレータＡ、Ｂとも実装基板の材料にジルコニアセラミックスを用い、その上面に低融点ガラスをあらかじめ塗布しておく。ジルコニアの熱膨張係数は１０．５×１０−６／℃であり、ファラデー回転子の熱膨張係数とほぼ同じであり、ファラデー回転子に実装基板からの応力の影響を受けない構成とした。 For both optical isolators A and B, zirconia ceramics is used as the material of the mounting substrate, and low melting point glass is applied in advance to the upper surface thereof. The thermal expansion coefficient of zirconia is 10.5 × 10 −6 / ° C., which is almost the same as the thermal expansion coefficient of the Faraday rotator, and the Faraday rotator is not affected by the stress from the mounting board.

低融点ガラスについても同様にファラデー回転子への応力を考慮して１０．５×１０−６／℃より若干小さく、８×１０−６／℃のものを選択した。 Similarly, a low melting point glass having a size slightly smaller than 10.5 × 10 −6 / ° C. and 8 × 10 −6 / ° C. was selected in consideration of stress on the Faraday rotator.

実装基板のサイズは幅Ｗ＝３．２ｍｍ、長さＤ＝１．５ｍｍ、厚みｔ＝０．３ｍｍで、光アイソレータＡに用いる実装基板上面のほぼ全面に低融点ガラスを塗布した。光アイソレータＢに用いる実装基板は、そのほぼ中央部に幅Ｗ＝１ｍｍ、長さＤ＝１．５ｍｍの段差（高さは０．２５ｍｍである）を形成し、第一の低融点ガラス（熱膨張係数８×１０−６／℃）を塗布し、段差の両側に幅Ｗ＝０．８ｍｍ、長さＤ＝１．５ｍｍの第二の低融点ガラス（熱膨張係数６×１０−６／℃）を塗布し、第一の低融点ガラスと第二の低融点ガラスは段差により完全に分離させた。磁石は幅Ｗ＝０．８ｍｍ、長さＤ＝１．４ｍｍ、厚みＴ＝１．４ｍｍの略直方体の磁石を２個用いた。 The size of the mounting substrate was a width W = 3.2 mm, a length D = 1.5 mm, and a thickness t = 0.3 mm. Low melting point glass was applied to almost the entire upper surface of the mounting substrate used for the optical isolator A. The mounting substrate used for the optical isolator B is formed with a step (having a height of 0.25 mm) having a width W = 1 mm and a length D = 1.5 mm at substantially the center thereof, and the first low-melting glass (heat The second low melting point glass (thermal expansion coefficient 6 × 10 −6 / ° C.) having a width W = 0.8 mm and a length D = 1.5 mm on both sides of the step. The first low-melting glass and the second low-melting glass were completely separated by a step. Two magnets having a substantially rectangular parallelepiped shape having a width W = 0.8 mm, a length D = 1.4 mm, and a thickness T = 1.4 mm were used.

光アイソレータＡ、Ｂとも試作条件は同じくし、低融点ガラスを介して偏光子とファラデー回転子と偏光子の各光学素子の基準辺、および磁石を光アイソレータＡの実装基板、あるいは光アイソレータＢの実装基板に接合した。接合は、低融点ガラスの溶融温度３８０度、１分で焼成した。 The optical isolators A and B have the same prototype conditions, and the reference side of each optical element of the polarizer, the Faraday rotator and the polarizer, and the magnet are mounted on the mounting substrate of the optical isolator A or the optical isolator B through the low melting point glass. Bonded to the mounting board. The bonding was performed at a melting temperature of 380 ° C. for 1 minute for the low-melting glass.

表１は試作した５個の光アイソレータのアイソレーション特性とその平均値を示す。

Table 1 shows the isolation characteristics and average values of the five optical isolators made as a prototype.

光アイソレータＡについては、アイソレーション特性の平均値が２１．５ｄＢと非常に低く、磁石の高熱膨張の影響をファラデー回転子が受けていることが予想される。これに対し、光アイソレータＢはアイソレーション特性の平均値が４５．０ｄＢと高く、本発明による特性の改善が確認できた。 For the optical isolator A, the average value of the isolation characteristic is very low at 21.5 dB, and it is expected that the Faraday rotator is affected by the high thermal expansion of the magnet. On the other hand, the optical isolator B has an average isolation characteristic as high as 45.0 dB, confirming the improvement of the characteristics according to the present invention.

以上の試作の結果から、５０個の光アイソレータＢを作製し特性を測定した。その結果すべての光アイソレータは、挿入損失が０．３ｄＢ以下、アイソレーションが３５ｄＢ以上の、良好で均一な特性を有することを確認した。 From the results of the above trial manufacture, 50 optical isolators B were manufactured and the characteristics were measured. As a result, all the optical isolators were confirmed to have good and uniform characteristics with an insertion loss of 0.3 dB or less and an isolation of 35 dB or more.

次に作製した光アイソレータの信頼性評価を行った。試験は、Ｔｅｌｃｏｒｄｉａ１２２１に示される振動試験、衝撃試験、温度サイクル試験、高温保持試験、低温保持試験、高温高湿試験を実施し、すべての試験において、挿入損失の変化量が±０．２ｄＢ以下、アイソレーションの変化量が±３ｄＢ以下と良好な結果を得ることができた。 Next, the reliability of the produced optical isolator was evaluated. The tests were conducted vibration test, impact test, temperature cycle test, high temperature holding test, low temperature holding test, high temperature high humidity test shown in Telcordia 1221. In all tests, the amount of change in insertion loss is ± 0.2 dB or less, A good result was obtained in which the amount of change in isolation was ± 3 dB or less.

以上の試作により、光学特性が安定し、かつ、組み立てが容易で工数が少なく、光学素子の脱落、クラック、特性劣化がない信頼性に優れた光アイソレータを提供することができる。 By the above trial manufacture, it is possible to provide an optical isolator having stable optical characteristics, easy assembly, less man-hours, and excellent in reliability without dropping, cracking, and characteristic deterioration of optical elements.

本発明の第２の実施例として、本発明と従来の光アイソレータの熱応力の数値解析を行った。解析条件としては、ファラデー回転子の熱膨張係数を１０．５×１０−６（１／℃）、偏光子の熱膨張係数を６．３４×１０−６（１／℃）、磁石の熱膨張係数を光軸方向を６．５×１０−６（１／℃）、光軸と垂直方向を１３．０×１０−６（１／℃）、接合剤の熱膨張係数を以下の組み合わせで９．０×１０−６（１／℃）及び６．０×１０−６（１／℃）の二種類のものを、また、接合剤の融点を３８０℃とし、２０℃まで温度を下げた際の熱応力を見た。この時の実装基板の材質はアルミナセラミックスとし、その熱膨張係数を７．１×１０−６（１／℃）とした。 As a second embodiment of the present invention, numerical analysis of the thermal stress of the present invention and the conventional optical isolator was performed. As analysis conditions, the thermal expansion coefficient of the Faraday rotator was 10.5 × 10 −6 (1 / ° C.), the thermal expansion coefficient of the polarizer was 6.34 × 10 −6 (1 / ° C.), and the thermal expansion of the magnet The coefficient is 6.5 × 10 −6 (1 / ° C.) in the optical axis direction, the direction perpendicular to the optical axis is 13.0 × 10 −6 (1 / ° C.), and the thermal expansion coefficient of the bonding agent is 9 in the following combinations: 0.0 × 10-6 (1 / ° C.) and 6.0 × 10 −6 (1 / ° C.), when the melting point of the bonding agent is 380 ° C. and the temperature is lowered to 20 ° C. I saw the thermal stress. The material of the mounting substrate at this time was alumina ceramics, and its thermal expansion coefficient was 7.1 × 10 −6 (1 / ° C.).

解析のパターンとしては、図２（ｂ）の光アイソレータで接合剤５の熱膨張係数が９．０×１０−６（１／℃）（パターン１）、図２（ｂ）の光アイソレータで接合剤５の熱膨張係数が６．０×１０−６（１／℃）（パターン２）、図２（ａ）の光アイソレータで接合剤５０の熱膨張係数が９．０×１０−６（１／℃）（パターン３）、図２（ａ）の光アイソレータで接合剤５０の熱膨張係数が６．０×１０−６（１／℃）（パターン４）の４パターンについて解析を行った。解析結果を表２に示す。また、パターン２、４についての応力分布を図３に示す。

As an analysis pattern, the thermal expansion coefficient of the bonding agent 5 is 9.0 × 10 −6 (1 / ° C.) (pattern 1) using the optical isolator shown in FIG. 2B, and the optical isolator shown in FIG. The thermal expansion coefficient of the agent 5 is 6.0 × 10 −6 (1 / ° C.) (Pattern 2), and the thermal expansion coefficient of the bonding agent 50 is 9.0 × 10 −6 (1 in the optical isolator of FIG. / ° C.) (Pattern 3) and 4 patterns having a thermal expansion coefficient of 6.0 × 10 −6 (1 / ° C.) (Pattern 4) were analyzed using the optical isolator of FIG. The analysis results are shown in Table 2. Moreover, the stress distribution about the

patterns

2 and 4 is shown in FIG.

以上の解析より、光学素子と実装基板を接合する低融点ガラスは、ファラデー回転子と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以下の熱膨張係数を有するものを採用したほうが（パターン２、パターン４）、ファラデー回転子への応力が低くなることがわかった。さらに、図２（ｂ）に示される接合剤５ａ、ｂの分離は（パターン１、パターン２）、さらにファラデー回転子２の応力低減に有効であり、クラックや特性劣化に効果があることが確認できた。なお、半田についても実験例１、２と同様の実験をおこなったが、光学素子と実装基板を接合する半田は、ファラデー回転子と実装基板の熱膨張係数のいずれか小さい方と同じかそれ以上の熱膨張係数を有するものを採用したほうが、ファラデー回転子への応力が低くなり、良好なアイソレーション特性が実現することがわかった。 From the above analysis, it is better to adopt the low melting point glass that joins the optical element and the mounting substrate, which has a thermal expansion coefficient equal to or smaller than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting substrate ( It was found that the stress on the pattern 2, the pattern 4) and the Faraday rotator was lowered. Furthermore, it is confirmed that the separation of the bonding agents 5a and b shown in FIG. 2B is effective for reducing the stress of the Faraday rotator 2 (pattern 1 and pattern 2), and is effective for cracks and deterioration of characteristics. did it. The same experiment as in Experimental Examples 1 and 2 was performed for solder, but the solder for joining the optical element and the mounting board is equal to or higher than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting board. It was found that the use of the one having the thermal expansion coefficient of the lower the stress on the Faraday rotator and realizes good isolation characteristics.

本発明の光アイソレータの実施形態を示す斜視図である。It is a perspective view which shows embodiment of the optical isolator of this invention. 本発明の効果について説明する断面図である。It is sectional drawing explaining the effect of this invention. 応力解析結果の応力分布の斜視図である。It is a perspective view of stress distribution of a stress analysis result. 従来の小型化された光アイソレータの構成を示す図である。It is a figure which shows the structure of the conventional optical isolator miniaturized.

Explanation of symbols

１、２１：光学素子
１０、１１、１５：光アイソレータ
２、１６：ファラデー回転子
３、４、１７、１８：偏光子
５：接合剤
６、２０：実装基板
７、１９、２２：磁石
９：段部 1, 2: Optical elements 10, 11, 15: Optical isolator 2, 16: Faraday rotator 3, 4, 17, 18: Polarizer 5: Bonding agent 6, 20: Mounting substrate 7, 19, 22: Magnet 9: Step

Claims

The optical element including the Faraday rotator and the polarizer and the magnet are arranged on the upper surface of the flat mounting substrate so as to face each other, and the optical element and the magnet are integrated on the upper surface of the mounting substrate via a bonding agent. In the optical isolator, the bonding agent forms a step for arranging the optical element on a part of the upper surface of the mounting substrate, and the step joins the region where the bonding agent is bonded to the optical element on the mounting substrate and the magnet. An optical isolator characterized by being separated from a region to be operated.

A low-melting glass is used as the bonding agent, and the low-melting glass for bonding the optical element and the mounting substrate is equal to or smaller than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting substrate. The optical isolator according to claim 1, comprising:

A low-melting glass is used as the bonding agent, and the low-melting glass for bonding the magnet and the mounting board has a thermal expansion coefficient equal to or lower than the smaller one of the thermal expansion coefficients of the magnet and the mounting board. The optical isolator according to claim 1 or 2, wherein

Solder is used as the bonding agent, and the solder for bonding the optical element and the mounting board has a thermal expansion coefficient equal to or higher than the smaller one of the thermal expansion coefficients of the Faraday rotator and the mounting board. The optical isolator according to claim 1.

Solder is used as the bonding agent, and the solder for bonding the magnet and the mounting board has a thermal expansion coefficient equal to or greater than the smaller one of the thermal expansion coefficients of the magnet and the mounting board. The optical isolator according to claim 1 or 4.