JP3973975B2 - Optical isolator - Google Patents

Description

【００３４】
試作したアイソレータの特性を測定したところ、このアイソレータの１５５０ｎｍにおける特性は、偏光子１０５方向から入射した入射光の順方向挿入損失は０．３０ｄＢで、偏光子１０５と偏光子１０７の透過偏光方向は同一であり、偏光子１０７方向から入射した入射光の逆方向挿入損失は６４ｄＢであった。
【００３５】
（実施例２）
図２に示したような本発明の光アイソレータを構成した。各光学素子の材料は、実施例１と同様の材料を用いた。
サイズ１５×１５×０．５ｍｍであり、片面に対空気ＡＲコート、もう一方の片面に対接着剤ＡＲコートを施した偏光ガラスから成る偏光子２０５，２０６の各々の接着剤ＡＲコート面に、サイズ１５×１５×０．６ｍｍであり、両面に対接着剤ＡＲコートを施した（ＧａＢｉ）_３（ＦｅＧａ）_５Ｏ_１２から成るファラデー回転子２０３の対接着剤ＡＲコート面をエポキシ接着剤を介して、偏光子の相対角度が４５度（偏光子２０５から見て偏光子２０６の透過偏光方向が時計方向に４５度回転）となるよう接合固定し、その後に１．２５×１．２５ｍｍのサイズに切断した。
【００３６】
次に、サイズ１５×１５×０．５ｍｍであり、片面に対空気ＡＲコート、もう一方の片面に対接着剤ＡＲコートを施した偏光ガラスから成る偏光子２０７，２０８の各々の対接着剤ＡＲコート面に、サイズ１５×１５×０．６ｍｍであり、両面に対接着剤ＡＲコートを施した（ＴｂＥｕＢｉ）_３（ＦｅＧａ）_５Ｏ_１２から成るファラデー回転子２０４の両面にエポキシ接着剤を介して接合し、この時の両端の偏光ガラスはその透過偏光方向が相対的に４５度（偏光子２０７から見て偏光子２０８が反時計方向に回転）になるように設定し、接合固定した後、１．２５×１．２５ｍｍのサイズに切断した。
【００３７】
片側８度に傾斜加工を施した基台２０１にＳｍ−Ｃｏ磁石、及び１．２５×１．２５ｍｍに切断した上記光学素子である、偏光子２０５−ファラデー回転子２０３−偏光子２０６、偏光子２０７−ファラデー回転子２０４−偏光子２０８を接合固定し、図２の光透過方向と同じ方向に磁化方向を有するように、磁石を着磁し、アイソレータを組み立てた。
【００３８】
試作したアイソレータの特性を測定したところ、このアイソレータの１５５０ｎｍにおける特性は、偏光子２０５方向から入射した入射光の順方向挿入損失は０．３４ｄＢで、偏光子２０５と偏光子２０８の透過偏光方向は同一であり、偏光子２０８方向から入射した入射光の逆方向挿入損失は７８ｄＢであった。
【００３９】
（実施例３）
実施例１におけるファラデー回転子１０３，１０４にラッチングタイプファラデー回転子を用い、実施例１同様の接合加工工程を経た後、ファラデー回転子１０３が時計方向に４５度ファラデー回転を起こすよう磁化し、ファラデー回転子１０４が反時計方向に４５度回転するよう磁化させるようにして光アイソレータを組立てた。
ラッチングタイプファラデー回転子は、実施例１における磁石１１０，１１１を配置する必要は無いため、この実施例３においては磁石は配置しなかった。
【００４０】
試作したアイソレータの特性を測定したところ、このアイソレータは、順方向挿入損失０．２４ｄＢで偏光子１０５，１０７の透過偏光方向は同一であり、逆方向挿入損失６７ｄＢであった。
なお、本発明では、実施例２の光アイソレータにおいても、ファラデー回転子２０３，２０４をラッチングタイプとし、磁石無しの配置にすることも可能である。
【００４１】
（実施例４）
図４に示したような本発明の光アイソレータを構成した。実施例１同様の光学材料を用いて偏光子４０５，ファラデー回転子４０３の材料を貼り合せ、切断時に偏光子４０５−ファラデー回転子４０３が基台４０１と接する面及びその対となる面を８度傾斜するように切断加工した。磁石も実施例１と同様のものである。なお基台４０１は傾斜加工させず平板状の加工とした。それ以外は実施例１と同様にして光アイソレータを製作した。
【００４２】
本実施例では、光学素子を傾斜加工することで、基台を傾斜加工する手間が省け、また入射光に対する偏光子４０５の対空気ＡＲコート面の残存反射は入射光とは異なる方向へ除去出来た。この場合、図５の従来例のように光学素子を垂直に切り出し、基台５０１に横方向に傾斜配置した場合は、光透過部分に対して光学素子が有効配置されない状態となり、また磁石５１０−５１１間の距離を余分にとる必要があり、アイソレータ小型化には不向きとなる。しかし、図４（ｂ）に示すように、入射側光学素子を傾斜加工することで、磁石間距離を広げることなくアイソレータの小型化を図ることができ、また光学素子材料を無駄に使用することも無いという利点がある。
【００４３】
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。
【００４４】
【発明の効果】
以上詳細に説明したように、本発明の光アイソレータは、高い逆方向挿入損失を有し、かつ入出射透過偏光方向が同一の信頼性の高い光アイソレータであり、これを容易に量産し、低コストで供給することが可能となる。
【図面の簡単な説明】
【図１】本発明の光アイソレータの第１の態様を示す説明図である。
（ａ）平面図、（ｂ）Ａ−Ａ線断面図。
【図２】本発明の光アイソレータの第２の態様を示す断面図である。
【図３】図１および図２における各光学素子表面での光の透過偏光方向を示す。
【図４】本発明の光アイソレータの第３の態様を示す説明図である。
（ａ）平面図、（ｂ）Ｂ−Ｂ線断面図、（ｃ）正面図、
【図５】従来例として従来の光アイソレータの態様を示す説明図である。
（ａ）平面図、 （ｂ）側面図、 （ｃ）正面図。
【符号の説明】
１０１…基台、 １０３、１０４…ファラデー回転子、
１０５、１０６、１０７…偏光子、 １１０、１１１…磁石、
２０１…基台、 ２０３、２０４…ファラデー回転子、
２０５、２０６、２０７、２０８…偏光子、 ２１０、２１１…磁石、
４０１…基台、 ４０３、４０４…ファラデー回転子、
４０５、４０６、４０７…偏光子、 ４１０、４１１…磁石、
５０１…基台、 ５０３…ファラデー回転子、
５０５、５０６…偏光子、 ５１０、５１１…磁石、
▲１▼、▲２▼、▲３▼、▲４▼、▲５▼、▲６▼、▲７▼、▲８▼…各光学素子の表面。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical isolator used for optical communication and optical measurement, and more particularly to an optical isolator having a high light blocking ability (reverse insertion loss) in which Faraday rotators are configured in multiple stages.
[0002]
[Prior art]
In recent optical fiber communication, a high-performance semiconductor laser is used as a light source for high-speed and large-capacity transmission. Since this laser is sensitive to the oscillation characteristics due to the influence of reflected light from a fiber or the like, an optical isolator having a high reverse insertion loss is essential.
[0003]
In addition, with the high performance of lasers and the high integration of optical elements, it is becoming necessary to make the polarization directions of the optical isolators the same.
The configuration of the conventional multistage optical isolator is toward the light traveling direction,
(1) Connect two isolators whose magnetic poles are opposite to each other.
{Circle around (2)} A radially oriented magnet is used so that a single magnet can apply a reverse magnetic field to two Faraday rotators (see Japanese Laid-Open Patent Publication No. 1-142525).
(3) The arrangement of the magnetic poles of one magnet is devised (see Japanese Patent Laid-Open No. 2-108017).
The method is mentioned.
[0004]
However, according to the above method,
In {circle around (1)}, there is a problem in assembling configuration that magnets in opposite directions are brought close to each other.
In (2), the configuration is unsuitable for a small magnet configuration.
In {circle around (3)}, the magnetic pole configuration is complicated, and it is difficult to magnetize the magnets once assembled.
However, none of these is a configuration suitable for mass production, and the processing method is costly.
[0005]
In addition to the above, a method of arranging an optical rotator or a Faraday rotator on the incident or output side is also conceivable as a method for making the incident and outgoing transmission polarization directions the same, but the number of components is increased and the light transmittance is decreased. However, the increase in the size of parts due to an increase in the optical distance becomes a problem and cannot be an effective solution.
[0006]
[Problems to be solved by the invention]
Therefore, the present invention has been made in view of the above problems, and has a high reverse insertion loss, the same input and output transmission polarization directions, high reliability, excellent productivity, and low cost multi-stage optical isolator. The main purpose is to provide
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, an optical isolator according to the present invention is an optical isolator in which an optical element having at least three polarizers and two Faraday rotators is arranged in at least the light traveling direction, Are arranged opposite to each other with the optical element interposed therebetween, and the optical element includes a first polarizer, a first Faraday rotator, a second polarizer, a second Faraday rotator, and a third polarizer. The transmission polarization directions of the first and third polarizers are in the same direction and in the same magnetic field direction, the Faraday rotation direction of the first Faraday rotator and the second direction in the light traveling direction. It is characterized in that the Faraday rotation direction of the Faraday rotator is different .
[0008]
In this way, if a multi-stage optical isolator is configured, a multi-stage optical isolator having high reverse insertion loss, the same input / output transmission polarization direction, high reliability, excellent productivity, and low cost is provided. can do.
[0009]
In this case, the optical element may be formed by further arranging a fourth polarizer between the first Faraday rotator and the second Faraday rotator .
As described above, the optical element of the multi-stage optical isolator additionally provided with the fourth polarizer has a structure in which the input / output transmission polarization direction is the same and a larger reverse insertion loss can be obtained, and the reliability is high. Therefore, it is possible to provide a multi-stage optical isolator with excellent productivity and low cost.
[0010]
Further, in this case, the first and second Faraday rotators may be latching type Faraday rotators, and the magnet may be omitted .
As described above, when a latching type (self-saturation) Faraday rotator that does not require a magnet is used, the magnet can be omitted if the magnet is assembled in advance so as to cause Faraday rotation in opposite directions. Therefore, a highly reliable optical isolator having a high reverse insertion loss and the same input / output transmission polarization direction can be further downsized.
[0011]
In the optical isolator, the optical element (polarizer, Faraday rotator) and / or magnet is fixed on the flat base, and both ends of the light traveling direction with respect to the installation plane of the base at the time of mounting. It is possible that the transmission polarization direction of the polarizer disposed in is parallel .
[0012]
Thus, if an optical element is arrange | positioned and assembled on a flat plate type base, the optical element can be easily aligned accurately, and an optical isolator with high accuracy and high reliability can be obtained.
Further, by mounting the lower surface of the base on an LD (laser diode) module, it is possible to accurately match the incident polarization direction of the LD chip. Further, since the outgoing polarization direction is the same as the incident polarization direction, the optical coupling efficiency does not deteriorate even if a component having polarization dependency such as a waveguide is arranged after the outgoing light.
[0013]
In addition, in the above optical isolator, it is Nozomu Mashiku polarizer at least incident side is arranged obliquely, is inclined arrangement of the optical elements comprises inclined processed cut surface of the optical element, the optical element inclined arrangement of, an inclined direction perpendicular to the optical element and the base of the contact surface, the inclined along the traveling direction of light good preferable.
[0014]
As described above, in order to avoid light reflection on the incident surface, the optical element may be inclined with respect to the incident direction. In this case, if an optical element whose cut surface is inclined is used, the cost is increased. This eliminates the need to tilt the base for which accuracy is difficult to ensure. Further, if the inclination direction is inclined along the light traveling direction from the direction perpendicular to the contact surface between the optical element and the base, the light transmittance is reduced without reducing the effective area of the optical element. It is possible to obtain a highly reliable optical isolator having a high reverse insertion loss and the same input / output transmission polarization direction.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.
In the present invention, the Faraday rotator constituting the optical element of the multi-stage optical isolator uses a material having a different chemical composition in the Faraday rotation direction in the same magnetic field direction.
(1) The magnet configuration can be simplified,
(2) Collective magnet magnetization is possible after assembly adjustment.
(3) It is possible to make the incident and outgoing transmission polarization directions the same,
(4) By using a Faraday rotator having a different composition, it has a high reverse insertion loss, and the temperature dependence and wavelength dependence of the optical characteristics of the multistage optical isolator are reduced.
I did it.
[0016]
That is, the first aspect of the present invention is an optical isolator in which optical elements having at least three polarizers and two Faraday rotators are arranged in at least the light traveling direction, and both ends are attached to different polarities. Magnetized rectangular parallelepiped magnets are arranged opposite to each other with the optical element interposed therebetween, and the optical elements are arranged in the order of the first polarizer, the first Faraday rotator, the second polarizer, the second Faraday rotator, and the third polarizer. Thus, the transmission polarization directions of the first and third polarizers are the same, and the Faraday rotation direction of the first Faraday rotator is different from the Faraday rotation direction of the second Faraday rotator in the light traveling direction. It is characterized by.
[0017]
The first embodiment of the present invention is shown in FIG.
1A is a plan view, and FIG. 1B is a cross-sectional view taken along line AA along the light transmission direction.
In this optical isolator, an optical element having three polarizers 105, 106, 107 and two Faraday rotators 103, 104 is arranged on a base 101 with respect to the traveling direction of light, and both ends are different from each other. The rectangular parallelepiped magnets 110 and 111 are arranged opposite to each other with the optical element interposed therebetween. This optical element is formed by arranging a first polarizer 105, a first Faraday rotator 103, a second polarizer 106, a second Faraday rotator 104, and a third polarizer 107 in this order, and the first and third polarizers. The transmission polarization directions are the same, and the Faraday rotation direction of the first Faraday rotator and the Faraday rotation direction of the second Faraday rotator are different from each other in the light traveling direction.
[0018]
In order to place the first polarizer 105 and the first Faraday rotator 103 which are optical elements on the incident side in an inclined manner, the incident side surface of the base 101 is inclined. The transmission deflection directions of the first polarizer 105 and the third polarizer 107 are in the horizontal direction with respect to the base. The magnets 110 and 111 are magnetized (magnetized after the isolator is assembled) in the light traveling direction (or the reverse direction), and in the same direction of the magnetic field, the first Faraday rotator 103 and the second Faraday rotator 104 are mutually connected. Materials with different chemical compositions with the Faraday rotation direction in the opposite direction are arranged.
[0019]
FIG. 3A shows the transmission polarization direction of light on the surface of each optical element (the state in which the light incident on the (1) plane is transmitted through the (6) plane). (1) and (6) The transmission polarization directions of the surfaces are the same.
By using the optical isolator configured in this way, it is possible to easily make the incident / outgoing / transmission / deflection direction the same, and by accurately mounting the bottom surface of the base on the LD module, it can accurately match the incident polarization direction of the LD chip. It becomes possible to make it. Further, since the outgoing polarization direction is the same as the incident polarization direction, the optical coupling efficiency does not deteriorate even if a component having polarization dependency such as a waveguide is arranged after the outgoing light.
[0020]
Next, the second embodiment of the present invention is shown in FIG.
In this optical isolator, optical elements having four polarizers 205, 206, 207, 208 and two Faraday rotators 203, 204 are arranged on a base 201 with respect to the traveling direction of light, and both ends are arranged. A rectangular parallelepiped magnet 210 and 211 (not shown) magnetized with different polarities are arranged opposite to each other with the optical element interposed therebetween. This optical element is formed by arranging a first polarizer 205, a first Faraday rotator 203, a second polarizer 206, a fourth polarizer 207, a second Faraday rotator 204, and a third polarizer 208 in this order. And the third polarizer have the same transmission polarization direction, and the Faraday rotation direction of the first Faraday rotator and the Faraday rotation direction of the second Faraday rotator are different from each other in the light traveling direction.
[0021]
In FIG. 2, the second polarizer 206 and the fourth polarizer 207 and two polarizers are arranged between the first and second Faraday rotators. In this case as well, this is shown in FIG. Thus, the transmitted polarization directions of the (1) and (8) planes are the same. In addition, the incident side surface of the base 201 is inclined so that the first polarizer 205, the first Faraday rotator 203, and the second polarizer 206, which are optical elements on the incident side, are inclined.
This mechanism and operational effects can be explained in the same manner as in the first embodiment (see FIG. 3B).
As described above, the optical element of the multi-stage optical isolator additionally provided with the fourth polarizer has a structure in which the input / output transmission polarization direction is the same and a larger reverse insertion loss can be obtained, and the reliability is high. Therefore, it is possible to provide a multi-stage optical isolator with excellent productivity and low cost.
[0022]
FIG. 4 shows a third aspect of the present invention.
4A is a plan view, and FIG. 4B is a cross-sectional view taken along the line BB along the light transmission direction. In this optical isolator, an optical element having three polarizers 405, 406, and 407 and two Faraday rotators 403 and 404 is arranged on a base 401 with respect to the traveling direction of light, and both ends have different polarities. Magnets 410 and 411 having a rectangular parallelepiped shape magnetized to each other are arranged opposite to each other with the optical element interposed therebetween.
Then, in order to place the first polarizer 405 and the first Faraday rotator 403, which are the optical elements on the incident side, incliningly, the base contact surface of the optical element is subjected to an inclination process, and the inclination direction is determined between the optical element and the base. It was perpendicular to the tangent surface and inclined along the direction of light travel.
The transmission polarization direction of light in this aspect can be explained in the same manner as in the first aspect (see FIG. 3A).
[0023]
In recent years, a configuration like a flat plate type optical isolator (see Japanese Patent Laid-Open No. 10-227996) has been used. In the present invention, the alignment of optical elements can be achieved by using a flat plate base. Thus, an optical isolator with high accuracy and high reliability can be obtained.
According to the present invention, in the optical isolator, the optical element (polarizer, Faraday rotator) and / or magnet is fixed on a flat base, and the light is transmitted to the installation plane of the base at the time of mounting. The transmission polarization directions of the polarizers arranged at both ends in the traveling direction are made parallel to each other.
In this way, it is possible to accurately match the incident polarization direction of the LD chip by mounting the lower surface of the base on the LD (laser diode) module. Further, since the outgoing polarization direction is the same as the incident polarization direction, the optical coupling efficiency does not deteriorate even if a component having polarization dependency such as a waveguide is arranged after the outgoing light.
[0024]
Furthermore, in the above aspect of the present invention, when an optical element is arranged on a flat plate base, the optical element is arranged to be inclined with respect to the incident direction in order to avoid light reflection on the incident surface. In this case, if an element that is simply cut vertically is tilted in a direction parallel to the contact surface between the optical element and the base, the effective area of the optical element is reduced. Further, if the required effective diameter is to be ensured, the lateral dimension of the optical isolator becomes large. Therefore, as in the first and second aspects, it is preferable to tilt the optical element from the direction perpendicular to the contact surface of the base in the light traveling direction. However, if the base itself is tilted as in the first and second aspects, problems may arise that the base processing cost increases and it becomes difficult to align the bases.
[0025]
In order to solve these problems, it is preferable to process the optical element in advance so as to have an end face inclined at a predetermined angle as in the third aspect.
By tilting the contact surface of the optical element in order to place the optical element in an inclined manner,
(1) Freed from the difficulty of ensuring the accuracy of tilting the base.
(2) The horizontal dimension of the base can be reduced and the size can be reduced.
(3) In addition, the distance between the magnets is reduced, and a necessary and sufficient magnetic field can be supplied to the Faraday rotator.
(4) By matching the inclined surface to the base plane, the accuracy of the inclination angle is improved compared to using the side surface magnet as the reference surface.
Convenient effects can be obtained at the time of coupling, such as matching of optical distances and matching of light emission axes during mass production.
[0026]
Furthermore, as a fourth aspect (not shown) of the present invention, the first and second Faraday rotators may be latching type Faraday rotators, and the magnet may be omitted.
In this way, when a latching type (self-saturation) Faraday rotator that does not require magnets is used, high reverse insertion loss can be achieved by pre-magnetizing the Faraday rotations in opposite directions. In addition, a highly reliable optical isolator having the same incident / exit transmission polarization direction can be obtained.
[0027]
As a conventional example, an optical element obtained by bonding a polarizer 505, a Faraday rotator 503, and a polarizer 506 as shown in FIG. An optical isolator was formed by inclining the light transmission axis and arranging the bar magnets 510 and 511 in parallel with the light transmission direction.
As is apparent from the figure, when the optical element is processed into a rectangular parallelepiped shape, when the incident surface is inclined, the effective area becomes narrower with respect to light traveling straight on the incident end surface and the output end surface. In addition, when the base is processed into a flat plate shape, it is necessary to be inclined with respect to the base in the horizontal direction, so that the outer shape of the horizontal isolator becomes large. In addition, the distance between the magnets increases, and there is a possibility that a necessary and sufficient magnetic field may not be supplied to the Faraday rotator.
[0028]
【Example】
Examples of the present invention will be described below, but the present invention is not limited thereto.
Example 1
The optical isolator of the present invention as shown in FIG. 1 was constructed.
In this example, a polarizing glass Polarcor manufactured by Corning was used as a polarizing material for the polarizer. As a material for the Faraday rotator, (TbEuBi) ₃ (FeGa) ₅ O ₁₂ or (GaBi) ₃ (FeGa) ₅ O ₁₂ was used.
[0029]
First, the size 15 × 15 × 0.5 mm is applied to the adhesive AR coating surface of the polarizer 105 made of polarizing glass having an air AR coating on one side and an adhesive AR coating on the other surface. Adhesive AR of Faraday rotator 103 made of (GaBi) ₃ (FeGa) ₅ O ₁₂ , which is × 15 × 0.6 mm, coated with adhesive AR coating on one side and air AR coating on the other side The coated surface was bonded and fixed via an epoxy adhesive, and then cut to a size of 1.25 × 1.25 mm.
[0030]
Next, two polarizers 106 and 107 made of polarizing glass having a size of 15 × 15 × 0.5 mm and having an anti-air AR coat on one side and an anti-adhesive AR coat on the other side were prepared. Each of the polarizers 106 and 107 has an adhesive AR coating surface of a size of 15 × 15 × 0.6 mm, and is made of (TbEuBi) ₃ (FeGa) ₅ O ₁₂ having an adhesive coating AR on both surfaces. The Faraday rotator 104 was bonded to both surfaces via an epoxy adhesive. At this time, the polarizing glass at both ends was set so that the transmission polarization direction was relatively 45 degrees, and was bonded and fixed, and then cut into a size of 1.25 × 1.25 mm.
[0031]
Polarizer 105-Faraday rotator 103, which is the above-described optical element cut into Sm-Co magnets 110, 111, and a size of 1.25 × 1.25 mm on a base 101 that has been inclined at 8 degrees on one side, The child 106-Faraday rotator 104-polarizer 107 were bonded and fixed, and the magnet was magnetized so as to have the magnetization direction in the same direction as the light transmission direction of FIG. By tilting the base 101, it is possible to remove the residual reflection on the air AR coating surface of the polarizer 105 in a direction (angle) different from the incident light with respect to the incident light from the direction of the polarizer 105.
[0032]
The function of the assembled optical isolator will be described with reference to FIG. The laser beam incident on the {circle around (1)} surface transmits only the polarization component parallel to the base 101 through the polarizer 105 and reaches {circle around (2)}. Here, the polarization direction is rotated 45 degrees clockwise by the Faraday rotator 103 to reach the polarizer 106. The laser beam reaches the Faraday rotator 104 by previously matching the transmission polarization direction of the polarizer 106 with the polarization direction (3) at the time of assembly. The polarization direction of the Faraday rotator 104 is rotated by 45 degrees in the opposite direction (counterclockwise) to the Faraday rotator 103 and is transmitted. The polarizer 107 is set so that the relative angle with respect to the polarizer 106 is 45 degrees as described above, and the transmission polarization direction of (5) and the transmission direction of the polarizer 107 coincide with each other as shown in (6). The base 101 and the transmission polarization direction are parallel to each other, and the transmission direction (1) at the time of incidence coincides. For this reason, the transmission polarization direction at the time of incidence is the same after the isolator emission, and the polarization direction is maintained.
[0033]

[0034]
When the characteristics of the prototyped isolator were measured, the characteristics of this isolator at 1550 nm were as follows. The forward insertion loss of incident light incident from the direction of the polarizer 105 was 0.30 dB, and the transmission polarization directions of the polarizer 105 and the polarizer 107 were The reverse insertion loss of the incident light incident from the direction of the polarizer 107 was 64 dB.
[0035]
(Example 2)
The optical isolator of the present invention as shown in FIG. 2 was constructed. As the material of each optical element, the same material as in Example 1 was used.
On the adhesive AR coating surface of each of the polarizers 205 and 206 made of polarizing glass having a size of 15 × 15 × 0.5 mm and having an anti-air AR coat on one side and an anti-adhesive AR coat on the other side, The Faraday rotator 203 made of (GaBi) ₃ (FeGa) ₅ O ₁₂ having a size of 15 × 15 × 0.6 mm and anti-adhesive AR coating on both sides was bonded to the anti-adhesive AR coating surface of the Faraday rotator 203 via an epoxy adhesive. The polarizer is bonded and fixed so that the relative angle of the polarizer is 45 degrees (the transmitted polarization direction of the polarizer 206 is rotated 45 degrees clockwise as viewed from the polarizer 205), and then the size is 1.25 × 1.25 mm. Disconnected.
[0036]
Next, the adhesive AR of each of the polarizers 207 and 208 made of polarizing glass having a size of 15 × 15 × 0.5 mm and having an anti-air AR coat on one side and an anti-adhesive AR coat on the other side. The Faraday rotator 204 made of (TbEuBi) ₃ (FeGa) ₅ O ₁₂ having a size of 15 × 15 × 0.6 mm on the coated surface and coated with an adhesive AR coating on both surfaces via an epoxy adhesive The polarizing glass at both ends at this time is set so that the transmission polarization direction is relatively 45 degrees (the polarizer 208 rotates counterclockwise when viewed from the polarizer 207), and is fixed by bonding. Cut to a size of 1.25 × 1.25 mm.
[0037]
Polarizer 205-Faraday rotator 203-polarizer 206, polarizer, which is the above-described optical element cut into 1.25 × 1.25 mm on a base 201 that is tilted to 8 degrees on one side The 207-Faraday rotator 204-polarizer 208 were bonded and fixed, magnets were magnetized so as to have a magnetization direction in the same direction as the light transmission direction in FIG. 2, and an isolator was assembled.
[0038]
When the characteristics of the prototyped isolator were measured, the characteristics of this isolator at 1550 nm were as follows. The forward insertion loss of incident light incident from the direction of the polarizer 205 was 0.34 dB, and the transmission polarization directions of the polarizer 205 and the polarizer 208 were The reverse insertion loss of incident light incident from the direction of the polarizer 208 was 78 dB.
[0039]
(Example 3)
A latching type Faraday rotator is used for the Faraday rotators 103 and 104 in the first embodiment, and after undergoing a joining process similar to that in the first embodiment, the Faraday rotator 103 is magnetized so as to cause a 45 degree Faraday rotation in the clockwise direction. The optical isolator was assembled such that the rotor 104 was magnetized so as to rotate 45 degrees counterclockwise.
In the latching type Faraday rotator, the magnets 110 and 111 in the first embodiment do not need to be disposed. Therefore, no magnet is disposed in the third embodiment.
[0040]
When the characteristics of the prototyped isolator were measured, this isolator had a forward insertion loss of 0.24 dB, the transmitted polarization directions of the polarizers 105 and 107 were the same, and a reverse insertion loss of 67 dB.
In the present invention, also in the optical isolator of the second embodiment, the Faraday rotators 203 and 204 can be of a latching type and can be arranged without magnets.
[0041]
Example 4
The optical isolator of the present invention as shown in FIG. 4 was constructed. The materials of the polarizer 405 and the Faraday rotator 403 are bonded using the same optical material as in Example 1, and the surface where the polarizer 405 to the Faraday rotator 403 contacts with the base 401 and the paired surface are 8 degrees when cut. Cutting was performed to incline. The magnet is the same as that of the first embodiment. In addition, the base 401 was made into the flat plate process without carrying out the inclination process. Otherwise, an optical isolator was manufactured in the same manner as in Example 1.
[0042]
In this embodiment, by tilting the optical element, the labor of tilting the base can be saved, and the residual reflection on the air AR coating surface of the polarizer 405 with respect to the incident light can be removed in a direction different from the incident light. It was. In this case, when the optical element is cut vertically as in the conventional example of FIG. 5 and is inclined in the lateral direction on the base 501, the optical element is not effectively disposed with respect to the light transmitting portion, and the magnet 510- It is necessary to make an extra distance between 511, which is not suitable for miniaturization of the isolator. However, as shown in FIG. 4B, the incident side optical element can be inclined to reduce the size of the isolator without increasing the distance between the magnets, and the optical element material can be used wastefully. There is also an advantage that there is no.
[0043]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0044]
【The invention's effect】
As described in detail above, the optical isolator of the present invention is a highly reliable optical isolator having a high reverse insertion loss and the same input / output transmission polarization direction, and can be easily mass-produced to achieve a low It becomes possible to supply at a cost.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a first mode of an optical isolator according to the present invention.
(A) Top view, (b) AA sectional view taken on the line.
FIG. 2 is a cross-sectional view showing a second aspect of the optical isolator of the present invention.
3 shows the direction of transmission polarization of light on the surface of each optical element in FIGS. 1 and 2. FIG.
FIG. 4 is an explanatory view showing a third aspect of the optical isolator of the present invention.
(A) Top view, (b) BB line sectional view, (c) Front view,
FIG. 5 is an explanatory diagram showing an aspect of a conventional optical isolator as a conventional example.
(A) Top view, (b) Side view, (c) Front view.
[Explanation of symbols]
101 ... Base, 103, 104 ... Faraday rotator,
105, 106, 107 ... polarizer, 110, 111 ... magnet,
201 ... Base, 203, 204 ... Faraday rotator,
205, 206, 207, 208 ... Polarizer, 210, 211 ... Magnet,
401 ... Base, 403, 404 ... Faraday rotator,
405, 406, 407 ... Polarizers, 410, 411 ... Magnets,
501 ... Base, 503 ... Faraday rotator,
505, 506 ... Polarizer, 510, 511 ... Magnet,
(1), (2), (3), (4), (5), (6), (7), (8) ... the surface of each optical element.

Claims (6)

An optical isolator in which an optical element having at least three polarizers and two Faraday rotators is arranged with respect to the traveling direction of light, and a magnet having opposite ends magnetized is sandwiched between the optical elements. The optical elements are arranged to face each other in the order of a first polarizer, a first Faraday rotator, a second polarizer, a second Faraday rotator, and a third polarizer. An optical isolator, wherein the transmitted polarization directions are the same and the Faraday rotation direction of the first Faraday rotator is different from the Faraday rotation direction of the second Faraday rotator in the same magnetic field direction toward the light traveling direction. .   2. The optical isolator according to claim 1, wherein the optical element further includes a fourth polarizer disposed between the first Faraday rotator and the second Faraday rotator. The optical isolator of claim 1 or claim 2, the optical element (polarizer, a Faraday rotator) fixed on the and / or magnets tabular base, to the base of the installation plane in mounting The optical isolator is characterized in that the transmission polarization directions of the polarizers arranged at both ends of the light traveling direction are parallel directions. The optical isolator according to any one of claims 1 to 3 , wherein at least an incident-side polarizer is inclined. The optical isolator according to claim 4 , wherein the inclined arrangement of the optical element is formed by inclining a cut surface of the optical element. 6. The optical isolator according to claim 5 , wherein the inclined arrangement of the optical element is inclined along the light traveling direction from a direction perpendicular to the contact surface between the optical element and the base.

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