JPH05341229A - Optical isolator - Google Patents

Abstract

PURPOSE:To obtain the optical isolator of a polarized wave non-dependence type by disposing in order a polarizer, a Faraday rotator and a polarized light rotator on two optical paths between two elements, and providing the polarizer at every optical path so as to coincide with a plane of polarization of each separated polarized light. CONSTITUTION:A return light which is made incident from an emitting side, first of all, is separated into polarized light components of two optical paths A, B having the same specific plane of polarization by an operation of a polarized light separating/ synthesizing element 4, and as for a polarized light for advancing along the optical path A, its plane of polarization is rotated by 90 degrees by a lambda/2 plate 7, and thus, coincides with the plane of polarization of the return light for advancing along the optical path B. Subsequently, the plane of polarization is rotated by total 90 degrees, that is, 45 degrees by an operation of a polarized light rotor 10, and also, 45 degrees by a Faraday rotor 9. Accordingly, the plane of polarization of the polarized light components of these two optical paths A, B makes an angle of 90 degrees against the plane of polarization of a polarizer 8, therefore, the return light cannot pass through the polarizer 8, and does not return to the incident side. In such a manner, a function as the optical isolator is displayed without considering the plane of polarization of an incident light.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、光アイソレータ、特に
入射光の偏光面を考慮することなく作動しうるようにし
た偏波無依存型光アイソレータに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator, and more particularly to a polarization independent optical isolator which can operate without considering the polarization plane of incident light.

【０００２】[0002]

【従来の技術】図３は従来の光アイソレータの構成例を
示している。この光アイソレータでは入射光が第一の偏
光子１を通過した後にファラデー回転子２によってその
偏光面が４５度回転し、更に該第一の偏光子１に対して
４５度傾いた偏光面を有する第二の偏光子３を通過す
る。一方、上記入射光とは逆方向の反射戻り光は第二の
偏光子３に対して偏光面が一致した成分のみが該第二の
偏光子３を通過し、この後上記ファラデー回転子２によ
ってその偏光面が更に４５度回転する。従って、ファラ
デー回転子２を通過したかかる反射戻り光は第一の偏光
子１に対してその偏光面が９０度回転していることにな
り、これにより、上記入射光の入射側までには到達する
ことができなくなる。このように従来の光アイソレータ
によれば上記逆方向の反射戻り光が遮断され、この種の
光アイソレータ機能が発揮される。2. Description of the Related Art FIG. 3 shows a configuration example of a conventional optical isolator. In this optical isolator, after the incident light passes through the first polarizer 1, the Faraday rotator 2 rotates its polarization plane by 45 degrees, and further has a polarization plane inclined by 45 degrees with respect to the first polarizer 1. It passes through the second polarizer 3. On the other hand, in the reflected return light in the opposite direction to the incident light, only the component whose polarization plane matches that of the second polarizer 3 passes through the second polarizer 3, and then the Faraday rotator 2 The plane of polarization is further rotated 45 degrees. Therefore, the reflected return light that has passed through the Faraday rotator 2 has its polarization plane rotated by 90 degrees with respect to the first polarizer 1, and thereby reaches the incident side of the incident light. Can not do. As described above, according to the conventional optical isolator, the reflected return light in the opposite direction is blocked, and this type of optical isolator function is exhibited.

【０００３】[0003]

【発明が解決しようとする課題】しかしながら、かかる
従来の光アイソレータでは、入射光の偏光面に対して第
一の偏光子１の偏光面を一致させておく必要があるた
め、特に偏光面を予め特定することができない光伝送系
においては、その機能を有効に発揮することができない
という問題があった。これは入射光の偏光面の傾きに依
存せざるを得ない構造になっているためである。However, in such a conventional optical isolator, it is necessary to match the polarization plane of the first polarizer 1 with the polarization plane of the incident light. In the optical transmission system which cannot be specified, there is a problem that the function cannot be effectively exhibited. This is because the structure has no choice but to depend on the inclination of the polarization plane of the incident light.

【０００４】本発明はこのような実情に鑑み、入射光の
偏光面を全く考慮することなく光アイソレータとしての
機能が発揮されるようにした偏波無依存型の光アイソレ
ータを提供することを目的とする。In view of the above situation, it is an object of the present invention to provide a polarization-independent optical isolator capable of exerting its function as an optical isolator without considering the plane of polarization of incident light. And

【０００５】[0005]

【課題を解決するための手段】上記目的を達成するため
本発明の光アイソレータの第１は、任意の偏光面を有す
る偏光を、互いに９０度の角度をなす偏光面を持つ２つ
の偏光に分離すると共に一方の偏光は入射光と同一の光
軸で出射し、他方の偏光は該光軸と並行な別の光軸で出
射する偏光分離・合成素子一対を対向配置し、この２素
子間の２光路上に偏光子、ファラデー回転子及び偏光回
転子を順に配設し、該偏光子は分離された各偏光の偏光
面と一致するように光路毎に設けられている点に特徴が
ある。In order to achieve the above object, the first of the optical isolators of the present invention is to separate polarized light having an arbitrary polarization plane into two polarized lights having polarization planes forming an angle of 90 degrees with each other. At the same time, one polarized light is emitted with the same optical axis as the incident light, and the other polarized light is emitted with another optical axis parallel to the optical axis. A feature is that a polarizer, a Faraday rotator, and a polarization rotator are sequentially arranged on the two optical paths, and the polarizer is provided for each optical path so as to match the polarization planes of the respective polarized lights.

【０００６】又、本発明の光アイソレータの第２は、任
意の偏光面を有する偏光を、互いに９０度の角度をなす
偏光面を持つ２つの偏光に分離すると共に一方の偏光は
入射光と同一の光軸で出射し、他方の偏光は該光軸と平
行な別の光軸で出射する偏光分離・合成素子一対を対向
配置し、該各素子に近接して何れか一方の光路にλ／２
板を置いて２光路の偏光面を一致させ、前記２つのλ／
２板の間の２光路上に偏光子、ファラデー回転子及び偏
光回転子を順に配設し、該偏光子は前記２光路の偏光面
と一致するようにされている点に特徴がある。The second aspect of the optical isolator of the present invention is to separate polarized light having an arbitrary polarization plane into two polarized lights having polarization planes forming an angle of 90 degrees, and one polarization is the same as the incident light. A pair of polarization separating / combining elements that emit the other polarized light and emit the other polarized light in a different optical axis parallel to the optical axis are arranged so as to face each other, and λ / Two
A plate is placed so that the polarization planes of the two optical paths coincide with each other, and the two λ /
A feature is that a polarizer, a Faraday rotator and a polarization rotator are sequentially arranged on two optical paths between two plates, and the polarizer is made to coincide with the polarization plane of the two optical paths.

【０００７】[0007]

【作用】本発明によれば任意の偏光面を有する入射光は
先ず入射側の偏光分離・合成素子によって互いに９０度
の角度をなす偏光面を有する二つの偏光に分離される。
そして、各々の光路の偏光成分に偏光面を合わせた偏光
子へそれぞれ入射される。次にファラデー回転子によっ
てその偏光面が４５度回転した後、偏光回転子によって
再びもとの偏光面にもどされ、かかる二つの偏光成分は
出射側の偏光分離・合成素子により合成される。According to the present invention, the incident light having an arbitrary polarization plane is first separated by the polarization separating / combining element on the incident side into two polarized lights having polarization planes forming an angle of 90 degrees with each other.
Then, the light is incident on a polarizer whose polarization plane is matched with the polarization component of each optical path. Next, the polarization plane is rotated by 45 degrees by the Faraday rotator and then returned to the original polarization plane by the polarization rotator, and the two polarization components are combined by the polarization separating / combining element on the emission side.

【０００８】他方、任意の偏光面を有する逆方向の光は
まず出射側の偏光分離・合成素子により特定の偏光面を
有する二つの光路に分離される。次に偏光回転子によっ
てその偏光面が４５度回転した後、ファラデー回転子に
よってさらに４５度回転する。そのためかかる二つの光
路の偏光面は偏光子の偏光面に対して９０度回転してい
ることになり、入射側へは戻ることができない。On the other hand, light in the opposite direction having an arbitrary polarization plane is first split into two optical paths having a specific polarization plane by the polarization splitting / combining element on the output side. Next, the plane of polarization is rotated by 45 degrees by the polarization rotator, and then further rotated by 45 degrees by the Faraday rotator. Therefore, the polarization planes of the two optical paths are rotated by 90 degrees with respect to the polarization plane of the polarizer and cannot return to the incident side.

【０００９】[0009]

【実施例】図１は本発明の光アイソレータの１構成例を
示す図である。図の上段は各素子の配列を表し、中段は
入射光の各段階における偏光面の変化、下段は戻り光の
各段階における偏光面の変化を示しており、偏光面を示
す矢印は光軸端から見た状態で示してある。図２、図３
においても同様である。まず図１において、偏光分離・
合成素子４は偏光ビームスプリッタ５、反射プリズム６
から成り、偏光ビームスプリッタ側にλ／２板が配置さ
れている。また、８は偏光子、９はファラデー回転子で
あり１０はλ／２板より成る偏光回転子である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing one configuration example of an optical isolator according to the present invention. The upper part of the figure shows the arrangement of each element, the middle part shows the change of the polarization plane at each stage of the incident light, and the lower part shows the change of the polarization plane at each stage of the return light. It is shown as viewed from above. 2 and 3
The same is true for. First, referring to FIG.
The combining element 4 is a polarization beam splitter 5 and a reflecting prism 6.
And a λ / 2 plate is arranged on the polarization beam splitter side. Further, 8 is a polarizer, 9 is a Faraday rotator, and 10 is a polarization rotator composed of a λ / 2 plate.

【００１０】上記の場合、入射光はまず偏光分離・合成
素子４を構成する偏光ビームスプリッタ５の作用により
互いに９０度の角度をなす特定な偏光面を有する二つの
偏光に分離される。このとき二つの偏光のうち一方は入
射光と同一の光軸を持つ光路Ｂを、他方は光路Ｂと９０
度の角度をなす光軸を有する光路Ａを進行する。In the above case, the incident light is first separated into two polarized lights having specific polarization planes forming an angle of 90 degrees by the action of the polarization beam splitter 5 constituting the polarization separation / combination element 4. At this time, one of the two polarized lights is the optical path B having the same optical axis as the incident light, and the other is the optical path B and the optical path 90.
The optical path A having an optical axis forming an angle of degrees is traveled.

【００１１】光路Ａには偏光分離・合成素子４を構成す
る反射プリズム１０が配設されており、光路Ａを進行す
る偏光は反射プリズム１０によって反射されて光路Ｂと
平行な光軸を有する偏光となる。また、光路Ｂには偏光
分離・合成素子４に近接してλ／２板７が配設されてお
り、光路Ｂを進行する偏光はλ／２板７によって偏光面
が９０度回転する。すなわち、入射光は偏光分離・合成
素子４によって、特定な同一の偏光面をもち入射光に平
行な光軸をもつ二つの光路Ａ，Ｂの偏光成分に分離され
たことになる。A reflecting prism 10 which constitutes the polarization splitting / combining element 4 is disposed on the optical path A, and the polarized light traveling on the optical path A is reflected by the reflecting prism 10 and has a light axis parallel to the optical path B. Becomes Further, a λ / 2 plate 7 is disposed in the optical path B in the vicinity of the polarization separation / combination element 4, and the polarized light traveling on the optical path B has its polarization plane rotated by 90 ° by the λ / 2 plate 7. That is, the incident light is separated by the polarization separating / combining element 4 into the polarization components of the two optical paths A and B having the same specific polarization plane and having the optical axis parallel to the incident light.

【００１２】次に、これら分離された２つの偏光成分は
上記偏光子８を通過する。このとき偏光子８の偏光面は
光路Ａ，Ｂの偏光成分の偏光面に一致するように配置さ
れる。さらに二つの光路の偏光成分はファラデー回転子
９によって偏光面が４５度回転し、偏光回転子１０によ
って分離された時と同一の偏光面に戻される。したがっ
て光路Ａ，Ｂの偏光成分は入射側の偏光分離・合成素子
４と同様に構成されて成る出射側の偏光分離・合成素子
４によって再び合成され出射する。Next, the two separated polarized light components pass through the polarizer 8. At this time, the polarization plane of the polarizer 8 is arranged so as to match the polarization planes of the polarization components of the optical paths A and B. Further, the polarization components of the two optical paths are rotated by 45 degrees by the Faraday rotator 9 and returned to the same polarization plane as when separated by the polarization rotator 10. Therefore, the polarized light components of the optical paths A and B are combined again by the polarized light separation / combination element 4 on the exit side, which is configured similarly to the polarized light separation / combination element 4 on the incident side, and then emitted.

【００１３】他方、出射側より入射する戻り光は、まず
偏光分離・合成素子８の作用により特定な同一の偏光面
をもつ二つの光路Ａ，Ｂの偏光成分に分離され、光路Ａ
を進行する偏光はλ／２板７によって偏光面が９０度回
転する結果、光路Ｂを進行する戻り光の偏光面と一致す
る。そして、偏光回転子１０の作用によって偏光面が４
５度、さらにファラデー回転子９によって４５度、合計
９０度回転する。したがってかかる二つの光路Ａ，Ｂの
偏光成分の偏光面は偏光子８の偏光面に対して９０度の
角度をなすため偏光子８を通過することが出来ず、入射
側へは戻らない。On the other hand, the return light entering from the exit side is first separated by the action of the polarization separating / combining element 8 into the polarization components of the two optical paths A and B having the same specific polarization plane, and the optical path A
As a result of the polarization plane traveling 90 ° being rotated by 90 ° by the λ / 2 plate 7, it coincides with the polarization plane of the return light traveling on the optical path B. Then, the polarization plane is changed to 4 by the action of the polarization rotator 10.
The Faraday rotator 9 rotates 45 degrees, which is a total of 90 degrees. Therefore, the polarization planes of the polarization components of the two optical paths A and B form an angle of 90 degrees with the polarization plane of the polarizer 8, so that they cannot pass through the polarizer 8 and do not return to the incident side.

【００１４】又、図２において、１１は入射側および出
射側に配置されたＴｉＯ₂ （ルチル）複屈折板より成る
偏光分離・合成素子である。また、８ａ，８ｂは偏光面
が９０°異なる偏光子である。Further, in FIG. 2, reference numeral 11 denotes a polarization separating / combining element composed of a TiO ₂ (rutile) birefringent plate arranged on the incident side and the emitting side. Further, 8a and 8b are polarizers whose polarization planes differ by 90 °.

【００１５】上記の場合、入射光はまず偏光分離・合成
素子４の作用により互いに９０度の角度をなす特定な偏
光面をもち入射光に平行な光軸をもつ二つの光路Ａ，Ｂ
の偏光成分に分離される。そして、これら分離された２
つの偏光成分はそれぞれの光路Ａ，Ｂに配置された上記
偏光子８ａ，８ｂを通過する。この時偏光子８ａ，８ｂ
の偏光面はそれぞれの光路の偏光面に一致するように配
置される。さらに、二つの光路の偏光成分はファラデー
回転子９によって偏光面が４５度回転し、偏光回転子１
０によって分離された時と同一の偏光面に戻される。し
たがって光路Ａ，Ｂの偏光成分は偏光分離・合成素子４
によって再び合成され出射される。In the above case, the incident light first has two optical paths A and B having a specific plane of polarization which makes an angle of 90 degrees with each other by the action of the polarization separating / combining element 4 and has an optical axis parallel to the incident light.
Are separated into polarized light components of. And these two separated
The two polarization components pass through the polarizers 8a and 8b arranged in the respective optical paths A and B. At this time, the polarizers 8a and 8b
The polarization planes of are arranged so as to match the polarization planes of the respective optical paths. Further, the polarization components of the two optical paths are rotated by 45 degrees by the Faraday rotator 9, and the polarization rotator 1
It is returned to the same plane of polarization as when it was separated by zero. Therefore, the polarization components of the optical paths A and B are polarized light separating / combining element 4
Are again combined and emitted.

【００１６】他方、出射側より入射した戻り光はまず偏
光分離・合成素子４の作用により互いに９０度の角度を
なす特定な偏光面をもつ上記二つの光路Ａ，Ｂの偏光成
分に分離される。そして、偏光回転子１０によって偏光
面が４５度、さらにファラデー回転子９によって４５
度、合計９０度回転する。したがって二つの光路Ａ，Ｂ
の偏光成分の偏光面はそれぞれの光路に配置された偏光
子８ａ，８ｂの偏光面に対して９０度の角度をなすため
偏光子８ａ，８ｂを通過することが出来ず、入射側へは
戻らない。On the other hand, the return light incident from the exit side is first separated by the action of the polarization separating / combining element 4 into the polarization components of the two optical paths A and B having specific polarization planes forming an angle of 90 degrees with each other. .. Then, the plane of polarization is 45 degrees by the polarization rotator 10 and 45 by the Faraday rotator 9.
Rotate 90 degrees in total. Therefore, the two optical paths A and B
Since the polarization planes of the polarization components of are at an angle of 90 degrees with respect to the polarization planes of the polarizers 8a and 8b arranged in the respective optical paths, they cannot pass through the polarizers 8a and 8b and return to the incident side. Absent.

【００１７】図２の２つの複屈折板１１に近接して光路
Ａ，Ｂの何れか一方に図１に示すようなλ／２板を配置
すれば２つの光路の偏光面は一致するので偏光子は図１
のように１個にすることができ、一方図１のλ／２板を
取除けば、２つの光路の偏光面は９０°変るので、偏光
子８は図２のように２個必要となる。If a λ / 2 plate as shown in FIG. 1 is arranged in either one of the optical paths A and B in the vicinity of the two birefringent plates 11 in FIG. 2, the polarization planes of the two optical paths are coincident with each other. Child is Figure 1
, But if the λ / 2 plate in FIG. 1 is removed, the polarization planes of the two optical paths change by 90 °, so two polarizers 8 are required as shown in FIG. ..

【００１８】[0018]

【発明の効果】このように本発明によれば、入射光の偏
光面が予め特定できないような光伝送系であっても偏光
面の状態を考慮することなく光アイソレータとしての機
能を十分有効に発揮させることができるので実用的効果
等の点でも優れている。また、空間ビーム光や光ファイ
バー用として利用することができるのはもちろんである
が、その場合に既存の光アイソレータと簡単に置換する
ことが可能であり工業上極めて有用である。As described above, according to the present invention, even in an optical transmission system in which the plane of polarization of incident light cannot be specified in advance, the function as an optical isolator is sufficiently effective without considering the state of the plane of polarization. Since it can be exhibited, it is also excellent in practical effects. In addition, it can be used as a space beam light or an optical fiber, but in that case, it can be easily replaced with an existing optical isolator, which is extremely useful industrially.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明による光アイソレータの１構成例を示す
図である。FIG. 1 is a diagram showing one configuration example of an optical isolator according to the present invention.

【図２】本発明による光アイソレータの他の構成例を示
す図である。FIG. 2 is a diagram showing another configuration example of the optical isolator according to the present invention.

【図３】従来の光アイソレータの構成例を示す図であ
る。FIG. 3 is a diagram showing a configuration example of a conventional optical isolator.

【符号の説明】[Explanation of symbols]

１ 第一の偏光子 ２ ファラデー回転子 ３ 第二の偏光子 ４ 偏光分離・合成素子 ５ 偏光ビームスプリッタ ６ 反射プリズム ７ λ／２板 ８，８ａ，８ｂ 偏光子 ９ ファラデー回転子 １０ 偏光回転子 １１ ＴｉＯ₂ （ルチル）複屈折板1 First Polarizer 2 Faraday Rotor 3 Second Polarizer 4 Polarization Separation / Combining Element 5 Polarizing Beam Splitter 6 Reflection Prism 7 λ / 2 Plate 8, 8a, 8b Polarizer 9 Faraday Rotator 10 Polarization Rotator 11 TiO ₂ (rutile) birefringent plate

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】 任意の偏光面を有する偏光を、互いに９
０度の角度をなす偏光面を持つ２つの偏光に分離すると
共に一方の偏光は入射光と同一の光軸で出射し、他方の
偏光は該光軸と並行な別の光軸で出射する偏光分離・合
成素子一対を対向配置し、この２素子間の２光路上に偏
光子、ファラデー回転子及び偏光回転子を順に配設し、
該偏光子は分離された各偏光の偏光面と一致するように
光路毎に設けられてなる、光アイソレータ。1. Polarized light beams having arbitrary planes of polarization are separated from each other by 9
A polarized light that is split into two polarized light having a plane of polarization that forms an angle of 0 degree, and one polarized light is emitted on the same optical axis as the incident light, and the other polarized light is emitted on another optical axis parallel to the optical axis. A pair of separating / combining elements are arranged to face each other, and a polarizer, a Faraday rotator and a polarization rotator are sequentially arranged on two optical paths between these two elements,
An optical isolator in which the polarizer is provided for each optical path so as to match the polarization planes of the respective polarized lights. 【請求項２】 任意の偏光面を有する偏光を、互いに９
０度の角度をなす偏光面を持つ２つの偏光に分離すると
共に一方の偏光は入射光と同一の光軸で出射し、他方の
偏光は該光軸と平行な別の光軸で出射する偏光分離・合
成素子一対を対向配置し、該各素子に近接して何れか一
方の光路にλ／２板を置いて２光路の偏光面を一致さ
せ、前記２つのλ／２板の間の２光路上に偏光子、ファ
ラデー回転子及び偏光回転子を順に配設し、該偏光子は
前記２光路の偏光面と一致するようにされてなる、光ア
イソレータ。2. Polarized light beams having arbitrary planes of polarization are separated from each other by 9
A polarized light that is split into two polarized light having a plane of polarization that forms an angle of 0 degree, one polarized light is emitted on the same optical axis as the incident light, and the other polarized light is emitted on another optical axis parallel to the optical axis. A pair of separating / combining elements are arranged so as to face each other, and a λ / 2 plate is placed in the optical path of one of the elements in close proximity to each other so that the polarization planes of the two optical paths coincide with each other, and the two optical paths between the two λ / 2 plates An optical isolator, in which a polarizer, a Faraday rotator and a polarization rotator are sequentially arranged, and the polarizer is aligned with the polarization planes of the two optical paths.