JPH05232520A - Polarization separating element - Google Patents
Polarization separating elementInfo
- Publication number
- JPH05232520A JPH05232520A JP3551192A JP3551192A JPH05232520A JP H05232520 A JPH05232520 A JP H05232520A JP 3551192 A JP3551192 A JP 3551192A JP 3551192 A JP3551192 A JP 3551192A JP H05232520 A JPH05232520 A JP H05232520A
- Authority
- JP
- Japan
- Prior art keywords
- optical waveguide
- directional coupler
- optical
- electrodes
- buffer layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/29—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the position or the direction of light beams, i.e. deflection
- G02F1/31—Digital deflection, i.e. optical switching
- G02F1/313—Digital deflection, i.e. optical switching in an optical waveguide structure
- G02F1/3132—Digital deflection, i.e. optical switching in an optical waveguide structure of directional coupler type
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- Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Integrated Circuits (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は偏光分離素子に関し、特
にニオブ酸リチウム基板上に形成される導波型偏光分離
素子に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization separation element, and more particularly to a waveguide type polarization separation element formed on a lithium niobate substrate.
【０００２】[0002]
【従来の技術】ニオブ酸リチウムは大きな電気光学効果
と電気機械結合係数を持つため、導波型光機能素子の基
板材料として広く用いられている。ニオブ酸リチウムを
基板とする光導波路には屈折率異方性があるため、機能
素子は偏光に依存して動作する。このため、偏光（ＴＭ
／ＴＥ偏光）を分離する素子が必要となる。2. Description of the Related Art Lithium niobate has a large electro-optic effect and an electromechanical coupling coefficient, and is therefore widely used as a substrate material for a waveguide type optical functional device. Since the optical waveguide using lithium niobate as a substrate has a refractive index anisotropy, the functional element operates depending on the polarized light. Therefore, polarized light (TM
An element for separating / TE polarized light) is required.
【０００３】従来の技術としては、以下に挙げる例があ
る。The following are examples of conventional techniques.
【０００４】図３はエレクトロニクス・レター第２６巻
２２号１８５５〜１８５６頁（Ｅｌｅｃｔｒｏｎｉｃｓ
Ｌｅｔｔｅｒｓ，Ｖｏｌ．２６，Ｎｏ．２２，ｐｐ．
１８５５−１８５６，１９９０）より引用した偏光分離
素子である。ニオブ酸リチウム基板３１に作製された方
向性結合器構造を持つチタン熱拡散光導波路３２ａ，３
２ｂに２００オングストローム程度の薄い酸化アルミニ
ウム膜３３を介して金属アルミニウム片３４を装荷して
いる。この金属アルミニウム片３４によって、ＴＭ偏光
に関して、隣接する２つの光導波路間の一様分布結合が
生じなくなる。また、ＴＥ偏光は金属アルミニウム片３
４の影響をほとんど受けなく、方向性結合器の結合長は
ＴＥ偏光の完全結合長に合わせてあるので、光導波路３
２ｂに入射したランダム偏光によって入力端に励起され
たＴＥ／ＴＭモードのうち、ＴＭ偏光成分は光導波路３
２ｂの出力端に向かい導波し、ＴＥ偏光は方向性結合器
部分で隣接する光導波路３２ａに移行し導波する。FIG. 3 is an Electronics Letter Vol. 26, No. 22, pp. 1855 to 1856 (Electronics).
Letters, Vol. 26, No. 22, pp.
1855-1856, 1990). Titanium thermal diffusion optical waveguides 32a, 3 having a directional coupler structure formed on a lithium niobate substrate 31
A metal aluminum piece 34 is loaded on 2b through a thin aluminum oxide film 33 of about 200 angstroms. The metal aluminum piece 34 prevents uniform distribution coupling between two adjacent optical waveguides with respect to TM polarized light. In addition, TE polarized light is a metal aluminum piece 3
4 is almost unaffected, and the coupling length of the directional coupler is adjusted to the perfect coupling length of TE polarized light.
Of the TE / TM modes excited at the input end by the randomly polarized light incident on 2b, the TM polarization component is the optical waveguide 3
The TE polarized light is guided toward the output end of 2b, and the TE polarized light is transferred to the adjacent optical waveguide 32a at the directional coupler portion and guided.
【０００５】[0005]
【発明が解決しようとする課題】上述した従来の偏光分
離素子では、 （１）高い消光比を得るためには、方向性結合器の結合
長ｌを完全結合長Ｌに正確に合わせる必要がある。 （２）万が一、作製プロセス条件の変動などで結合長ｌ
がずれた場合には偏光分離特性が劣化し、調整すること
も不可能である。 （３）方向性結合器の一様分布結合は波長依存性があ
り、広帯域な光波長に対しては偏光分離特性が劣化す
る。 という問題点がある。In the conventional polarization separation element described above, (1) In order to obtain a high extinction ratio, it is necessary to accurately match the coupling length l of the directional coupler with the complete coupling length L. .. (2) In the unlikely event that there is a change in the manufacturing process conditions, the bond length l
If the deviation occurs, the polarization separation characteristics deteriorate and it is impossible to adjust the polarization separation characteristics. (3) The uniform distribution coupling of the directional coupler has wavelength dependence, and the polarization separation characteristic deteriorates for a wide wavelength of light. There is a problem.
【０００６】本発明の目的は、このような問題点を解決
した偏光分離素子を提供することにある。An object of the present invention is to provide a polarization beam splitting element that solves such problems.
【０００７】[0007]
【課題を解決するための手段】第１の発明の偏光分離素
子は、電気光学効果を有する基板上に作製された方向性
結合器構造を有する光導波路と、方向性結合器部分の一
方の光導波路上にバッファ層を介して２つに分割した電
極を装荷し、もう一方の光導波路を挟むように光導波路
近傍に２つに分割した電極を装荷したことを特徴とす
る。The polarization splitting element of the first invention is an optical waveguide having a directional coupler structure formed on a substrate having an electro-optical effect, and one optical waveguide of the directional coupler portion. It is characterized in that an electrode divided into two is loaded on the waveguide via a buffer layer, and an electrode divided into two is loaded in the vicinity of the optical waveguide so as to sandwich the other optical waveguide.
【０００８】第２の発明の偏光分離素子は、電気光学効
果を有する基板上に作製された方向性結合器構造を有す
る光導波路と、方向性結合器部分の一方の光導波路上に
バッファ層を介して２つに分割した電極を装荷し、もう
一方の光導波路上に前記バッファ層と厚さが異なるバッ
ファ層を介して２つに分割した電極を装荷したことを特
徴とする。In the polarization beam splitting element of the second invention, an optical waveguide having a directional coupler structure formed on a substrate having an electro-optical effect, and a buffer layer on one optical waveguide of the directional coupler portion. It is characterized in that the electrode divided into two is loaded via the above-mentioned, and the electrode divided into two is loaded onto the other optical waveguide via a buffer layer having a thickness different from that of the buffer layer.
【０００９】[0009]
【作用】第１の発明では、方向性結合器の一方の光導波
路を挟むように光導波路近傍に装荷した２つに分割した
電極によって、また、第２の発明では方向性結合器部分
のそれぞれの光導波路上に設けた厚さの異なるバッファ
層を介して装荷した２つに分割した電極によって、正負
の屈折率変化を光導波路に与えることができ、これらの
作用によって （１）従来はｌ＝Ｌにする必要があった結合長ｌの条件
が、Ｌ＜ｌ＜３Ｌの範囲に広がり、素子設計の自由度が
広がる。 （２）作製プロセス条件の変動、形状誤差などで結合長
ｌがずれた場合にも、偏光分離特性の劣化を電圧調整に
より抑えることができる。 （３）光波長依存性のある方向性結合器の一様分布結合
を電圧調整により補正することができ、広帯域な偏光分
離素子を実現することができる。According to the first aspect of the invention, the two divided electrodes are provided in the vicinity of the optical waveguide so as to sandwich one of the optical waveguides of the directional coupler, and in the second aspect, each of the directional coupler portions. The positive and negative refractive index changes can be given to the optical waveguide by the electrodes divided into two loaded through the buffer layers having different thicknesses provided on the optical waveguide of (1) The condition of the coupling length l that has to be set to = L spreads to the range of L <l <3L, and the degree of freedom in device design expands. (2) Even if the coupling length l is deviated due to a change in manufacturing process conditions, a shape error, or the like, it is possible to suppress deterioration of the polarization separation characteristic by adjusting the voltage. (3) The uniform distribution coupling of the directional coupler having the light wavelength dependency can be corrected by voltage adjustment, and a wideband polarization separation element can be realized.
【００１０】[0010]
【実施例】次に本発明について図面を参照して説明す
る。The present invention will be described below with reference to the drawings.
【００１１】図１は第１の発明の実施例を説明するため
の偏光分離素子の斜視図である。この偏光分離素子の構
造を、その製造方法とともに説明する。ＹカットＸ軸伝
搬ニオブ酸リチウム基板１１上に、幅６〜１２μｍ，膜
厚４００〜６００オングストロームのチタン薄膜による
方向性結合器型の光導波路パターンを形成し、９５０〜
１１００℃で熱拡散を行い、単一モードチタン熱拡散光
導波路１２ａ，１２ｂを作製する。FIG. 1 is a perspective view of a polarization beam splitting element for explaining an embodiment of the first invention. The structure of this polarization separation element will be described together with its manufacturing method. On the Y-cut X-axis propagation lithium niobate substrate 11, a directional coupler type optical waveguide pattern made of a titanium thin film having a width of 6 to 12 μm and a film thickness of 400 to 600 angstroms is formed.
Thermal diffusion is performed at 1100 ° C. to produce single mode titanium thermal diffusion optical waveguides 12a and 12b.
【００１２】ニオブ酸リチウム基板１１表面上に厚さ１
００〜２０００オングストロームの二酸化珪素（ＳｉＯ
2 ）などの誘電体から成る薄膜のバッファ層１３を積層
する。A thickness of 1 on the surface of the lithium niobate substrate 11
Silicon dioxide (SiO 2) of 00 to 2000 angstrom
2 ) A thin film buffer layer 13 made of a dielectric material such as 2 ) is laminated.
【００１３】バッファ層１３上にフォトリソグラフィ法
を用いて、方向性結合器部分の一方の光導波路部分と、
もう一方の光導波路を挟むように光導波路近傍に２分割
した金属電極１４を作製する。金属は光波長領域では誘
電率が負でかつ極めて損失の大きな誘電体として振る舞
い、ＴＭ偏光は電界成分を基板に対し垂直な方向に持つ
ためバッファ層１３厚が薄い場合、光導波路上の金属電
極１４の影響を大いに受け、方向性結合器部分で一様分
布結合が生じなくなる。そのため、光導波路１２ｂに励
起されたＴＭモードは方向性結合器部分をそのまま素通
りし、光導波路１２ｂの出力端から光出力される。Using photolithography on the buffer layer 13, one optical waveguide portion of the directional coupler portion and
The metal electrode 14 divided into two is produced in the vicinity of the optical waveguide so as to sandwich the other optical waveguide. Metal acts as a dielectric having a negative permittivity and extremely large loss in the light wavelength region, and TM polarized light has an electric field component in the direction perpendicular to the substrate. Therefore, when the buffer layer 13 is thin, a metal electrode on the optical waveguide It is greatly affected by 14 and uniform distribution coupling does not occur in the directional coupler portion. Therefore, the TM mode excited in the optical waveguide 12b passes through the directional coupler portion as it is, and is optically output from the output end of the optical waveguide 12b.
【００１４】また、ＴＥ偏光は電界成分を基板に対し平
行な方向に持つため、薄いバッファ層１３に対しても金
属電極１４の影響をほとんど受けない。方向性結合器の
結合長ｌは、ＴＥ偏光の完全結合長Ｌの１〜３倍の範囲
内で作製しておく。２分割した金属電極１４にそれぞれ
正負の電圧を印加し、光導波路に正負の屈折率変化を発
生させることで、方向性結合器部分において隣接する光
導波路に１００％の光パワー移行を起こすことができ
る。Further, since the TE polarized light has an electric field component in a direction parallel to the substrate, the thin buffer layer 13 is hardly affected by the metal electrode 14. The coupling length l of the directional coupler is prepared within the range of 1 to 3 times the complete coupling length L of TE polarized light. By applying positive and negative voltages to the two divided metal electrodes 14 to generate positive and negative refractive index changes in the optical waveguide, 100% optical power transfer can occur in the adjacent optical waveguides in the directional coupler portion. it can.
【００１５】以上のように、光導波路１２ｂに入射した
ランダム偏光のうち、ＴＭ偏光成分は光導波路１２ｂの
出力端に、ＴＥ偏光は光導波路１２ａの出力端に導波し
て偏光分離することができる。As described above, of the randomly polarized light incident on the optical waveguide 12b, the TM polarized light component can be guided to the output end of the optical waveguide 12b and the TE polarized light can be guided to the output end of the optical waveguide 12a to be polarized and separated. it can.
【００１６】図２は第２の発明の実施例を説明するため
の偏光分離素子の斜視図である。ＹカットＺ軸伝搬ニオ
ブ酸リチウム基板２１上に前述のチタン拡散光導波路と
同様のプロセスで、同様の構成である単一モードチタン
拡散光導波路２２ａ，２２ｂを作製する。ニオブ酸リチ
ウム基板２１に作製した方向性結合器の一方の光導波路
２２ｂ部分上に厚さ１００〜２０００オングストローム
の薄いバッファ層２３ｂを積層し、もう一方の光導波路
２２ａ部分上には厚さ２０００〜３０００オングストロ
ームの厚いバッファ層２３ａを積層する。FIG. 2 is a perspective view of a polarization beam splitting element for explaining an embodiment of the second invention. On the Y-cut Z-axis propagation lithium niobate substrate 21, single-mode titanium diffusion optical waveguides 22a and 22b having the same configuration are manufactured by the same process as the titanium diffusion optical waveguide described above. A thin buffer layer 23b having a thickness of 100 to 2000 angstrom is laminated on one optical waveguide 22b portion of the directional coupler formed on the lithium niobate substrate 21, and a thickness of 2000 to about 2000 Å is formed on the other optical waveguide 22a portion. A thick buffer layer 23a having a thickness of 3000 angstrom is laminated.
【００１７】バッファ層２３上にフォトリソグラフィ法
を用いて、方向性結合器部分の一方の光導波路部分と、
もう一方の光導波路部分にそれぞれ２分割した金属電極
２４を作製する。Using photolithography on the buffer layer 23, one optical waveguide portion of the directional coupler portion and
A metal electrode 24 divided into two is produced in the other optical waveguide portion.
【００１８】前述したようにＴＭ偏光は、薄いバッファ
層２３ｂにおいて光導波路の上にある金属電極２４の影
響を大いに受け、方向性結合器部分で一様分布結合が生
じなくなる。厚いバッファ層２３ａ下の光導波路２２ａ
においては金属電極２４による損失はほとんど無く、光
導波路２２ａに励起されたＴＭモードは方向性結合器部
分をそのまま素通りし、光導波路２２ａの出力端から光
出力される。As described above, the TM polarized light is greatly affected by the metal electrode 24 on the optical waveguide in the thin buffer layer 23b, and uniform distribution coupling does not occur in the directional coupler portion. Optical waveguide 22a under thick buffer layer 23a
, There is almost no loss due to the metal electrode 24, and the TM mode excited in the optical waveguide 22a passes through the directional coupler portion as it is, and is optically output from the output end of the optical waveguide 22a.
【００１９】また、前述したようにＴＥ偏光は薄いバッ
ファ層２３ｂ下の光導波路に対しても金属電極２４の影
響をほとんど受けないため、方向性結合器部分において
隣接する光導波路に１００％の光パワー移行を起こす。Further, as described above, the TE polarized light is hardly affected by the metal electrode 24 even with respect to the optical waveguide below the thin buffer layer 23b, so that the optical waveguide adjacent to the optical waveguide in the directional coupler portion has 100% light. Causes power transfer.
【００２０】以上のように、光導波路２２ａに入射した
ランダム偏光のうち、ＴＭ偏光成分は光導波路２２ａの
出力端に、ＴＥ偏光は光導波路２２ｂの出力端に導波し
て偏光分離することができる。As described above, of the randomly polarized light incident on the optical waveguide 22a, the TM polarized light component can be guided to the output end of the optical waveguide 22a and the TE polarized light can be guided to the output end of the optical waveguide 22b for polarization separation. it can.
【００２１】[0021]
【発明の効果】以上説明したように、第１の発明では、
方向性結合器の一方の光導波路を挟むように光導波路近
傍に装荷した２つに分割した電極によって、また、第２
の発明では方向性結合器部分のそれぞれの光導波路上に
設けた厚さの異なるバッファ層を介して装荷した２つに
分割した電極によって、正負の屈折率変化を光導波路に
与えることができ、これにより、 （１）結合長の条件範囲が広がり、素子設計の自由度が
大きくなる。 （２）作製プロセス条件の変動、形状誤差などに対する
偏光分離比の変動を電圧調整により抑えることができ
る。 （３）光波長依存性のある方向性結合器の一様分布結合
を電圧調整により補正することができ、広帯域な偏光分
離素子を実現することができる。 などの効果があり、偏光分離機能を必要とする光集積回
路において広い光波長帯域にわたり高い偏光分離比を保
証でき、作製トレランスの大きい偏光分離素子を供給で
きる効果は極めて大きなものであるといえる。As described above, according to the first invention,
By the two divided electrodes loaded near the optical waveguide so as to sandwich one optical waveguide of the directional coupler,
In the invention, the positive and negative refractive index changes can be given to the optical waveguide by the two divided electrodes loaded via the buffer layers having different thicknesses provided on the respective optical waveguides of the directional coupler portion, As a result, (1) the condition range of the coupling length is widened, and the degree of freedom in device design is increased. (2) It is possible to suppress variations in the polarization separation ratio due to variations in manufacturing process conditions, shape errors, and the like by voltage adjustment. (3) The uniform distribution coupling of the directional coupler having the light wavelength dependency can be corrected by voltage adjustment, and a wideband polarization separation element can be realized. It can be said that the effect of being able to supply a polarized light separating element having a large manufacturing tolerance can be ensured with a high polarized light separation ratio over a wide optical wavelength band in an optical integrated circuit requiring a polarized light separating function.
【図１】第１の発明の光変調器の一実施例を説明するた
めの斜視図である。FIG. 1 is a perspective view for explaining an embodiment of an optical modulator of the first invention.
【図２】第２の発明の光変調器の一実施例を説明するた
めの斜視図である。FIG. 2 is a perspective view for explaining one embodiment of the optical modulator of the second invention.
【図３】従来の技術を説明するための図である。FIG. 3 is a diagram for explaining a conventional technique.
１１，２１，３１ ニオブ酸リチウム基板 １２ａ，１２ｂ，２２ａ，２２ｂ，３２ａ，３２ｂ チ
タン拡散光導波路 １３，２３ｂ ３３ 薄いバッファ層 ２３ａ 厚いバッファ層 １４，２４，３４ ２分割した金属電極11, 21, 31 Lithium niobate substrate 12a, 12b, 22a, 22b, 32a, 32b Titanium diffused optical waveguide 13, 23b 33 Thin buffer layer 23a Thick buffer layer 14, 24, 34 2 Separated metal electrodes
Claims (2)
方向性結合器構造を有する光導波路と、方向性結合器部
分の一方の光導波路上にバッファ層を介して２つに分割
した電極を装荷し、もう一方の光導波路を挟むように光
導波路近傍に２つに分割した電極を装荷したことを特徴
とする偏光分離素子。1. An optical waveguide having a directional coupler structure formed on a substrate having an electro-optical effect, and an electrode divided into two via a buffer layer on one optical waveguide of a directional coupler portion. And a divided electrode in the vicinity of the optical waveguide so as to sandwich the other optical waveguide.
方向性結合器構造を有する光導波路と、方向性結合器部
分の一方の光導波路上にバッファ層を介して２つに分割
した電極を装荷し、もう一方の光導波路上に前記バッフ
ァ層と厚さが異なるバッファ層を介して２つに分割した
電極を装荷したことを特徴とする偏光分離素子。2. An optical waveguide having a directional coupler structure formed on a substrate having an electro-optical effect, and an electrode divided into two via a buffer layer on one optical waveguide of the directional coupler portion. And a divided electrode divided into two via a buffer layer having a thickness different from that of the buffer layer on the other optical waveguide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3551192A JP2792306B2 (en) | 1992-02-24 | 1992-02-24 | Polarization separation element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3551192A JP2792306B2 (en) | 1992-02-24 | 1992-02-24 | Polarization separation element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05232520A true JPH05232520A (en) | 1993-09-10 |
| JP2792306B2 JP2792306B2 (en) | 1998-09-03 |
Family
ID=12443788
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3551192A Expired - Fee Related JP2792306B2 (en) | 1992-02-24 | 1992-02-24 | Polarization separation element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2792306B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9461753B2 (en) | 2012-07-30 | 2016-10-04 | Fujitsu Optical Components Limited | Optical receiver circuit |
-
1992
- 1992-02-24 JP JP3551192A patent/JP2792306B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9461753B2 (en) | 2012-07-30 | 2016-10-04 | Fujitsu Optical Components Limited | Optical receiver circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2792306B2 (en) | 1998-09-03 |
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