JP2004133130A - Optical circuit, optical circuit device, and manufacturing method for optical circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical circuit and an optical circuit device which can efficiently exhibit thermooptic effect with lower power consumption and are easy to manufacture and high in reliability. <P>SOLUTION: An optical waveguide layer 3 which has a core 1 and a clad 2 is provided on a silicon substrate 7 and on the optical waveguide layer 3, a temperature control means 8 is provided which locally varies and controls the temperature of a portion of the core 1. An optical waveguide layer removed part 5 is formed by removing up to the surface of the silicon substrate 7 areas of optical waveguide layers on both sides of the formation position of the temperature control means 8 which are at intervals with the core 1 along the length of the core 1. A rectangular recessed part 4 is formed at a surface position of the silicon substrate 7 including the entire area facing the lower part of the optical waveguide layer removed part 5. The surface of the silicon substrate 7 is the (100) crystal plane of silicon, the flank of the recessed part 4 which is formed along the length of the core 1 is the (100) crystal plane of silicon nearly perpendicular to the silicon substrate surface, and the bottom surface of the recessed part 4 is the (100) crystal plane of silicon nearly parallel to the silicon substrate surface. <P>COPYRIGHT: (C)2004,JPO

Description

【０１４０】
図１４には、温度制御手段８を形成するヒータ９ｂの形成部の拡大図が模式的に示されており、このヒータ９ｂには、通電手段４５と通電用の電極４４が接続されている。また、図１４はヒータ９ｂを示しているが、ヒータ９ａもヒータ９ｂと同様にアレイ導波路１４の形成領域の設定領域に形成されており、ヒータ９ａにも通電用の電極と通電手段が接続されている。
【０１４１】
第８実施形態例は、ヒータ９（９ａ，９ｂ）による加熱により、それぞれのチャンネル導波路１４ａの屈折率を調整することによって、設定位相分布が上記のような実質的に偶関数的分布となるようにする。
【０１４２】
上記設定位相分布は可変可能と成しており、前記通電手段によりヒータ９（９ａ，９ｂ）に通電する通電量を可変することによって、ヒータ９（９ａ，９ｂ）によるチャンネル導波路１４ａの加熱量を可変し、対応するチャンネル導波路１４ａの屈折率の調整量を可変する。
【０１４３】
なお、ヒータ９（９ａ，９ｂ）の形成形態は特に限定されるものではないが、本実施形態例においては、図１に示すように、ヒータ９（９ａ）とヒータ９（９ｂ）は互いに間隔を介して形成されている。ヒータ９（９ａ）とヒータ９（９ａ）に通電する通電手段は、正分散補償用位相シフタとして機能し、ヒータ９（８ｂ）とヒータ９（９ｂ）に通電する通電手段は、負分散補償用位相シフタとして機能する。
【０１４４】
第８実施形態例の光回路装置は以上のように構成されており、第８実施形態例の光回路装置は、±１００ｐｓ／ｎｍの波長分散補償量を得るのに温度制御手段８に投入する電力は約８Ｗ必要だった。第８実施形態例の光回路装置と同様の光導波路構成と温度制御手段８とを有して、光導波路層除去部５とシリコン基板７の凹部４を有していない比較例の光回路装置において検討を行ったところ、上記温度制御手段８への必要投入電力は約２０Ｗであった。
【０１４５】
このように、第８実施形態例の光回路装置は、省電力で、必要な波長分散補償量を得ることができた。
【０１４６】
なお、本発明は上記実施形態例に限定されることはなく、様々な実施の態様を採り得る。例えば光回路や光回路装置を構成する光導波路（コア）の構成は特に限定されるものでなく適宜設定されるものである。
【０１４７】
また、上記各実施形態例の光回路装置は、上記第１実施形態例の光回路の構成を適用して形成したが、光回路装置は上記第２実施形態例の光回路の構成を適用して形成してもよい。この場合も、上記各実施形態例の光回路装置と同様の効果を奏することができる。
【０１４８】
【発明の効果】
本発明の光回路によれば、基板上にコアを有する光導波路層を形成し、コアの一部の温度を局所的に可変制御する温度制御手段の形成部位を挟む両側の光導波路層を除去し、この除去部の全領域を包含するシリコン基板表面部位に断面矩形状の凹部を設け、前記シリコン基板の表面と、前記凹部の側面、底面の結晶面を定めることにより、低消費電力で効率的に熱光学効果を発揮することができ、製造が容易で信頼性が高い光回路を実現できる。
【０１４９】
また、本発明の光回路は、上記のような構成とすることで熱応力が効果的に解放され、複屈折による光伝搬特性の偏波依存性を低減することができる。
【０１５０】
また、本発明の光回路において、シリコン基板表面、凹部のコア長手方向に沿って形成されている側面、凹部の底面をいずれもシリコン（１００）結晶面とした構成によれば、シリコン基板の異方性ウエットエッチングを適用することによって、シリコン基板の表面から下方へのエッチング速度と、光導波路除去部から、温度制御手段が形成されている側の光導波路層方向へと進むサイドエッチングが共にシリコン基板の（１００）結晶面に対するエッチングとなり、等速度で進行する。
【０１５１】
したがって、光導波路層除去部と対向するシリコン基板の表面を始点として開始されるシリコン基板のエッチングは、シリコン基板の表面に対して垂直な側壁形状と、シリコン基板の表面に対して平行な底面形状とを保ちつつ、側方と下方へ当速度で進行することになる。
【０１５２】
したがって、エッチングの深さ（凹部の形成深さ）をシリコン基板の表面から測定することにより、温度制御手段の長手方向に直交する方向のエッチング長さを同時に把握することができ、温度制御手段が形成されている光導波路層の下部のシリコン基板の幅（温度制御手段の長手方向に直交する方向の幅）を適切に調節でき、上記優れた効果を奏する光回路を歩留まり良く形成できる。
【０１５３】
また、本発明の光回路において、シリコン基板の表面と凹部の底面がシリコン（１１１）結晶面と成し、凹部の、コアの長手方向に沿って形成されている側面がシリコン（１１０）結晶面と成している構成によれば、アルカリ溶液によるシリコン基板の（１１０）結晶面のエッチング速度は（１１１）結晶面のエッチング速度の数十〜数百倍であるので、２種類のエッチングを組み合わせて適切な凹部を形成できる。
【０１５４】
つまり、例えば異方性ドライエッチングにて光導波路層除去部とほぼ同じ平面形状のシリコン基板除去部を形成し、その後、アルカリ溶液による異方性ウエットエッチングを行うと、凹部の底面方向へのエッチングと側面方向へのエッチングの制御が行いやすくなり、所望の凹部を形成でき、上記優れた効果を奏する光回路を歩留まり良く形成できる。
【０１５５】
また、本発明の光回路において、シリコン基板の凹部をアルカリ溶液によるシリコンの異方性エッチングにより形成した構成は、シリコン基板のエッチング速度の結晶面依存性により再現性良く凹部を形成することができる。
【０１５６】
さらに、本発明の光回路において、シリコンの異方性ドライエッチングと該異方性ドライエッチングに続いて行われるアルカリ溶液によるシリコンの異方性エッチングにより形成したりした構成は、シリコン基板の表面に垂直な方向と水平な方向のエッチングをほぼ独立して行うことができ、再現性良くエッチングをしてシリコン基板の凹部を形成できる。
【０１５７】
さらに、本発明の光回路において、前記温度制御手段は薄膜ヒータとした構成によれば、温度制御手段を容易に形成でき、上記優れた効果を奏する光回路を容易に実現できる。
【０１５８】
さらに、本発明の光回路において、前記光導波路層は石英系ガラスにより形成されている構成によれば、光導波路層を容易に形成できるし、石英系ガラス屈折率の温度依存性を利用して熱光学効果を良好に発揮できる。
【０１５９】
さらに、本発明の光回路装置によれば、光の分岐と結合の少なくとも一方を行う少なくとも２つの光分岐結合器同士を接続用コアにより接続し、この接続用コアの少なくとも１本に温度制御手段を形成し、この温度制御手段近傍の構成を上記本発明の光回路の構成とすることにより、熱光学効果を効率的に発揮でき、かつ、歩留まりよく光回路装置を製造できる。
【０１６０】
さらに、本発明の光回路装置において、マッハツェンダ光干渉計回路を有する構成によれば、マッハツェンダ光干渉計回路の位相部が接続用コアとなるので、この接続用コアに形成した温度制御手段により接続用コアの温度を制御し、光可変減衰器や光スイッチ等の様々な機能を有する光回路装置を歩留まり良く形成できる。
【０１６１】
さらに、本発明の光回路装置において、少なくとも１本の光入力導波路と、第１スラブ導波路と、アレイ導波路と、第２スラブ導波路と光出力導波路とを有し、前記アレイ導波路が接続用コアを成している構成によれば、位相部となるアレイ導波路に温度制御手段を形成してアレイ導波路の温度を制御し、光可変減衰器や光スイッチ等の様々な機能を有する光回路装置を歩留まり良く形成できる。
【０１６２】
さらに、本発明の光回路装置において、光可変減衰器、光スイッチ、波長可変合分波器、光可変分散補償器と成している構成によれば、温度制御手段に投入する電力が少なくてもそれぞれの機能を効率的に発揮でき、かつ、歩留まりの良好な光回路装置を実現できる。
【０１６３】
さらに、本発明の光回路の製造方法によれば、シリコン基板表面側に凹部を形成する方法を、アルカリ溶液によるシリコンの異方性エッチングとしたり、シリコンの異方性ドライエッチングと該異方性ドライエッチングに続いて行われるアルカリ溶液によるシリコンの異方性エッチングとしたりすることにより、容易に、かつ、歩留まり良く光回路を製造することができる。
【０１６４】
さらに、本発明の光回路の製造方法において、アルカリ溶液は水酸化カリウム水溶液とした構成によれば、入手が容易な水酸化カリウム水溶液を用い、シリコン基板に凹部をより一層再現性良く形成できるので、確実に歩留まり良く光回路を製造することができる。
【図面の簡単な説明】
【図１】本発明に係る光回路の第１実施形態例を示す要部構成図である。
【図２】上記第１実施形態例の光回路の製造工程を示す説明図である。
【図３】本発明に係る光回路の第２実施形態例を示す要部構成図である。
【図４】上記第２実施形態例の光回路の製造工程を示す説明図である。
【図５】本発明に係る光回路装置の第１、第２実施形態例を示す要部構成図である。
【図６】上記第１実施形態例の光回路装置の投入電力と光減衰量との関係を比較例における関係と共に示すグラフである。
【図７】本発明に係る光回路装置の第３実施形態例を示す要部平面構成図である。
【図８】第３実施形態例の光回路装置における波長と結合効率との関係を示すグラフである。
【図９】上記第３実施形態例の光回路装置と比較例の光回路装置の温度制御手段への投入電力と中心波長との関係を比較例における関係と共に示すグラフである。
【図１０】本発明に係る光回路装置の第５、第６、第７実施形態例の平面構成図である。
【図１１】上記第５実施形態例の光回路装置の投入電力と透過率との関係を比較例における関係と共に示すグラフである。
【図１２】本発明に係る光回路装置の第６実施形態例における温度制御手段への投入電力と設定波長光の光減衰量との関係を示す
【図１３】本発明に係る光回路装置の第８実施形態例の要部構成を示す平面図である。
【図１４】上記第８実施形態例における温度制御手段形成部の拡大図である。
【図１５】上記第８実施形態例において温度制御手段がアレイ導波路に与える設定位相分布の例を示すグラフである。
【図１６】マッハツェンダ光干渉計回路を備えた光回路装置の例を示す説明図である。
【図１７】従来の光回路装置の断面構成例を示す説明図である。
【図１８】従来提案された光回路装置の断面構成例を示す説明図である。
【図１９】従来提案された光回路装置の断面構成の別の例を示す説明図である。
【図２０】従来提案された光回路装置の断面構成のさらに別の例を示す説明図である。
【図２１】従来提案された光回路装置の例を平面図により示す説明図である。
【符号の説明】
１　コア
２　クラッド
３　光導波路層
４　凹部
５　光導波路層除去部
７　シリコン基板
８　温度制御手段
９　薄膜ヒータ
１２　光入力導波路
１３　第１スラブ導波路
１４　アレイ導波路
１４ａ　チャンネル導波路
１５　第２スラブ導波路
１６　光出力導波路
２１　結合器形成コア
２２　接続用コア[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical circuit, an optical circuit device, and an optical circuit manufacturing method applied to the field of optical communication and the like.
[0002]
[Background Art]
An optical circuit applied to optical communication or the like generally has a silicon substrate and an optical waveguide layer having a core and a clad formed on the silicon substrate. In an optical circuit, an optical circuit device having various functions can be formed by variously setting an optical waveguide configuration (core pattern) formed by the core.
[0003]
As an example of the optical circuit device, there is an optical circuit device having a Mach-Zehnder optical interferometer circuit 30 as shown in FIG. In the optical circuit device shown in FIG. 16, the core 1 of the optical circuit includes at least two (here, two) coupler forming cores 21 that perform at least one of branching and coupling of light, and these coupler forming cores 21. It has at least two connection cores 22 that connect each other.
[0004]
In the Mach-Zehnder optical interferometer circuit 30, the coupler-forming core 21 is formed with two cores 1 (1a, 1b) arranged side by side, and the connecting cores 22 are arranged side by side with an interval therebetween. It is formed by the cores 1 (1a, 1b) of the book. In the Mach-Zehnder optical interferometer circuit 30, the coupler forming core 21 is a 2 × 2 optical coupler.
[0005]
In the optical circuit device shown in FIG. 16, the temperature control means 8 for locally variably controlling the temperature of a part of the connection core 22 is formed on at least one (here, two) of the connection cores 22. ing. The temperature control means 8 is formed by, for example, a thin film heater 9. In FIG. 16, reference numeral 44 denotes an electrode for supplying power to the thin-film heater 9.
[0006]
When the temperature of a part of the connection core 22 is locally variably controlled by the temperature control means 8, the refractive index of the connection core 22 on which the variable control is performed changes, and the effective core of the changed part is changed. The refractive index changes. This utilizes a thermo-optic effect, which is a phenomenon in which the refractive index of quartz-based glass or the like changes with temperature, and the above-described effect causes a change in the phase of light propagating through the core whose refractive index has changed.
[0007]
That is, the phase shifter is formed by changing the effective optical waveguide length difference between the two connection cores 22 by the thermo-optic effect due to the heat generated by the thin film heater 9, and the transmittance of the Mach-Zehnder optical interferometer circuit 30 is changed. Can be done. Therefore, the optical circuit device shown in FIG. 16 is an optical waveguide interferometer that can change the light transmittance and the light branching ratio, and can obtain the functions of an optical switch, a variable optical attenuator, and the like.
[0008]
FIG. 17 shows a cross-sectional configuration of a conventional optical circuit device having the Mach-Zehnder optical interferometer circuit 30 and the temperature control means 8 by an AA cross-sectional view of FIG. As shown in FIG. 17, an optical waveguide layer 3 having a core 1 and a clad 2 formed on a silicon substrate 7 has a buried optical waveguide configuration made of silica-based glass. The temperature control means 8 is formed on the surface of the substrate 2.
[0009]
In this configuration, when the temperature control means 8 is energized and the core 1 is heated via the clad 2 by the thin film heater 9 of the temperature control means 8, the effective refractive index of the core 1 increases due to the thermo-optic effect. Then, the effective optical path length of the connection optical waveguide below the temperature control means 8 changes, and the phase of the propagating light can be changed.
[0010]
The temperature coefficient dn / dT of the refractive index of the quartz glass is 10 ^-5 (1 / ° C.), for example, if the temperature of the core 1 is raised by 20 ° C. over a length of 5 mm, the effective optical path length can be changed by about 1 μm.
[0011]
However, the phase shifter using the thermo-optic effect has the following problems. First, the heat generated by the temperature control means 8 diffuses into the clad 2 and the silicon substrate 7 near the core 1, resulting in poor heating efficiency. Second, a birefringence occurs in the optical waveguide layer 3 due to anisotropic internal stress generated in the optical waveguide layer 3 due to heating, and there is a problem that the polarization characteristics of the propagation characteristics of light propagating through the core 1 are large. there were.
[0012]
Therefore, as a configuration that can efficiently utilize the thermo-optic effect, for example, an optical circuit device having an optical waveguide configuration and a temperature control unit 8 shown in FIG. 16 and a cross-sectional configuration as shown in FIG. 18 is proposed. (For example, see Non-Patent Document 1).
[0013]
The cross-sectional configuration shown in FIG. 18 shows the above-described optical circuit device by cutting it along the line AA in FIG. 16, and the area along the temperature control unit 8 on both sides of the thin film heater 9 of the temperature control unit 8. The optical waveguide layer removal part 5 is formed by removing the optical waveguide layer 3 of FIG. The birefringence is reduced by using the optical waveguide layer removing portion 5 as a stress release groove. Note that the optical waveguide layer removing portion 5 is formed with an interval from the core 1.
[0014]
Further, as a configuration that can efficiently use the thermo-optic effect, for example, a configuration as shown in FIGS. 19 and 20 has been proposed (for example, see Non-Patent Document 2).
[0015]
The configuration shown in FIGS. 19 and 20 removes the optical waveguide layer 3 in the region along the thin film heater 9 on both sides of the temperature control means 8 and removes the silicon substrate 7 in the region facing the optical waveguide layer removal portion 5. Is removed by etching to form a recess 4 on the surface side of the silicon substrate 7. Note that, also in these configurations, the optical waveguide layer removing portion 5 is formed with an interval from the core 1.
[0016]
The concave portion 4 is formed so as to cover the entire region facing the lower portion of the optical waveguide layer removing portion 5, has a width larger than the width of the optical waveguide layer removing portion 5, and is formed on the lower side of the core 1. An overhang is formed. With this configuration, the lower surface of the optical waveguide layer 3 (3a) including the core 1 in the region where the temperature control means 8 is formed is partially exposed.
[0017]
The configuration shown in FIGS. 19 and 20 separates the optical waveguide layer 3a from the silicon substrate 7 by forming the concave portion 4 in the silicon substrate 7 facing the optical waveguide layer removing portion 5 as described above. Alternatively, by reducing the contact area between the optical waveguide layer 3a and the silicon substrate 7, heat diffusion to the silicon substrate 7 is suppressed, and power consumption is reduced.
[0018]
Various optical circuit devices using the Mach-Zehnder optical interferometer circuit 30 have been proposed. As an example of an optical circuit device having a plurality of Mach-Zehnder optical interferometer circuits 30, as shown in FIG. A compensator has been proposed (for example, see Non-Patent Document 3).
[0019]
In the proposed optical circuit device, a lattice type filter 24 formed by connecting a plurality of Mach-Zehnder optical interferometer circuits 30 in series is connected to respective output ends of an arrayed waveguide diffraction grating 25 via a connecting fiber 32. Things.
[0020]
The temperature control means 8 is provided in the phase part of each Mach-Zehnder optical interferometer circuit 30 forming the lattice type filter 24. A variable coupler 33 is provided at a connection portion between the adjacent Mach-Zehnder optical interferometer circuits 30.
[0021]
The arrayed waveguide diffraction grating 25 includes at least one (here, a plurality of) optical input waveguides 12, a first slab waveguide 13 connected to the output side of the optical input waveguide 12, and the first slab waveguide. An arrayed waveguide connected to the output side of the waveguide, a second slab waveguide connected to the output side of the arrayed waveguide, and a plurality of connected slab waveguides connected to the output side of the second slab waveguide; And an optical output waveguide 16 of the same.
[0022]
The arrayed waveguide 14 is composed of a plurality of channel waveguides 14a having a length different from each other by a predetermined amount (ΔL). The array waveguide 14 is usually provided with a large number of channel waveguides 14a, for example, 100. In FIG. 21, for simplification of the drawing, these channel waveguides 14a and the light output The number of waveguides 16 and optical input waveguides 12 is shown in a simplified manner.
[0023]
Also, one end of each of the connection fibers 32 is connected to one corresponding optical output waveguide 16 of the arrayed waveguide diffraction grating 25 via optical fiber arrays 31a and 31b. The end side is connected to one corresponding optical input waveguide 29 of the lattice filter 24.
[0024]
[Non-patent document 1]
Yasyuuki Inoue, et al. "Polarization Sensitivity of a Silica Waveguide Thermooptic Phase Shifter for Planar Lightwave Circuit, IEEE Phototechniques Technology, IEEE Photonics Technology." 4, No. 1, Jan. 1992, p. 36
[0025]
[Non-patent document 2]
Akio Sugita, et al. "Bridge-Suspended Silica-Waveguide Thermo-Optic Phase Shifter and Its Application to Mach-Zehnder Type Optical Switch. E73, No1, Jan, 1990, p. 105
[0026]
[Non-Patent Document 3]
Takiguchi et al., “Waveguide-type dispersion slope compensator for 10Gb / s × N-wave, WDM transmission,” IEICE Electronics Society Conference 2000, C-3-16
[0027]
[Problems to be solved by the invention]
Incidentally, as described above, in the optical circuit device, configurations as shown in FIGS. 18, 19, and 20 have been proposed as optical circuit configurations that can efficiently use the thermo-optic effect. With the configuration proposed by Inoue et al., The power consumption is not sufficiently reduced.
[0028]
Further, the configuration proposed by Sugita et al. As shown in FIG. 19 can sufficiently reduce power consumption, but since isotropic etching is performed as a method for removing the silicon substrate 7, The removal portion has a semicircular shape.
[0029]
Therefore, in the configuration of FIG. 19, even if the width of the contact portion between the optical waveguide layer 3 and the silicon substrate 7 is reduced, the width of the lower portion becomes wider and the thermal conductivity increases, so that large power consumption is achieved. In order to obtain the reduction effect, it is necessary to make the width of the contact portion between the optical waveguide layer 3 and the silicon substrate 7 extremely small.
[0030]
Further, in the configuration of FIG. 19, it is difficult to control the amount of side etching in isotropic etching, and the remaining portion (Si-Base) of the silicon substrate 7, that is, the core 1 below the portion where the temperature control means 8 is formed is formed. There is a manufacturing problem that it is difficult to control the width of the silicon substrate 7 (7a) left on the lower side. Further, in the configuration of FIG. 19, even when the silicon substrate 7 and the optical waveguide layer 3 are completely separated, there is a problem in reliability because the shape of the removed portion of the silicon substrate 7 is irregular.
[0031]
On the other hand, in the configuration as shown in FIG. 20 proposed by Sugita et al., Since the concave portion 4 has a rectangular cross section, the silicon substrate 7 left on the lower side of the core 1 below the portion where the temperature control means 8 is formed. (7a) has a substantially rectangular cross section having a width substantially equal to the width of the contact portion between the silicon substrate 7a and the optical waveguide layer 3, and is excellent in heat insulation and easily obtains shape reproducibility.
[0032]
However, Sugita et al. Do not disclose in the above-mentioned document the details of the method of forming the concave portion 4 and the crystal plane in the configuration shown in FIG. 20, and the present inventor has described the cross-sectional configuration shown in FIG. We thought that it was necessary to propose a configuration that could be formed accurately with good reproducibility.
[0033]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical circuit that can efficiently exhibit a thermo-optic effect with low power consumption, is easy to manufacture, and has high reliability. An object of the present invention is to provide an optical circuit device and an optical circuit manufacturing method.
[0034]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has means for solving the problem with the following configuration. That is, an optical circuit according to a first aspect of the present invention includes a silicon substrate, an optical waveguide layer having a core and a clad formed on the silicon substrate, and a temperature of a part of the core formed on the optical waveguide layer. Temperature control means for locally variably controlling the temperature control means, and the optical waveguide layers on both sides of the portion where the temperature control means is formed have an optical waveguide layer along a longitudinal direction of the core in a region interposed with the core. The silicon substrate has been removed from its surface to the surface of the silicon substrate, and a concave portion having a rectangular cross section is provided in a silicon substrate surface portion including an entire region opposed to a lower portion of the optical waveguide layer removed portion. The surface has a silicon (100) crystal plane, and the concave portion has a silicon (100) crystal plane whose side surface formed along the longitudinal direction of the core is substantially perpendicular to the silicon substrate surface. Recessed Surface has a means for solving the problems with the configuration that forms a substantially parallel silicon (100) crystal face to the surface of the silicon substrate.
[0035]
An optical circuit according to a second aspect of the present invention includes an optical circuit layer having a silicon substrate, a core and a clad formed on the silicon substrate, and a temperature of a part of the core formed on the optical waveguide layer. Temperature control means for locally variably controlling the temperature control means, and the optical waveguide layers on both sides of the portion where the temperature control means is formed have an optical waveguide layer along a longitudinal direction of the core in a region interposed with the core. The silicon substrate has been removed from its surface to the surface of the silicon substrate, and a concave portion having a rectangular cross section is provided in a silicon substrate surface portion including an entire region opposed to a lower portion of the optical waveguide layer removed portion. The surface has a silicon (111) crystal plane, and the concave portion has a silicon (110) crystal plane whose side surface formed along the longitudinal direction of the core is substantially perpendicular to the silicon substrate surface. Bottom of recess And a means for solving the problems with the configuration that forms a substantially parallel silicon (111) crystal face to the surface of the silicon substrate.
[0036]
Further, an optical circuit according to a third aspect of the present invention is a means for solving the problem by a configuration in which the concave portion of the silicon substrate is formed by anisotropic etching of silicon with an alkaline solution in addition to the configuration of the first aspect. .
[0037]
Further, in the optical circuit according to a fourth aspect of the present invention, in addition to the configuration of the second aspect, the concave portion of the silicon substrate has anisotropic dry etching of silicon and a silicon solution formed by an alkaline solution performed subsequent to the anisotropic dry etching. Is a means for solving the problem with the configuration formed by the anisotropic etching.
[0038]
Further, in the optical circuit according to a fifth aspect of the present invention, in addition to the configuration of any one of the first to fourth aspects of the present invention, the temperature control means is a means for solving the problem by using a thin film heater.
[0039]
Further, an optical circuit according to a sixth aspect of the present invention is a means for solving the problem by having a configuration in which the optical waveguide layer is formed of quartz glass in addition to the configuration of any one of the first to fifth aspects. .
[0040]
Further, an optical circuit device according to a seventh aspect of the present invention includes the optical circuit according to any one of the first to sixth aspects, wherein a core of the optical circuit has at least two optical fibers that perform at least one of branching and coupling of light. It has a coupler forming core forming an optical branching coupler, and at least two connecting cores for connecting these coupler forming cores, and at least one of the connecting cores is provided with a temperature control means. It is a means to solve the problem with a certain configuration.
[0041]
Further, in the optical circuit device according to an eighth aspect of the present invention, in addition to the configuration of the seventh aspect, the coupler forming core is formed with two cores arranged in parallel and the connecting cores are spaced from each other. This is a means for solving the problem with a configuration having a Mach-Zehnder optical interferometer circuit formed by two cores arranged side by side.
[0042]
Further, in the optical circuit device according to a ninth aspect, in addition to the configuration of the seventh aspect, at least one optical input waveguide and a first slab waveguide connected to an output side of the optical input waveguide are provided. An array waveguide composed of a plurality of channel waveguides connected to the output side of the first slab waveguide and having a length different from each other by a predetermined amount; and a second slab connected to the output side of the array waveguide. A waveguide, and at least one optical output waveguide connected to the output side of the second slab waveguide, wherein the optical input waveguide, the first slab waveguide, and the first of the array waveguides An end on the slab waveguide side forms a first coupler forming core forming a first optical branching coupler, and an end on the second slab waveguide side of the arrayed waveguide and the second slab waveguide are connected to each other. The optical output waveguide forms a second coupler forming core forming a second optical branch coupler. And a means for solving the problems with the construction of an array waveguide between said second coupler forming core first coupler formation core forms a connecting core.
[0043]
Further, an optical circuit device according to a tenth aspect has at least one optical circuit device according to the eighth or ninth aspect, and controls the temperature of temperature control means to reduce the intensity of at least one set wavelength light. A variable optical attenuation control unit is provided to change the optical attenuation.
[0044]
Further, an optical circuit device according to an eleventh aspect has at least one optical circuit device according to the eighth or ninth aspect, and controls the temperature of the temperature control means to output at least one set wavelength light output unit. An optical switch control unit for changing the value is provided so as to solve the problem by using an optical switch.
[0045]
Furthermore, an optical circuit device according to a twelfth aspect has at least one optical circuit device according to the eighth or ninth aspect, and controls at least one of multiplexing and demultiplexing by controlling the temperature of the temperature control means. A means for solving the problem is provided by providing a wavelength tunable control unit for tunable wavelength to constitute a wavelength tunable multiplexer / demultiplexer.
[0046]
Further, an optical circuit device according to a thirteenth aspect has at least one optical circuit device according to the eighth or ninth aspect, and controls the temperature of the temperature control unit to control the dispersion of at least one set wavelength light. Is provided as a means for solving the problem by providing a variable optical dispersion compensator for reducing the chromatic dispersion of the connection partner side by providing a variable dispersion controller for varying the wavelength dispersion.
[0047]
Further, a fourteenth invention provides a method for manufacturing an optical circuit according to the first or third optical circuit, wherein after forming the removed portion of the optical waveguide layer, the silicon substrate is anisotropically treated with an alkaline solution. This is a means for solving the problem by a configuration in which a concave portion is formed on the silicon substrate surface side at a position corresponding to the removed portion of the optical waveguide layer by performing a reactive etching.
[0048]
Further, a method of manufacturing an optical circuit according to a fifteenth aspect is the method of manufacturing an optical circuit according to the second or fourth aspect, wherein the anisotropic silicon is formed on the silicon substrate after forming the removed portion of the optical waveguide layer. This is a means for solving the problem by a configuration in which dry etching is performed, and then anisotropic etching using an alkaline solution is performed to form a concave portion on the surface of the silicon substrate at a position corresponding to the removed portion of the optical waveguide layer.
[0049]
Further, a method of manufacturing an optical circuit according to a sixteenth aspect of the present invention is a means for solving the problem by using a configuration in which the alkaline solution is a potassium hydroxide aqueous solution in addition to the configuration of the fourteenth or fifteenth aspect.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the present embodiment, the same reference numerals are given to the same parts as those in the conventional example, and the overlapping description will be omitted or simplified.
[0051]
FIG. 1 shows a main configuration of an optical circuit according to a first embodiment of the present invention. FIG. 1A is a schematic diagram illustrating a planar configuration of an optical circuit according to the present embodiment, and FIG. 1B is a schematic diagram illustrating a cross section taken along line AA of FIG.
[0052]
As shown in these figures, the optical circuit according to the first embodiment includes an optical waveguide layer 3 having a silicon substrate 7, a core 1 and a clad 2 formed on the silicon substrate 7, and an optical waveguide layer 3. 3 has a temperature control means 8 for locally controlling the temperature of a part of the core 1. The temperature control means 8 comprises a thin film heater 9, and a power supply electric wire (not shown) and a power supply means (not shown) for supplying power to the thin film heater 9 through the power supply electric wiring (not shown) are connected to the thin film heater 9. .
[0053]
Further, the optical waveguide layers 3 on both sides of the portion where the temperature control means 8 is formed are arranged such that a region with an interval from the core 1 extends from the surface of the optical waveguide layer 3 to the surface of the silicon substrate 7 along the longitudinal direction of the core 1. Thus, the optical waveguide layer removed portion 5 is formed. In addition, a concave portion 4 having a rectangular cross section is provided in the surface portion of the silicon substrate 7 including the entire region facing the lower portion of the optical waveguide layer removing portion 5.
[0054]
The feature of this embodiment is that the surface of the silicon substrate 7 is formed of a silicon (100) crystal plane, and the recess 4 has a side surface formed along the longitudinal direction of the core 1. 7 has a silicon (100) crystal plane substantially perpendicular to the surface of the silicon substrate 7, and the bottom surface of the recess 4 has a silicon (100) crystal plane substantially parallel to the surface of the silicon substrate 7.
[0055]
In the present embodiment, the width of the optical waveguide layer 3a below the thin film heater 9 is 50 μm, and the width of the silicon substrate 7a below this optical waveguide layer 3a is 10 μm. FIG. 1B shows the size of the core 1 in an exaggerated manner.
[0056]
Hereinafter, a method of manufacturing the optical circuit according to the present embodiment will be described. First, as shown in FIG. 2A, a single crystal silicon substrate 7 having a (100) crystal plane as a surface is prepared, and a flame hydrolysis deposition method (FHD method) is used on this silicon substrate 7. Then, as shown in FIG. 2B, an under cladding layer 2a is formed.
[0057]
Next, as shown in FIG. 2C, the core layer 11 is formed on the under cladding layer 2a. The core layer 11 has GeO ₂ Is added so that the refractive index of the core layer 11 is 0.8% higher than that of the under cladding layer 2a.
[0058]
Next, as shown in FIG. 2D, photolithography and dry lithography are performed so that the optical waveguide (core 1) of the portion where the thin film heater 9 is formed is along the (100) plane perpendicular to the surface of the silicon substrate 7. The core 1 is formed by patterning by etching. Thereafter, as shown in FIG. 2E, the over cladding layer 2b is formed by using the FHD method, and the core 1 is buried to form the optical waveguide layer 3.
[0059]
Next, using a sputtering method and a lift-off method, a Ni thin-film heater 9 having a length of 5 mm, a width of 30 μm, and a thickness of 0.5 μm is placed along the core 1 along the optical waveguide layer as shown in FIG. 3 is formed. At this time, a 0.1 μm-thick Ti film is formed below the Ni film in order to improve the adhesion between the Ni film and the optical waveguide layer 3. Next, a power supply wiring (not shown) composed of three layers of Ti, Ni and Au is formed in the same manner.
[0060]
Next, as shown in FIG. 2G, the optical waveguide layers 3 on both sides of the thin-film heater 9 are removed by photolithography and dry etching into a rectangular shape parallel to the thin-film heater 9, and the optical waveguide layer 3 is removed. A portion (optical waveguide layer removing portion 5) is formed.
[0061]
Next, as shown in FIG. 2H, the surface side of the silicon substrate 7 is etched by anisotropic etching using an aqueous solution of potassium hydroxide, and the entire region facing the lower part of the optical waveguide layer removing portion 5 is removed. The recess 4 having a rectangular cross section is formed in the surface portion of the silicon substrate 7 to be included. The width of the concave portion 4 in the direction orthogonal to the longitudinal direction of the temperature control means 8 is formed wider than that of the optical waveguide layer removing portion 5. Therefore, a part of the bottom surface of the optical waveguide layer 3 is exposed by forming the concave portion 4.
[0062]
As described above, when the surface of the silicon substrate 7 is made to have a silicon (100) crystal plane and anisotropic wet etching is applied, the etching rate from the surface of the silicon substrate 7 to the lower side and the opposing to the optical waveguide layer removing portion 5. The speed at which the silicon substrate 7 below the optical waveguide layer 3 is etched from the region of the silicon substrate 7 in the direction orthogonal to the longitudinal direction of the temperature control means 8 advances at a constant speed.
[0063]
Therefore, the etching of the silicon substrate 7 starting from the surface of the silicon substrate 7 facing the optical waveguide layer removing portion 5 is performed with respect to the sidewall shape perpendicular to the surface of the silicon substrate 7 and the etching of the surface of the silicon substrate 7. Thus, the vehicle moves sideways and downwards at a constant speed while maintaining a parallel bottom shape.
[0064]
Therefore, by measuring the etching depth (depth of the recess 4) from the surface of the silicon substrate 7, the etching length in the direction perpendicular to the longitudinal direction of the temperature control means 8 can be simultaneously grasped, The width of the silicon substrate 7 (7a) below the optical waveguide layer 3 on which the control means 8 is formed (the width in the direction orthogonal to the longitudinal direction of the temperature control means 8) can be appropriately adjusted.
[0065]
The optical circuit according to the present embodiment is configured as described above. For the optical circuit according to the present embodiment, the power required to change the optical path length by a half wavelength with respect to the propagating light having a wavelength of 1.55 μm is measured. The result was 100 mW.
[0066]
On the other hand, for comparison, an optical circuit having the same optical waveguide configuration and temperature control means 8 as that of the present embodiment and having no optical waveguide layer removing section 5 and the concave portion 4 of the silicon substrate 7 has the same power. Upon measurement, power of 700 mW was required.
[0067]
As described above, it was confirmed that the optical circuit of the present embodiment can efficiently exhibit the thermo-optic effect of the core 1 with low power consumption.
[0068]
Further, when 20 optical circuits according to the present embodiment were manufactured by applying the above-described manufacturing method, the value of the power consumption was almost constant at 100 ± 2 mW, and it was possible to manufacture the optical circuit stably with high yield. It could be confirmed.
[0069]
Next, a second embodiment of the optical circuit according to the present invention will be described. As shown in FIG. 3, the optical circuit according to the second embodiment has substantially the same configuration as the optical circuit according to the first embodiment. In the description of the optical circuit according to the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.
[0070]
The second embodiment is different from the first embodiment in that the surface of the silicon substrate 7 and the silicon crystal plane forming the recess 4 are as follows. That is, as shown in FIG. 3, in the optical circuit according to the second embodiment, the surface of the silicon substrate 7 is formed of a silicon (111) crystal plane, and the recess 4 is formed along the longitudinal direction of the core 1. The side surface forms a silicon (110) crystal plane substantially perpendicular to the surface of the silicon substrate 7, and the bottom surface of the recess 4 forms a silicon (111) crystal plane substantially parallel to the surface of the silicon substrate 7. ing.
[0071]
Hereinafter, a method of manufacturing the optical circuit according to the second embodiment will be described. First, as shown in FIG. 4A, a single-crystal silicon substrate 7 having a (111) crystal plane as a surface is prepared, and this silicon substrate 7 is provided on the silicon substrate 7 as shown in FIGS. 4B and 4C. As described above, the under cladding layer 2a and the core layer 11 are sequentially formed in the same manner as in the first embodiment.
[0072]
Next, as shown in FIG. 4D, patterning is performed by photolithography and dry etching so that the portion of the core 1 where the thin film heater 9 is formed is along the (110) plane perpendicular to the surface of the silicon substrate 7. To form a core 1. Thereafter, as shown in FIG. 4E, the over cladding layer 2b is formed by using the FHD method, and the core 1 is buried to form the optical waveguide layer 3.
[0073]
Next, similarly to the first embodiment, as shown in FIGS. 4F and 4G, the formation of the thin film heater 9 and the removal of the optical waveguide layer 3 on both sides of the thin film heater 9 are performed.
[0074]
Next, as shown in FIG. 4H, the silicon substrate 7 below the optical waveguide layer removing portion 5 is removed by anisotropic dry etching to form the recess 4. In the etching of the silicon substrate 7, only the region of the silicon substrate 7 facing the optical waveguide layer removing portion 5 is removed almost perpendicularly to the surface of the silicon substrate 7.
[0075]
Next, as shown in FIG. 4I, the surface side of the silicon substrate 7 below the optical waveguide layer 3a having the core 1 is etched by anisotropic etching using an aqueous solution of potassium hydroxide to form a concave portion. 4 is formed so as to protrude below the optical waveguide layer 3.
[0076]
As described above, the side surface of the concave portion 4 formed along the longitudinal direction of the core 1 forms a silicon (110) crystal plane, and the bottom surface of the concave portion 4 is substantially parallel to the surface of the silicon substrate 7. When the anisotropic dry etching and the anisotropic wet etching of the silicon substrate 7 are applied as the method for forming the concave portion 4, the following effects are obtained.
[0077]
That is, the etching rate of the (110) crystal plane of the silicon substrate 7 by the alkaline solution is several tens to several hundreds times the etching rate of the (111) crystal plane. Therefore, as shown in FIG. 4H, a silicon substrate removal portion having substantially the same planar shape as the optical waveguide layer removal portion 5 is formed by anisotropic dry etching, and thereafter, as shown in FIG. As shown, when the anisotropic wet etching using the alkaline solution is performed, the control of the etching toward the bottom surface and the etching toward the side surface of the concave portion 4 becomes easy, and a desired concave portion 4 can be formed.
[0078]
The optical circuit of the second embodiment is configured as described above, and can provide the same effects as those of the optical circuit of the first embodiment.
[0079]
Next, a first embodiment of the optical circuit device according to the present invention will be described. In the description of the optical circuit device according to the first embodiment, the same reference numerals are given to the same components as those used in the above description, and the description thereof will be omitted or simplified.
[0080]
The optical circuit device of the first embodiment has a Mach-Zehnder optical interferometer circuit 30 having a planar configuration shown in FIG. 5A, and temperature is applied to both of the connection cores 22 connecting the coupler-forming cores 21 together. Control means 8 is formed. The optical circuit device according to the first embodiment has a cross-sectional configuration shown in FIG. FIG. 5B is a cross-sectional view taken along line AA of FIG.
[0081]
As shown in FIG. 5B, the optical circuit device of the present embodiment is formed by applying the configuration of the optical circuit of the first embodiment. In other words, the temperature control means 8 is formed along a part of the core 1, the optical waveguide layer removing parts 5 are formed on both sides of the temperature control means 8, and further, the lower part of the optical waveguide layer removing part 5 is opposed. A concave portion 4 having a rectangular cross section is provided in a surface portion of the silicon substrate 7 including the region. The configuration of the concave portion 4 also applies the configuration of the optical circuit of the first embodiment.
[0082]
In the optical circuit device of the first embodiment, the phase shifter is formed by forming the temperature control means 8 on the connection core 22. Further, the temperature control means 8 controls the temperature of the temperature control means 8 to give a temperature difference between the connecting cores 22a and 22b to generate a refractive index difference due to a thermo-optic effect. A variable light attenuation control unit (not shown) that changes the intensity of at least one set wavelength light by changing the interference state of the propagation light in the optical circuit device is connected to the optical circuit device of the first embodiment. It consists of a variable optical attenuator.
[0083]
The Mach-Zehnder optical interferometer circuit 30 forming the optical circuit device of the first embodiment is input from the incident side 17 of the core 1 (1a) when power is not supplied to the temperature control means 8, and the core 1 ( The connection cores 22 of the cores 1 (1a, 1b) are mutually connected so that the attenuation of the light output from the emission side 20 of 1b) becomes substantially zero except for the loss of the waveguide and the connection loss to the optical fiber. Is set to zero.
[0084]
The optical circuit device according to the first embodiment is configured as described above. TE and TM polarized lights having a wavelength of 1.55 μm are input to the optical circuit device according to the present embodiment, and attenuation of these lights is performed. The difference between the quantity and the optical attenuation due to polarization was measured.
[0085]
Specifically, the above-mentioned polarized light is input from the incident side 17 of the core 1 (1a), output from the output side 20 of the core 1 (1b), and is transmitted to the temperature control means 8 as shown in FIG. The difference between the supplied electric power and the polarization attenuation and optical attenuation due to the polarization was measured. The characteristic line a indicates the TE-polarized light attenuation, the characteristic line b indicates the TM-polarized light attenuation, and the characteristic line c indicates the difference in the optical attenuation due to polarization.
[0086]
For comparison, the optical waveguide device has the same optical waveguide configuration as the optical circuit device of the first embodiment, and has a temperature control means 8 so that the optical waveguide layer removing portion 5 and the concave portion 4 of the silicon substrate 7 are provided. The same measurement was performed for an optical circuit device having no. The results are shown by characteristic lines a to c in FIG. 6B, similarly to FIG. 6A.
[0087]
As is clear from these characteristic lines, the optical variable attenuator of the comparative example requires about 600 mW to obtain the optical attenuation of 10 dB, and the difference in the optical attenuation due to the polarization at that time is about 2.5 dB. In contrast, the optical circuit device of the first embodiment has an optical attenuation of 10 dB with a power of only 75 mW. At this time, the difference in the amount of light attenuation due to the polarization can be greatly suppressed to 0.2 dB.
[0088]
As described above, the optical circuit device according to the first embodiment can efficiently exhibit the thermo-optic effect of the core 1 with low power consumption, and can efficiently obtain a desired optical attenuation. Further, in the optical circuit device of the present embodiment, the difference in the amount of optical attenuation due to polarization can be very small.
[0089]
Also, when 20 optical circuit devices of the first embodiment were manufactured by applying the above-described manufacturing method, the power consumption at the time of 10 dB light attenuation was almost constant at 75 ± 1 mW, and the polarization dependence was The value was almost constant at 0.2 ± 0.03 dB, and it was confirmed that the product could be manufactured stably with good yield. That is, according to the present embodiment, it is possible to realize an optical variable attenuator that is power-saving, has low polarization dependence, and can be stably produced.
[0090]
Next, a second embodiment of the optical circuit device according to the present invention will be described. The optical circuit device according to the second embodiment is configured substantially in the same manner as the optical circuit device according to the first embodiment. In the description of the optical circuit device according to the second embodiment, the optical circuit device according to the first embodiment will be described. The same reference numerals are given to the same parts as those of the circuit, and the overlapping description is omitted or simplified.
[0091]
The optical circuit device of the second embodiment has the same optical waveguide configuration and temperature control means 8 as those of the first embodiment shown in FIG. 5A, and also has a cross-sectional configuration of FIG. This is similar to the configuration shown in FIG.
[0092]
The optical circuit device according to the second embodiment is different from the optical circuit device according to the first embodiment in that the temperature of the temperature control means 8 is controlled to reduce the temperature difference between the connection cores 22a and 22b. An optical switch control unit that varies the output unit of at least one set wavelength light by giving a refractive index difference due to the thermo-optic effect and changing the interference state of the propagation light between the cores 1a and 1b. (Not shown). The optical circuit device according to the second embodiment functions as an optical switch because it has the optical switch control unit.
[0093]
The optical circuit device according to the second embodiment is configured as described above, and has the same optical waveguide configuration and temperature control means 8 as the optical circuit device according to the second embodiment. Then, an optical switch of the optical circuit device of the comparative example not having the concave portion 4 of the silicon substrate 7 was formed, and the switching power of the optical switch of the comparative example and the optical circuit device of the second embodiment were compared. .
[0094]
As a result, the switching power of the optical circuit device of the comparative example was about 750 mW, whereas the switching power of the optical circuit device of the second embodiment was about 100 mW, so that the switching power was significantly reduced. .
[0095]
Next, a third embodiment of the optical circuit device according to the present invention will be described. The optical circuit device according to the third embodiment has substantially the same configuration as the optical circuit device according to the first embodiment. In the description of the optical circuit device according to the third embodiment, the optical circuit device according to the first embodiment will be described. The same reference numerals are given to the same parts as those of the circuit, and the overlapping description is omitted or simplified.
[0096]
As shown in FIG. 7, the optical circuit device according to the third embodiment has a Mach-Zehnder optical interferometer circuit 30, and connection cores 22 are formed to have different lengths. The Mach-Zehnder optical interferometer circuit 30 has a difference ΔL between the lengths of the two connection cores 22 and an effective refraction of the connection core 22 so as to have an optical multiplexing / demultiplexing function at an interval of about 0.8 nm in a wavelength of 1550 nm. Rate n _c Product n _c ΔL has been determined.
[0097]
That is, an integral multiple of the wavelength light λ1 input from the input side 17 of the core 1 (1a) and output from the output side 20 of the core 1 (1b), and input from the input side 17 of the core 1 (1a). ΔL is set to 1035.5 μm so as to be a half integral multiple of the wavelength light λ2 output from the emission side 19 of the core 1 (1a).
[0098]
Further, in the third embodiment, the temperature of the temperature control means 8 is controlled to give a temperature difference between the connecting cores 22a and 22b to generate a refractive index difference due to a thermo-optic effect. A wavelength variable control unit (not shown) for changing at least one wavelength of multiplexing and demultiplexing by changing the interference state of the propagating light in the optical circuit device is provided. Is a wavelength tunable multiplexer / demultiplexer.
[0099]
The Mach-Zehnder optical interferometer circuit 30 forming the optical circuit device of the third embodiment, when power is not supplied to the temperature control means 8, as shown in FIG. The coupling efficiency of light that is input from the output side and output from the output side 20 of the core 1 (1b) has a periodic wavelength dependency.
[0100]
Therefore, the center wavelength of the upward convex peak appearing at a wavelength of about 1550 nm is defined as λ1, and the central wavelength of the downward convex peak appearing at a wavelength of about 1549.2 nm is defined as λ2. In the optical circuit device according to the embodiment, power supply (input) power to the temperature control means 8 and changes in wavelengths λ1 and λ2 were measured.
[0101]
Further, for comparison, the optical circuit device has the same optical waveguide configuration and temperature control means 8 as the optical circuit device of the third embodiment, and does not have the optical waveguide layer removing portion 5 and the concave portion 4 of the silicon substrate 7. The same measurement was performed for the optical circuit device.
[0102]
FIG. 9 shows the measurement results of the input power to the temperature control means 8 and the changes of the wavelengths λ1 and λ2 of the optical circuit device of the third embodiment and the optical circuit device of the comparative example. The measurement result of the wavelength λ1 of the optical circuit device of the third embodiment is shown by a characteristic line a, and the measurement result of the wavelength λ2 is shown by a characteristic line b. The measurement result of the wavelength λ1 of the optical circuit device of the comparative example is shown on a characteristic line c, and the measurement result of the wavelength λ2 is shown on a characteristic line d.
[0103]
As is clear from the comparison between the characteristic line a and the characteristic line c and the comparison between the characteristic line b and the characteristic line d, for example, the power required to shift the wavelength λ1 and the wavelength λ2 by one period (about 1.6 nm). Is about 1400 mW in the comparative example, whereas it is about 200 mW in the optical circuit device of the third embodiment, which is a significant reduction.
[0104]
In the description of the optical circuit device of the third embodiment, the example in which the wavelength multiplexer / demultiplexer is applied as the wavelength demultiplexer has been described. By appropriately setting the relationship between the waveguides to be output and the waveguides to be output (for example, light of wavelengths λ1 and λ2 is input from the output ends 19 and 20 of the core 1 (1a, 1b)), the waveguide is applied as a wavelength multiplexer. You can also.
[0105]
Next, a fourth embodiment of the optical circuit device according to the present invention will be described. The optical circuit device of the fourth embodiment has the same optical waveguide configuration and temperature control means 8 as the optical circuit device shown in FIG. 21, and the cross-sectional configuration in the area where the temperature control means 8 is formed is shown in FIG. This is the configuration shown in FIG.
[0106]
The optical circuit device of the fourth embodiment controls the temperature of the temperature control means 8 and changes the refractive index of the core of the portion to which the temperature control means 8 is provided, thereby controlling the phase state of the propagating light. This is an optical tunable dispersion compensator provided with a dispersion variable control unit (not shown) for varying the amount of dispersion of one set wavelength light to reduce the chromatic dispersion on the connection partner side.
[0107]
The optical circuit device according to the fourth embodiment has the optical waveguide configuration and the temperature control means 8 shown in FIG. 21, and does not include the optical waveguide layer removing portion 5 and the concave portion 4 of the silicon substrate 7. As compared with the circuit device, the dispersion compensation performance was improved as follows.
[0108]
In other words, in order to compensate for the dispersion value of the 640 km dispersion-shifted optical fiber for 16 wavelengths, the comparative example requires about 20 W of power consumption, but the optical circuit device of the fourth embodiment has a large power consumption of about 5 W. Power consumption was reduced. As described above, the optical circuit device according to the fourth embodiment can efficiently compensate the dispersion value of the dispersion-shifted optical fiber with low power consumption.
[0109]
FIG. 10 shows a partially omitted planar configuration of the fifth embodiment of the optical circuit device according to the present invention. The optical circuit device according to the fifth embodiment has the waveguide configuration of the arrayed waveguide diffraction grating 25 and the temperature control unit 8, and the cross-sectional configuration in the formation region of the temperature control unit 8 is shown in FIG. ). In FIG. 10, the configurations of the optical waveguide layer removing portion 5 and the concave portion 4 are omitted.
[0110]
In the optical waveguide configuration of the arrayed waveguide diffraction grating 25 shown in FIG. 10, the end of the optical input waveguide 12, the first slab waveguide 13, and the arrayed waveguide 14 on the first slab waveguide 13 side is a first optical branch. The first coupler forming core 21 (21a) that forms the coupler is formed.
[0111]
A second coupler forming core 21 in which the end of the arrayed waveguide 14 on the second slab waveguide 15 side, the second slab waveguide 15 and the optical output waveguide 16 form a second optical branching coupler. (21b) is achieved. The array waveguide 14 between the second coupler-forming core 21b and the first coupler-forming core 21a forms a connection core 22.
[0112]
Each channel waveguide 14a forming the array waveguide 14 is provided with a temperature control means 8. In addition, a wavelength variable control unit (not shown) that varies the wavelength of at least one of multiplexing and demultiplexing by controlling the temperature of the temperature control unit 8 is provided, and the optical circuit of the fifth embodiment is provided. The device is a tunable multiplexer / demultiplexer.
[0113]
As is well known, the center wavelength λc of the arrayed waveguide diffraction grating formed of a quartz glass film on a silicon substrate has a temperature dependence of about 0.011 nm / ° C. Therefore, when the temperature of the channel waveguide 14a is variably controlled by the temperature control means 8, it can function as a wavelength variable multiplexer / demultiplexer.
[0114]
In the optical circuit device of the fifth embodiment, the difference between the lengths of the respective channel waveguides 14a is appropriately set so that the frequency spacing is 25 GHz and the center wavelength when no power is supplied is 1545.322 nm. Have been.
[0115]
When the input power and the output spectrum to the temperature control means 8 were measured using the wavelength variable light of the TE polarization and the TM polarization in the optical circuit device of the fifth embodiment, the result was as shown in FIG. The result was obtained. In addition, the same measurement was performed for an optical circuit device of a comparative example having the optical waveguide configuration and the temperature control means 8 shown in FIG. 10 and having no optical waveguide layer removed portion 5 and the concave portion 4 of the silicon substrate 7. However, the result shown in FIG. 11B was obtained.
[0116]
In these figures, characteristic lines a1, b1, c1, and d1 are output spectra of TE polarized light, and characteristic lines a2, b2, c2, and d2 are output spectra of TM polarized light.
[0117]
In FIG. 11A, characteristic lines a1 and a2 indicate that the input power to the temperature control unit 8 is 0, and that the characteristic lines b1 and b2 indicate that the input power to the temperature control unit 8 is 100 mW. The characteristic lines c1 and c2 show the case where the input power to the temperature control unit 8 is 200 mW, and the characteristic lines d1 and d2 show the case where the input power to the temperature control unit 8 is 300 mW.
[0118]
On the other hand, in FIG. 11B, the characteristic lines a1 and a2 indicate that the input power to the temperature control unit 8 is 0, and the characteristic lines b1 and b2 indicate that the input power to the temperature control unit 8 is 1000 mW. The characteristic lines c1 and c2 indicate the case where the input power to the temperature control unit 8 is 2000 mW, and the characteristic lines d1 and d2 indicate the case where the input power to the temperature control unit 8 is 3000 mW.
[0119]
As shown in FIG. 11B, the optical circuit device of the comparative example requires 2000 mW to obtain a wavelength variable range of two channels, that is, about 0.4 nm. Was as large as 0.1 nm. On the other hand, as shown in FIG. 11A, the optical circuit device according to the fifth embodiment can obtain a wavelength tunable range of about 0.4 nm with only 300 mW of power, The difference between the center wavelengths was also significantly suppressed to 0.02 nm.
[0120]
When 20 similar optical circuit devices were manufactured in the same manner as in the fifth embodiment, the power consumption when changing the wavelength by 0.4 nm was 300 ± 3 mW, and the polarization dependency was 0.02. It could be suppressed to ± 0.01 nm, and the yield was good.
[0121]
As described above, the optical circuit device according to the fifth embodiment was able to realize a wavelength tunable optical multiplexer / demultiplexer having low power consumption, low polarization dependence, and a good production yield. Therefore, using the optical circuit device of the fifth embodiment, optical circuit devices having various functions such as a wavelength tunable light source and a wavelength tunable optical add / drop filter can be stably operated with low power consumption and low polarization dependency. Can be made.
[0122]
Next, a sixth embodiment of the optical circuit device according to the present invention will be described. The optical circuit device of the sixth embodiment has the same optical waveguide configuration and temperature control means 8 as the optical circuit device of the fifth embodiment, and the sixth embodiment is different from the fifth embodiment. Characteristically, an optical variable attenuator is provided by providing an optical variable optical attenuation controller (not shown) that varies the intensity of at least one set wavelength light by controlling the temperature of the temperature controller 8. It is.
[0123]
In the optical circuit device of the sixth embodiment, the circuit of the arrayed waveguide diffraction grating 25 is formed with a design having a channel spacing of 25 GHz, and outputs light from only one optical output waveguide 16. The transmission wavelength spectrum is shifted by changing the temperature of the channel waveguide 14a by the temperature control means 8, and the intensity of the set wavelength light is varied by changing the transmittance at the design center wavelength.
[0124]
A characteristic line a and a characteristic line b in FIG. 12 show the relationship between the input power to the temperature control means 8 and the optical attenuation of the set wavelength light in the sixth embodiment. The characteristic lines c and d in FIG. 12 have the same optical waveguide configuration and temperature control means 8 as those of the optical circuit device of the sixth embodiment, and the optical waveguide layer removing section 5 and the silicon substrate 7 are provided. The relationship between the power supplied to the temperature control means 8 and the amount of light attenuation of the set wavelength light in the optical circuit device of the comparative example having no concave portion 4 is shown.
[0125]
Note that the characteristic lines a and c in FIG. 12 indicate the optical attenuation of the TM polarized light, and the characteristic lines b and d indicate the optical attenuation of the TE polarized light.
[0126]
As is clear from the characteristic lines a to d in FIG. 12, in the optical circuit device of the comparative example, it is necessary to supply about 700 mW to the temperature control means 8 in order to obtain an optical attenuation of 10 dB. The difference in the amount of light attenuation due to waves is as large as about 2 dB, whereas the optical circuit device of the sixth embodiment requires about 180 mW of power input to the temperature control means 8 to obtain a 10 dB light attenuation. In this case, the difference in optical attenuation due to polarization at that time is as small as about 0.5 dB.
[0127]
That is, the optical circuit device of the sixth embodiment was able to realize a power-saving, low-polarization-dependent optical variable attenuator using the waveguide configuration of the arrayed waveguide diffraction grating 25.
[0128]
Next, an optical circuit device according to a seventh embodiment of the present invention will be described. The optical circuit device of the seventh embodiment has the same optical waveguide configuration and temperature control means 8 as the optical circuit device of the fifth embodiment.
[0129]
In the seventh embodiment, the circuit of the arrayed waveguide diffraction grating 25 is formed with a design having a channel spacing of 25 GHz, and is an optical switch that switches and outputs light from two optical output waveguides 16. The temperature control unit 8 is provided with an optical switch control unit (not shown) that changes the output unit of at least one set wavelength light by controlling the temperature of the temperature control unit.
[0130]
The seventh embodiment is configured as described above, and includes the optical circuit device of the seventh embodiment, the same optical waveguide configuration and the temperature control means 8 as the optical circuit device of the seventh embodiment. Then, the switching power was obtained in the optical circuit device of the comparative example not having the optical waveguide layer removing portion 5 and the concave portion 4 of the silicon substrate 7.
[0131]
As a result, the switching power of the optical circuit device of the comparative example was about 1000 mW, whereas the switching power of the optical circuit device of the seventh embodiment was about 150 mW, and a large reduction in the switching power was realized. .
[0132]
FIG. 13 is a plan view showing the main configuration of an optical circuit device according to an eighth embodiment of the present invention. The optical circuit device according to the eighth embodiment includes an optical circuit chip 41 having the waveguide configuration shown in FIG.
[0133]
The optical circuit chip 41 is obtained by forming a waveguide forming region having the following optical waveguide configuration on a silicon substrate 7. The optical waveguide configuration includes at least one (here, one) optical input waveguide 12, a first slab waveguide 13 connected to the output side of the optical input waveguide 12, and the first slab waveguide. 13, an arrayed waveguide 14 connected to the output side of the array waveguide 13, a second slab waveguide 15 connected to the output side of the arrayed waveguide 14, and at least one connected to the output side of the second slab waveguide 15. And one (here, one) optical output waveguide 16.
[0134]
The arrayed waveguide 14 is composed of a plurality of channel waveguides 14a having a length different from each other by a predetermined amount (ΔL). Although a large number of channel waveguides 14a constituting the arrayed waveguide 14 are usually provided, for example, 100, in FIG. 13, for simplification of the drawing, the number of these channel waveguides 14a is reduced. It is shown in a simplified manner.
[0135]
A temperature control means 8 is formed in each of the channel waveguides 14a, and the temperature control means 8 serves as a phase distribution applying section for giving a set phase distribution to the arrayed waveguide 14. The temperature control means 8 is formed by a thin film heater 9 (9a, 9b).
[0136]
Further, a dispersion variable control unit (not shown) for varying the amount of dispersion of at least one set wavelength light by controlling the temperature of the temperature control means 8 is provided. , An optical tunable dispersion compensator for reducing the chromatic dispersion of the connection partner.
[0137]
In the set phase distribution, the number of the channel waveguides 14a of the arrayed waveguide 14 is M (M is a positive integer), and the number of the channel waveguides 14a assigned in the arrangement order of the channel waveguides 14a is k (k = 0 to k = 0). M-1), an even function distribution that is substantially line-symmetric with respect to the center (M-1) / 2 of the channel waveguide number k.
[0138]
This even function distribution is, for example, a quadratic function distribution as shown in FIG. 15, and can be a phase distribution P (k) expressed by an equation including the coefficient A and (Equation 1). The expression of the phase distribution is not particularly limited and may be appropriately set, and may be any even-function distribution described above.
[0139]
(Equation 1)

[0140]
FIG. 14 schematically shows an enlarged view of a formation portion of a heater 9b forming the temperature control means 8, and a current supply means 45 and a current supply electrode 44 are connected to the heater 9b. FIG. 14 shows the heater 9b, but the heater 9a is also formed in the set area of the formation area of the arrayed waveguide 14 similarly to the heater 9b, and the heater 9a is also connected with an electrode for energization and an energizing means. Have been.
[0141]
In the eighth embodiment, by adjusting the refractive index of each channel waveguide 14a by heating by the heater 9 (9a, 9b), the set phase distribution becomes substantially an even distribution as described above. To do.
[0142]
The set phase distribution can be varied, and the amount of heating of the channel waveguide 14a by the heater 9 (9a, 9b) can be changed by varying the amount of electricity to be applied to the heater 9 (9a, 9b) by the energizing means. And the amount of adjustment of the refractive index of the corresponding channel waveguide 14a is varied.
[0143]
The form of the heater 9 (9a, 9b) is not particularly limited, but in the present embodiment, as shown in FIG. 1, the heater 9 (9a) and the heater 9 (9b) are spaced from each other. Is formed through. The energizing means for energizing the heater 9 (9a) and the heater 9 (9a) functions as a positive dispersion compensating phase shifter, and the energizing means for energizing the heater 9 (8b) and the heater 9 (9b) are adapted for negative dispersion compensating. Functions as a phase shifter.
[0144]
The optical circuit device according to the eighth embodiment is configured as described above. The optical circuit device according to the eighth embodiment is supplied to the temperature control means 8 to obtain a chromatic dispersion compensation amount of ± 100 ps / nm. Electric power required about 8W. An optical circuit device of a comparative example which has the same optical waveguide configuration and temperature control means 8 as the optical circuit device of the eighth embodiment, and does not have the optical waveguide layer removing portion 5 and the concave portion 4 of the silicon substrate 7. As a result, the required input power to the temperature control means 8 was about 20 W.
[0145]
As described above, the optical circuit device according to the eighth embodiment was able to obtain a required amount of chromatic dispersion compensation with power saving.
[0146]
Note that the present invention is not limited to the above embodiment, but can adopt various embodiments. For example, the configuration of an optical waveguide (core) constituting an optical circuit or an optical circuit device is not particularly limited, and is appropriately set.
[0147]
Further, the optical circuit device of each of the above embodiments is formed by applying the configuration of the optical circuit of the first embodiment, but the optical circuit device is formed by applying the configuration of the optical circuit of the above second embodiment. May be formed. In this case, the same effects as those of the optical circuit device of each of the above embodiments can be obtained.
[0148]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the optical circuit of this invention, the optical waveguide layer which has a core on a board | substrate is formed, and the optical waveguide layer on both sides which sandwich the formation part of the temperature control means which locally variably controls the temperature of a part of a core is removed. Then, a concave portion having a rectangular cross section is provided in the silicon substrate surface portion encompassing the entire region of the removed portion, and the surface of the silicon substrate and the crystal planes of the side surface and the bottom surface of the concave portion are determined, thereby achieving low power consumption and efficiency. The optical circuit can exhibit a thermo-optic effect, and an optical circuit which is easy to manufacture and has high reliability can be realized.
[0149]
Further, the optical circuit of the present invention has the above-described configuration, whereby the thermal stress is effectively released, and the polarization dependence of the light propagation characteristic due to birefringence can be reduced.
[0150]
Further, in the optical circuit of the present invention, according to the configuration in which the silicon substrate surface, the side surface formed along the longitudinal direction of the core of the concave portion, and the bottom surface of the concave portion are all silicon (100) crystal planes, By applying anisotropic wet etching, both the etching rate downward from the surface of the silicon substrate and the side etching that proceeds from the optical waveguide removal section toward the optical waveguide layer on the side where the temperature control means is formed are silicon. Etching is performed on the (100) crystal plane of the substrate, and proceeds at a constant speed.
[0151]
Therefore, the etching of the silicon substrate starting from the surface of the silicon substrate facing the optical waveguide layer removing portion is performed in a sidewall shape perpendicular to the silicon substrate surface and a bottom shape parallel to the silicon substrate surface. While maintaining the above, the vehicle will travel sideways and downward at the same speed.
[0152]
Therefore, by measuring the etching depth (depth of the concave portion) from the surface of the silicon substrate, the etching length in the direction perpendicular to the longitudinal direction of the temperature control means can be simultaneously grasped. The width of the silicon substrate below the formed optical waveguide layer (the width in the direction perpendicular to the longitudinal direction of the temperature control means) can be appropriately adjusted, and an optical circuit exhibiting the above-described excellent effects can be formed with high yield.
[0153]
Further, in the optical circuit of the present invention, the surface of the silicon substrate and the bottom surface of the recess form a silicon (111) crystal plane, and the side surface of the recess formed along the longitudinal direction of the core has a silicon (110) crystal plane. According to the configuration, the etching rate of the (110) crystal plane of the silicon substrate by the alkaline solution is several tens to several hundreds times the etching rate of the (111) crystal plane. Thus, an appropriate concave portion can be formed.
[0154]
In other words, for example, when a silicon substrate removal portion having substantially the same planar shape as the optical waveguide layer removal portion is formed by anisotropic dry etching, and then anisotropic wet etching is performed with an alkaline solution, etching toward the bottom surface direction of the concave portion is performed. In addition, it becomes easier to control the etching in the side direction, a desired concave portion can be formed, and an optical circuit having the above-described excellent effects can be formed with a high yield.
[0155]
In the optical circuit of the present invention, the configuration in which the concave portion of the silicon substrate is formed by anisotropic etching of silicon with an alkaline solution can form the concave portion with good reproducibility due to the crystal plane dependence of the etching rate of the silicon substrate. .
[0156]
Further, in the optical circuit of the present invention, a configuration formed by anisotropic dry etching of silicon and anisotropic etching of silicon with an alkaline solution performed subsequent to the anisotropic dry etching is formed on the surface of the silicon substrate. The etching in the vertical direction and the etching in the horizontal direction can be performed almost independently, and the concave portion of the silicon substrate can be formed by etching with good reproducibility.
[0157]
Further, in the optical circuit of the present invention, according to the configuration in which the temperature control means is a thin film heater, the temperature control means can be easily formed, and an optical circuit having the above-described excellent effects can be easily realized.
[0158]
Further, in the optical circuit of the present invention, according to the configuration in which the optical waveguide layer is formed of quartz glass, the optical waveguide layer can be easily formed, and the temperature dependence of the refractive index of the silica glass is utilized. Good thermo-optic effect can be exhibited.
[0159]
Further, according to the optical circuit device of the present invention, at least two optical branching couplers for performing at least one of light branching and coupling are connected to each other by the connection core, and at least one of the connection cores is connected to the temperature control means. By forming the structure in the vicinity of the temperature control means as the structure of the optical circuit of the present invention, a thermo-optic effect can be efficiently exhibited, and an optical circuit device can be manufactured with high yield.
[0160]
Further, in the optical circuit device of the present invention, according to the configuration having the Mach-Zehnder optical interferometer circuit, the phase portion of the Mach-Zehnder optical interferometer circuit becomes the connection core, so that the connection is made by the temperature control means formed on the connection core. By controlling the temperature of the optical core, optical circuit devices having various functions such as an optical variable attenuator and an optical switch can be formed with a high yield.
[0161]
Further, in the optical circuit device of the present invention, the optical circuit device includes at least one optical input waveguide, a first slab waveguide, an array waveguide, a second slab waveguide, and an optical output waveguide. According to the configuration in which the waveguide forms the connection core, the temperature control of the array waveguide is controlled by forming the temperature control means on the array waveguide serving as the phase section, and various optical attenuators, optical switches, etc. An optical circuit device having a function can be formed with high yield.
[0162]
Further, in the optical circuit device according to the present invention, according to the configuration including the variable optical attenuator, the optical switch, the variable wavelength multiplexer / demultiplexer, and the variable optical dispersion compensator, the power supplied to the temperature control means is small. Can efficiently exhibit their respective functions, and can realize an optical circuit device having a good yield.
[0163]
Further, according to the method of manufacturing an optical circuit of the present invention, the method of forming the concave portion on the silicon substrate surface side can be anisotropic etching of silicon with an alkaline solution, or anisotropic dry etching of silicon and the anisotropic dry etching of silicon. By performing anisotropic etching of silicon with an alkaline solution following the dry etching, an optical circuit can be easily manufactured with a high yield.
[0164]
Furthermore, in the optical circuit manufacturing method of the present invention, according to the configuration in which the alkaline solution is a potassium hydroxide aqueous solution, a concave portion can be formed on the silicon substrate with higher reproducibility using an easily available potassium hydroxide aqueous solution. An optical circuit can be reliably manufactured with a high yield.
[Brief description of the drawings]
FIG. 1 is a main part configuration diagram showing a first embodiment of an optical circuit according to the present invention.
FIG. 2 is an explanatory view showing a manufacturing process of the optical circuit according to the first embodiment.
FIG. 3 is a main part configuration diagram showing a second embodiment of the optical circuit according to the present invention.
FIG. 4 is an explanatory diagram showing a manufacturing process of the optical circuit according to the second embodiment.
FIG. 5 is a main part configuration diagram showing first and second embodiments of the optical circuit device according to the present invention.
FIG. 6 is a graph showing the relationship between the input power and the optical attenuation of the optical circuit device of the first embodiment, together with the relationship in the comparative example.
FIG. 7 is a plan view showing a main part of an optical circuit device according to a third embodiment of the present invention.
FIG. 8 is a graph showing a relationship between wavelength and coupling efficiency in the optical circuit device according to the third embodiment.
FIG. 9 is a graph showing the relationship between the power input to the temperature control means of the optical circuit device of the third embodiment and the optical circuit device of the comparative example and the center wavelength together with the relationship in the comparative example.
FIG. 10 is a plan view of an optical circuit device according to fifth, sixth, and seventh embodiments of the present invention.
FIG. 11 is a graph showing the relationship between the input power and the transmittance of the optical circuit device of the fifth embodiment, together with the relationship in the comparative example.
FIG. 12 shows the relationship between the input power to the temperature control means and the optical attenuation of the set wavelength light in the sixth embodiment of the optical circuit device according to the present invention.
FIG. 13 is a plan view showing a main configuration of an optical circuit device according to an eighth embodiment of the present invention.
FIG. 14 is an enlarged view of a temperature control means forming portion in the eighth embodiment.
FIG. 15 is a graph showing an example of a set phase distribution given to an arrayed waveguide by a temperature controller in the eighth embodiment.
FIG. 16 is an explanatory diagram illustrating an example of an optical circuit device including a Mach-Zehnder optical interferometer circuit.
FIG. 17 is an explanatory diagram showing a cross-sectional configuration example of a conventional optical circuit device.
FIG. 18 is an explanatory diagram illustrating an example of a cross-sectional configuration of a conventionally proposed optical circuit device.
FIG. 19 is an explanatory diagram showing another example of a cross-sectional configuration of an optical circuit device conventionally proposed.
FIG. 20 is an explanatory view showing still another example of a cross-sectional configuration of an optical circuit device conventionally proposed.
FIG. 21 is an explanatory diagram showing a plan view of an example of a conventionally proposed optical circuit device.
[Explanation of symbols]
1 core
2 clad
3 Optical waveguide layer
4 recess
5 Optical waveguide layer removal section
7 Silicon substrate
8 Temperature control means
9 Thin film heater
12. Optical input waveguide
13 1st slab waveguide
14 Array waveguide
14a channel waveguide
15 Second slab waveguide
16 Optical output waveguide
21 Coupling forming core
22 Connection core

Claims (16)

A silicon substrate, an optical waveguide layer having a core and a clad formed on the silicon substrate, and a temperature control unit formed on the optical waveguide layer and locally variably controlling a temperature of a part of the core. And the optical waveguide layers on both sides of the portion where the temperature control unit is formed are removed from the surface of the optical waveguide layer along the longitudinal direction of the core to the silicon substrate surface along the longitudinal direction of the core. A concave portion having a rectangular cross section is provided in a surface portion of the silicon substrate including an entire region opposed to a lower portion of the optical waveguide layer-removed portion, and the surface of the silicon substrate forms a silicon (100) crystal plane. The side surface of the recess formed along the longitudinal direction of the core is a silicon (100) crystal plane substantially perpendicular to the surface of the silicon substrate, and the bottom surface of the recess is substantially perpendicular to the surface of the silicon substrate. Optical circuit, characterized in that it forms a row silicon (100) crystal plane. A silicon substrate, an optical waveguide layer having a core and a clad formed on the silicon substrate, and a temperature control unit formed on the optical waveguide layer and locally variably controlling a temperature of a part of the core. And the optical waveguide layers on both sides of the portion where the temperature control unit is formed are removed from the surface of the optical waveguide layer along the longitudinal direction of the core to the silicon substrate surface along the longitudinal direction of the core. A concave portion having a rectangular cross section is provided in a surface portion of the silicon substrate including an entire region opposed to a lower portion of the optical waveguide layer removed portion, and the surface of the silicon substrate is formed as a silicon (111) crystal plane. The concave portion has a side surface formed along the longitudinal direction of the core and a silicon (110) crystal plane substantially perpendicular to the silicon substrate surface, and the bottom surface of the concave portion is substantially perpendicular to the silicon substrate surface. Optical circuit, characterized in that it forms a row silicon (111) crystal face. 2. The optical circuit according to claim 1, wherein the concave portion of the silicon substrate is formed by anisotropic etching of silicon with an alkaline solution. 3. The optical circuit according to claim 2, wherein the concave portion of the silicon substrate is formed by anisotropic dry etching of silicon and subsequent to the anisotropic dry etching of the silicon with an alkaline solution. . The optical circuit according to any one of claims 1 to 4, wherein the temperature control means is a thin film heater. The optical circuit according to claim 1, wherein the optical waveguide layer is formed of quartz glass. A coupler forming core comprising the optical circuit according to any one of claims 1 to 6, wherein a core of the optical circuit forms at least two optical branching couplers that perform at least one of branching and coupling of light. And at least two connecting cores for connecting the coupler forming cores to each other, wherein at least one of the connecting cores is provided with a temperature control means. The coupler forming core has two Mach-Zehnder optical interferometer circuits formed by juxtaposing two cores arranged side by side, and the connecting core has two cores arranged side by side with an interval therebetween. The optical circuit device according to claim 7, wherein At least one optical input waveguide, a first slab waveguide connected to an output side of the optical input waveguide, and a plurality of lengths connected to an output side of the first slab waveguide and having different lengths from each other by a predetermined amount. An array waveguide composed of juxtaposed channel waveguides, a second slab waveguide connected to the output side of the array waveguide, and at least one light connected to the output side of the second slab waveguide A first coupler having an output waveguide, wherein ends of the optical input waveguide, the first slab waveguide, and the arrayed waveguide on the first slab waveguide side form a first optical branching coupler; A second coupler forming core which forms a forming core, and wherein the end of the arrayed waveguide on the side of the second slab waveguide, the second slab waveguide and the optical output waveguide form a second optical branching coupler; And an array waveguide between the second coupler-forming core and the first coupler-forming core. There optical circuit device according to claim 7, characterized in that it forms a connecting core. An optical variable optical attenuation control unit, comprising at least one optical circuit device according to claim 8 or 9, wherein an optical variable optical attenuation control unit that varies the intensity of at least one set wavelength light by controlling a temperature of a temperature control unit is provided. An optical circuit device comprising a variable optical attenuator. An optical switch control unit, comprising: at least one optical circuit device according to claim 8 or 9; and an optical switch control unit that varies an output unit of at least one set wavelength light by controlling a temperature of a temperature control unit. An optical circuit device comprising a switch. A wavelength variable control unit that has at least one optical circuit device according to claim 8 or 9 and that controls at least one wavelength of multiplexing and demultiplexing by controlling the temperature of a temperature control unit; An optical circuit device comprising a variable wavelength multiplexer / demultiplexer. A connection comprising a dispersion variable control unit having at least one optical circuit device according to claim 8 or 9 and varying a dispersion amount of at least one set wavelength light by controlling a temperature of a temperature control unit. An optical circuit device comprising an optical tunable dispersion compensator for reducing chromatic dispersion of a partner. 4. The method of manufacturing an optical circuit according to claim 1, wherein after forming the removed portion of the optical waveguide layer, the silicon substrate is subjected to anisotropic etching of silicon with an alkaline solution to remove the optical waveguide layer. A method for manufacturing an optical circuit, comprising forming a concave portion on a silicon substrate surface side at a corresponding position. 5. The method for manufacturing an optical circuit according to claim 2, wherein anisotropic dry etching of silicon is performed on the silicon substrate after forming the removed portion of the optical waveguide layer, and then anisotropic etching with an alkaline solution. A method of manufacturing an optical circuit, comprising: performing etching to form a concave portion on a surface of a silicon substrate at a position corresponding to a removed portion of the optical waveguide layer. 16. The method according to claim 14, wherein the alkaline solution is an aqueous solution of potassium hydroxide.

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