JP2004125855A - Method for adjusting phase difference of optical waveguide element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase difference adjusting method for optical waveguide element such that the precision of phase difference adjustment of an optical waveguide element is high, the adjustment is easy, and its adjustment effect can be maintained for a long period. <P>SOLUTION: In the phase difference adjusting method for the optical waveguide element equipped with a substrate having electrooptic effect and a Mach Zehnder optical waveguide formed on the substrate, the optical waveguide element is constituted as a module (10) and the substrate is heated when the phase difference of the optical waveguide element is adjusted to a specified value by irradiating a portion of the Mach Zehnder optical waveguide with the laser light from a laser light source 12 and the irradiation time and the area irradiated with the laser light are controlled while variation of a light signal from the projection light from the optical waveguide is monitored (17). <P>COPYRIGHT: (C)2004,JPO

Description

【００３５】
基板温度を５００℃以上に設定した場合には、光導波路素子内の光導波路を形成しているＴｉ拡散の一部が変化したり、光導波路素子と光ファイバーとの接続部が変形するなどの弊害が生じた。
上述の結果より、基板の温度を１８０〜２００℃に安定させ、光導波路にレーザを照射するのが、最も効果的と言える。
また、基板の加熱時間やレーザ光照射時間は、調整すべき位相差の大きさにより変化するが、平均約５分程度であった。
さらに、光損傷効果を加速的に劣化（消去）するためには、レーザ照射終了直後、約１００℃の高温で、一定の時間（約２４時間）、光導波路素子の基板を保持することにより、可能となる。
【００３６】
本発明の別の実施例としては、　光損傷による屈折率変化を効率よく行うために、基板内のレーザ光を照射する領域にのみ、光損傷に対する感度を上昇させる物質（Ｆｅ，Ｍｎ，Ｃｏなど）を添加することも可能である。
なお、本発明の応用として、上述した本発明の構成に加え、先に示した先行技術文献などの位相差を調整する手段を、適宜組合せて用いることも可能である。
また、本発明の光導波路素子は、上述した光変調器に限らず、光電界センサシステム用の電界センサ素子の動作点制御に利用できることは、言うまでもない。
【００３７】
【発明の効果】
以上、説明したように、本発明のように加熱しながらレーザ光を光導波路、特にマッハツェンダー型光導波路の分岐導波路に照射することにより、光損傷効果を与え、該光損傷効果を長時間維持することが可能となる。
これにより、光導波路素子の位相差調整の精度が高く、該調整が容易であると共に、その調整効果を長期に渡り持続可能な光導波路素子の位相差調整方法を提供できる。
【図面の簡単な説明】
【図１】（ａ）光強度変調器と（ｂ）方向性結合器の変調曲線を示す図
【図２】（ａ）光強度変調器と（ｂ）方向性結合器を有する光導波路素子における各光導波路の配置を示す図
【図３】本発明の光導波路素子の位相差調整方法を説明する図
【符号の説明】
１　ＬＮ基板
２　入力用導波路
３，５　Ｙ分岐導波路
４　分岐導波路
６，８，９　出力用導波路
７　方向性結合器
１０　光変調器モジュール
１１　微動台
１２　光損傷用レーザ光源
１３　ミラー
１４　試験用レーザ光源
１５　光検出器
１６　ＲＦ発生器
１７　オシロスコープ
２０，２１　レーザ光照射領域[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for adjusting a phase difference of an optical waveguide element, and more particularly to an optical waveguide having a Mach-Zehnder type optical waveguide such as an optical intensity modulator or an operation bias point control of an optical waveguide element including a directional coupler. The present invention relates to a phase difference adjusting method for adjusting a phase difference of a light wave passing through a branched optical waveguide in an element.
[0002]
[Prior art]
2. Description of the Related Art Optical communication has attracted attention in response to the growing demand for high-speed, large-capacity information communication in recent years. Above all, an optical waveguide device that forms a Mach-Zehnder optical waveguide on a substrate having an electro-optical effect is capable of high-speed operation, has no optical wavelength dependence, and is easy to control the amount of chirp. Because of this, it is widely known as an optical control element suitable for optical communication in a broadband frequency, and is used particularly as an optical modulator adapted to high-density wavelength division multiplexing (DWDM) and high-speed communication.
[0003]
In an optical waveguide device using a Mach-Zehnder optical waveguide, a signal voltage is applied to two optical waveguides branched by a Y-branch waveguide by a signal electrode formed near the two optical waveguides. The phase of the light wave passing through the optical waveguide is changed by the strength of the electric field generated by the applied voltage. From the viewpoint that the change is linear and stable, the operating point of the applied voltage is changed by the light guide for the applied voltage. A modulation curve (hereinafter, may be simply referred to as a modulation curve) indicating a change in the intensity of the output light from the waveguide element is used by setting it at a middle point (inflection point).
For example, a Y-Y type in which an input waveguide is branched into two waveguides by a Y-branch waveguide, each of which passes through a straight waveguide, and is multiplexed again by a Y-branch waveguide to form an output waveguide. In the case where the Mach-Zehnder type optical waveguide is used, as shown in FIG. 1A, in order to place the operating point at the middle point A or B of the modulation curve, half of the half-wave voltage of the modulation curve is required. A voltage needs to be applied to the Mach-Zehnder type optical waveguide with a positive polarity or a negative polarity.
[0004]
On the other hand, a Y-BBI-type Mach in which an input waveguide is branched into two waveguides by a Y-branch waveguide, and after passing through each straight waveguide, each of the straight waveguides comes close to each other to form a directional coupler. In the case where a twisted waveguide is used, the middle points C and D of the modulation curve correspond to the position of the applied voltage of 0 V, as shown in FIG. Therefore, in this case, it is not necessary to apply a half-wavelength voltage as in the above-described YY-type Mach-Zehnder optical waveguide.
[0005]
However, the modulation curves of the Mach-Zehnder type optical waveguides such as the YY type and the Y-BBI type have the above-mentioned modulation curves due to variations in the fabrication parameters of the optical waveguide element, the method of fixing the element chip, and various other causes. In order to deviate from the ideal state and make the inflection point as described above an operating point, it is necessary to separately apply a DC voltage to the signal voltage.
[0006]
Further, in the Y-Y type, as described above, it is necessary to apply a voltage that is a half of the half-wavelength voltage of the modulation curve. However, the application of the DC voltage induces a space charge in the waveguide substrate. In addition, there is a problem that an operating point called a DC drift changes with time.
Therefore, as a method of controlling an operating point which does not require application of a DC voltage, it is desired to develop an operating point adjusting method in which the midpoint of the modulation curve at an applied voltage of 0 V becomes the operating point. I was
[0007]
As a conventionally known method of adjusting the operating point, basically, the refractive index of the optical waveguide is changed by changing the stress applied to the substrate. For example, Japanese Unexamined Patent Publication No. 4-337707 discloses that an operating point adjusting film of a metal film is provided on at least one of the branched optical waveguides of a Mach-Zehnder type optical waveguide, and the amount of adhesion is trimmed to thereby control the operation. A method for adjusting a point is disclosed. Japanese Patent Application Laid-Open No. 7-28006 discloses a method in which a light transmitting film is formed on at least a part of a waveguide, and an operating point is adjusted by using a change in a refractive index due to stress of the light transmitting film. Japanese Patent Application Laid-Open No. H8-15354 discloses that stress is applied by changing the optical length of two branched waveguides of a Mach-Zehnder type optical waveguide and providing a polymer substance to one of the branched waveguides. A method is disclosed.
The method of forming a film for stress adjustment on such an optical waveguide requires a process of forming a film during the manufacturing process of the optical waveguide element, which complicates the manufacturing process and increases the film thickness and film thickness. It is necessary to precisely control the formation region, which makes stress adjustment difficult. In addition, when the film once formed is removed by trimming or the like, the film material may be scattered on the substrate and re-attached, thereby deteriorating the characteristics of the optical waveguide element.
[0008]
As another method for applying a stress to a substrate, Japanese Patent Application Laid-Open No. 7-218881 discloses a method in which a stress applying member is provided on a side surface of a substrate and an operating point is adjusted by the stress from this member. As disclosed in Japanese Patent Application Laid-Open No. H11-157, a method of applying a stress by forming a groove near an optical waveguide has been proposed.
In such a method of applying a stress by a mechanical structure, particularly in the case of Japanese Patent Application Laid-Open No. 7-218881, it is difficult to finely adjust the operating point, and if the stress is excessive, the substrate may be damaged. Occurs. In the case of Japanese Patent Application Laid-Open No. 11-271552, a processing technique for accurately forming a groove is required, and an appropriate groove is easily formed by a signal electrode or a ground electrode disposed on or near the optical waveguide. There was a problem that it was difficult.
[0009]
As another method of adjusting the operating point, Japanese Patent Application Laid-Open No. Hei 7-159264 discloses a photorefractive (optical damage) method by irradiating at least a part of a branched optical waveguide of a Mach-Zehnder type optical waveguide. A) A method of adjusting an operating point using an effect is disclosed.
However, the optical damage effect tends to decrease with time, and has a drawback that it is difficult to maintain the state of the adjusted operating point for a long time.
[0010]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, to achieve high accuracy in adjusting the phase difference of an optical waveguide element, to easily perform the adjustment, and to maintain the effect of adjusting the phase difference of the optical waveguide element for a long period of time. Is to provide a way.
[0011]
[Means for Solving the Problems]
In order to solve the above problem, in the invention according to claim 1, in a method of adjusting a phase difference of an optical waveguide element including a substrate having an electro-optical effect and a Mach-Zehnder optical waveguide formed on the substrate, After modularizing the optical waveguide device, a part of the Mach-Zehnder optical waveguide is irradiated with laser light, and while monitoring a change in an optical signal of light emitted from the optical waveguide device, the irradiation time of the laser light is monitored. And controlling the irradiation area to heat the substrate when adjusting the phase difference of the optical waveguide element to a predetermined value.
[0012]
According to the first aspect of the present invention, the optical waveguide element is modularized to irradiate a laser beam, thereby generating an optical damage effect, easily adjusting a phase difference, and heating the substrate during laser beam irradiation. As a result, it is possible to achieve an excellent effect that the durability of the optical damage effect is much longer than that of the conventional one. "Modulation" in the present invention means to assemble the optical waveguide element into an optical modulator or the like.For example, a step of fixing the optical waveguide element to a case of the optical modulator, light waves are input to the optical waveguide element, The method includes a step of installing various members (such as an optical fiber and a lens) for emitting light, and a step of connecting a signal electrode or the like on the optical waveguide element to a connection terminal.
[0013]
According to a second aspect of the present invention, in the method for adjusting the phase difference of the optical waveguide element according to the first aspect, the heating temperature of the substrate is 100 to 300 ° C.
[0014]
According to the second aspect of the present invention, by setting the heating temperature of the substrate in the range of 100 to 300 ° C., the effect can be maintained several times or more as compared with the optical damage effect at room temperature, and the optical waveguide device can be maintained. It is possible to minimize the state change and deterioration of characteristics due to overheating of each member / portion constituting the module. In particular, at 180 to 200 ° C., the duration of the photodamage effect does not decrease even after one year.
[0015]
According to a third aspect of the present invention, in the method for adjusting a phase difference of an optical waveguide device according to the first or second aspect, the laser light is irradiated simultaneously on two branched optical waveguides of the Mach-Zehnder optical waveguide. It is characterized by doing.
[0016]
According to the invention of claim 3, since the two branched optical waveguides of the Mach-Zehnder optical waveguide are both optically damaged, even if the optical damage effect is reduced, the reduction is applied to both optical waveguides. , The relative phase difference between the two optical waveguides changes more slowly than the fluctuation of the optical damage effect of each optical waveguide, and the phase difference adjusted over a long period of time can be maintained. .
[0017]
According to a fourth aspect of the present invention, in the method for adjusting a phase difference of an optical waveguide device according to any one of the first to third aspects, an irradiation spot diameter of the laser light is 100 to 500 μm. .
[0018]
According to the invention of claim 4, in order to adjust the irradiation spot diameter of the laser light to 100 to 500 μm, the laser light can be simultaneously irradiated to the two branched optical waveguides by the same light source, and the irradiation area becomes large. There is no fear that the accuracy of the phase difference adjustment of the optical waveguide device is deteriorated.
[0019]
According to a fifth aspect of the present invention, in the method for adjusting a phase difference of an optical waveguide device according to any one of the first to fourth aspects, the sensitivity of the substrate to the laser beam irradiation area on the laser beam is increased. A substance is added.
[0020]
According to the fifth aspect of the present invention, by adding a substance that increases the sensitivity to light damage, it becomes possible to generate the required light damage effect with a shorter irradiation time or irradiation intensity, and to achieve an optical waveguide device with high working efficiency. A phase difference adjusting method can be provided.
[0021]
According to a sixth aspect of the present invention, in the method for adjusting a phase difference of an optical waveguide element according to any one of the first to fifth aspects, the optical waveguide element comprises an input waveguide and a Y-branch waveguide. An optical intensity modulator having a Y-Y type Mach-Zehnder optical waveguide, which branches into optical waveguides, passes through a straight waveguide, and is multiplexed again by a Y-branch waveguide to form an output waveguide. In order to control an operating bias point of a signal voltage applied to the light intensity modulator, the phase difference is adjusted to a predetermined value.
[0022]
According to the sixth aspect of the present invention, it is possible to provide a light intensity modulator having substantially no DC bias even in a light intensity modulator having a Y-Y type Mach-Zehnder optical waveguide. .
[0023]
According to a seventh aspect of the present invention, in the method for adjusting a phase difference of an optical waveguide device according to any one of the first to fifth aspects, the optical waveguide device has two input waveguides formed by a Y-branch waveguide. A Y-BBI-type Mach-Zehnder optical waveguide in which each of the linear waveguides is adjacent to each other to form a directional coupler after branching into a waveguide and passing through each of the linear waveguides; The phase difference is adjusted to a predetermined value in order to control the operating bias point of the signal voltage applied to the first and second signals.
[0024]
According to the seventh aspect of the present invention, even in an optical waveguide device having a Y-BBI type Mach-Zehnder optical waveguide, the operating point may be reduced due to variations in manufacturing parameters of the optical waveguide device, a method of fixing an element chip, and the like. Even when they are displaced from the ideal state, their operating points can be easily set to 0V.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail using preferred examples.
2A and 2B are diagrams illustrating an optical waveguide device according to the present invention. FIG. 2A illustrates an optical intensity modulator having a YY-type Mach-Zehnder optical waveguide, and FIG. 2B illustrates a Y-BBI-type optical intensity modulator. 1 shows an optical waveguide device having a Mach-Zehnder optical waveguide.
As a substrate 1 constituting an optical waveguide element including these optical modulators, a material having an electro-optical effect, for example, lithium niobate (LiNbO ₃ ; hereinafter, referred to as LN), lithium tantalate (LiTaO ₃ ), PLZT ( LiNbO ₃ crystal, LiTaO ₃ crystal, or LiNbO ₃ and LiTaO ₃ , because they are composed of a lanthanum lead zirconate titanate) and a quartz-based material, and are particularly easy to configure as an optical waveguide device and have a large anisotropy. It is preferable to use a solid solution crystal of No. ₃ . In this embodiment, an example using lithium niobate (LN) will be mainly described.
[0026]
As a method of manufacturing an optical waveguide device, an optical waveguide is formed by thermally diffusing Ti on an LN substrate, and then an electrode is directly formed on the LN substrate without providing a buffer layer over a part or the whole of the substrate. In order to reduce the propagation loss of light in the optical waveguide, a buffer layer such as a dielectric SiO ₂ is provided on the LN substrate, and a Ti / Au electrode pattern is formed thereon, and a gold plating method is used. There is a method of forming a modulation electrode and a ground electrode having a height of several tens of μm and indirectly forming the electrodes.
In general, a plurality of optical waveguide elements are formed on one LN wafer, and finally separated into individual optical waveguide element chips, whereby the optical waveguide elements ((a) and (b) in FIG. 2) are manufactured. .
The optical waveguide device is usually used in the form of a module.Specifically, the optical waveguide device is housed in a metal case, and the optical waveguide device body is connected to the outside of the metal case for inputting and outputting light waves. Lead wires for supplying electricity to the optical fiber, the signal electrode and the like are led out.
[0027]
Various shapes can be selected for the shape of the optical waveguide formed on the surface of the light intensity modulator. In this embodiment (FIG. 2A), a Y-Y type Mach-Zehnder (MZ) type optical waveguide is used. Has adopted.
The shape of the YY type MZ type optical waveguide is such that the input optical waveguide 2 is divided into two optical waveguides 4 by the Y-shaped branch optical waveguide 3 and then divided by the other Y-shaped branch optical waveguide 5. The two optical waveguides 4 are merged and connected to the output optical waveguide 6.
The light input to the light intensity modulator travels along the YY type MZ type optical waveguide. In particular, in the two optical waveguides 4, a signal electrode and a ground electrode are provided near the optical waveguide 4. Light that is arranged and propagates through the optical waveguide in response to a signal applied to the signal electrode undergoes phase modulation. After the phase modulation, the respective guided lights are multiplexed in the other branched optical waveguides 5 and interfere with each other to generate intensity-modulated signal light.
The signal light propagates through the output optical waveguide, and is extracted from the output fiber (not shown) to the outside of the light intensity modulator module.
[0028]
As an example of the directional coupler, as shown in FIG. 2B, a Y-BBI type MZ optical waveguide is used.
The shape of the Y-BBI type MZ optical waveguide is such that the input optical waveguide 2 is divided into two optical waveguides 4 by the Y-shaped branch optical waveguide 3, and then the output optical waveguide 2 is output through the directional coupler 7. It is configured to be connected to the optical waveguides 8 and 9.
Light input to the optical waveguide element travels along the Y-BBI type MZ optical waveguide, and a signal electrode and a ground electrode are separately arranged on the optical waveguide element, and the light is applied in accordance with a signal applied to the signal electrode. The optical waveguides 8 and 9 through which light travels are switched.
In the conventional optical waveguide device having a directional coupler, in particular, an electrode is provided near two optical waveguides 4 so that the phase can be adjusted. However, in the present invention, as described later, Y It is basically not necessary to adjust the phase difference of the optical waveguide element from the U-shaped branch optical waveguide 3 to the directional coupler 7 so as to match the phases of the two branched light waves. However, it is also possible to add a conventional configuration as needed.
[0029]
Next, a method for adjusting the phase difference of the optical waveguide device according to the present invention will be described with reference to FIG.
Reference numeral 10 in FIG. 3 denotes an optical modulator module 10 having a built-in optical waveguide element. The optical modulator module 10 is placed on or in contact with a heater (not shown), and is further positioned on a fine movement table 11 shown. It is also possible to configure the heater with a thermal radiation generator and heat the optical waveguide element in a non-contact state from above the optical modulator module.
A test laser beam is emitted from the laser light source 14 and is incident on the optical modulator module 10. The light wave emitted from the other end of the light modulator module is received by the light detector 15. On the other hand, a signal voltage is applied to the optical modulator module by the RF generator 16, and a light wave emitted from the optical modulator module is modulated according to the signal voltage.
[0030]
The signal of the RF generator and the signal of the photodetector 15 are both input to the X and Y terminals of the oscilloscope 17, and the change in the amount of light output from the optical modulator (modulation curve) depending on the change in the signal voltage is monitored. You.
On the other hand, the laser light from the laser light source 12 for light damage is applied to a predetermined position on the surface of the optical waveguide element in the optical modulator module 10 via the mirror 13. Provides light damage effect.
The laser light from the laser light source for optical damage is converged by an optical component such as a lens (not shown) as necessary in order to narrow the laser light to a predetermined spot diameter.
The wavelength of the laser light from the laser light source for photodamage can be from visible light to near-infrared light. In the experiments according to the present invention, an Ar laser was used.
[0031]
An operating point adjustment region is provided on the optical waveguide element, such as a region 20 in FIG. 2A and a region 21 in FIG.
The range of the operating point adjustment region is such that the modulation curve observed by the oscilloscope 17 is optimal (for example, in the case of a light intensity modulator, the point A or B in FIG. In the case of a coupler, it is changed so as to be as shown in FIG. Methods for changing the operating point adjustment region include a method of moving the fine adjustment table 11 supporting the optical modulator module in the direction of arrow a or b in FIG. 3 and a method of rotating the mirror 13 in the direction of arrow c. Can be selected according to.
The movement of the fine table 11 or the mirror 13 may be performed manually while the operator observes the oscilloscope 17, or the oscilloscope may be electrically determined and automatically variably adjusted. May be.
Further, in the case of an optical waveguide device using an X-cut substrate, even in a completed product after modularization, the waveguide is exposed between the control electrodes, so that laser irradiation for optical damage is sufficiently possible. In the case of an optical waveguide element using a cut substrate, it is necessary to intentionally provide a portion where no electrode exists on the waveguide as an operating point adjustment region.
[0032]
Regarding the spot diameter of the laser irradiated on the optical waveguide, the distance between the two branch waveguides of the MZ type optical waveguide is about 30 to 50 μm, and the optical damage effect is preferably given to both branch waveguides. Since the relative phase difference between the branch waveguides is unlikely to change even if the damage effect is reduced, the spot diameter is adjusted so that two beams are irradiated simultaneously. Specifically, the spot diameter of the laser may be 100 to 500 μm, but the experiment was performed at 300 μm.
Further, when a spot diameter of 500 μm or more is used, a region where the optical damage effect occurs becomes too large, so that a defect such as a minute phase difference adjustment becomes impossible.
Further, in the case where the optical damage is caused at the same time, it is desirable that the distribution of the light amount of the laser beam on each branch waveguide is not the same. This is because the two branch waveguides are optically damaged at the same time, so that the degree of the optical damage needs to be different in order to increase or decrease the phase difference.
In the examples of the present invention, the irradiation to each waveguide was monitored while irradiating without particularly considering the right and left balance, and when the optimum value was reached, the characteristics were evaluated as being completed.
[0033]
Normally, the optical damage effect on the optical waveguide due to the laser irradiation returns to the original state due to a change over time. In the present invention, as a countermeasure, the change with time is minimized by increasing the substrate temperature during laser irradiation. Specifically, the results as shown in Table 1 were obtained.
The “time of change with time” in Table 1 indicates the time until the photodamage effect is reduced to about half.
[0034]
[Table 1]

[0035]
When the substrate temperature is set to 500 ° C. or higher, adverse effects such as a change in a part of the Ti diffusion forming the optical waveguide in the optical waveguide element and a deformation of a connection portion between the optical waveguide element and the optical fiber are caused. Occurred.
From the above results, it is most effective to stabilize the temperature of the substrate at 180 to 200 ° C. and irradiate the optical waveguide with laser.
The heating time of the substrate and the irradiation time of the laser beam vary depending on the magnitude of the phase difference to be adjusted, but are about 5 minutes on average.
Further, in order to accelerate the deterioration (erasing) of the optical damage effect, the substrate of the optical waveguide element is held at a high temperature of about 100 ° C. for a certain time (about 24 hours) immediately after the end of the laser irradiation. It becomes possible.
[0036]
As another embodiment of the present invention, in order to efficiently change the refractive index due to optical damage, a substance (Fe, Mn, Co, etc.) that increases the sensitivity to optical damage only in the region of the substrate irradiated with laser light. ) Can also be added.
As an application of the present invention, in addition to the above-described configuration of the present invention, it is also possible to appropriately combine the means for adjusting the phase difference, such as the above-mentioned prior art documents, as appropriate.
Further, it goes without saying that the optical waveguide device of the present invention can be used not only for the above-described optical modulator but also for operating point control of an electric field sensor element for an optical electric field sensor system.
[0037]
【The invention's effect】
As described above, by irradiating a laser beam to an optical waveguide, particularly a branch waveguide of a Mach-Zehnder type optical waveguide while heating as in the present invention, an optical damage effect is provided, and the optical damage effect is maintained for a long time. Can be maintained.
This makes it possible to provide a method of adjusting the phase difference of the optical waveguide element, which has high accuracy in adjusting the phase difference of the optical waveguide element, facilitates the adjustment, and can maintain the adjustment effect for a long period of time.
[Brief description of the drawings]
FIG. 1 is a diagram showing modulation curves of (a) a light intensity modulator and (b) a directional coupler. FIG. 2 (a) in an optical waveguide device having a light intensity modulator and (b) a directional coupler. FIG. 3 is a diagram showing an arrangement of each optical waveguide. FIG. 3 is a diagram for explaining a phase difference adjusting method of the optical waveguide device of the present invention.
DESCRIPTION OF SYMBOLS 1 LN board 2 Input waveguide 3,5 Y branch waveguide 4 Branch waveguide 6,8,9 Output waveguide 7 Directional coupler 10 Optical modulator module 11 Fine adjustment table 12 Laser light source for optical damage 13 Mirror 14 Test laser light source 15 Photodetector 16 RF generator 17 Oscilloscope 20, 21 Laser irradiation area

Claims (7)

In a method for adjusting a phase difference of an optical waveguide element including a substrate having an electro-optic effect and a Mach-Zehnder optical waveguide formed on the substrate,
After modularizing the optical waveguide device, a part of the Mach-Zehnder optical waveguide is irradiated with laser light, and while monitoring a change in an optical signal of light emitted from the optical waveguide device, the irradiation time of the laser light is monitored. And adjusting the phase difference of the optical waveguide element to a predetermined value by controlling an irradiation area, and heating the substrate when adjusting the phase difference of the optical waveguide element to a predetermined value. 2. The method for adjusting a phase difference of an optical waveguide device according to claim 1, wherein the heating temperature of the substrate is 100 to 300 [deg.] C. 3. The method for adjusting a phase difference of an optical waveguide device according to claim 1, wherein the laser light is applied to two branched optical waveguides of a Mach-Zehnder type optical waveguide at the same time. Phase difference adjustment method. 4. The phase difference adjusting method for an optical waveguide device according to claim 1, wherein an irradiation spot diameter of the laser beam is 100 to 500 [mu] m. 5. The method for adjusting a phase difference of an optical waveguide device according to claim 1, wherein a substance that increases sensitivity to optical damage is added to an area of the substrate irradiated with the laser light. To adjust the phase difference of the optical waveguide element. 6. The method for adjusting a phase difference of an optical waveguide device according to claim 1, wherein the optical waveguide device branches an input waveguide into two waveguides by a Y-branch waveguide, and each of the input waveguides includes a linear waveguide. A light intensity modulator having a YY type Mach-Zehnder type optical waveguide in which the output waveguide is formed by being multiplexed again in the Y branch waveguide after passing through, and a signal voltage applied to the optical intensity modulator is A phase difference adjusting method for an optical waveguide device, comprising: adjusting the phase difference to a predetermined value in order to control an operation bias point. 6. The method for adjusting a phase difference of an optical waveguide device according to claim 1, wherein the optical waveguide device branches an input waveguide into two waveguides by a Y-branch waveguide, and each of the input waveguides includes a linear waveguide. After that, each linear waveguide has a Y-BBI type Mach-Zehnder type optical waveguide in which a directional coupler is formed close to each other, and an operating bias point of a signal voltage applied to the optical waveguide element is set. A method for adjusting the phase difference of an optical waveguide device, wherein the phase difference is adjusted to a predetermined value for control.

Images