JP2005241768A - Optical waveguide module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fabricate an optical waveguide module in a small size and with ease and to control light attenuation with high accuracy and with efficiency. <P>SOLUTION: The optical waveguide module 6 is equipped with a first optical waveguide block 1 having a core part 11 composed of a thermooptic material and a cladding part 12 and a second optical waveguide block 2 having a core part 21 composed of a thermooptic material and a cladding part 22 bonded to the first optical waveguide block 1 with light coupling. Thermooptic constants in both optical waveguide blocks 1, 2 are different from each other. The optical waveguide block 2 has a heater part 4 disposed on a surface of the cladding part 22 in the vicinity of a bonding part 5. When the heater part 4 is liberating heat, refractive index distribution on both sides of the bonding part 5 are different from each other and light is attenuated by being reflected on a discontinuity surface of the refractive index. Also by lowering of light binding force of the core part 21 and by deviation of an optical axis, recombination of irradiating light to the core part 11 is interrupted so as to locally and efficiently attenuate light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical waveguide module used in an optical communication system, and in particular, has an optical coupling portion between an optical waveguide, another optical waveguide, and an optical element such as an optical fiber, and the optical intensity of optical coupling is variable optical attenuation. The present invention relates to an optical waveguide module.

  Conventionally, in an optical communication system using an optical waveguide, an optical attenuator that can be variably controlled is used to adjust the signal intensity to an appropriate value. In order to attenuate light, various optical effects such as a method of mechanically changing the optical axis with respect to an optical fiber or an optical waveguide, or a magneto-optic effect, an electro-optic effect, a thermo-optic effect, etc. are applied to the waveguide. An optical attenuator using the method has been proposed. The damping method using a mechanical structure has a complicated mechanism for damping, and the cost for assembly and adjustment is high, resulting in an expensive module. The attenuation method that causes various optical effects to act on the waveguide has a simpler structure than the mechanical method, and therefore can be expected to reduce cost and increase productivity. However, the method using the magneto-optic effect and the electro-optic effect has dependency characteristics such as the polarization direction, temperature, and wavelength, so that a complicated waveguide pattern is required and a relatively large module is required.

Therefore, a method using a thermo-optic effect has attracted attention. For example, as shown in FIG. 15A, the heater 104 is disposed on the upper portion of the optical waveguide composed of the core 101 and the clad 102, and the heat radiating substrate 103 is disposed on the lower portion. A heat-induced core portion having a refractive index higher than that of the surroundings is generated in a part of the clad 102 due to a temperature gradient generated between the heat dissipation substrate 103 and the heat dissipation substrate 103 and a thermo-optic effect in the optical waveguide member. There is known a variable optical attenuator that attenuates the guided light in the core 101 of the optical waveguide by optically coupling the light to the radiation mode of the thermally induced core (see, for example, Patent Document 1).
JP 2000-241774 A

  However, the configuration of the optical attenuator as shown in FIG. 15A and Patent Document 1 described above has the following problems. First, the operation of the above-described optical attenuator will be described. In the operating state of the optical attenuator shown in FIG. 15A, the temperature distribution and the state of the optical waveguide in the cross section passing through the core 101 and the heater 104 are as shown in FIG. The temperature distribution is substantially symmetrical from the center of the heater 104 as indicated by the isotherm a. Corresponding to this temperature distribution, the refractive index of the core 101 and the clad 102 gradually changes from the right toward the left, reaches a maximum immediately under the center of the heater 104, and changes gradually after passing through this. Return to zero. When a material having a negative thermo-optic constant is used as the optical waveguide member, the refractive index near the heater 104 is greatly decreased, and the refractive index on the heat dissipation substrate 103 side is not significantly decreased. Therefore, a heat-induced core appears in the cladding 102 portion on the heat dissipation substrate 103 side, and light guided through the core 101 is deflected toward the heat dissipation substrate 103 in the vicinity of the heater 104.

  Therefore, a part of the light p1 traveling in the direction from the right to the left heater 104 in the core 101 is separated from the core 101 like the lights p2 and p3 with the gradually changing refractive index. A part of the light travels toward the heat dissipation substrate 103 and is absorbed by the heat dissipation substrate 103 like the light p5. However, there is a light that returns to the core 101 like the light p4, and the light that passes through the portion heated by the heater 104 becomes light p6 that is partially attenuated from the light p1. Since the coupling of the guided light with the radiation mode proceeds gradually according to the change in the refractive index, a waveguide having a predetermined length or more is required to obtain a desired light attenuation. Since the optical attenuation performance depends on the size of the waveguide pattern, miniaturization of the optical waveguide module is limited.

  In addition, since the guided light is absorbed toward the heat dissipation substrate 103 and gradually attenuates in only one direction, the polarization dependence on the optical attenuation becomes more significant as the optical attenuation increases, and the stable optical attenuation characteristic is obtained. Is difficult to obtain. In addition, since polarization dependence occurs in the light that has passed through the optical attenuator, the light quality is deteriorated. In the configuration of the optical attenuator described above, in order to improve the attenuation characteristic, there is a proposal of a method of providing a core part for generating a multimode in a part of the optical waveguide or a multistage configuration of the heating part and the attenuation part. Both of these are factors for increasing the size of the module.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical waveguide module that solves the above-described problems and that can be easily manufactured in a small size and that can perform highly accurate and efficient optical attenuation control.

  In order to achieve the above object, a first optical waveguide block having a first core portion and a first cladding portion made of a thermo-optic material, and a second optical waveguide block made of a thermo-optic material. An optical waveguide module comprising a second optical waveguide block having a core portion and a second cladding portion and joined to be optically coupled to the first optical waveguide block, wherein the second core portion and The second clad portion is made of a thermo-optic material having a thermo-optic constant different from the materials of the first core portion and the first clad portion, and the second optical waveguide block is made of the second clad portion. A heater portion is provided on the surface and in the vicinity of the joint portion with the first optical waveguide block.

  According to a second aspect of the present invention, in the optical waveguide module according to the first aspect, an absolute value of a thermo-optic constant of the second core portion and the second cladding portion is the first core portion and the first cladding. It is larger than the absolute value of the thermo-optic constant of the part.

  According to a third aspect of the present invention, in the optical waveguide module according to the first aspect, the heater portion is disposed at an end portion of the second optical waveguide block on the side of the joint portion with the first optical waveguide block. It is.

  According to a fourth aspect of the present invention, in the optical waveguide module according to the first aspect, the thermo-optic constants of the second core portion and the second cladding portion are the heat of the first core portion and the first cladding portion. The optical constants and the signs of the positive and negative are different.

  According to a fifth aspect of the present invention, in the optical waveguide module according to the first aspect, the junction between the first optical waveguide block and the second optical waveguide block is the first core portion and the second core portion. It is constituted by a surface having an inclination of 5 ° to 10 ° with respect to a surface perpendicular to the optical axis.

  According to a sixth aspect of the present invention, in the optical waveguide module according to the first aspect, the amount of heat generation increases as the heater portion is closer to a joint portion between the first optical waveguide block and the second optical waveguide block. It is formed as follows.

  According to a seventh aspect of the present invention, in the optical waveguide module according to the first aspect, a high refractive index layer is provided in the vicinity of the first core portion.

  According to an eighth aspect of the present invention, there is provided the optical waveguide module according to the first aspect, wherein the optical waveguide module includes a first optical waveguide block, a third core portion made of a thermo-optic material, and a third cladding portion. A waveguide block is integrally formed on the substrate, and the formed first and third optical waveguide blocks include a cut-out portion from which the core portion and the clad portion are removed, and the second cut-out portion includes the second block. These optical waveguide blocks are embedded, and these first, second, and third optical waveguide blocks are optically coupled to each other.

  According to a ninth aspect of the present invention, in the optical waveguide module according to the first aspect, light is emitted from the second optical waveguide block having the heater portion toward the first optical waveguide block at the joint portion of the both blocks. It is guided.

  According to the first aspect of the present invention, the refractive index distribution at the junction between the first waveguide block and the second waveguide block can be made discontinuous by heating the heater, and thus light attenuation is caused by reflection at the junction. Therefore, a large amount of light attenuation can be efficiently obtained with a small amount of heating. Since an optical attenuation effect can be obtained only in a minute region near the junction, an optical waveguide module having a variable optical attenuation function can be reduced in size. An optical component (waveguide, optical fiber, etc.) is placed adjacent to a joint where such a light attenuation effect can be obtained, and the optical coupling state with the optical component is controlled using the refractive index change at the joint, so that the light output is controlled. By attenuating, it is possible to obtain an optical waveguide module that is mounted by forming a variable optical attenuation function with small size and high accuracy by simple manufacture.

  According to the invention of claim 2, since the heater is provided in the second waveguide block having a larger absolute value of the thermo-optic constant and excellent thermal sensitivity to the thermo-optic effect, the refractive index can be easily controlled. Thus, a large change in the refractive index at the junction (a larger discontinuity in the refractive index distribution at the junction) can be easily obtained, and highly efficient optical attenuation control can be performed.

  According to the invention of claim 3, since the heater portion is arranged at the junction between the first waveguide block and the second waveguide block made of thermo-optic materials having different thermo-optic constants, the discontinuous refractive index The light attenuation can be efficiently controlled by forming the distribution with a small heating amount.

  According to the fourth aspect of the present invention, the difference in refractive index at the joint can be increased during heating, so that it is possible to obtain better light attenuation controllability than when the signs of the thermo-optic constants in both blocks are the same.

  According to the fifth aspect of the present invention, when the light is attenuated by heating, the light is easily reflected at the joint portion, so that the light attenuation can be increased. Further, since the joint surface is not orthogonal to the optical axis, the reflected return light is reduced when the light is not attenuated, and the deterioration of the S / N ratio due to the return light can be prevented.

  According to the invention of claim 6, the substantial optical axis position is gradually shifted from the optical axis of the core by heating, and the superheat is concentrated in the vicinity of the joint, so that the refractive index distribution is concentrated on the joint. The light attenuation controllability can be further improved and efficient light attenuation control can be performed.

  According to the seventh aspect of the present invention, the light scattered at the junction having the refractive index discontinuous is supplemented by the high refractive index layer provided in the vicinity of the first core portion, and recombined with the first core portion. Therefore, efficient light attenuation control can be performed.

  According to the invention of claim 8, since the second optical waveguide block can be placed and embedded on the cutout portion of the substrate, the first, second, and third optical waveguide blocks are interposed via the air layer. Can be optically coupled, and the refractive index difference can be increased by the air layer. Moreover, the heat insulation effect can be given to a junction part and an edge part can be heated efficiently.

  According to the ninth aspect of the present invention, the light is gradually shifted from the original optical axis and hits the discontinuous portion of the refractive index, so that the light is attenuated more efficiently than in the reverse case. Can do. Further, since the light is shifted from the optical axis, there is little return light due to reflection, and control when the amount of attenuation is small is facilitated.

  Hereinafter, an optical waveguide module according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the optical waveguide module 6 and its operating state. As shown in FIG. 1A, the optical waveguide module 6 includes a first optical waveguide block 1 having a first core portion 11 and a first cladding portion 12 made of a thermo-optic material, and a thermo-optic material. And a second optical waveguide block 2 having a second core portion 21 and a second cladding portion 22 that are joined to be optically coupled to the first optical waveguide block 1. The second core portion 21 and the second cladding portion 22 are made of a thermo-optic material having a thermo-optic constant different from the material of the first core portion 11 and the first cladding portion 12. The second optical waveguide block 2 includes a heater portion 4 disposed on the surface of the second cladding portion 22 and in the vicinity of the joint portion 5 with the first optical waveguide block 1. The heater unit 4 is energized through the electrode 40. The first optical waveguide block 1 and the second optical waveguide block 2 are formed on the first substrate 13 and the second substrate 23, respectively. In the following description, the names “first” and “second” are omitted as appropriate.

  The light attenuation operation of the optical waveguide module 6 will be described with reference to FIG. Since the heater unit 4 is disposed in the direction orthogonal to the optical axis of the core unit 21 and in the vicinity of the joint 5 of the two optical waveguide blocks 1 and 2, the temperature distribution during the heat generation of the heater unit 4 is As shown by the isotherms a and b, both sides of the joint 5 are substantially symmetrical. However, since the thermo-optic constants of the thermo-optic materials forming the waveguides of the two optical waveguide blocks 1 and 2 are different from each other, the refractive index distributions are different on both sides of the joint portion 5.

  That is, as a result of heating by the heater unit 4, the light binding force by the core unit 21 becomes weak, and the refractive index distribution at the joint 5 between the optical waveguide block 1 and the optical waveguide block 2 becomes discontinuous. Therefore, the light passing through the joint portion 5 of the optical waveguide module 6 passes through the discontinuous surface of the refractive index. Therefore, reflection at the joint portion 5 occurs, and thereby light attenuation can be caused in the light traveling toward the optical waveguide block 1. The amount of light attenuation due to this reflection can be controlled by the input power to the heater unit 4. Next, the light attenuation will be described.

  In the optical waveguide module 6, the thermo-optic constant of the thermo-optic material forming the waveguides of the two optical waveguide blocks 1 and 2 is set to the following configuration as an example. Both blocks use a material having a negative thermo-optic constant, and the absolute values of the thermo-optic constants of the core portion 21 and the cladding portion 22 are larger than the absolute values of the thermo-optic constants of the core portion 11 and the cladding portion 12. To do. As a material having an excellent thermo-optic effect with a negative thermo-optic constant and a large absolute value, polymer materials such as acrylic, epoxy, silicone, and polyimide can be used.

  With the above-described thermo-optic constant configuration, when the heater unit 4 is energized, the refractive index near the heater unit 4 of the optical waveguide block 2 greatly decreases, but the refractive index on the substrate 23 side does not decrease much. This refractive index distribution causes light leakage, and the light guided through the core portion 21 is deflected toward the substrate 23 in the vicinity of the joint portion 5.

  At this time, the refractive index near the heater portion 4 of the optical waveguide block 1 is not so lowered, and the refractive index on the substrate 13 side is hardly lowered. In such a state of the optical waveguide module 6, a part of the light p <b> 1 traveling from the right side toward the joint portion 5 in the core portion 21 is like the light p <b> 2 and p <b> 3 due to the change in the refractive index depending on the location. Proceed away from the core 21. That is, the light traveling in the optical waveguide block 2 toward the joint 5 travels along an optical axis that gradually shifts from the original optical axis formed by the core 21 and the core 11.

  When the light traveling away from the original optical axis passes through the discontinuous surface of the refractive index of the junction 5, the optical axis is displaced before and after the junction 5. The light cannot return, and travels like light p4 and p5 and is absorbed by the substrate 13 or radiated to the outside of the optical waveguide block 1 and the optical waveguide block 2. Then, a part of the light p1 becomes the light p6 and is further guided through the core portion 11. The intensity of the light p6 is controlled and blocked by the input power to the heater unit 4. In this way, until reaching the joint portion 5, the light restraining force by the core portion 21 is weakened and the light oozes out, and the optical axis is shifted due to the difference in the refractive index distribution before and after the joint portion 5. Therefore, the effect of light attenuation is more surely effective, and efficient light attenuation is realized. If the excess loss at the time of optical coupling between the optical waveguide blocks is 30 dB or less, an attenuation amount of 20 dB or more can be added by controlling the refractive index distribution.

  Here, the manufacture of the optical waveguide module 6 will be described. The optical waveguide module 6 is formed by separately forming two optical waveguide blocks 1 and 2 and then optically coupling them together. Therefore, of the two optical waveguide blocks, the second optical waveguide block 2 having a heater portion will be described. As the substrate 23, a substrate having high thermal conductivity, for example, a Si wafer is used. Note that a substrate is not particularly required when an optical waveguide is formed by molding such as mold transfer. The optical waveguide is composed of a core portion 21 and a clad portion 22 having a difference in refractive index, and the formation thereof is performed using various lamination techniques and patterning techniques depending on the waveguide material. For example, techniques such as chemical vapor deposition, physical vapor deposition, a sol-gel method, a method of forming a combination of dipping or dropping, and spin coating, and a technique such as mold transfer can be used. The core portion 21 is formed using techniques such as direct exposure development using a predetermined mask pattern, reactive ion etching through a patterned photoresist, and mold transfer. The single mode optical waveguide preferably has a refractive index difference of 0.3% between the core portion 21 and the cladding portion 22 and a cross-sectional shape of the core portion 21 of 5 to 10 μm.

  An optical waveguide having an optical waveguide formed using the above technique has a waveguide end face substantially perpendicular to the optical axis for optical coupling with other optical waveguides and optical fibers. And the heater part 4 is formed in the formed waveguide end surface vicinity. The heater unit 4 is formed of a metal thin film patterned in a thin line only at a necessary portion, and is configured to be heated by Joule heat. For the metal thin film, the material and the cross-sectional dimension (resistance value) may be determined according to the power required for heating. Examples of the thin film material include Ti, Au, Al, Ni, Cr, NiCr, and the like. For example, when using Au, the heater part 4 excellent in environmental resistance can be formed. In the heater section 4 made of an Au thin film having a width of 10 μm and a thickness of 0.2 μm, the resistance value is several tens to several hundreds Ω, and heating of about several tens mW can be performed.

  Next, the positional relationship between the heater section 4 and the joint section 5 and the light attenuation efficiency will be described with reference to FIG. The heater portion 4 is more effective in controlling light attenuation as it is closer to the joint portion 5, and is preferably formed by patterning within 50 μm from the joint portion 5, for example. As can be seen by paying attention to the temperature distribution, the heater unit 4 is joined as shown in FIG. 2 (b) to the state where the heater unit 4 is closest to the joint 5 as shown in FIG. 2 (a). This is because the same problem as in the state shown in FIG. 15 (b) describing the conventional example occurs in the state away from the unit 5.

  In relation to the above, an optical waveguide module according to another embodiment will be described with reference to FIG. As shown in FIGS. 3 (a) and 3 (b), the heater section 4 may be disposed in the joint section 5 so as to straddle both optical waveguide blocks 1 and 2. Such arrangement of the heater unit 4 is possible if the heater unit 4 is formed after the optical waveguide block 1 and the optical waveguide block 2 are optically coupled and joined. The location of the energization electrodes 30 and 40 to the heater unit 4 is not particularly limited. Whether the heater section 4 is formed before or after the joining of both optical waveguide blocks can be appropriately selected as the degree of freedom in designing and manufacturing the optical waveguide module 6.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. In this optical waveguide module 6, the thermo-optic constants of the core part 21 and the clad part 22 have negative values, and the thermo-optic constants of the core part 11 and the clad part 12 have positive values. Are different from each other in sign. The structure of the heater part and the waveguide is the same as that of the embodiment shown in FIG. 1 as shown in FIG. The refractive index distribution in the waveguide thickness direction X1 in the vicinity of the joint 5 of the optical waveguide block 1 is as shown in FIG. A distribution curve a0 shows a refractive index distribution when the heater unit 4 is not energized. The refractive index distribution is high in the core portion 11 and is generally distributed as an optical waveguide low in the upper clad portion 12a and the lower clad portion 12b. A distribution curve a <b> 1 indicates a refractive index distribution when the heater unit 4 is energized. Since the thermo-optic constant is positive, the refractive index n of each part is increased by energization of the heater part 4, and the rate of increase is closer to the heater part 4. Similarly, the refractive index distribution in the waveguide thickness direction X2 in the vicinity of the joint 5 of the optical waveguide block 2 is as shown in FIG. In this case, since the thermo-optic constant is negative, the refractive index n of each part is decreased by energization of the heater unit 4, and the rate of the decrease is closer to the heater unit 4.

  In this way, when the heater unit 4 is heated, the direction of change in the refractive index is different between before and after the bonded portion 5, so that a state of large discontinuity in the refractive index before and after the bonded portion 5 is realized. . Therefore, efficient light attenuation control can be performed.

The optical waveguide module 6 described above can be configured using the following optical materials. As a material having a positive thermo-optical effect, a quartz-based material or an inorganic crystal material such as quartz, sapphire, LiTaO ₃ , LiNbO ₃ can be used. As a material having a negative thermo-optical effect, a polymer material such as acrylic, epoxy, silicone, or polyimide can be used.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. In this optical waveguide module 6, a heat insulating layer 51 is formed at the joint between the optical waveguide blocks 1 and 2. The heat insulating layer 51 can be formed by bonding using an adhesive material having a heat insulating effect when the optical waveguide blocks 1 and 2 are bonded. The optimum thickness of the heat insulating layer 51 is selected and determined according to the refractive index difference between the core portion 11 and the cladding portion 12, the refractive index difference between the core portion 21 and the cladding portion 22, the wavelength of light to be guided, and the optical waveguide mode. For example, when light having a refractive index difference of 0.3%, a waveguide mode of a single mode, and a wavelength of 1.55 μm is propagated, the thickness of the heat insulating layer 51 is preferably within 10 μm. By providing such a heat insulating layer 51, only the side of the optical waveguide block 2 provided with the heater section 4 can be heated and heated with high efficiency. Therefore, the thermo-optic constant of the material constituting the optical waveguide blocks 1 and 2 can be increased. Even if the signs are not different from each other, the refractive index difference at the joint can be efficiently increased.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. In this optical waveguide module 6, the joint portion of the optical waveguide blocks 1 and 2 is configured by a surface having an inclination angle θ = 5 ° to 10 ° with respect to a surface perpendicular to the optical axis of the core portion 11 and the core portion 21. Yes. Each optical waveguide block 1, 2 having an inclined end face can be easily manufactured by forming a waveguide and cutting it into each block, and then polishing the end face of the waveguide obliquely. The optical waveguide module 6 having such a junction 5 increases the ratio of light reflection at the junction more than the junction perpendicular to the optical axis, thereby increasing the light attenuation effect. That is, the light p9 deflected by the refractive index change during heating by the heater unit 4 is incident obliquely on the junction 5 at an incident angle on which the inclination angle θ is added, so that the light p10 reflected by the junction 5 increases. Therefore, the passing light p11 is reduced.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. The optical waveguide module 6 is formed so that the amount of heat generation increases as the heater portion 4 is closer to the joint portion 5 between the optical waveguide block 1 and the optical waveguide block 2. The heater unit 4 is formed by changing the width or thickness along the optical axis direction. The heater part 4 whose width is not constant along the optical axis direction can be easily manufactured by patterning by photolithography. The heater unit 4 having a thickness that is not constant along the optical axis direction can be manufactured with a thickness distribution by sputtering using a gray mask when the heater unit 4 is formed of a metal thin film. The heater width is narrowed (or the heater thickness is reduced) as it approaches the joint 5, the optical axis is gradually shifted at a low power far from the joint 5, and the heater is concentrated near the joint 5. By overheating at 4, the temperature distribution change, and hence the refractive index distribution change, can be concentrated on the junction to further improve the light attenuation controllability, and efficient light attenuation control can be performed.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. The optical waveguide module 6 shown in FIG. 8A includes a region 21a in which the width of the core portion 21 of the optical waveguide block 2 is narrowed in the vicinity of the joint portion 5, and the optical waveguide module shown in FIG. 6 includes a region 21 b in which the width of the core portion 21 of the optical waveguide block 2 is increased in the vicinity of the joint portion 5. The optical waveguide in which the width of the core portion 21 is changed can be easily manufactured by patterning using a photolithography method. As the width of the core portion 21 changes, the light that is guided by the core portion 21 becomes unstable in the region 21a or the region 21b. It becomes easy to shift from the axis, and efficient light attenuation is possible. Both the optical waveguide modules are preferably used by being incident on the optical waveguide block 1 side from the optical waveguide block 2 side as indicated by an arrow P0. The optical waveguide in which single-mode light stably propagates has a core portion shape of 5 to 10 μm when the difference in refractive index between the core portion and the cladding portion is 0.3%. The widths of 21a and 21b are within the range of such a core shape.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIGS. In this optical waveguide module 6, the optical waveguide block 1 is connected to the light incident / exit ends on both sides of the optical axis of the optical waveguide block 2. As shown in FIGS. 9A and 9B, a heater portion 4 is disposed at both joints 5 of the optical waveguide block 2 so that they can be heated at the same time. The heater resistors R4 and R4 are connected in series (or in parallel). Connected) and simultaneously turned ON / OFF. If the optical waveguide length of the optical waveguide block 2 is short, as shown in FIG. 10, the joint portions 5 at both ends are close to each other, so that the heater portions 4 of both joint portions 5 are integrated on both sides of the light incident / exit. It is said. By providing junctions 5 at both ends of the optical waveguide block 2 to provide an optical attenuation function, a large attenuation effect can be obtained for light entering and exiting the optical waveguide block 2, and heater portions on both sides of the optical input and output If the is integrated, the attenuation area can be reduced.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. As shown in FIG. 11A, the second optical waveguide block 2 of this optical waveguide module includes a 1 × 2 TO optical switch having a Y-branched core portion 22 therein. The first optical waveguide block 1 is two optical fibers each having a first core portion 11 and a first cladding portion 12. The optical waveguide block 2 has optical switching heaters 41 and 43 in the vicinity of both branches of the branching portion of the Y branching waveguide, and a light attenuating portion in the vicinity of the junction 5 with the first optical waveguide block 1 made of an optical fiber. Heater sections 42 and 44 are provided. For example, as shown in FIG. 11B, the optical switch heater unit and the optical attenuation heater unit are electrically connected to resistors R41 to R44, a power source E, and a circuit switch SW. The extinction ratio is improved. When the light that has entered the core 21 from the direction of the arrow L0 heats the optical switch heater 41 (resistor R41), the optical path becomes the arrow L2 side, and the optical path on the arrow L1 side is turned off. At this time, the OFF state can be made more reliable by simultaneously heating the light attenuating heater section 42 (resistor R42) in the optical path on the OFF side. Note that the interlocking combination of heaters (heater circuit) is not limited to the circuit shown here, and is appropriately selected depending on the configuration of the optical switch.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. As shown in FIG. 12 (a), the optical waveguide module 6 includes a region 21c having a curvature ρ in the waveguide plane in the core portion 21 in the vicinity of the joint 5, and FIG. 12 (b). As shown in FIG. 4, the heater unit 4 is provided that is offset from the optical axes of the core units 21 and 11 by an offset d2. As indicated by an arrow L0, light is preferably used by being incident from the optical waveguide block 2 side to the optical waveguide block 1 side. According to the optical waveguide module 6 having such a configuration, as will be described below, the optical axis can be easily shifted, so that optical attenuation can be performed efficiently, and improved optical attenuation characteristics can be obtained with respect to polarization dependent loss (PDL). It is done.

  The effect of the region 21c will be described. When light propagates through a straight waveguide, the light travels symmetrically distributed on the central axis of the waveguide (core portion). However, in the case of a curved waveguide, the light intensity distribution is not symmetric with respect to the central axis, and for example, in the case of an arc waveguide, it is known that the light intensity distribution proceeds with a large amount of leakage outside the center of curvature. Yes. Therefore, when a material having a negative thermo-optic constant is used, as shown in FIG. 12A, the heater portion 4 is disposed on the curvature center side (inner side) of the bent region 21c of the core portion 21 to be attenuated. If the light is emitted to the outside, the optical axis can be easily shifted by the amount of light oozing out, and light can be emitted and attenuated at low power. Attenuation can be obtained. On the other hand, for a material having a positive thermo-optic constant, the heater unit 4 may be shifted to the opposite side of the center of curvature.

The effect of the offset d2 will be described. When the guided light is considered as an electromagnetic field component, light that is easily attenuated is TM mode light whose vibration direction is perpendicular to the surface of the substrate 23, and TE mode light that vibrates in a direction parallel to the surface of the substrate 23 is difficult to attenuate. For this reason, the polarization dependent loss (PDL) that hardly occurs in the non-heated state increases as the heater heating power increases. there,
By setting the positional relationship in which the heater unit 4 and the region 21c heated by the heater unit 4 are shifted by the offset d2, a temperature gradient in an oblique direction is formed with respect to the region 21c. As a result, the refractive index distribution is also an oblique distribution, and the light distribution in the region 21 c is a distribution far from the substrate 23. Therefore, radiated light is generated in the plane direction of the optical waveguide, and attenuation due to absorption by the substrate 23 is reduced. That is, the difference in attenuation between the TE mode light and the TM mode light is suppressed, and an increase in polarization dependent loss (PDL) is suppressed.

  In addition, since an excessive loss will generate | occur | produce if an optical waveguide (core part 21) is given an extreme curvature, a curvature is set so that this loss may be within 0.1 dB. Further, the heater unit 4 is disposed with an offset of 5 to 30 μm from the waveguide so as to be inside the curvature.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. The optical waveguide module 6 includes a high refractive index layer 14 in the vicinity of the core portion 11 of the optical waveguide block 1. Light is preferably used by being incident on the optical waveguide block 1 side from the optical waveguide block 2 side. The optical waveguide block 1 is manufactured as follows. First, a layer for the cladding portion 12 is formed with a predetermined thickness on a silicon substrate to be a substrate, and a layer for the high refractive index layer 14 is formed thereon. The refractive index may be approximately the same as the refractive index of the core portion 11. Thereafter, the core part 11 and the clad part 12 are formed on the substrate on which the refractive index layer is formed by the method described with reference to FIG. 1, and the optical waveguide block 1 is obtained by cutting and polishing. According to the optical waveguide module 6 having such a configuration, the light scattered at the joint 5 having a discontinuous refractive index is supplemented by the high refractive index layer 14 provided in the vicinity of the core 11 and recombined with the core 11. Can be prevented, and efficient light attenuation control can be performed.

  Next, still another embodiment of the optical waveguide module will be described with reference to FIG. As shown in FIGS. 14A and 14B, the optical waveguide module 6 includes three optical waveguide blocks 1, 2, and 3. A first optical waveguide block 1 and a third optical waveguide block 3 including a third core portion 31 and a third cladding portion 32 made of a thermo-optic material are integrally formed on a substrate 7. . The first and third optical waveguide blocks 1 and 3 are provided with cutout portions 71 from which the core portions 11 and 31 and the cladding portions 12 and 32 are removed. The second optical waveguide block 2 is embedded in the cutout portion 71, and the first, second, and third optical waveguide blocks 1, 2, and 3 are optically coupled to each other.

  A manufacturing method will be described. The integrally formed optical waveguide blocks 1 and 3 are patterned in advance so as to remove the cutout portion 71 when the waveguide layer is formed, or after all the layers are laminated, It is formed by chemical or thermal removal. As a method of patterning in advance, the same method as the formation by patterning of the core part described in relation to FIG. 1 can be used. The optical waveguide block 2 is fixed to the substrate 7 exposed on the bottom surface of the cutout portion 71 with an adhesive 72. This fixing may be performed between the side surface of the optical waveguide block 2, that is, the surface where the core portion 21 is not exposed and the inner wall of the cutout portion 71 (the surface where the core portions 11 and 31 are not exposed). Good.

  According to the optical waveguide module 6 configured as described above, the first, second, and third optical waveguide blocks 1, 2, and 3 can be optically coupled through the air layer, and the refractive index difference is increased by the air layer, A large light attenuation can be obtained. Moreover, the heat insulation effect by an air layer can be given to the junction part 5, and the edge part of the optical waveguide block 2 can be heated efficiently. The heater unit 4 may be provided at both ends. Also, the end of the optical waveguide block 2 is left floating from the substrate, and a distortion occurs in the joint portion 5 due to thermal expansion when the heater portion 4 is heated, causing a geometrical optical axis shift and light. It may be attenuated. When the heating of the heater unit is stopped, the distortion is eliminated together with the refractive index distribution, and the deviation of the optical axis is eliminated.

  This is the end of the description of the optical waveguide module 6 of each embodiment. Although the optical waveguide direction has been individually described above, the optical waveguide module 6 of the present invention has the first optical waveguide from the second optical waveguide block 2 having the heater unit 4 at the joint 5 of the optical waveguide blocks 1 and 2. It is preferable that light is guided toward the waveguide block 1. The present invention is not limited to the above-described configuration, and various modifications can be made. For example, although an optical waveguide has been described as the first optical waveguide block 1, if the optical element can be optically coupled to the joint portion of the second optical waveguide block 2, the light attenuated as the first optical waveguide block 1 A signal can be received. For example, an optical element such as an optical fiber can be used as the first optical waveguide block 1.

(A) is a perspective view of the optical waveguide module which concerns on one Embodiment of this invention, (b) is an optical axis direction sectional view of the optical waveguide module. (A) is sectional drawing of an optical axis direction of an optical waveguide module same as the above, (b) is sectional drawing of the optical waveguide module which shows a comparative example. (A) is a perspective view of the other optical waveguide module which concerns on one Embodiment of this invention, (b) is an optical axis direction sectional drawing of the optical waveguide module. (A) is a sectional view in the optical axis direction of still another optical waveguide module according to an embodiment of the present invention, and (b) and (c) are refracted with respect to the thickness direction position of two waveguide blocks constituting the optical waveguide module. The figure which shows rate distribution about the ON state and OFF state of a heater, respectively. The optical axis direction sectional view of the further another optical waveguide module concerning one embodiment of the present invention. The optical axis direction sectional view of the further another optical waveguide module concerning one embodiment of the present invention. The perspective view of the further another optical waveguide module which concerns on one Embodiment of this invention. (A) and (b) are the top views seen from the clad part surface side of the further another optical waveguide module of this invention. (A) Optical-axis direction sectional drawing of the other optical waveguide module which concerns on one Embodiment of this invention, (b) is an electric circuit diagram of the heater part of the optical waveguide module. The optical axis direction sectional view of the further another optical waveguide module concerning one embodiment of the present invention. (A) is the top view which looked at the further another optical waveguide module which concerns on one Embodiment of this invention from the clad part surface side, (b) is an electrical circuit diagram of the heater part of the optical waveguide module. (A) is the top view seen from the clad part surface side of the further another optical waveguide module which concerns on one Embodiment of this invention, (b) is AA sectional drawing in (a). The optical axis direction sectional view of the further another optical waveguide module concerning one embodiment of the present invention. (A) is an exploded perspective view of still another optical waveguide module according to an embodiment of the present invention, (b) is a cross-sectional view in the optical axis direction of the optical waveguide module. (A) is a perspective view of the conventional optical waveguide module, (b) is an optical axis direction sectional view of the waveguide module.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st optical waveguide block 2 2nd optical waveguide block 3 3rd optical waveguide block 4 Heater part 5 Junction part 6 Optical waveguide module 11 1st core part 12 1st clad part 14 High refractive index layer 21 1st 2 core part 22 2nd clad part 31 3rd core part 32 3rd clad part 71 Cut-out part

Claims (9)

A first optical waveguide block having a first core portion and a first cladding portion made of a thermo-optic material; a second core portion and a second cladding portion made of a thermo-optic material; An optical waveguide module comprising a second optical waveguide block joined so as to be optically coupled to the optical waveguide block of
The second core part and the second cladding part are made of a thermo-optic material having a thermo-optic constant different from the material of the first core part and the first cladding part,
The second optical waveguide block includes a heater portion disposed on the surface of the second cladding portion and in the vicinity of a joint portion with the first optical waveguide block.   The absolute value of the thermo-optic constant of the second core part and the second cladding part is larger than the absolute value of the thermo-optic constant of the first core part and the first cladding part. 2. The optical waveguide module according to 1.   2. The optical waveguide module according to claim 1, wherein the heater portion is disposed at an end portion of the second optical waveguide block on a joint portion side with the first optical waveguide block.   The thermo-optic constants of the second core part and the second cladding part are different in sign from the thermo-optic constants of the first core part and the first cladding part. Optical waveguide module.   The junction between the first optical waveguide block and the second optical waveguide block is inclined at 5 ° to 10 ° with respect to a plane perpendicular to the optical axis of the first core portion and the second core portion. The optical waveguide module according to claim 1, wherein the optical waveguide module is configured by a surface having the same.   2. The light guide according to claim 1, wherein the heater portion is formed such that a heat generation amount increases as it is closer to a joint portion between the first optical waveguide block and the second optical waveguide block. Waveguide module.   The optical waveguide module according to claim 1, wherein a high refractive index layer is provided in the vicinity of the first core portion.   The first optical waveguide block and a third waveguide block including a third core portion and a third clad portion made of a thermo-optic material are integrally formed on a substrate, and the formed The first and third optical waveguide blocks have cutout portions from which the core portion and the cladding portion are removed, and the second optical waveguide block is embedded in the cutout portions, and the first, second, and second optical waveguide blocks are embedded in the cutout portions. The optical waveguide module according to claim 1, wherein the three optical waveguide blocks are optically coupled to each other.   2. The optical waveguide module according to claim 1, wherein light is guided from a second optical waveguide block having the heater portion toward the first optical waveguide block at a joint portion between the two blocks. .

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