JP2008015088A - Optical waveguide module, manufacturing method therefor and optical communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin optical waveguide substrate in which the occurrence of separation and cracks affecting performance are suppressed without requiring special structure or additional work. <P>SOLUTION: The optical waveguide module 100 is provided with, on the optical waveguide substrate 101, a core 200 to be an optical propagation region and a clad 201 covering the periphery of the core 200. The clad 201 has a lower clad and an upper clad, at least the upper clad comprising an organic polymer material. The clad 201 is composed of a narrow clad 300 on the end face side optically coupling to an optical fiber 400 and an LD chip 401 and of a wide clad 301 other than the narrow clad. In the connecting part between both clads 300, 301, a circular arc clad 302 is formed. The width W of the narrow clad 300 is made so narrow, in the portion coupling with an optical element, that no separation due to residual stress is caused and that no propagating optical signal is affected. The width of the wide clad 301 is made fully wider than the width W. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical waveguide module, a method for manufacturing the same, and an optical communication device, and more particularly to an optical waveguide used in an apparatus that performs optical communication using an optical fiber.

  With the recent development of communication technology, optical modules that transmit and receive optical signals using optical fibers have been put into practical use. In particular, an optical module that mounts an optical element and converts an optical signal and an electric signal needs to be small, high-speed, and low in price. In particular, an optical module using an organic polymer material (hereinafter simply referred to as “resin”) is low in manufacturing cost, and demand is increasing because an electric / optical hybrid module can be manufactured in a small size.

  For example, a liquid resin for the lower cladding layer is applied by spin coating, etc., cured by ultraviolet rays or heat, and a core layer is formed on it by the same method, and photolithography or RIE (Reactive Ion Etching) The unnecessary part is removed. Furthermore, an upper clad layer is formed thereon to form an optical waveguide. However, the resin shrinks when cured, and cracks, peeling from the substrate, and the like are likely to occur. In particular, in the optical waveguide substrate, when cracks or separation from the substrate occurs, there is a problem that excess loss occurs when the optical waveguide is disconnected or optically coupled to another optical element.

Thus, for example, Patent Document 1 proposes that a stress relaxation layer is provided under the upper cladding layer to absorb the stress generated when the resin of the upper cladding layer contracts and to suppress cracks and peeling. Further, Patent Document 2 proposes to prevent cracks and peeling by covering the vicinity of the resin pattern end with resin. In Patent Document 3, it is proposed that the stress pattern concentration is suppressed and cracks and peeling are prevented by forming the vicinity of the pattern end portion of the resin in an inclined shape.
Japanese Patent Laying-Open No. 2004-295118 (FIG. 1) JP 2004-039056 A (FIG. 2) JP-A-6-29662 (FIG. 1)

  However, the structures disclosed in Patent Documents 1 to 3 have the following problems.

  For example, the problem of the structure disclosed in Patent Document 1 is that a laminated structure is added and the number of processes is increased. This is because a stress relaxation layer having an elastic modulus lower than that of the cladding layer and the core layer and optically stable is required. Stress relaxation layers with such elastic modulus and optical properties must be prepared for each resin, which not only increases costs, but also increases costs due to an increase in the number of laminated structures. Absent.

  Moreover, the problem of the structure disclosed in Patent Document 2 and Patent Document 3 is that the optical waveguide core is not formed up to the end of the pattern formed of resin. The optical waveguide module is used by being optically coupled to other optical elements, optical fibers, LD (Laser Diode) chips, and PD (Photo Diode) chips. For this reason, the optical waveguide core needs to be formed up to the end face of the optical waveguide in a portion that is optically coupled to another optical element. However, in Patent Document 2, since the end of the formed pattern is separately covered with a resin, the optical waveguide core cannot be formed up to the end of the final pattern. Further, in Patent Document 3, it is difficult to form the optical waveguide core up to the end of the pattern because the pattern is formed in an inclined or stepped shape. For this reason, the optical coupling | bonding with another optical element will be inhibited.

  An object of the present invention is to provide a resin optical waveguide substrate that suppresses peeling and cracking that affect performance without requiring a special structure or additional processing.

  As a result of intensive efforts to achieve the above object, the present inventor has made the width of the clad layer of the optical waveguide module to be separated from the optical element without separation due to residual stress, and to propagate the optical signal. The present invention was completed by paying attention to the fact that it was made narrow so as not to affect the area, and the other parts were made sufficiently wide.

  In other words, an optical waveguide module according to the present invention includes a core layer serving as a light propagation region and a clad layer covering the periphery of the core layer on an optical waveguide substrate, and at least a part of the clad layer is an organic polymer. A module having an optical waveguide made of a material, wherein the clad layer has a narrower width at the end surface side optically coupled to the optical element than at other portions.

  In the present invention, the clad layer has at least a width of the end face side portion, a residual stress determined by a volume of the clad layer, a shrinkage rate when the organic polymer material is cured, and an elastic modulus of the organic polymer material. In the relationship between the adhesion between the optical waveguide substrate and the organic polymer material, the residual stress is preferably formed so as to be smaller than the adhesion. In the cladding layer, at least the width of the end face side portion is wider than the width of the spread of the signal light determined by the difference between the refractive index of the core and the refractive index of the cladding and the cross-sectional area of the core. Preferably it is formed.

  In the present invention, it is preferable that the clad layer is connected by a gentle curve at a portion where the width between the portion on the end face side and the other portion changes. The clad layer may have a width of the end face side portion of 100 micrometers or less.

  In the present invention, the clad layer has a first clad layer located between the front optical waveguide recording substrate and the core layer, and a second clad layer located on the core layer, One clad layer may be made of the organic polymer material. The first cladding layer may be composed of the organic polymer material. The first cladding layer may be configured integrally with the optical waveguide substrate. The first cladding layer may be made of an inorganic material that is transparent to the wavelength of the optical signal.

  In the present invention, the optical element may be at least one of a light emitting element, a light receiving element, and an optical fiber.

  An optical waveguide module manufacturing method according to the present invention includes a step of forming a core layer serving as a light propagation region on an optical waveguide substrate, and a cladding layer formed at a position covering the periphery of the core layer on the optical waveguide substrate. A method of manufacturing the optical waveguide module, wherein the step of forming the cladding layer includes a step of forming at least a part of the cladding layer with an organic polymer material, and the cladding layer is an optical element. The portion on the end face side optically coupled with is narrower than the other portions.

  An optical communication apparatus according to the present invention uses the above optical waveguide module.

  ADVANTAGE OF THE INVENTION According to this invention, the optical waveguide module which suppresses peeling and a crack which influence a performance without requiring a special structure and an additional process, and its manufacturing method can be provided.

  Next, an embodiment of an optical waveguide module and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view of the optical waveguide module of the present embodiment.

  An optical waveguide module 100 shown in FIG. 1 has an optical waveguide that optically couples optical elements of an optical fiber 400, an LD chip 401, and a PD chip 402 via a dielectric multilayer filter 403. The optical waveguide includes a core (core layer) 200 that serves as a light propagation region and a clad (cladding layer) 201 that covers the core 200, and is formed on the optical waveguide substrate 101. The clad 201 is provided with an electrode (not shown) for mounting the PD chip 402 and a slit 103 for sandwiching the dielectric multilayer filter 403 at predetermined positions. Further, an electrode (not shown) for mounting the LD chip 401 is provided at a predetermined position on the end face side of the optical waveguide that is optically coupled to the LD chip 401.

  The optical waveguide is optically coupled to another optical element at its end face, and is narrowed so that the width W of the clad 201 does not affect the light propagation region in the vicinity of the end face. That is, the width W of the clad 201 is propagated by making it wider than the spread width of the signal light determined by the difference between the refractive index of the core 200 and the refractive index of the clad 200 and the cross-sectional area of the core 200. The width is narrowed while satisfying conditions that do not affect the optical signal.

  The clad 201 includes a clad narrowed to a width W (hereinafter referred to as “narrow clad”) 300 and a clad having a portion wider than the other width W (hereinafter referred to as “wide clad”) 301. It consists of and. The narrow clad 300 and the wide clad 301 are gently connected via an arcuate curved clad (hereinafter referred to as “arc clad”) 302.

  FIG. 2 is a perspective view of the end face side optically coupled to the optical fiber 400 of the optical waveguide. In the figure, the optical fiber 400 is omitted for convenience. As shown in FIG. 2, an optical fiber guide 102 for facilitating the coupling between the optical fiber 400 and the core 200 is formed in the vicinity of the end face of the optical waveguide on the optical fiber 400 side. As shown in FIG. 2, the clad 201 includes a lower clad (first clad layer) 202 and an upper clad (second clad layer) 203, and at least the upper clad 202 is made of an organic polymer material (resin). Is formed.

  The core 200 is exposed on the end face of the clad 201 at a portion coupled with the optical fiber 400 and a portion coupled with the LD chip 401. In the portion exposed at the end face, the width of the clad 201 is such a narrow width clad 300 that the side surface of the clad 201 does not affect the signal light that oozes out from the core 200. On the other hand, the portion other than the end face is a wide clad 301 that is sufficiently wider than the end face, so that cracks do not reach the waveguide core even if cracks occur with minute defects in the resin as nuclei. It has become. Further, an electrode (not shown) for mounting the PD chip 402 is formed on the wide clad 301 at a predetermined position.

  FIG. 3 is a cross-sectional view illustrating the stress 500 with respect to the resin constituting the wide clad 301, and FIG. 4 is a cross-sectional view illustrating the stress 500 with respect to the resin constituting the narrow clad 300.

  In general, cracking of the resin and peeling of the resin from the substrate are caused by stress generated due to contraction when the resin is cured. As shown in the wide clad 301 formed on the optical waveguide substrate 101 in FIG. 3, a tensile stress 500 is applied to the resin. In particular, when the tensile stress 500 is greater than the tensile strength of the resin or the adhesive strength of the resin at the end portion of the resin, cracks and peeling occur. At this time, since the shrinkage ratio of the resin is constant, as shown in the narrow-width clad 300 formed on the optical waveguide substrate 101 in FIG. Can be greatly suppressed. Specifically, the width of the narrow clad 300 is such that, as described above, the residual stress determined by the volume of the clad 200, the shrinkage rate when the resin is cured, and the elastic modulus of the resin, within a range that does not affect the propagating optical signal. In the relationship between the adhesion between the optical waveguide substrate 101 and the resin, the residual stress is set to be smaller than the adhesion.

  Further, as shown in FIG. 5, the crack 600 is generated when the stress 500 is concentrated at a portion where the pattern and width of the clad 201 change abruptly. Therefore, as shown in FIG. 6, the portions of the clad 201 whose pattern and width are changed are connected by a gentle arc, so that the stress 500 is not concentrated in one place, and cracks can be greatly suppressed.

  However, the resin contains small defects that are not visible to the eye, and such small defects may serve as nuclei and cause large cracks. Since such a crack is caused by a defect inside the resin, it is unpredictable in which part of the resin the crack occurs. In particular, when the resin is generated in a portion where the area of the resin is narrowed as shown in FIG. 4, the resin may be divided.

  Therefore, in the clad 201 of the present embodiment, a narrow-width clad 300 having a reduced resin area is formed at the portion coupled with the optical element to suppress the peeling. On the other hand, a wide clad 301 having a wide width so as not to affect the waveguide even if a crack occurs, and an arc clad 302 having a gentle curve so as not to have a corner portion are formed in other portions. By doing so, it is possible to configure an optical waveguide substrate in which there is no peeling at the coupling portion with the optical element that particularly affects the optical characteristics, and cracks due to defects inside the resin do not affect the waveguide core.

  That is, the narrow clad 300 and the wide clad 301 are subjected to tensile stress from the optical waveguide substrate 101 due to shrinkage when the resin is cured. When this is compared in cross section, the narrow clad 300 and the wide clad 301 have the same tensile stress per unit length, but the narrow clad 300 has a smaller total stress and can suppress delamination.

  In addition, in order to optically couple with the optical fiber 400 and the LD chip 401, high-precision alignment is required three-dimensionally. However, in the portion of the narrow clad 300 where there is no crack, alignment can be easily performed. It can be carried out.

  Further, the narrow clad 300 and the wide clad 301 are gently connected by an arc clad 302. Further, the corners of the clad 201 are also gently formed by the arc clad 302. With this shape, the stress is not concentrated at one point, and the occurrence of cracks and peeling can be suppressed.

  Furthermore, even if a crack occurs in the clad 201 with a minute defect existing inside the resin in the wide clad 301 portion, the crack does not reach the core because the clad 201 is sufficiently wide in this portion. .

  As described above, according to the present embodiment, the width of the clad layer of the optical waveguide is set so that the portion coupled with the optical element does not cause separation due to residual stress and does not affect the propagating optical signal. It is narrow and the rest is wide enough. Accordingly, it is possible to provide a resin optical waveguide substrate that suppresses peeling and cracking that affect performance without requiring a special structure or additional processing.

  Hereinafter, specific examples of the present invention will be described.

  The resins used in this example are as follows.

  First, as a material for the clad layer, a precursor of highly fluorinated polybenzoxazole A (PBO-A) was used as a solution A, and the clad layer was formed using this solution A. Further, as a material for the core layer, a precursor of highly fluorinated polybenzoxazole B (PBO-B) was used as solution B, and the core layer was formed using this solution B. At this time, the solutions A and B were set so that the refractive index of the core layer was higher than the refractive index of the cladding layer by changing the mixing ratio of the additives.

  Using the solutions A and B, the optical waveguide module 100 shown in FIG. 1 was produced as follows.

  First, as shown in FIG. 7, a fiber guide 102 was formed by performing anisotropic etching on a silicon substrate 101 having a diameter of 100 mm and a thickness of 0.8 mm using a thermal oxide film as a mask. On top of that, the above solution A was applied by spin coating, and heated and cured for a predetermined temperature and time in a heating furnace to form a lower cladding layer 202 having a thickness of about 10 μm. By this heating, the ring closure reaction of the precursor constituting the solution A was promoted, and a resin to be the lower cladding layer 202 was formed.

  Next, as shown in FIG. 8, the above-mentioned solution B is applied onto the lower clad layer 201 by spin coating, heated in a heating furnace for a predetermined temperature and time, and cured, so that a core having a thickness of about 5 μm is obtained. Layer 200 was formed. By this heating, the ring closing reaction of the precursor constituting the solution B was promoted, and a resin to be the core layer 200 was formed.

  Next, as shown in FIG. 9, the core shape was patterned with a photoresist, and the core 200 was formed by RIE. The photoresist was removed after the core was formed.

  Next, as shown in FIG. 10, the above solution A was applied by spin coating so that the thickness from the upper surface of the core 200 to the surface of the upper cladding layer 203 was 10 μm. Similarly to the lower clad layer 202, the upper clad layer 203 was also formed by heating in a heating furnace at a predetermined temperature for a time. By this heating, the ring closing reaction of the precursor constituting the solution A was promoted, and a resin to be the upper clad layer 203 was formed.

  Next, as shown in FIG. 11, the lower cladding layer 202 and the upper cladding layer 203 were etched until they reached the silicon substrate 101. In other words, as described above, the end width side portion (the narrow clad 300) coupled with the optical element is set by the photoresist so that the clad width is narrower than the other portions (the wide clad 301 and the arc clad 302). The resulting cladding shape was patterned. Then, etching was performed by RIE until the lower clad layer 202 and the upper clad layer 203 reached the silicon substrate 101. After the etching was completed, organic cleaning was performed to remove the photoresist. By doing so, an optical waveguide module 100 was obtained.

  In the obtained optical waveguide module 100, in order to evaluate the effect of suppressing the peeling by the narrow clad 300, the width of the narrow clad 300 was changed from 50 μm to 1000 μm, and the peel amount was measured. FIG. 12 shows the correlation.

  According to this, when the cladding width becomes 200 μm or more, the amount of peeling increases rapidly. On the other hand, when the clad width was 200 μm, the peel amount was 30 μm, when the clad width was 100 μm, the peel amount was 3 μm, and when the clad width was 50 μm, the peel amount was 0 μm. From this result, the effect of the narrow clad 300 was remarkably recognized when the clad width was 100 μm or less, and an optical waveguide having no peeling amount could be obtained especially when the clad width was 50 μm or less.

  In this embodiment, the case where highly fluorinated polybenzoxazole is used as the organic polymer material of the core layer and the clad layer is described. However, the present invention is not limited to this. For example, polyimide, benzocyclohexane An organic polymer material such as butene is also applicable.

As mentioned above, although embodiment and the Example of this invention were described in detail, this invention is not limited to the above-mentioned embodiment and Example which were illustrated typically, Those skilled in the art will be able to Based on the description of the scope of the claims, various modifications and changes can be made without departing from the scope of the present invention. These modified examples and modified examples also belong to the scope of the right of the present invention.
(Modification)
For example, in the above embodiment, a case where a silicon substrate is used as the optical waveguide substrate 101 and the clad 200 is constituted by the upper clad 203 and the lower clad 202 has been described. However, the present invention is not necessarily limited to this. It is not something. For example, the optical waveguide substrate 101 may be a quartz substrate or a resin substrate in addition to the silicon substrate. In particular, when a substrate transparent to the wavelength of the optical signal is used, as shown in FIG. Since the optical waveguide substrate 101 can also serve as 202, the process can be shortened. At this time, as shown in the figure, the narrow clad 300 is composed of only the upper clad 203.

  The lower clad 202 may be made of an inorganic material such as quartz as long as it is not resin but transparent to the wavelength of the optical signal.

  The present invention relates to an optical module that transmits and receives an optical signal through an optical fiber, an optical module that mounts an optical element and converts an optical signal and an electrical signal, a resin optical waveguide substrate that is used in an optical module using an organic polymer material, It is applicable to the manufacturing method and the use of the optical communication apparatus.

It is a top view which shows the optical waveguide module which concerns on embodiment of this invention. It is a perspective view of a narrow clad vicinity. It is sectional drawing of description of the stress with respect to a wide clad. It is sectional drawing of description of the stress with respect to a narrow clad. It is a top view explaining generation | occurrence | production of the crack by the concentration of the stress in the inflection point of a clad. It is a top view explaining suppression of the crack by circular arc cladding. In the manufacturing method of the optical waveguide module of an Example, it is a perspective view explaining the first process. FIG. 8 is a perspective view illustrating a step subsequent to FIG. 7. FIG. 9 is a perspective view illustrating the next process of FIG. 8. FIG. 10 is a perspective view illustrating a step subsequent to FIG. 9. It is a perspective view explaining the next process of FIG. It is a figure which shows the correlation of the clad width and peeling amount of an Example. It is a perspective view which shows the optical waveguide module which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical waveguide module 101 Optical waveguide board | substrate 102 Optical fiber guide 103 Slit 200 Core (core layer)
201 Cladding (cladding layer)
202 Lower cladding (first cladding layer)
203 Upper cladding (second cladding layer)
300 Narrow clad 301 Wide clad 302 Arc clad (curved clad)
400 Optical fiber (optical element)
401 LD chip (optical element)
402 PD chip (optical element)
403 Dielectric multilayer filter 500 Stress 600 Crack

Claims (12)

A module having an optical waveguide comprising a core layer serving as a light propagation region and a clad layer covering the periphery of the core layer on an optical waveguide substrate, wherein at least a part of the clad layer is made of an organic polymer material. There,
The clad layer is an optical waveguide module characterized in that a portion on an end face side optically coupled to an optical element is narrower than other portions.   The clad layer has a residual stress whose width at least on the end face side is determined by a volume of the clad layer, a shrinkage ratio when the organic polymer material is cured, and an elastic modulus of the organic polymer material, and the optical waveguide 2. The optical waveguide module according to claim 1, wherein the residual stress is set to be smaller than the adhesion force in relation to the adhesion force between the substrate and the organic polymer material.   In the cladding layer, at least the width of the end face side portion is wider than the width of the spread of the signal light determined by the difference between the refractive index of the core and the refractive index of the cladding and the cross-sectional area of the core. The optical waveguide module according to claim 1, wherein the optical waveguide module is set to be   4. The clad layer according to any one of claims 1 to 3, wherein a portion where the width between the portion on the end face side and the other portion changes is connected by a gentle curve. Optical waveguide module.   5. The optical waveguide module according to claim 1, wherein the clad layer has a width of a portion of the end face side of 100 μm or less. The clad layer has a first clad layer located between the optical waveguide substrate and the core layer, and a second clad layer located on the core layer,
The optical waveguide module according to claim 1, wherein the second cladding layer is made of the organic polymer material.   The optical waveguide module according to claim 6, wherein the first cladding layer is made of the organic polymer material.   The optical waveguide module according to claim 6, wherein the first cladding layer is configured integrally with the optical waveguide substrate.   The optical waveguide module according to claim 6, wherein the first cladding layer is made of an inorganic material that is transparent with respect to the wavelength of the optical signal.   The optical waveguide module according to any one of claims 1 to 9, wherein the optical element is at least one of a light emitting element, a light receiving element, and an optical fiber. Forming a core layer serving as a light propagation region on the optical waveguide substrate;
Forming a clad layer at a position covering the periphery of the core layer on the optical waveguide substrate,
The step of forming the clad layer includes a step of forming at least a part of the clad layer with an organic polymer material, and the clad layer has a portion on the end face side that is optically coupled to the optical element. An optical waveguide module manufacturing method characterized in that the width is narrower than that of a portion.   An optical communication device using the optical waveguide module according to claim 1.

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