Optical waveguide apparatus

There is provided an optical waveguide apparatus. The optical waveguide apparatus includes: a first clad layer; a core layer formed on the first clad layer; and a second clad layer formed on the first clad layer to cover the core layer. At least one of the first clad layer and the second clad layer includes a fully cured portion and a semi-cured portion.

This application claims priority from Japanese Patent Application No. 2017-089792, filed on Apr. 28, 2017, the entire contents of which are herein incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an optical waveguide apparatus.

2. Background Art

In the background art, there is provided an optical waveguide apparatus in which an optical waveguide for transmitting an optical signal is formed on a wiring substrate for transmitting an electric signal. The optical waveguide apparatus is a photoelectric composite substrate which can transmit the optical signal through a high-speed portion in order to compensate for a limit of transmission speed of the electric signal.

Optical path converting mirrors are disposed on end sides of the optical waveguide, and optical devices are mounted on the wiring substrate so as to be optically coupled to the optical path converting mirrors of the optical waveguide respectively (see e.g., JP-A-2011-118163).

As will be described in an undermentioned preliminary matter, a first clad layer, core layers and a second clad layer are formed in order from bottom to top in the optical waveguide apparatus. An outer peripheral portion of the second clad layer is disposed on an upper surface of the first clad layer.

Therefore, when a TC test (Thermal Cycle test) is performed, stress is apt to be concentrated at contact portions between side surfaces of the outer peripheral portion of the second clad layer and the upper surface of the first clad layer.

As a result, cracking may occur in the first clad layer, or the second clad layer may be peeled off from the first clad layer, thereby resulting in lowering of a manufacturing yield and insufficient reliability.

SUMMARY

According to one or more aspects of the present disclosure, there is provided an optical waveguide apparatus.

The optical waveguide apparatus comprises:

a first clad layer;

a core layer formed on the first clad layer; and

a second clad layer formed on the first clad layer to cover the core layer.

At least one of the first clad layer and the second clad layer comprises a fully cured portion and a semi-cured portion.

DETAILED DESCRIPTION

Embodiments will be described below with reference to the accompanying drawings.

A preliminary matter underlying the embodiments will be described prior to description of the embodiments. Description of the preliminary matter is about the details of personal study of the present inventor, which contain novel techniques rather than known techniques.

FIGS. 1 to 4are views showing a method for manufacturing an optical waveguide apparatus according to the preliminary matter. In each ofFIGS. 1 to 4, an upper drawing is a plan view while a lower drawing is a sectional view.

In the method for manufacturing the optical waveguide apparatus according to the preliminary matter, first, a wiring substrate100is prepared, as shown inFIG. 1. The wiring substrate100is a substrate which deals with an electric signal. Wiring layers (not shown) are formed in opposite surfaces of the wiring substrate100respectively.

Next, a first clad layer200is formed on the wiring substrate100, as shown inFIG. 2. A photocurable resin is completely cured so that the first clad layer200is obtained.

Further, core layers300are formed on the first clad layer200, as shown in FIG.3. A photocurable resin is irradiated with ultraviolet light through a photomask, and then developed. Thus, the photocurable resin is patterned into strips so that the core layers300are formed.

Successively, a second clad layer400is formed on the first clad layer200to cover the core layers300, as shown inFIG. 4. A photocurable resin is completely cured in a manner similar to or the same as the first clad layer200so that the second clad layer400is obtained.

An area of the second clad layer400is set to be smaller than an area of the first clad layer200. An outer peripheral portion of the second clad layer400is disposed on an upper surface of the first clad layer200. In other words, the second clad layer400is formed on the first clad layer200so that the surface of the first clad layer200is partially exposed from the second clad layer400.

As described above, each of the first clad layer200and the second clad layer400is formed of the resin which has been completely cured. Therefore, when a TC test (Thermal Cycle test) is performed on an optical waveguide shown inFIG. 4, stress is apt to be concentrated at contact portions between side surfaces of the outer peripheral portion of the second clad layer400and the upper surface of the first clad layer200.

Therefore, cracking is apt to occur inside the first clad layer200from the contact portions of the first clad layer200with the side surfaces of the outer peripheral portion of the second clad layer400.

Moreover, in some cases, the outer peripheral portion of the second clad layer400may be peeled off from the first clad layer200and the core layers300particularly due to the stress applied to the outer peripheral portion of the second clad layer400.

Thus, the cracking may occur in the first clad layer200or the second clad layer400may be peeled off from the optical waveguide apparatus having the structure shown inFIG. 4, thereby resulting in lowering of a manufacturing yield and insufficient reliability.

The aforementioned problems can be solved by an optical waveguide apparatus according to any of the embodiments which will be described below.

First Embodiment

FIGS. 5A to 11Bare views showing a method for manufacturing an optical waveguide apparatus according to a first embodiment.FIG. 12andFIG. 13are views showing the optical waveguide apparatus according to the first embodiment. The structure of the optical waveguide apparatus will be described below together with description of the method for manufacturing the optical waveguide apparatus.

In the method for manufacturing the optical waveguide apparatus according to the first embodiment, first, a wiring substrate10which deals with an electric signal is prepared, as shown inFIGS. 5A and 5B.FIG. 5Ais a plan view.FIG. 5Bis a sectional view taken along a line ofFIG. 5A. The same thing will be also applied to the subsequent drawings corresponding toFIGS. 5A and 5B.

In the wiring substrate10, a wiring layer20is formed on each of opposite surfaces of an insulating substrate12, as shown inFIGS. 5A and 5B. Through holes TH are provided in the insulating substrate12to penetrate the insulating substrate12in a thickness direction. The through holes TH are filled with through conductors22. The wiring layers20on the opposite surface sides are connected to each other through the through conductors22. The wiring layers20and the through conductors22are formed of copper or the like.

Alternatively, the wiring layers20on the opposite surface sides may be connected to each other via through hole plating layers formed on side walls of the through holes TH, and the remaining holes of the through holes TH may be filled with a resin.

In addition, the insulating substrate12may be a rigid substrate or may be a flexible substrate. When the rigid substrate is used as the insulating substrate12, the insulating substrate12is formed, for example, of a glass epoxy resin or the like.

On the other hand, when the flexible substrate is used as the insulating substrate12, the insulating substrate12is formed, for example, of a polyimide film or the like. In addition, the number of wiring layers20to be disposed on each of the opposite surface sides of the insulating substrate12can be set desirably.

The through holes TH of the wiring substrate10are formed by a drill, laser, or the like. The wiring layers20and the through conductors22are formed by photolithography and plating techniques or the like.

Next, a first clad layer30is formed on the wiring substrate10, as shown inFIGS. 6A and 6B. A photocurable resin is irradiated with ultraviolet light, and then subjected to heat treatment at a temperature of 100° C. to 150° C. so as to be fully cured. Thus, the first clad layer30is obtained. The term “fully cured” represents a state in which the photocurable resin is completely cured by the light exposure and the heat treatment.

The first clad layer30may be patterned to adjust an outer shape thereof. In this case, the photocurable resin is irradiated with ultraviolet light through a photomask and then developed. Thus, the first clad layer30is obtained.

In the first embodiment, the entire first clad layer30is formed in the fully cured state.

As a method for forming the photocurable resin, a resin sheet may be disposed, or a liquid resin may be applied. The first clad layer30is, for example, about 10 μm to 30 μm thick.

Successively, as shown inFIGS. 7A and 7B, a photocurable resin (not shown) for obtaining core layers is formed on the first clad layer30. Further, the photocurable resin is irradiated with ultraviolet light through a photomask and then developed. Then, the photocurable resin is subjected to heat treatment at a temperature of about 100° C. to 150° C. so as to be fully cured.

Thus, a plurality of core layers32are arranged and disposed side by side as strip-like patterns on the first clad layer30. The entire core layers32are formed in the fully cured state.

For example, each of the core layers32is set to be 5 μm to 50 μm wide and set to be 5 μm to 50 μm thick.

Next, as shown inFIGS. 8A and 8B, each of the core layers32is machined in the thickness direction from its surface by a rotary blade (not shown) of a cutting apparatus. Thus, V-shaped groove portions32aprovided with slopes S for converting optical paths by 90° are formed in the core layer32. The groove portions32aare formed at opposite end portions of the core layer32, where optical path converting mirrors should be disposed.FIG. 8Bis a sectional view taken along a line II-II of the plan view ofFIG. 8A.

Further, light-reflective metal layers are formed partially on the slopes S of the groove portions32aof the core layer32by mask vapor deposition or the like. Thus, the optical path converting mirrors M are obtained. Gold or aluminum etc. can be used as the light-reflective metal.

Next, as shown inFIGS. 9A and 9B, a photocurable resin34xfor obtaining a second clad layer34is formed on the first clad layer30and the core layers32. The photocurable resin34xis formed with its upper surface flat in a state in which the photocurable resin34xcovers upper surfaces and side surfaces of the core layers32.

In a step ofFIGS. 9A and 9B, the entire photocurable resin34xis uncured. The term “uncured” represents a state in which the photocurable resin is not subjected to irradiation with ultraviolet light and heat treatment at all.

As the photocurable resin34x, for example, a negative type photosensitive epoxy resin or polyimide resin or the like can be used. A similar photocurable resin or the same photocurable resin can be also used for the aforementioned first clad layer30and the aforementioned core layers32.

The photocurable resin34xcontains a reactive functional group contributing to photocuring, and a reactive functional group contributing to thermal curing. Therefore, the photocurable resin34xcan be cured by the photocuring and the thermal curing.

A first photomask40used for primary light exposure of the photocurable resin34xis shown inFIG. 10A. As shown inFIG. 10A, a light transmitting portion40ais provided at a center portion of the first photomask40, and a frame-like light shielding portion40bis provided at an outer peripheral portion of the first photomask40.

The aforementioned photocurable resin34xofFIG. 9Ais irradiated with ultraviolet light through the light transmitting portion40aof the first photomask40ofFIG. 10A. Accordingly, primary light exposure is performed on the photocurable resin34x. In the primary light exposure, a light exposure amount is adjusted to thereby turn the photocurable resin34xinto a semi-cured state.

As shown inFIG. 10B, the primary light exposure is performed on a rectangular first region R1of the photocurable resin34x, which is defined by a broken line. The first region R1is a region corresponding to an outer shape of a second clad layer which will be finally obtained.

For example, a time for the irradiation with the ultraviolet light is set to be shorter than a time required for full curing, or the ultraviolet light having lower intensity than intensity of the ultraviolet light used for the full curing is radiated.

Further, the photocurable resin34xon which the primary light exposure has been performed is subjected to first heat treatment at a temperature of 100° C. to 150° C. In this manner, the primary light exposure and the first heat treatment are performed under conditions that the photocurable resin34xcan be in the semi-cured state. Thus, the first region R1of the photocurable resin34xis turned into the semi-cured state, as shown inFIG. 10B.

InFIG. 10B, in the photocurable resin34x, the semi-cured first region R1is indicated as a dot region, and an uncured region is indicated as a diagonally hatched region.

The term “semi-cured” represents a state in which crosslinking reaction has partially occurred in the photocurable resin34xso that the entire photocurable resin34xhas not been completely cured. A crosslinking ratio (curing ratio) of the photocurable resin34xto attain the semi-cured state is set at 10% to 80% (e.g. 50%) as high as a crosslinking ratio (curing ratio) of the “fully cured” one.

Successively, as shown inFIG. 11A, a second photomask42used for secondary light exposure of the photocurable resin34xis prepared. The second photomask42is provided with a light transmitting portion42afor fully curing a center portion of the first region R1of the photocurable resin34x, and a light shielding portion42bfor maintaining an outer peripheral portion of the first region R1of the photocurable resin34xat the semi-cured state.

Therefore, the light transmitting portion42aof the second photomask42is one size smaller than the light transmitting portion40aof the first photomask40.

The aforementioned photocurable resin34xofFIG. 10Bis irradiated with ultraviolet light through the light transmitting portion42aof the second photomask42ofFIG. 11A. Accordingly, secondary light exposure is performed on the photocurable resin34x. In the secondary light exposure, a light exposure amount is adjusted to thereby fully cure a region of the photocurable resin34xcorresponding to the light transmitting portion42aof the second photomask42.

Specifically, light exposure conditions of the secondary light exposure are set to be the same as the aforementioned light exposure conditions of the primary light exposure.

As shown inFIG. 11B, the secondary light exposure is performed on a second region R2of the photocurable resin34x, which is enclosed with a broken line. The second region R2on which the secondary light exposure is performed is a region one size smaller than the semi-cured rectangular first region R1.

Further, the photocurable resin34xon which the secondary light exposure has been performed is subjected to second heat treatment at a temperature of 100° C., to 150° C.

Thus, the second region R2of the photocurable resin34xis completely cured and turned into a fully cured state by total treatment including the primary light exposure with the first heat treatment and the secondary light exposure with the second heat treatment. InFIG. 11B, the fully cured second region R2of the photocurable resin34xis indicated as a white blank region.

On the other hand, a frame-like region R3which is obtained by removing the second region R2from the first region R1of the photocurable resin34xis however shielded against the secondary light exposure due to the light shielding portion42bof the second photomask42. Therefore, the frame-like region R3is maintained at the semi-cured state. The semi-cured frame-like region R3of the photocurable resin34xis indicated as a dot region.

The frame-like region R3of the photocurable resin34xis a rectangular region corresponding to an outer peripheral portion of the second clad layer which will be finally obtained.

Then, the photocurable resin34xofFIG. 11Bwhich has been exposed to the light is processed by a developer so that, of the photocurable resin34x, opposite end portions (diagonally hatched regions) which are unexposed to the light are dissolved and removed, as shown inFIG. 12.

Thus, the second clad layer34is formed on the first clad layer30to cover the core layers32. An area of the second clad layer34is set to be smaller than an area of the first clad layer30. In other words, the second clad layer34is formed on the first clad layer30so that a surface of the first clad layer30is partially exposed from the second clad layer34.

The second clad layer34is formed to include a fully cured portion34aand a semi-cured portion34b. The fully cured portion34ais disposed at a center portion of the second clad layer34. The semi-cured portion34bis disposed at an outer peripheral portion of the second clad layer34. The semi-cured portion34bis exposed in side surfaces of the second clad layer34.

In this manner, the second clad layer34is formed so that the outer peripheral portion of the second clad layer34is constituted by the frame-like semi-cured portion34bwith which an outer periphery of the fully cured portion34ais covered.

In the aforementioned manner, the optical waveguide apparatus1according to the first embodiment can be obtained, as shown inFIG. 12andFIG. 13.

As shown inFIG. 13, the optical waveguide apparatus1according to the first embodiment is provided with the aforementioned wiring substrate10which has been described inFIGS. 5A and 5B. In the wiring substrate10, the wiring layers20are formed on the opposite surfaces of the insulating substrate12respectively. The wiring layers20on the opposite surface sides are connected to each other through the through conductors22.

The first clad layer30is formed on the wiring substrate10. The entire first clad layer30is completely cured and fully cured. In addition, the core layers32are formed to be arranged side by side on the first clad layer30.

Further, the groove portions32a(FIG. 8B) provided with the slopes S are formed at the opposite end portions of each of the core layers32. The optical path converting mirrors M (FIG. 8B) which are formed of the metal layers and each of which is configured to convert an optical path of light are formed on the slopes S of the groove portions32a.

Further, the second clad layer34is formed on the first clad layer30and the core layers32. The area of the second clad layer34is set to be smaller than the area of the first clad layer30. Therefore, the side surfaces of the second clad layer34are disposed on an inner side than side surfaces of the first clad layer30.

As shown inFIG. 12andFIG. 13, the second clad layer34has the fully cured portion34a, and the semi-cured portion34bwhich is formed at the outer peripheral portion of the second clad layer34. The second clad layer34includes the fully cured portion34awhich is formed at the center portion of the second clad layer34, and the semi-cured portion34bwhich is formed at the outer peripheral portion of the second clad layer34.

The fully cured portion34aand the semi-cured portion34bin the second clad layer34are formed to be connected to each other integrally. All the core layers32are covered with the fully cured portion34aof the second clad layer34. An optical waveguide5is constructed from the first clad layer30, the core layers32and the second clad layer34. A refractive index of each of the core layers32is set to be higher than a refractive index of each of the first clad layer32and the second clad layer34.

Thus, the second clad layer34whose center portion is formed of the fully cured portion34a, and whose outer peripheral portion is formed of the semi-cured portion34bis disposed on the first clad layer30which has been fully cured as a whole.

As described above in the aforementioned preliminary matter, when a TC test (Thermal Cycle test) is performed on the optical waveguide apparatus1shown inFIG. 13, stress is concentrated at contact portions between the side surfaces of the outer peripheral portion of the second clad layer34and the upper surface of the first clad layer30. In the TC test, a thermal cycle test is performed, for example, in a temperature range of −55° C. to 125° C.

In the embodiment, the outer peripheral portion of the second clad layer34is the semi-cured portion34b. Accordingly, the aforementioned stress can be dispersed by the semi-cured portion34bof the second clad layer34.

Accordingly, cracking can be prevented from occurring inside the first clad layer30from the contact portions of the first clad layer30with the side surfaces of the outer peripheral portion of the second clad layer34. Thus, a manufacturing yield of the optical waveguide apparatus can be improved, and sufficient reliability can be obtained.

In addition, the fully cured portion34aof the second clad layer34is disposed in the region where the core layers32are arranged and disposed side by side and where the optical waveguide5is constructed. All the core layers32are covered with the fully cured portion34aof the second clad layer34. Therefore, optical properties as excellent as those of a background-art structure can be obtained by the optical waveguide5according to the embodiment.

Incidentally, in order to form the second clad layer34having the fully cured portion34aand the semi-cured portion34bin the aforementioned manufacturing method according to the first embodiment, light exposure is performed twice using the first photomask40and the second photomask42.

Besides this method, the second clad layer34having the fully cured portion34aand the semi-cured portion34bmay be formed by light exposure performed once using one gray-tone mask as a photomask, as will be described in an undermentioned third embodiment.

In this case, the photocurable resin is irradiated with ultraviolet light through the gray-tone mask provided with a light transmitting portion and a light semi-transmitting portion. Accordingly, light exposure is performed on the photocurable resin. Thus, the fully cured portion34aof the second clad layer34is obtained from one region of the photocurable resin corresponding to the light transmitting portion of the gray-tone mask. In addition, the semi-cured portion34bof the second clad layer34is obtained from the other region of the photocurable resin corresponding to the light semi-transmitting portion of the gray-tone mask.

Modification of First Embodiment

Next, an optical waveguide apparatus1A according to a modification of the first embodiment will be described below with reference toFIGS. 14A to 17. As shown inFIG. 17, the optical waveguide apparatus1A according to the modification of the first embodiment is different from the optical waveguide apparatus1according to the first embodiment in that two through holes Hc and Hd are formed in a second clad layer34, and semi-cured portions34cand34dare formed in the second clad layer34to surround the through holes Hc and Hd. In addition, a method for manufacturing the optical waveguide apparatus1A according to the modification is different from the method for manufacturing the optical waveguide apparatus1according to the first embodiment in that a first photomask140and a second photomask142are used in place of the first photomask40and the second photomask42. That is, by use of the first photomask140and the second photomask142, not only the two through holes Hc and Hd but also the semi-cured portions34cand34dare formed in the second clad layer34of the optical waveguide apparatus1A. First, the method for manufacturing the optical waveguide apparatus1A will be described briefly with reference toFIGS. 14A to 15B.

FIG. 14Ashows the first photomask140used for primary light exposure of a photocurable resin34x. As shown inFIG. 14A, the first photomask140has a light transmitting portion140a, a frame-like light shielding portion140b, and circular light shielding portions140cand140d. As shown inFIG. 14B, the photocurable resin34xis irradiated with ultraviolet light through the first photomask140(primary light exposure step). In the primary light exposure step, a light exposure amount of the ultraviolet light is adjusted to thereby turn the photocurable resin34xinto a semi-cured state. For example, the light exposure amount of the ultraviolet light can be adjusted to thereby shorten an irradiation time for the irradiation with the ultraviolet light or reduce intensity of the ultraviolet light.

As shown inFIG. 14B, the photocurable resin34xis irradiated with the ultraviolet light in a region R10corresponding to the light transmitting portion140aof the first photomask140. The region R10is designated by a broken line. On this occasion, portions of the photocurable resin34xcorresponding to the circular light shielding portions140cand140dare however shielded against the irradiation with the ultraviolet light. Next, the photocurable resin34xon which the primary light exposure has been performed is heated at a temperature of 100° C. to 150° C. so as to be turned into the semi-cured state. As shown inFIG. 14B, a dot-hatched portion of the photocurable resin34xis in the semi-cured state while diagonally hatched portions of the photocurable resin34x(particularly the portions of the photocurable resin34xcorresponding to the light shielding portions140cand140d) are in an uncured state.

Next, as shown inFIG. 15A, the second photomask142used for secondary light exposure of the photocurable resin34xis prepared. The second photomask142has a light transmitting portion142a, a frame-like light shielding portion142b, and circular light shielding portions142cand142d. An area of the light transmitting portion142ais smaller than an area of the light transmitting portion140aof the first photomask140. Further, the center of the light shielding portion142cis coincident with the center of the light shielding portion140cof the first photomask140, and an outer diameter of the light shielding portion142cis smaller than an outer diameter of the light shielding portion140c. Moreover, the center of the light shielding portion142dis coincident with the center of the light shielding portion140dof the first photomask140, and an outer diameter of the light shielding portion142dis smaller than an outer diameter of the light shielding portion140d.

As shown inFIG. 15B, the photocurable resin34xis irradiated with ultraviolet light through the second photomask142(secondary light exposure step). In the secondary light exposure step, a light exposure amount of the ultraviolet light is adjusted suitably to thereby completely cure the photocurable resin34x.

The photocurable resin34xis irradiated with the ultraviolet light in a region R20corresponding to the light transmitting portion142aof the second photomask142. On this occasion, portions of the photocurable resin34xcorresponding to the circular light shielding portions142cand142dare however shielded against the irradiation with the ultraviolet light.

Next, the photocurable resin34xon which the secondary light exposure has been performed is heated at a temperature of 100° C. to 150° C. to be turned into a fully cured state. As shown inFIG. 15B, a white blank portion of the photocurable resin34xis in the fully cured state. In addition, a dot-hatched portion of the photocurable resin34xis in a semi-cured state. Particularly, in a frame-like region R30which is surrounded by the region R10and the region R20, the photocurable resin34xis in the semi-cured state. Further, at ring-like regions R32and R33, the photocurable resin34xis in the semi-cured state. Further, diagonally hatched portions of the photocurable resin34xare in an uncured state.

Then, the photocurable resin34xis developed by a developer so that the uncured portions of the photocurable resin34x(i.e. the diagonally hatched portions of the photocurable resin34x) are removed. Thus, the optical waveguide apparatus1A can be obtained, as shown inFIG. 16andFIG. 17. Differently from the optical waveguide apparatus1according to the first embodiment, the two through holes Hc and Hd are formed in the second clad layer34of the optical waveguide apparatus1A, as shown inFIG. 16andFIG. 17. Further, the second clad layer34has a fully cured portion34a, a semi-cured portion34bdisposed at an outer peripheral portion of the second clad layer34, the ring-like semi-cured portion34csurrounding the through hole Hc, and the ring-like semi-cured portion34dsurrounding the through hole Hd.

Thus, according to the optical waveguide apparatus1A according to the modification, stress generated between the outer peripheral portion of the second clad layer34and an upper surface of a first dad layer30can be dispersed by the semi-cured portion34b. Further, stress generated between the portion of the second dad layer34surrounding the through hole Hc and the upper surface of the first clad layer30can be dispersed by the semi-cured portion34c. Moreover, stress generated between the portion of the second clad layer34surrounding the through hole Hd and the upper surface of the first clad layer30can be dispersed by the semi-cured portion34d. In this manner, the semi-cured portions34bto34dare formed in the second clad layer34. As a result, a manufacturing yield of the optical waveguide apparatus1A can be improved, and reliability of the optical waveguide apparatus1A can be improved. Incidentally, the shape of each of the through holes Hc and Hd in top view is circular in the modification. However, the shape of the through hole Hc, Hd in top view is not limited particularly. The shape of each of the light shielding portions140cand140dformed in the first photomask140, and the shape of each of the light shielding portions142cand142dformed in the second photomask142can be changed suitably in accordance with the shape of the through hole Hc, Hd in top view.

Second Embodiment

FIG. 18AtoFIG. 23Bare sectional views showing a method for manufacturing an optical waveguide apparatus according to a second embodiment.FIG. 24andFIG. 25are sectional views showing the optical waveguide apparatus according to the second embodiment.

The second embodiment has a configuration in which a semi-cured portion is also formed at a portion of a first clad layer corresponding to a semi-cured portion of a second clad layer, and the semi-cured portion of the second clad layer is disposed on the semi-cured portion of the first clad layer.

In the second embodiment, detailed description about the same steps and the same constituent elements as those in the first embodiment will be omitted.

As shown inFIGS. 18A and 18B, in the method for manufacturing the optical waveguide apparatus according to the second embodiment, a g substrate10which is similar to or the same as the aforementioned wiring substrate10inFIGS. 5A and 5Baccording to the first embodiment is prepared. A first photocurable resin30xwhich is uncured without being subjected to irradiation with ultraviolet light and heat treatment is formed on the wiring substrate10. The first photocurable resin30xmay be formed as a resin sheet or as a coating of a liquid resin.

As shown inFIG. 19A, a photomask50used for primary light exposure of the first photocurable resin30xis prepared. In the photomask50, a center portion and an outer peripheral portion are light transmitting portions50a, and a frame-like region between the center portion and the outer peripheral portion is a light shielding portion50b.

The aforementioned first photocurable resin30xofFIG. 18Ais irradiated with ultraviolet light through the light transmitting portions50aof the photomask50. Accordingly, primary light exposure is performed on the first photocurable resin30x. On this occasion, light exposure conditions are adjusted to thereby turn the light-exposed regions of the first photocurable resin30xinto a semi-cured state.

Further, the first photocurable sin30xon which the primary light exposure has been performed is subjected to first heat treatment at a temperature of 100° C. to 150° C. Thus, the primary light exposure and the first heat treatment are performed on conditions that the first photocurable resin30xcan be in the semi-cured state. As a result, a center portion and an outer peripheral portion of the first photocurable resin30xare turned into the semi-cured state (dot regions), as shown inFIG. 19B.

On the other hand, a frame-like region of the first photocurable resin30xwhich has been shielded from the light due to the light shielding portion50bof the photomask50is left uncured (diagonally hatched region).

Next, the entire first photocurable resin30xofFIG. 19Bis irradiated with ultraviolet light without using a photomask, so that secondary light exposure (whole surface light exposure) is performed on the first photocurable resin30x, as shown inFIGS. 20A and 20B.

Further, the first photocurable resin30xon which the secondary light exposure has been performed is subjected to second heat treatment at a temperature of 100° C. to 150° C.

On this occasion, light exposure conditions and heating conditions are adjusted to thereby turn the center portion and the outer peripheral portion of the first photocurable resin30xinto a fully cured state by total treatment including the primary light exposure with the first heat treatment and the secondary light exposure with the second heat treatment.

In addition, on this occasion, the conditions of the secondary light exposure and the second heat treatment are adjusted to thereby turn the uncured frame-like region of the first photocurable resin30xofFIG. 19Binto a semi-cured state.

Thus, a first clad layer30is formed. A center portion and an outer peripheral portion of the first clad layer30are completely cured and formed into fully cured portions30a(white blank regions). In addition, a frame-like region between the center portion and the outer peripheral portion of the first clad layer30is formed into a semi-cured portion30b(dot region).

The frame-like region of the first clad layer30according to the second embodiment is a rectangular ring-like region disposed in an inner portion of the first clad layer30shaped like a rectangle.

In this manner, the first clad layer30having the fully cured portions30aand the semi-cured portion30bwhich is disposed in the frame-like region in plan view is formed.

Incidentally, the first clad layer30including the fully cured portions30aand the semi-cured portion30bmay be formed by light exposure performed once using a gray-tone mask provided with light transmitting portions and a light semi-transmitting portion as in a manufacturing method according to the undermentioned third embodiment.

Next, as shown inFIGS. 21A and 21B, core layers32are formed on the first clad layer30by a method similar to or the same as the aforementioned step ofFIGS. 7A and 7Bin the first embodiment. Further, as shown inFIG. 21A, optical path converting mirrors M are formed on opposite end portions of each of the core layers32by a method similar to or the same as the aforementioned step ofFIGS. 8A and 8B.

Then, as shown inFIGS. 22A and 22B, an uncured photocurable resin34xis formed on the first clad layer30and the core layers32. The photocurable resin34xmay be formed as a resin sheet or as a coating of a liquid resin.

Further, primary light exposure and first heat treatment are performed on a first region R1of the photocurable resin34xofFIG. 22Athrough a first photomask40in a manner similar to or the same as the aforementioned step ofFIGS. 10A and 10Bin the first embodiment.

Further, secondary light exposure and second heat treatment are performed on a second region R2of the photocurable resin34xthrough a second photomask42in a manner similar to or the same as the aforementioned step ofFIGS. 11A and 11Bin the first embodiment.

Thus, as shown inFIG. 23A, of the photocurable resin34x, the second region R2which is enclosed with a broken line is completely cured and turned into a fully cured state (white blank region) in a manner similar to or the same as in the aforementionedFIG. 11Bin the first embodiment.

On the other hand, a frame-like region R3which is obtained by removing the second region R2from the first region R1of the photocurable resin34xis however shielded against the secondary light exposure due to a light shielding portion42bof the second photomask42. Therefore, the frame-like region R3is maintained at the semi-cured state (dot region).

Then, the photocurable resin34xshown inFIG. 23Ais processed by a developer so that, of the photocurable resin34x, opposite end portions (diagonally hatched regions) which are unexposed to the light are dissolved and removed, as shown inFIG. 23B.

Thus, a second clad layer34is formed to have a fully cured portion34aprovided at a center portion of the second clad layer34, and a semi-cured portion34bprovided at an outer peripheral portion of the second clad layer34, in a manner similar to or the same as in the aforementionedFIG. 12in the first embodiment. The semi-cured portion34bof the second clad layer34is disposed at a position corresponding to the frame-like semi-cured portion30bof the first clad layer30.

Incidentally, also in order to form the second clad layer34, the fully cured portion34aand the semi-cured portion34bmay be formed by light exposure performed once using a gray-tone mask provided with a light transmitting portion and a light semi-transmitting portion as in the manufacturing method according to the undermentioned third embodiment.

In the aforementioned manner, the optical waveguide apparatus1aaccording to the second embodiment can be obtained, as shown inFIG. 24.

As shown inFIG. 24, the optical waveguide apparatus1aaccording to the second embodiment is different from the aforementioned optical waveguide apparatus1according to the first embodiment in that the frame-like semi-cured portion30bis also formed in the region of the first clad layer30corresponding to the semi-cured portion34bformed in the outer peripheral portion of the second clad layer34. Other constituent elements than the first clad layer30are the same as those in the optical waveguide apparatus1according to the first embodiment.

When the first clad layer30is seen in plan view with reference to the aforementionedFIGS. 20A and 20B, the center portion and the outer peripheral portion are formed into the fully cured portions30a, and the frame-like region between the center portion and the outer peripheral portion is formed into the semi-cured portion30b.

The semi-cured portion34bof the second clad layer34is disposed on the frame-like semi-cured portion30bof the first clad layer30. The semi-cured portion30bof the first clad layer30is set to be wider than the semi-cured portion34bof the second clad layer34.

Thus, the first clad layer30has the fully cured portions30aand the frame-like semi-cured portion30b. The outer peripheral portion of the second clad layer34is disposed on the semi-cured portion30bof the first clad layer30.

When a TC test (Thermal Cycle test) is also performed on the optical waveguide apparatus1aofFIG. 24according to the second embodiment, stress is concentrated at contact portions between side surfaces of the outer peripheral portion of the second clad layer34and an upper surface of the first clad layer30.

In the second embodiment, the first clad layer30and the second clad layer34are disposed on each other in a state in which the upper surface of the frame-like semi-cured portion30bof the first clad layer30contacts a lower surface of the semi-cured portion34bof the outer peripheral portion of the second clad layer34. In addition, the side surfaces of the semi-cured portion34bof the outer peripheral portion of the second clad portion34are disposed on the upper surface of the semi-cured portion30bof the first clad layer30.

Thus, the aforementioned stress can be dispersed by the semi-cured portion30bof the first clad layer30and the semi-cured portion34bof the second clad layer34. Consequently, cracking can be further prevented from occurring in the first clad layer30or the second clad layer34can be further prevented from being separated.

FIG. 25is a view showing an optical waveguide apparatus according to a modification of the second embodiment. As shown inFIG. 25, the optical waveguide apparatus1xaccording to the modification of the second embodiment is different from the optical waveguide apparatus1aofFIG. 24in that an entire second clad layer34is fully cured and a frame-like semi-cured portion30bis formed only in a first clad layer30.

Even when the entire second clad layer34is fully cured in the optical waveguide apparatus1xaccording to the modification of the second embodiment, side surfaces of an outer peripheral portion of the second clad layer34are disposed on the semi-cured portion30bof the first clad layer30.

Accordingly, the aforementioned stress can be dispersed by the semi-cured portion30bof the first clad layer30in a similar manner or the same manner. Consequently, cracking can be prevented from occurring in the first clad layer30or the second clad layer34can be prevented from being separated.

As described above, in the second embodiment, it is sufficient that at least the frame-like region of the first clad layer30on which the outer peripheral portion of the second clad layer34is disposed is the semi-cured portion30b.

Third Embodiment

FIG. 26AtoFIG. 32are views showing a method for manufacturing an optical waveguide apparatus according to the third embodiment.FIG. 33andFIG. 34are views showing the optical waveguide apparatus according to the third embodiment.

The optical waveguide apparatus according to the third embodiment is different from the aforementioned optical waveguide apparatus1aofFIG. 24according to the second embodiment in that semi-cured portions each shaped like a belt in plan view are divided and disposed in a first clad layer and a second clad layer correspondingly to core layers.

The core layers are disposed on the belt-like semi-cured portions of the first clad layer respectively. The core layers are covered with the semi-cured portions of the second clad layer respectively.

In the third embodiment, as shown inFIGS. 26A and 26B, a first photocurable resin30xwhich is uncured without being subjected to irradiation with ultraviolet light and heat treatment is formed on a wiring substrate10in a manner similar to or the same as the aforementioned step ofFIGS. 18A and 18Bin the second embodiment.

As shown inFIG. 27, a first gray-tone mask60(photomask) used for light exposure of the first photocurable resin30xis prepared. The first gray-tone mask60is provided with light transmitting portions60aand light semi-transmitting portions60b. Slits having a lower resolution than that of a light exposure apparatus are formed in the light semi-transmitting portions60b. The slits shield light partially so that intermediate light exposure can be performed.

Thus, normal light exposure is performed by the light transmitting portions60a. In addition, light exposure is suppressed by the light semi-transmitting portions60bso that the intermediate light exposure with a smaller light exposure amount than that by the light transmitting portions60acan be performed.

The first photocurable resin30xofFIG. 26Ais irradiated with ultraviolet light through the light transmitting portions60aand the light semi-transmitting portions60bof the first gray-tone mask60ofFIG. 27. Further, the first photocurable resin30xwhich has been exposed to the light is subjected to heat treatment at a temperature of 100° C. to 150° C.

On this occasion, light exposure conditions and heating conditions are adjusted so that regions of the first photocurable resin30xcorresponding to the light transmitting portions60aof the first gray-tone mask60can be completely cured and fully cured. On this occasion, light exposure conditions and heating conditions are simultaneously adjusted so that regions of the first photocurable resin30xcorresponding to the light semi-transmitting portions60bof the first gray-tone mask60can be turned into a semi-cured state.

Thus, as shown inFIGS. 28A and 28B, the regions of the first photocurable resin30xwhich have been exposed to the light through the light transmitting portions60aof the first gray-tone mask60are completely cured and formed into fully cured portions30a(white blank regions). Simultaneously, the regions of the first photocurable resin30xwhich have been exposed to the light through the light semi-transmitting portions60bof the first gray-tone mask60are formed into semi-cured portions30b(dot regions).

Thus, the first photocurable resin30xis exposed to the light by use of the first gray-tone mask60, and subjected to heat treatment. Consequently, the fully cured portions30aand the semi-cured portions30bare formed simultaneously in the first photocurable resin30x.

In this manner, a first clad layer30having the fully cured portions30aand the semi-cured portions30bis formed. The semi-cured portions30bof the first clad layer30are formed to include belt-like patterns P1corresponding to a plurality of core layers which will be formed in a next step.

In addition, the semi-cured portions30bof the first clad layer30are formed to include a frame-like pattern P2, which is disposed to surround a rectangular region in which the plurality of core layers should be disposed.

The other regions than the semi-cured portions30bof the first clad layer30are the fully cured portions30a, The fully cured portions30aare partially disposed between adjacent ones of the belt-like patterns P1of the semi-cured portions30bof the first clad layer30. In addition, the fully cured portions30aare partially disposed in the region between the belt-like patterns P1and the frame-like pattern P2of the semi-cured portions30bof the first clad layer30, and in the region surrounding the frame-like pattern P2.

The fully cured portions30aand the semi-cured portions30bin the first clad layer30are formed to be connected to one another integrally.

Incidentally, a halftone mask may be used in place of the first gray-tone mask60. In the halftone mask, a semi-transmitting film is disposed in regions where intermediate light exposure should be performed.

In addition, instead of using the gray-tone mask, the first clad layer30having the fully cured portions30aand the semi-cured portions30bmay be formed by light exposure performed twice as in the aforementioned manufacturing method according to the first embodiment.

In this case, first, the entire first photocurable resin30xofFIG. 26Ais exposed to light to be turned into a semi-cured state. Then, the first photocurable resin30xis exposed to light through a photomask which includes light transmitting portions corresponding to the fully cured portions30aand light shielding portions corresponding to the semi-cured portions30b. Thus, the fully cured portions30aare obtained.

Next, as shown inFIGS. 29A and 29B, core layers32are formed on the first clad layer30by a method similar to or the same as the aforementioned step ofFIGS. 7A and 7Bin the first embodiment. Further, by a method similar to or the same as the aforementioned step ofFIGS. 8A and 8B, optical path converting mirrors M are formed on opposite end portions of each of the core layers32.

The core layers32are disposed on the belt-like patterns P1of the semi-cured portions30bof the first clad layer30respectively. Each of the belt-like patterns P1of the semi-cured portions30bof the first clad layer30is set to be wider than each of the core layers32. In addition, the belt-like pattern P1of the semi-cured portion30bof the first clad layer30is set to be as long as or longer than the core layer32.

Next, as shown inFIGS. 30A and 30B, a photocurable resin34xwhich is uncured without being subjected to irradiation with ultraviolet light and heat treatment is formed on the first clad layer30and the core layers32.

Further, as shown inFIG. 31, a second gray-tone mask62is prepared. The second gray-tone mask62includes a light transmitting portion62a, light semi-transmitting portions62b, and a light shielding portion62c. The light transmitting portion62aand the light semi-transmitting portions62bin the second gray-tone mask62are disposed in regions corresponding to one of the light transmitting portions60aand the light semi-transmitting portions60bin the first gray-tone mask60respectively.

In addition, the light shielding portion62cof the second gray-tone mask62is disposed in a peripheral edge portion surrounding the frame-like light semi-transmitting portion62b.

The photocurable resin34xofFIG. 30Ais irradiated with ultraviolet light through the light transmitting portion62aand the light semi-transmitting portions62bof the second gray-tone mask62. Further, the photocurable resin34xwhich has been exposed to the light is subjected to heat treatment at a temperature of 100° C. to 150° C.

On this occasion, light exposure conditions and heating conditions are adjusted in a manner similar to or the same as the formation of the first clad layer30so that a region of the photocurable resin34xcorresponding to the light transmitting portion62aof the second gray-tone mask62can be completely cured and fully cured.

In addition, light exposure conditions and heating conditions are also adjusted so that regions of the photocurable resin34xcorresponding to the light semi-transmitting portions62bof the second gray-tone mask62can be turned into a semi-cured state.

Thus, as shown inFIG. 32, the region of the photocurable resin34xwhich has been exposed to the light through the light transmitting portion62aof the second gray-tone mask62is completely cured and formed into a fully cured portion34a(white blank region). Simultaneously, the regions of the photocurable resin34xwhich have been exposed to the light through the light semi-transmitting portions62bof the second gray-tone mask62are formed into semi-cured portions34b(dot regions).

Then, the photocurable resin34xofFIG. 32is processed by a developer so that, of the photocurable resin34x, the peripheral edge portion (diagonally hatched region) which is unexposed to the light is dissolved and removed, as shown inFIG. 33.

Thus, a second clad layer34including the fully cured portion34aand the semi-cured portions34bis formed. The fully cured portion34aand the semi-cured portions34bin the second clad layer34are disposed in the regions corresponding to one of the fully cured portions30aand the semi-cured portions30bin the first clad layer30.

The semi-cured portions34bof the second clad layer34include belt-like patterns P1xwhich are formed to cover upper surfaces and side surfaces of the core layers32, and a frame-like pattern P2xwhich is disposed to surround a rectangular region in which the core layers32have been disposed.

The fully cured portion34ais disposed in the region between adjacent ones of the belt-like patterns P1xof the semi-cured portions34hof the second clad layer34and between the belt-like patterns P1xand the frame-like pattern P2x.

In this manner, the second clad layer34having the fully cured portion34a, and the semi-cured portions34bcovering the upper surfaces and the side surfaces of the core layers32respectively is formed.

Incidentally, also in the second clad layer34, the fully cured portion34aand the semi-cured portions34bmay be formed by light exposure performed twice in a manner similar to or the same as that in the first embodiment.

In this case, first, a center portion of the photocurable resin34xofFIG. 30Ais exposed to light through a first photomask to be turned into a semi-cured state. Then, the photocurable resin34xis exposed to light through a second photomask which includes a light transmitting portion corresponding to the fully cured portion34aand light shielding portions corresponding to the semi-cured portions34b. Thus, the fully cured portion34ais obtained.

In the aforementioned manner, an optical waveguide apparatus1baccording to the third embodiment be obtained, as shown inFIG. 34.

As shown inFIG. 33andFIG. 34, the optical waveguide apparatus1baccording to the third embodiment is provided with the aforementioned wiring substrate10which has been described inFIGS. 5A and 5B.

The first clad layer30is formed on the wiring substrate10. The first clad layer30includes the fully cured portions30aand the semi-cured portions30b. Refer to the aforementionedFIGS. 28A and 28Badditionally. The semi-cured portions30bof the first clad layer30are formed to include the belt-like patterns P1and the frame-like pattern P2which is disposed to surround the belt-like patterns P1.

In addition, the fully cured portions30aof the first clad layer30are disposed in the regions between adjacent ones of the belt-like patterns P1of the semi-cured portions30b, the region between the belt-like patterns P1and the frame-like pattern P2, and the region surrounding the belt-like pattern P2.

The core layers32are disposed on the belt-like patterns P1of the semi-cured portions30bof the first clad layer30respectively. The optical path converting mirrors M (FIG. 29A) are formed on the opposite end portions of each of the core layers32. Each of the belt-like patterns P1of the semi-cured portions30bof the first clad layer30is set to be wider than each of the core layers32.

Further, the second clad layer34is formed on the first clad layer30and the core layers32.

The second clad layer34is provided with the fully cured portion34aand the semi-cured portions34b. As shown inFIG. 33, the semi-cured portions34bof the second clad layer34are formed to include the belt-like patterns P1xand the frame-like pattern P2x. The belt-like patterns P1xand the frame-like pattern P2xof the semi-cured portions34bof the second clad layer34are disposed correspondingly to the belt-like patterns P1and the frame-like pattern P2of the semi-cured portions30bof the first clad layer30.

As shown inFIG. 34, the belt-like patterns P1xof the semi-cured portions34bof the second clad layer34are disposed on the belt-like patterns P1of the semi-cured portions30bof the first clad layer30respectively. Each of the belt-like patterns P1xof the semi-cured portions34bof the second clad layer34is set to be wider than each of the core layers32. The core layers32are embedded in the belt-like patterns P1xof the semi-cured portions34bof the second clad layer34respectively.

In addition, the fully cured portion34ais disposed in the region between adjacent ones of the belt-like patterns of the semi-cured portions34bof the second clad layer34and between the belt-like patterns P1xand the frame-like pattern P2x.

In the second clad layer34, no fully cured portion is formed in the region surrounding the frame-like pattern P2xof the semi-cured portion34b, and side surfaces of the frame-like pattern P2xof the semi-cured portion34bare formed as outer ends and exposed to the outside.

An optical waveguide5is configured by the first clad layer30, the core layers32and the second clad layer34. Lower surfaces of the core layers32each shaped like a rectangle in section are covered with the semi-cured portions30bof the first clad layer30. The upper surfaces and the side surfaces of the core layers32are covered with the semi-cured portions34bof the second clad layer34.

The first clad layer30and the second clad layer34are disposed on each other in a state in which the belt-like patterns P1of the semi-cured portions30bof the first clad layer30contact the belt-like patterns P1xof the semi-cured portions34bof the second clad layer34.

The optical waveguide apparatus1baccording to the third embodiment has effects similar to or the same as those of the optical waveguide apparatus1aaccording to the second embodiment.

In addition, the core layers32are disposed on the semi-cured portions30bof the first clad layer30respectively. The upper surfaces and the side surfaces of the core layers32are covered with the semi-cured portions34bof the second clad layer34respectively.

Thus, the lower surfaces of the core layers32contact the semi-cured portions30bof the first clad layer30respectively, and the upper surfaces of the side surfaces of the core layers32contact the semi-cured portions34bof the second clad layer34respectively.

Thus, the first clad layer30has the fully cured portions30aand the semi-cured portions30b. The core layers32are disposed on the semi-cured portions30bof the first clad layer30respectively. Further, the second clad layer34has the fully cured portion34a, and the semi-cured portions34bwhich cover the upper surfaces and the side surfaces of the core layers32.

Therefore, even when stress is applied to the core layers32, the stress can be dispersed by the semi-cured portions30bof the first clad layer30and the semi-cured portions34bof the second clad layer34. Thus, cracking can be prevented from occurring in the first clad layer30or the second clad layer34can be prevented from being peeled off.

Further, one of the fully cured portions30ais disposed between adjacent ones of the semi-cured portions30bof the first clad layer30, and the fully cured portion34ais disposed between adjacent ones of the semi-cured portions34bof the second clad layer34.

In this manner, the fully cured portion30aof the first clad layer30and the fully cured portion34aof the second clad layer34are disposed on each other in the regions between adjacent ones of the core layers32. Therefore, fixed strength of the optical waveguide5can be secured.

An optical waveguide apparatus according to a modification of the third embodiment is shown inFIG. 35. As shown inFIG. 35, the frame-like pattern P2of the semi-cured portion30bof the first clad layer30in the aforementioned optical waveguide apparatus1bshown inFIG. 34is changed to a fully cured portion30ain the optical waveguide apparatus1yaccording to the modification of the third embodiment. In addition, the frame-like pattern P2xof the semi-cured portion34bof the second clad layer34in the aforementioned optical waveguide apparatus1bis changed to a fully cured portion34ain the optical waveguide apparatus1y.

Thus, the semi-cured portions30band34bof the first and second clad layers30and34may be disposed only around core layers32respectively so that the frame-like patterns P2and P2xof the semi-cured portions30band34bcan be omitted.

Stress to be applied to an optical waveguide5can be reduced by the semi-cured portions30bof the first clad layer30and the semi-cured portions34bof the second clad layer34with both of which the core layers32are covered respectively.

Fourth Embodiment

Next, a method for mounting optical devices on the aforementioned optical waveguide apparatus1shown inFIG. 13in the first embodiment will be described.

InFIG. 36, an optical waveguide5is illustrated as a section taken in the depth direction of the optical waveguide5shown inFIG. 13. As shown inFIG. 36, connection holes CH are formed in the second clad layer34and the first clad layer30of the optical waveguide apparatus1ofFIG. 13to reach one of the wiring layers20of the wiring substrate10.

Further, first pads P1and second pads P2are formed on the second clad layer34to be connected to the wiring layer20through via conductors with which the connection holes CH are filled. The first pads P1are disposed on one end sides of the core layers32of the optical waveguide apparatus1while the second pads P2are disposed on the other end sides of the same.

Light-emitting devices70are connected to the first pads P1on the one end sides of the core layers32through solder electrodes71. The light-emitting devices70are an example of the optical devices.

Each of the light-emitting devices70is provided with a light emitting portion70aat its lower surface. The light-emitting portion70ais optically coupled to a corresponding one of the optical path converting mirrors M of the optical paths of the optical waveguide apparatus1. As the light-emitting device70, a vertical cavity surface emitting laser (VCSEL) is preferably used.

In addition, light-receiving devices72are connected to the second pads P2on the other end sides of the core layers32through solder electrodes73. The light-receiving devices72is an example of the optical devices.

Each of the light-emitting devices72is provided with a light-receiving portion72aat its lower surface. The light-receiving portion72ais optically coupled to a corresponding one of the optical path converting mirrors M of the optical paths of the optical waveguide apparatus1. As light-receiving device72, a photodiode is preferably used.

An underfill resin is filled in each of lower sides of the light-emitting devices70and the light-receiving devices72.

In the optical waveguide apparatus1according to the embodiment, an electric signal outputted from a driver device (not shown) is supplied to one of the light-emitting devices70so that light can be emitted downward from a corresponding light-emitting portion70aof the light-emitting device70.

Light emitted from the light-emitting device70is transmitted through the second clad layer34to reach a corresponding optical path converting mirror M of the optical waveguide apparatus1. Further, the light is reflected by the optical path converting mirror M so that an optical path of the light is converted by 90° to be incident on a corresponding core layer32.

Next, the light entering the core layer32is totally reflected repeatedly and travels in the core layer32to thereby reach a corresponding optical path converting mirror M on the other end side. The light is reflected by the optical path converting mirror M on the other end side so that the optical path is converted by 90°. Then, the light is transmitted through the second clad layer34to be incident on a corresponding light-receiving portion72aof a light-receiving device72.

The light-receiving element72converts the optical signal into an electric signal so that the electric signal can be supplied to an amplifier device (not shown).

In the optical waveguide apparatus1according to the embodiment, stress to be applied to the optical waveguide5can be reduced, as described above. Accordingly, a manufacturing yield and reliability can be improved.

As described above, the exemplary embodiment and the modification are described in detail. However, the present invention is not limited to the above-described embodiment and the modification, and various modifications and replacements are applied to the above-described embodiment and the modifications without departing from the scope of claims.

Various aspects of the subject matter described herein are set out non-exhaustively in the following numbered clauses:

1) A method of manufacturing an optical waveguide apparatus, the method comprising:

a) forming a first clad layer on a substrate;

b) forming a core layer on the first clad layer; and

c) forming a second clad layer on the first clad layer so as to cover the core layer,

wherein at least one of the first clad layer and the second clad layer comprises a fully cured portion and a semi-cured portion.

2) The method according to the clause (1), wherein

the fully cured portion comprises a second fully cured portion which is formed in the second clad layer,

the semi-cured portion comprises a second semi-cured portion which is formed in the second clad layer,

the second fully cured portion covers the core layers, and

the second semi-cured portion surrounds at least a portion of an outer periphery of the second fully cured portion, and contacts the first clad layer.

3) The method according to clause (1), wherein

the fully cured portion comprises a first fully cured portion which formed the first clad layer,

the semi-cured portion comprises a first semi-cured portion which is formed in the first clad layer, and

the first semi-cured portion is formed into a frame shape in plan view, and contacts an outer peripheral portion of the second clad layer.

4) The method according to the clause (1), wherein

the fully cured portion comprises a first fully cured portion which is formed in the first clad layer, and a second fully cured portion which is formed in the second clad layer,

the semi-cured portion comprise first semi-cured portions which are formed in the first dad layer, and second semi-cured portions which are formed in the second dad layer,

the core layer comprises a plurality of core layers,

each of the core layers contacts a corresponding one of the first semi-cured portions, and

each of the second semi-cured portions covers a corresponding one of the core layers.

5) The method according to the clause (2), wherein

the step c) comprises:

c2) irradiating the photocurable resin with ultraviolet light through a first photomask so as to semi-cure the photocurable resin, wherein the first photomask comprises a first light transmitting portion at a center portion of the first photomask; and

c3) irradiating the photocurable resin with ultraviolet light through a second photomask so as to fully cure the photocurable resin, wherein the second photomask comprises a second light transmitting portion that is smaller in size than the first light transmitting portion.

6) The method according to the clause (4), wherein

the step c) comprises:

c4) forming a photocurable resin; and

c5) irradiating the photocurable resin with ultraviolet light through a photomask, wherein the photomask comprises a light transmitting portion and light semi-transmitting portions,

the second fully cured portion is obtained from a portion of the photocurable resin that is opposed to the light transmitting portion of the photomask, and

the second semi-cured portions are obtained from portions of the photocurable resin that are opposed to the light semi-transmitting portions of the photomask.