JP7217692B2 - Optical waveguide package and light emitting device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to optical waveguide packages and light emitting devices.

A prior art optical waveguide package and light emitting device is described, for example, in US Pat. In this prior art, an optical waveguide is formed on a substrate, and the optical waveguide has a core and a clad that has a lower refractive index than the core and is embedded so as to surround the core. A groove having a flat bottom surface and side surfaces is formed in the optical waveguide by etching and removing a portion of the optical waveguide in a concave shape. A metal wiring is formed on the bottom surface, and an optical element is mounted thereon. It has been proposed that the groove portion, in which the optical element is housed, is covered with a downward concave cap to shield and seal the optical element from the outside.

Japanese Patent No. 4579868

In the prior art disclosed in Patent Document 1, since the side surfaces of the groove are planes perpendicular to the bottom surface, thermal stress is generated on the side surfaces of the groove due to the light emission of the optical element mounted in the groove. There is a risk of damage due to deformation and cracks.

The optical waveguide package of the present disclosure includes a substrate,
an optical waveguide layer having a clad layer positioned on the substrate and a core layer positioned within the clad layer;
The cladding layer has an upper surface, a lower surface, and a through hole penetrating from the upper surface to the lower surface toward the substrate and accommodating a light emitting element ,
an end surface of the core layer is exposed to an inner wall surface of the through hole,
The inner wall surface of the through hole has a first opening perpendicular to the axis of the virtual cylindrical surface rather than a virtual cylindrical surface connecting a first opening intersecting the lower surface and a second opening intersecting the upper surface. In the direction, it protrudes outward from the virtual cylindrical surface, which is the side away from the axis of the virtual cylindrical surface, and the portion on the second opening side protrudes inward, which is the side opposite to the outer side. characterized in that

A light-emitting device according to the present disclosure includes the optical waveguide package and a light-emitting element housed in the through-hole of the optical waveguide package.

According to the optical waveguide package and the light emitting device of the present disclosure, it is possible to reduce thermal stress on the inner wall surface due to light emission from the light emitting element in the through hole, and reduce damage due to deformation and cracking of the inner wall surface.

1 is an exploded perspective view showing a light emitting device equipped with an optical waveguide package according to an embodiment of the present disclosure; FIG. FIG. 2 is a perspective view of the light emitting device shown in FIG. 1 omitting a sealing lid; FIG. 2 is a cross-sectional view of the light-emitting device viewed from the cross-sectional line III-III in FIG. 1; FIG. 3 is an enlarged cross-sectional view of part of the vicinity of a through hole of the light emitting device; It is a figure for demonstrating the formation procedure of a through-hole. FIG. 10 is an enlarged cross-sectional view of a part near a through hole 8 showing a light emitting device according to a second embodiment of the present disclosure; FIG. 11 is an enlarged cross-sectional view of a part near a through hole 8 showing a light emitting device according to a third embodiment of the present disclosure; FIG. 11 is an enlarged cross-sectional view of a part near a through hole 8 showing a light emitting device according to a fourth embodiment of the present disclosure; FIG. 11 is an enlarged cross-sectional view of a part near a through hole 8 showing a light emitting device according to a fifth embodiment of the present disclosure; FIG. 11 is an enlarged cross-sectional view of a part near a through hole 8 showing a light emitting device according to a sixth embodiment of the present disclosure;

Embodiments of the light-emitting device of the present disclosure will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is an exploded perspective view showing a light emitting device equipped with an optical waveguide package according to the first embodiment of the present disclosure, and FIG. 2 is a perspective view of the light emitting device shown in FIG. 1 with the sealing lid omitted. FIG. 3 is a cross-sectional view of the light-emitting device seen from the cross-sectional line III--III in FIG.

The optical waveguide package of this embodiment comprises a substrate 1 and an optical waveguide layer 5 located on an upper surface 2 of the substrate 1 and having a cladding layer 3 and a core layer 4 located within the cladding layer 3 . The clad layer 3 has an upper surface 6 , a lower surface 7 , and a through hole 8 penetrating from the upper surface 6 to the lower surface 7 toward the substrate 1 . The through hole 8 is defined by the through hole 8 and the upper surface 2 of the substrate 1 , and the sealing lid 11 is laminated on the upper surface 6 of the clad layer 3 so as to cover the through hole 8 . Between the lower surface 11 a of the sealing lid 11 and the upper surface 2 of the substrate 1 , the inner wall surface 13 facing the through-hole 8 of the clad layer 3 defines an accommodation space in which the light emitting element 10 is accommodated.

The optical waveguide package of this embodiment has a plurality of (three in this embodiment) through-holes 8 for accommodating the light-emitting elements 10 respectively, and the light-emitting device 20 is configured including each of the light-emitting elements 10 . A laser diode or the like is applied as the light emitting element 10 . The optical waveguide layer 5 is configured by integrally bonding the core layer 4 and the clad layer 3 . The substrate 1 may be formed by laminating a plurality of dielectric layers. The light-emitting element 10 may be mounted by passive alignment using image recognition with a marker written on the upper surface 2 of the substrate 1 .

The substrate 1 may be a ceramic wiring substrate whose dielectric layer is made of a ceramic material. Examples of ceramic materials used in ceramic wiring boards include aluminum oxide sintered bodies, mullite sintered bodies, silicon carbide sintered bodies, aluminum nitride sintered bodies, and glass ceramic sintered bodies. When the substrate 1 is a ceramic wiring substrate, the dielectric layer is provided with conductors such as connection pads, internal wiring conductors, and external connection terminals for electrical connection between the light-emitting element and the light-receiving element and an external circuit. be.

The material of the substrate 1 may be, for example, an organic wiring board in which the dielectric layer is made of an organic material. Examples of organic wiring boards include printed wiring boards, build-up wiring boards, and flexible wiring boards. Examples of organic materials used for organic wiring boards include epoxy resins, polyimide resins, polyester resins, acrylic resins, phenolic resins, and fluorine resins.

The optical waveguide layer 5 may be made of, for example, glass such as quartz, resin, or the like. The bottom surface 11a of the sealing lid 11 and the top surface 2 of the substrate 1 are bonded by a bonding layer 35 made of metal, glass, or the like, and the through hole 8 is hermetically sealed. As a result, the through holes 8 have a high gas barrier property, and are blocked from entering gas such as air having a different refractive index and foreign matter from the outside. The sealing lid 11 may be made of the same material as the clad layer 3, for example.

The materials forming the core layer 4 and the clad layer 3 of the optical waveguide layer 5 may be glass or resin, or one may be glass and the other may be resin. In this case, the core layer 4 and the clad layer 3 have different refractive indices, and the core layer 4 has a higher refractive index than the clad layer 3 . This difference in refractive index is used to cause total reflection of light. That is, by forming a path with a material with a high refractive index and surrounding it with a material with a low refractive index, light can be confined within the core layer 4 with a high refractive index.

FIG. 4 is an enlarged cross-sectional view of part of the vicinity of the through hole of the light emitting device. 1 to 3, the light-emitting device of the present embodiment has three light-emitting devices that emit red (R) light, green (G) light, and blue (B) laser light. The configuration associated with one of the three light emitting elements 10 will be described, as each of the elements has a common configuration housed within a through-hole 8 and mounted on the top surface 2 of the substrate 1 . Regarding the reference numerals corresponding to those described above, the suffixes a, b, and c may be omitted when there is no particular need to identify them. The inner wall surface 13 of the cladding layer 3 surrounding the through-hole 8 is closer to the virtual cylindrical surface M than the virtual cylindrical surface M connecting the first opening 14 positioned on the lower surface 7 and the second opening 15 positioned on the upper surface 6 . In a first direction A perpendicular to the axis L of the cylindrical surface M, the incident end surface 4a of the core layer 4 is exposed, protruding outward. As described above, the outer side in the first direction A refers to the direction from the inner wall side of the clad layer 3 to the outer wall side of the clad layer 3 in the direction of the first direction A.

The core layer 4 includes a plurality of dividing paths 41a, 41b, 41c having the incident end surfaces 4a to 4c as one end, and a plurality of dividing paths 41a between the plurality of incident end surfaces 4a, 4b, 4c and one output end surface 42. , 41b, and 41c meet, and a combining path 44 having an output end surface 42 as one end.

One condenser lens 45 is provided in common with the plurality of incident end surfaces 4a, 4b, and 4c. The condenser lens 45 is arranged to face the incident end surfaces 4a, 4b, and 4c of the core layer 4. As shown in FIG. The optical axis of the condensing lens 45 is arranged on the central axis of the output end face 42 .

Red (R) light, green (G) light, and blue (B) light emitted from each light-emitting element 10 enter split paths 41a, 41b, and 41c from incident end surfaces 4a, 4b, and 4c, and are combined. It passes through the wave portion 43 and the integration path 44, is condensed by the condensing lens 45, and exits.

The condenser lens 45 is, for example, a plano-convex lens having a plane entrance surface and a convex exit surface. The optical waveguide layer 5, the light emitting elements 10, and the condenser lens 45 are assembled so that the optical axes of the division paths 41a, 41b, 41c and the centers of the light emitting portions of the light emitting elements 10 are aligned.

FIG. 5 is a diagram for explaining the procedure for forming through holes. In FIG. 5, the upper stage shows the plane of the portion where one through hole 8 is formed, and the lower stage shows the cross section of the through hole 8 corresponding to the upper stage. As shown in FIG. 5(1), a film is formed on the upper surface 2 of the substrate 1 to form an optical waveguide layer 5. On the formed optical waveguide layer 5, as shown in FIG. 5(2), a resist is applied, As shown in FIG. 5(3), the coated resist is exposed and developed. Then, as shown in FIG. 5(4), the cladding layer surface exposed from the pattern openings not covered with the resist is etched. Therefore, after forming a space for accommodating the light emitting element 10, the resist is removed as shown in FIG. 5(5). As a result, a box-shaped through hole 8 surrounded by an inner wall surface 13 having a curved surface 31 having a curved point 30 on the outside in the second direction B along the axis L is formed.

During such an etching process, the etching gas flow rate and etching time are adjusted. As a result, the etching amount can be gradually increased from the upper surface 6 of the cladding layer 3 and gradually decreased from the bending point 30 toward the lower surface 7 . Therefore, the shape of the inner wall surface 13 corresponding to the pattern shape of the photomask can be made into a wall surface shape having the curved surface 31 by changing the exposure resolution of photolithography and the amount of erosion by etching.

In the present embodiment, since the pattern shape of the resist mask is square in plan view, the curved surface 31 can be formed as the inner wall surface 13 with a shape substantially similar to the pattern shape. By forming the inner wall surface 13 having such a bending point 30, even if the inner wall surface 13 is heated by the heat generated by the light emitting element 10 during light emission and thermal expansion occurs, the bending point 30 does not move away from the virtual cylindrical surface M. The bent surface 31 is induced in the direction of thermal expansion in the direction of displacement to the outside of the one direction A, so that the increase in thermal stress can be reduced and the amount of deformation of the inner wall surface 13 due to thermal expansion can be reduced. Therefore, deviations in the positions and orientations of the incident end surfaces 4a to 4c of each core layer 4 exposed on the bent surface 31 are greatly reduced, and the loss of light incident on the core layer 4 of the light emitting element 10 can be reduced. .

Further, in this embodiment, the bending point 30 of the inner wall surface 13 is formed at a height position about half the thickness of the clad layer 3, and the incident end surfaces 4a to 4c of each core layer 4 are bent surfaces on the substrate 1 side. 31 exposed. That is, the incident end surfaces 4a to 4c of the core layer 4 are located substantially in the center in the second direction B between the first opening 14 and the bending point 30 in the cross-sectional view of FIG. It faces close to the surface. Thereby, the incident loss of the light emitted from the light emitting element 10 to the core layer 4 can be reduced as much as possible.

(Second embodiment)
FIG. 6 is an enlarged cross-sectional view of a part near the through hole 8 showing the light emitting device of the second embodiment of the present disclosure. In addition, the same reference numerals are given to the parts corresponding to those of the above-described embodiment, and redundant explanations are omitted. In the light-emitting device of this embodiment, the bending point 30 of the inner wall surface 13 is formed at a position closer to the second opening 15 than the height position of about half the thickness of the clad layer 3 . Thus, by increasing the height position of the bending point 30 with respect to the upper surface 2 of the substrate 1, that is, by bringing it closer to the second opening 15, the heat from the light emitting element 10 is less likely to reach the bending point 30. Thermal stress at and around 30 can be reduced.

(Third embodiment)
FIG. 7 is an enlarged cross-sectional view of a part near the through hole 8 showing the light emitting device according to the third embodiment of the present disclosure. In addition, the same reference numerals are given to the parts corresponding to the above-described respective embodiments, and redundant explanations are omitted. In the light emitting device of this embodiment, the curved surface 31 of the inner wall surface 13 has a plurality of curved points 30a and 30b. As a result, the bending angles of the respective bending points 30a and 30b are reduced, and damage due to cracks or the like in the cladding layer 3 due to thermal stress at the respective bending points 30a and 30b can be more reliably reduced.

(Fourth embodiment)
FIG. 8 is an enlarged cross-sectional view of a part near the through hole 8 showing the light emitting device of the fourth embodiment of the present disclosure. In addition, the same reference numerals are given to the parts corresponding to the above-described respective embodiments, and redundant explanations are omitted. In the light emitting device of this embodiment, the inner wall surface 13 includes a curved surface 50 that is curved outward in the first direction A. As shown in FIG. In this way, by curving the inner wall surface 13 so as to protrude outward, the thermal stress due to the heat of the light emitting element 10 is dispersed, stress concentration on the inner wall surface 13 is eliminated, and damage due to cracks or the like is reduced. be able to. As described above, the outer side in the first direction A refers to the direction from the inner wall side of the clad layer 3 to the outer wall side of the clad layer 3 in the direction of the first direction A.

(Fifth embodiment)
FIG. 9 is an enlarged cross-sectional view of a part near the through hole 8 showing the light emitting device according to the fifth embodiment of the present disclosure. In addition, the same reference numerals are given to the parts corresponding to the above-described respective embodiments, and redundant explanations are omitted. In the light-emitting device of the present embodiment, the inner wall surface 13 is positioned closer to the second opening 15 than the core layer 4 in the second direction B, and the first curved surface 51 protruding outward in the first direction A and the second and a second curved surface 52 located closer to the first opening 14 than the first curved surface 51 in the direction B and convex inward in the first direction A. The inner side in the first direction A refers to the direction from the outer wall side of the clad layer 3 to the inner wall side of the clad layer 3 in the direction of the first direction A.

With such a configuration, the portion of the inner wall surface 13 on the side of the interface between the substrate 1 and the optical waveguide layer 5 is curved inwardly, thereby forming the portion of the optical waveguide layer 5 near the interface with the substrate 1 . volume increases, and damage such as peeling and cracking due to deformation due to thermal stress can be reduced. Further, since the incident end faces 4a to 4c of the core layer 4 are curved along the curved surface 52, the lens effect of the incident end faces 4a to 4c makes it easier for the light from the light emitting element 10 to enter the core layer 4. , the incidence efficiency of the light emitted from the light emitting element 10 can be improved.

Further, in the fifth embodiment, the radius of curvature R1 of the second curved surface 52 is configured to be less than or equal to the radius of curvature R2 of the first curved surface 51 (R1≦R2). As a result, the radius of curvature of each of the incident end faces 4a to 4c of each core layer 4 becomes the same as the radius of curvature of the second curved surface 52, and the condensing area of each of the incident end faces 4a to 4c is enlarged, so that the light emitted from the light emitting element 10 The light incidence efficiency can be further improved.

(Sixth embodiment)
FIG. 10 is an enlarged cross-sectional view of a part near the through hole 8 showing the light emitting device according to the sixth embodiment of the present disclosure. In addition, the same reference numerals are given to the parts corresponding to the above-described respective embodiments, and redundant explanations are omitted. In the light emitting device of this embodiment, the inner wall surface 13 is positioned between the first curved surface 51 and the second opening 15 in the second direction B in addition to the first curved surface 51 and the second curved surface 52 described above, A third curved surface 53 that is convex inward in the first direction A is further included.

With such a configuration, the inner wall surface 13 is curved so that the inner side protrudes in the vicinity of the interface between the optical waveguide layer 5 and the sealing lid 11 . Since the volume of the portion near the interface increases, it is possible to reduce damage due to peeling and cracking due to thermal stress.

Further, in the sixth embodiment, the radius of curvature R3 of the third curved surface 53 is configured to be less than or equal to the radius of curvature R1 of the first curved surface 51 (R3≦R1). As a result, the volume of the portion of the optical waveguide layer 5 near the interface of the sealing lid 11 is further increased, and peeling due to thermal stress and breakage due to cracks or the like can be more reliably reduced.

As in the first to sixth embodiments described above, the incident end surfaces 4a to 4c of each core layer 4 are exposed from the curved surface 31, the curved surface 50, and the second curved surface 52 toward the light emitting element 10, It is possible to provide an optical waveguide package and a light-emitting device which are excellent in efficiency of incidence of light from the light-emitting element and have little incidence loss of light to the core layer 4 .

In addition, since the sealing lid 11 positioned so as to cover the through hole 8 is airtightly joined to the upper surface 6 of the clad layer 3 , deformation due to thermal expansion is prevented from occurring in the optical waveguide layer 5 and the sealing lid 11 . It can be tolerated in one body, thereby distributing the thermal stress over the whole, lowering the peak value of the upper limit of the thermal stress, thereby reducing separation due to deformation and breakage due to cracks and the like.

In each of the above-described embodiments, the inner wall surface 13 surrounding the rectangular parallelepiped through-hole 8 has the curved surface 31, the curved surface 50, and the first to third curved surfaces 51 to 53 formed all around. However, in still another embodiment of the present disclosure, the curved surface 31, the curved surface 50, and the first to third curved surfaces 51 to 53 are formed only on a part of the inner wall surface facing the light emitting surface of the light emitting element 10. There may be. Also by this, there can exist an effect similar to each above-mentioned embodiment. Further, the through-hole 8 is not limited to the rectangular parallelepiped shape described above, and may be formed in a cylindrical shape, an elliptical columnar shape, a polygonal columnar shape, or the like as appropriate according to the mounted parts such as the light-emitting element accommodated in the through-hole 8, wiring, and the like. can be selected and adopted.

Further, in each of the above-described embodiments, the sealing lid 11 is a plate-like body having a rectangular planar shape, but in other embodiments of the present disclosure, it has a size that completely covers the through hole 8, In order to avoid contact with the bonding wire connected to the light emitting element 10 or the like, it may be a recessed part that is open downward.

In still another embodiment of the present disclosure, the light-emitting element 10 is not limited to a light-emitting diode (Light Emitting Diode; LED), but may be, for example, an LD (Laser Diode), a VCSEL (Vertical Cavity Surface Emitting Laser), or the like. good too.

Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. can be made without departing from the gist of the present disclosure. It is possible. It goes without saying that all or part of each of the above-described embodiments can be appropriately combined within a non-contradictory range.

Reference Signs List 1 substrate 2 upper surface of substrate 1 3 clad layer 4 core layer 4a, 4b, 4c incident end surface 5 optical waveguide layer 6 upper surface 7 lower surface 7a, 7b, 7c, 7d wall surface 8 through hole 10 light emitting element 11 sealing lid 13 inner wall surface 20 light emitting device 30, 30a, 30b bending point 31 bending surface 41a, 41b, 41c dividing path 42 emitting end surface 43 combining section 44 integrating path 45 condensing lens 50 curved surface 51 first curved surface 52 second curved surface 53 third curved surface

Claims (12)

a substrate;
an optical waveguide layer having a clad layer positioned on the substrate and a core layer positioned within the clad layer;
The cladding layer has an upper surface, a lower surface, and a through hole penetrating from the upper surface to the lower surface toward the substrate and accommodating a light emitting element ,
an end surface of the core layer is exposed to an inner wall surface of the through hole,
The inner wall surface of the through hole has a first opening perpendicular to the axis of the virtual cylindrical surface rather than a virtual cylindrical surface connecting a first opening intersecting the lower surface and a second opening intersecting the upper surface. In the direction, it protrudes outward from the virtual cylindrical surface, which is the side away from the axis of the virtual cylindrical surface, and the portion on the second opening side protrudes inward, which is the side opposite to the outer side. optical waveguide package . 2. The optical waveguide package according to claim 1, wherein said inner wall surface includes a curved surface having a curved point in a second direction along said axis. 3. The optical waveguide package according to claim 2, wherein said bending surface has a plurality of bending points. 2. The optical waveguide package according to claim 1, wherein said inner wall surface includes an outwardly convex curved surface in said first direction. The inner wall surface includes a first curved surface positioned closer to the second opening than the end surface of the core layer in the second direction along the axis and protruding outward in the first direction, and the 2. The optical waveguide package according to claim 1, further comprising a second curved surface positioned closer to said first opening than said first curved surface and projecting inwardly in said first direction. 6. The optical waveguide package according to claim 5, wherein the radius of curvature of said second curved surface is less than or equal to the radius of curvature of said first curved surface. The inner wall surface further includes a third curved surface located between the first curved surface and the second opening in a second direction along the axis and convex inward in the first direction. 7. The optical waveguide package according to 5 or 6. 8. The optical waveguide package according to claim 7, wherein the radius of curvature of said third curved surface is less than or equal to the radius of curvature of said first curved surface. 9. The optical waveguide package according to claim 5, wherein said end surface of said core layer is exposed to said second curved surface. 10. The optical waveguide package according to claim 1, further comprising a sealing lid positioned on said clad layer so as to cover said through hole. an optical waveguide package according to any one of claims 1 to 10;
and a light emitting element accommodated in the through hole of the optical waveguide package. The light emitting element includes three light emitting elements that emit red light, green light and blue light,
12. The light-emitting device according to claim 11, wherein three through-holes are positioned so as to accommodate each of said three light-emitting elements.

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