WO2024105846A1 - Optical element and method for manufacturing same - Google Patents

Abstract

This optical element (10) comprises: a fiber block (11) that has a V-groove substrate (112), a lid (113), and an optical fiber (111) fixed between the V-groove substrate and the lid; and an optical chip (12) that has a waveguide (121) in a surface thereof. An end surface of the optical fiber and an end surface of the waveguide are arranged facing each other, and a portion of an end surface of the V-groove substrate and/or the lid is extended and positioned so as to cover a portion of the back surface of the optical chip.　With this configuration, the present invention can provide an optical element in which the adhesion strength between the fiber block and the optical chip can be enhanced.

Description

Optical element and method for manufacturing the same

The present invention relates to an optical element that includes a fiber block having an optical fiber and an optical chip.

The rapid increase in Internet traffic has created a need to increase the transmission capacity of networks within data centers. To achieve this increase in transmission capacity while reducing power consumption, it is hoped that optical interconnections that perform optical communications will be introduced even for short- to medium-distance transmission in data centers and other locations.

When introducing optical interconnections, the wiring capacity index is important: the transmission capacity per unit length at the end of the optical communication device / power consumption per bit [= (bps/mm) / (pJ/bit)]. Compared to the wiring capacity index for conventional electrical wiring, the wiring capacity index for optical interconnections is said to be one to two orders of magnitude smaller.

Therefore, for optical elements used in optical interconnections, it is important to reduce the width of the optical chip (e.g., semiconductor laser diode or quartz-based optical planar circuit) and optical fiber array while increasing the transmission capacity. Here, the width direction refers to the direction perpendicular to the light propagation direction.

On the other hand, flip-chip mounting is used as a mounting form for optical chips in optical elements suitable for increasing the transmission capacity of conventional optical communications (see Patent Document 1). In flip-chip mounting, chips can be electrically connected over the shortest distance. This reduces the effect of inductance components due to the length of electrical wiring, making it possible to realize mounting suitable for high-frequency transmission. By applying flip-chip mounting to optical elements for optical communications, optical chips and electrical chips (such as laser diode drivers) can be mounted without degrading the high-frequency characteristics. This makes it possible to realize optical elements for optical communications that achieve large-capacity transmission.

Figure 17 shows a cross-sectional view of a conventional optical element 50. The optical element 50 comprises a fiber block (optical fiber array) 51 and an optical chip 52, which are optically connected to each other. In the fiber block 51, an optical fiber 511 is placed in the V-groove portion of a glass V-groove substrate 512, and a glass lid 513 is placed on its surface, and each is fixed with adhesive 514. In the optical chip 52, a waveguide layer 521 is formed on the top surface of a substrate made of Si or the like by photography or the like.

A wire 56 made of a glass material or the like is fixed to the top surface of the optical chip 52 with an adhesive (not shown). In this configuration, wire 56 is bonded to the fiber block 51 via adhesive 55 in addition to the optical chip 52, so the bonding area between the fiber block 51 and the optical chip 52 in the optical element 50 is increased and the bonding strength is ensured.

As mentioned above, there is a demand for miniaturization of optical chips, particularly narrowing their width (reducing width) in order to improve the performance index of optical communication transmission in optical elements. Therefore, in the future, it will be important to further reduce the bonding area between the optical fiber array and the optical chip in optical elements, as well as to ensure the adhesive strength.

Patent No. 7074012

However, in optical elements, it is difficult to attach the above-mentioned attachment to optical chips that are flip-chip mounted. Details are explained below.

Figure 18 shows an example of a cross-sectional view of a flip-chip mounted optical element 60. In the optical element 60, the surface of the optical chip 62 on which the waveguide 621 is formed (the bottom surface in Figure 18) faces the surface of the electrical chip 63 on which the electronic circuitry and wiring are formed (the top surface in Figure 18), and the optical chip 62 and electrical chip 63 are electrically connected by flip-chip mounting.

At the flip chip connection 64, the electrical pads on the surface of the optical chip 62 and the electrical chip 63 are connected by metal bumps or the like. Here, an underfill agent may be filled in to protect the connection.

When a wire (dotted line in FIG. 18) 66 is attached to the surface of the optical chip 62, the surface of the optical chip 62 to which the wire 66 is attached is connected to the surface of the electrical chip 63. Therefore, it is necessary to position the wire 66 and the electrical chip 63 so that they do not interfere with each other.

However, since only the back surface of the optical chip 62 can be seen during flip-chip mounting, it is difficult to directly check the position of the wire 66. As a result, compared to conventional processes, mounting time increases, and tolerance requirements for components become stricter to avoid interference, increasing the process load and mounting costs.

It is also possible to attach a wire to the back surface of the optical chip 62 (top surface in Figure 18), but this is difficult to achieve as described below. During normal flip-chip mounting, the optical chip 62 is fixed in place by vacuuming it with a jig (collet). At this time, if a wire is attached to the surface to be attached, contact (interference) between the jig (collet) and the wire will hinder adhesion. This contact (interference) can be avoided by design, but it is difficult to control the outer shape of the wire and the adhesion position of the jig (collet). As such, it is difficult to attach a wire to the back surface of the optical chip 62 (top surface in Figure 18).

In order to solve the problems described above, the optical element according to the present invention comprises a fiber block having a V-groove substrate, a lid, and an optical fiber fixed between the V-groove substrate and the lid, and an optical chip having a waveguide on its surface, in which an end face of the optical fiber and an end face of the waveguide are arranged opposite each other, and a portion of at least one of the end faces of the V-groove substrate and the lid extends and is arranged to cover a portion of the back surface of the optical chip.

The method for manufacturing an optical element according to the present invention is a method for manufacturing an optical element including a fiber block having a V-groove substrate, a lid, and an optical fiber fixed between the V-groove substrate and the lid, and an optical chip having a waveguide, and includes the steps of: arranging the optical fiber in the V-groove of the V-groove substrate; adhesively fixing the lid so as to press the optical fiber against the V-groove substrate; aligning the optical fiber and the waveguide; disposing an extended portion of one of the end faces of the V-groove substrate and the lid so as to cover a portion of the back surface of the optical chip; filling at least one of the space between the end face of the optical fiber and the end face of the waveguide and the space between the extended portion and the back surface of the optical chip with adhesive; aligning the optical fiber and the waveguide again; and hardening the adhesive.

The present invention provides an optical element that can improve the adhesive strength between the fiber block and the optical chip.

FIG. 1 is a schematic side sectional view showing the configuration of an optical element according to a first embodiment of the present invention. FIG. 2 is a schematic top perspective view showing the configuration of a fiber block in an optical element according to a first embodiment of the present invention. FIG. 3 is a schematic side cross-sectional view showing an example of the configuration of an optical element according to the first embodiment of the present invention. FIG. 4 is a schematic side cross-sectional view showing an example of the configuration of an optical element according to the first embodiment of the present invention. FIG. 5 is a flow chart for explaining a method for manufacturing an optical element according to the first embodiment of the present invention. FIG. 6 is a schematic cross-sectional side view showing an example of the configuration of a fiber block in the optical element according to the first embodiment of the present invention. FIG. 7 is a schematic side sectional view showing the configuration of a connection portion of an optical element according to the second embodiment of the present invention. FIG. 8 is a schematic side sectional view showing an example of the configuration of a connection portion of an optical element according to the second embodiment of the present invention. FIG. 9 is a schematic top view showing the configuration of a V-groove substrate in an optical element according to a modified example of the second embodiment of the present invention. FIG. 10 is a schematic side cross-sectional view showing an example of the configuration of a connection portion of an optical element according to the second embodiment of the present invention. FIG. 11 is a schematic side cross-sectional view showing an example of the configuration of a connection portion of an optical element according to the second embodiment of the present invention. FIG. 12 is a schematic cross-sectional side view showing the configuration of an optical element according to the third embodiment of the present invention. FIG. 13 is a schematic side sectional view showing the configuration of an optical element according to the fourth embodiment of the present invention. FIG. 14 is a schematic top perspective view showing the configuration of an optical element according to the fourth embodiment of the present invention. FIG. 15 is a schematic side sectional view showing an example of the configuration of an optical element according to the fourth embodiment of the present invention. FIG. 16 is a schematic side sectional view showing an example of the configuration of an optical element according to the fourth embodiment of the present invention. FIG. 17 is a schematic side sectional view showing an example of the configuration of a conventional optical element. FIG. 18 is a schematic side sectional view showing an example of the configuration of a conventional optical element.

First Embodiment
An optical element according to a first embodiment of the present invention will be described with reference to FIGS.

<Configuration of optical element>
1, an optical element 10 according to this embodiment includes a fiber block (e.g., an optical fiber array) 11, an optical chip 12, and an electrical chip 13. In the optical element 10, the fiber block 11 and the optical chip 12 are connected, and the optical chip 12 and the electrical chip 13 are connected by a flip chip connection portion 14.

As shown in FIG. 2, the fiber block 11 includes an optical fiber 111, a V-groove substrate 112, and a lid 113.

The V-groove substrate 112 is made of glass, and a V-groove is formed on the surface. In addition to glass, Si, metal, resin, etc. can also be used.

The optical fiber 111 is placed in the V-groove of the V-groove substrate 112 and fixed with adhesive 114. Here, an example is shown in which an optical fiber tape having multiple optical fibers is placed, but a single optical fiber may also be used.

The lid 113 is made of glass, and the optical fiber 111 is fixed with adhesive 114 onto the surface of the V-groove substrate 112 on which it is placed.

The lid 113 has a structure in which the end face (the face facing the optical chip 12) near the surface, including the surface (the face opposite to the face where the optical fiber 111 is fixed), extends (protrudes), and the side cross section of the lid 113 is L-shaped. Hereinafter, a structure in which the side cross section is L-shaped is referred to as an "L-shaped structure."

For example, the length of the lid 113 is about 8 mm, with the extension being about 2 mm to 3 mm. The height (thickness) of the lid 113 is about 1.00 mm, with the extension being about 0.10 mm to 0.24 mm thick. The width of the lid is about 1 mm.

The optical chip 12 has a waveguide 121 on its surface (the bottom surface in FIG. 1).

The electrical chip 13 has electronic circuits and wiring on its surface (top surface in Figure 1).

The optical chip 12 and electrical chip 13 are electrically connected by flip-chip mounting with their respective surfaces facing each other.

In the flip chip connection section 14, the electrical pads on the surface of each chip are connected by metal bumps or the like. Here, an underfill agent may be filled in to protect the connection.

The fiber block 11 and the optical chip 12 are bonded together via adhesive 15 so that the end face of the fiber block 11 including the optical fiber 111 faces the end face of the optical chip 12 including the waveguide 121. Here, it is desirable that the distance between the optical fiber 111 and the waveguide 121 is approximately 5 to 10 μm.

Here, in the fiber block 11 including the lid 113, the V-groove substrate 112, and the optical fiber 111, the end face facing the optical chip 12 is made flush by polishing or the like. This allows the optical fiber 111 and the waveguide 121 of the optical chip 12 to be placed close to each other with a distance of about several μm.

The extension (protrusion) of the lid 113 in the fiber block 11 is positioned so as to cover a portion (e.g., about 2 mm to 3 mm in the longitudinal direction) of the back surface (top surface in FIG. 1) of the optical chip 12, and adhesive 15 is filled between the back surface (bottom surface in FIG. 1) of the extension (protrusion) of the lid 113 and the back surface of the optical chip 12, and they are fixed in place.

In this way, in the optical element 10, the fiber block 11 and the optical chip 12 are bonded not only to the end faces having the optical fiber 111 and the waveguide 121, but also to the extension of the lid 113 and the back surface of the optical chip 12. This increases the bonding area, thereby increasing the bonding strength.

In this embodiment, an example has been shown in which the lid 113 has an L-shaped structure in which the end face near the surface, including the front surface, extends (protrudes), but this is not limited to this. As shown in FIG. 3, the V-groove substrate 112 may have an L-shaped structure in which the end face near the back surface, including the back surface (the surface opposite to the surface on which the optical fiber 111 is fixed), extends (protrudes). In this way, the front and back surfaces (top and bottom surfaces in the figure) of the fiber block 11 may be inverted, and the extension (protrusion) of the V-groove substrate 112 may be positioned and fixed so as to cover part of the back surface (top surface in the figure) of the optical chip 12.

Also, as shown in FIG. 4, the end face of the lid 113 may be protruded toward the optical chip 12 beyond the end face of the optical fiber 111, and the optical chip 12 may be sandwiched between the lid 113 and the extension of the L-shaped V-groove substrate 112. In this configuration, the back surface (top surface in the figure) of the lid 113 and the front surface (bottom surface in the figure) of the optical chip 12 are fixed with adhesive 15, and the back surface (bottom surface in the figure) of the extension of the V-groove substrate 112 and the back surface (top surface in the figure) of the optical chip 12 are fixed with adhesive 15. This can further increase the bonding area and increase the bonding strength.

Here, both the V-groove substrate 112 and the lid 113 may have extensions, and the optical chip 12 may be sandwiched and glued between the respective extensions.

<Method of manufacturing optical element>
An example of a method for manufacturing the optical element 10 according to the present embodiment will be described below. A flow chart for explaining the method for manufacturing the optical element 10 is shown in FIG.

First, the process for making the fiber block 11 will be explained.

First, the V-groove substrate 112 is created using a mask and chemical etching, etc.

Next, the optical fiber 111 is placed along the V-groove of the V-groove substrate 112 (step S1). At this time, the coating of the fiber is appropriately removed.

Next, adhesive 114 is applied onto the V-groove substrate 112 on which the optical fiber 111 is arranged, and the optical fiber 111 is pressed against the V-groove substrate 112 with the lid 113, thereby bonding and fixing the optical fiber 111 to the V-groove substrate 112 (step S2). Here, for example, an acrylic adhesive is used as the adhesive 114.

Next, the end face of the fiber block 11, which has the end face of the optical fiber 111, is partially polished to make the end faces of the optical fiber 111, the V-groove substrate 112, and the lid 113 that come into contact with the optical chip 12 flush.

In this way, the fiber block 11 is produced.

Fiber block 11 may also be produced by cutting a fiber block produced by a normal process into an L-shaped structure using a dicing saw or the like. In this case, by using a blade with uniform abrasive grain size so that the cut surface is flat, a flat optical fiber end face can be formed, reducing optical connection loss and achieving optical connections with high adhesive strength.

Fiber block 11 may also be fabricated as shown below.

First, the optical fiber 111 is bonded to the V-groove substrate 112 and polished so that the end face of the optical fiber 111 and the end face of the V-groove substrate 112 are flush with each other.

Next, as shown in Figure 6, the position of the L-shaped lid 113 is shifted toward the inside of the fiber block 11 by a predetermined distance (100 μm or more) and fixed so that the end face of the optical fiber 111 becomes the tip. In detail, the surface of the L-shaped lid 113 that faces the end face of the optical chip 12 is set back from the end face of the optical fiber 111 toward the inside of the fiber block 11 by a predetermined distance (100 μm or more).

This allows the end face of the optical fiber 111 to come into contact with the end face of the optical chip 12. This method of fabricating a fiber block has the advantage of simplifying the process, as it does not require partial polishing of the fiber block 11.

Next, the process of connecting the fiber block 11 and the optical chip 12 will be described.

First, the fiber block 11 having the L-shaped structure lid 113 or the L-shaped structure V-groove substrate 112 and the optical chip 12 are fixed to the fine movement stage using a jig.

Next, while visually checking the optical fiber (core) 111 of the fiber block 11 and the waveguide 121 of the optical chip 12 using an image or the like, the optical fiber (core) 111 and the waveguide 121 are roughly aligned. At this time, care is taken to ensure that the extended portion of the L-shaped structure does not come into contact with other components.

Next, the LD (laser diode) integrated in the optical chip 12 is made to emit light, and the pigtail fiber attached to the fiber block 11 is connected to an optical power meter or the like to check the optical coupling efficiency and perform active alignment (step S3).

Next, the coordinates of the fine movement stage upon completion of rough alignment (centering) are stored, and the fiber block 11 is temporarily removed.

Next, adhesive 15 (e.g., an acrylic adhesive) is applied to the end face of the waveguide 121 of the optical chip 12 and the back surface of the optical chip 12 (step S4). Here, adhesive is filled between the end face of the optical fiber 111 and the end face of the waveguide 121, and between the extension of the lid 113 and the back surface of the optical chip 12.

Next, the fiber block 11 is moved to the coordinates at the time of completion of the above-mentioned alignment, and alignment is performed again with adhesive 15 filled between the optical fiber 111 and the waveguide 121 (the fiber block 11 and the optical chip 12) (step S5).

Finally, the adhesive 15 is hardened by irradiating it with UV light, and the fiber block 11 having the optical fiber 111 and the optical chip 12 having the waveguide 121 are bonded and fixed together (step S6).

In this way, the fiber block 11 and the optical chip 12 are connected and fixed to produce the optical element 10.

In this embodiment, an example is shown in which glass is used as the lid material, but resin, metal, etc. may also be used.

In this embodiment, an example has been shown in which the lid or V-groove substrate has an L-shaped structure in which the end face near the front surface including the front surface of the lid or the end face near the back surface including the back surface of the V-groove substrate extends, but this is not limited to this. A structure in which an end face near the front surface or back surface not including the front surface or back surface extends is also possible. In this case, a step is formed on the front surface or back surface at the boundary between the main body of the lid or V-groove substrate and each extension portion. In this way, it is sufficient that a part of the end face of at least one of the lid and the V-groove substrate extends. For example, a structure in which at least the end face near the front surface of the lid (e.g., closer to the front surface than the center of the end face) or the end face near the back surface of the V-groove substrate (e.g., closer to the back surface than the center of the end face) extends is also possible.

Second Embodiment
An optical element according to a second embodiment of the present invention will be described with reference to FIGS.

<Configuration of optical element>
7, an optical element 20 according to this embodiment includes a fiber block (e.g., an optical fiber array) 11, a connecting waveguide 211, an optical chip 12, and an electric chip 13. In the optical element 20, an optical fiber 111 of the fiber block 11 and a waveguide 121 of the optical chip 12 are connected via the connecting waveguide 211. The other configurations are substantially similar to those of the first embodiment.

<Method of manufacturing optical element>
As an example of a method for manufacturing the optical element 20 according to this embodiment, a method in which a self-written optical waveguide is used for the connection waveguide 211 will be described below.

First, the coating of the optical fiber 111 is removed and the end face is cleaved. This optical fiber 111 is placed on the V-groove substrate 112. At this time, alignment is performed using image recognition so that the end face of the optical fiber 111 and the end face of the glass V-groove are roughly flush with each other. Normally, positioning can be performed with an accuracy of about 0.01 to 0.1 mm using image recognition. Methods other than image recognition can be used as long as they can achieve alignment with this accuracy. For example, a method using a jig manufactured by machining or the like can be used.

As a result, for example, as shown in FIG. 7, the end face of the optical fiber 111 is positioned so that it protrudes from the end face of the V-groove substrate 112. The length of this protrusion is 0.1 to 0.5 mm, and can be controlled with the above-mentioned positioning accuracy (approximately 0.01 to 0.1 mm).

Next, adhesive (not shown) is dropped onto the V-groove substrate 112 and the optical fiber 111, and the lid 113, the optical fiber 111, and the V-groove substrate 112 are each adhesively fixed together while the lid 113 presses the optical fiber 111 against the V-groove substrate 112.

In this way, the polishing process can be omitted and a fiber block 11 having an L-shaped structure can be produced.

Next, the fiber block 11 and the optical chip 12 are connected by a self-formed optical waveguide 211, as shown below.

First, the core of the optical fiber 111 and the waveguide 121 of the optical chip 12 are roughly aligned using image recognition or the like. At this time, the end face of the optical fiber 111 and the end face of the waveguide 121 of the optical chip 12 are positioned with a gap of 10 μm or more. This prevents contact between the protruding end face of the optical fiber 111 and the optical chip 12.

Next, the core of the optical fiber 111 and the waveguide 121 of the optical chip 12 are aligned by active alignment.

Next, the fiber block 11 is removed and a photocurable resin capable of forming a self-forming optical waveguide is dripped onto the end face of the optical chip 12.

Next, after performing active alignment again, resin curing light is irradiated from the end face of the optical fiber 111 of the fiber block 11. This allows a continuous waveguide, i.e., a self-forming optical waveguide 211, to be formed from the end face of the optical fiber 111.

Finally, the uncured photocurable resin is washed off with a solvent such as ethanol, and then resin for adhesion and for the cladding 212 of the self-forming optical waveguide (core) 211 is dripped and cured by UV irradiation or the like to bond and fix the fiber block 11 and the optical chip 12 together.

The above steps allow the optical element 20 of this embodiment to be manufactured.

In this embodiment, an example has been described in which the uncured photocurable resin is washed away after the self-forming optical waveguide is formed, and is replaced with a resin for adhesion and cladding, but this is not limiting. The self-forming optical waveguide (core) and cladding may be formed without washing away the uncured photocurable resin.

For example, two types of resin that harden at different wavelengths are mixed, and first, light of a first wavelength λ1 is irradiated onto the resin from the end face of the optical fiber 111 to harden and form the self-forming optical waveguide (core). Next, light of a second wavelength λ2 is irradiated onto the resin from around it to harden and form the cladding. In this way, a self-forming optical waveguide can be formed without washing away the unhardened photocurable resin.

Also, in photocurable resins, the initiator that contributes to the curing has a relatively broad absorption spectrum, so for example, a single resin can be cured with both 405 nm and 365 nm light. Furthermore, it has been reported that some photocurable resins have different refractive indices after curing depending on the curing wavelength or curing process (one-photon absorption, two-photon absorption, thermal curing, etc.). Therefore, for example, using a single type of resin, the self-forming optical waveguide (core) can be formed with λ1 light, and the cladding can be formed with λ2 light or thermal curing, etc. This allows a self-forming optical waveguide to be formed by creating a refractive index difference between the core and cladding using a single type of resin.

In this embodiment, an example of a configuration in which the end face of the optical fiber protrudes from the end face of the V-groove substrate 112 in the fiber block 11 has been shown, but this is not limiting. As shown in FIG. 8, a configuration in which the end face of the optical fiber 111 is recessed from the end face of the V-groove substrate 112 (positioned toward the inside of the fiber block 11) is also possible. In a configuration in which the end face of the optical fiber 111 is recessed, there is no physical contact between the end face of the optical fiber 111 and the end face of the optical chip 12. Therefore, it is possible to avoid bending or damage of the optical fiber due to contact of the optical fiber 111 during rough alignment of the optical fiber 111 and the optical chip 12.

＜Effects＞
In the first embodiment, an additional partial polishing step is required compared to the normal fiber block fabrication process, which results in a decrease in fabrication accuracy, an increase in optical signal loss due to misalignment of the optical axis, a decrease in yield, and an increase in manufacturing cost.

Also, unlike conventional fiber blocks, the presence of the extension section places stricter demands on the processing of the fiber block. For example, if the outer shape and thickness of this extension section are not controlled, the extension section will come into contact with the substrate of the optical chip. As a result, gaps on the order of tens to hundreds of microns and optical axis misalignment will occur between the fiber block and the optical chip, resulting in large losses when transmitting optical signals.

The optical element according to this embodiment can reduce connection loss between the fiber block and the optical chip by using a connection waveguide. In particular, when a self-forming optical waveguide is used as the connection waveguide, the irradiated area of the light-curing resin that is irradiated with the light emitted from the optical fiber or the waveguide of the optical chip (resin curing light) becomes the connection waveguide, so that the connection loss of light can be reduced.

<Modification 1>
An optical element according to a first modified example of the present embodiment will be described with reference to FIG.

As shown in FIG. 9, the optical element according to this modified example has a liquid-proof groove 22 on the surface of the V-groove substrate 112 of the fiber block 11, in a direction perpendicular to the longitudinal direction of the V-groove.

The liquid-proof groove 22 is formed by a dicing process or the like, and has a width (length of the V-groove in the longitudinal direction, vertical direction in FIG. 9) of 100 μm and a depth of 300 μm, for example.

The rest of the configuration is substantially the same as in the second embodiment.

＜Effects＞
In the first and second embodiments, when fabricating a fiber block, it is necessary to prevent the adhesive that bonds the glass V-groove, the optical fiber, and the lid from wrapping around the end face of the optical fiber. If the adhesive wraps around the end face of the optical fiber, a layer of the adhesive is formed on the end face of the optical fiber, causing optical connection loss due to diffraction. In addition, the resin curing light is significantly lost due to absorption by the adhesive. As a result, it is not possible to ensure the resin curing light intensity required to form a self-written optical waveguide. Therefore, it is necessary to adjust the viscosity and application amount of the resin used.

According to this modified example, the resin can be held back by the liquid-proof groove, preventing the adhesive from getting around the end face of the optical fiber. Therefore, the loss of transmitted light can be easily suppressed and the fiber block and optical chip can be connected and fixed without adjusting the viscosity or amount of resin used.

In this modified example, an example is shown in which the liquid-proof groove is formed in the V-groove substrate, but this is not limiting, and the liquid-proof groove may be formed in the lid, or in both the V-groove substrate and the lid.

In this embodiment, an example has been shown in which the self-forming optical waveguide is formed by resin curing light emitted from an optical fiber, but this is not limiting. The self-forming optical waveguide may also be formed by resin curing light emitted from a waveguide of an optical chip.

Also, the self-forming optical waveguide may be formed by resin curing light emitted from both the optical fiber and the waveguide of the optical chip. This forms an S-shaped self-forming optical waveguide 211 as shown in FIG. 10, and connection loss due to optical axis misalignment can be reduced. As a result, the tolerance required for V-groove substrates and the like can be greatly relaxed.

In this embodiment, the cross-sectional shape of the self-forming optical waveguide is approximately constant, but this is not limited to the above. A tapered self-forming optical waveguide can be formed by making the resin curing light intensity during the formation of the self-forming optical waveguide sufficiently greater than the resin curing threshold. For example, when the resin curing light is irradiated from the waveguide 121 of the optical chip 12, the intensity of the resin curing light can be made sufficiently strong to form a self-forming optical waveguide 211 whose cross-sectional area increases from the waveguide 121 of the optical chip 12 toward the fiber block 11 as shown in FIG. 11. This can reduce the connection loss due to the difference in the mode field diameter (MFD) of the light between the optical fiber 11 and the waveguide 121 of the optical chip 12.

In this embodiment, an example has been shown in which a self-forming optical waveguide is used as the connection waveguide, but this is not limiting. In addition to the self-forming optical waveguide, for example, a waveguide formed by high-resolution 3D modeling through two-photon absorption by irradiating an ultrashort pulse light source from the outside using an optical 3D modeling device may also be used.

Third Embodiment
An optical element according to a third embodiment of the present invention will be described with reference to FIG.

<Configuration of optical element>
12, an optical element 30 according to this embodiment includes a fiber block (e.g., an optical fiber array) 11, an optical chip 12, and an electrical chip 13. In the optical element 30, the fiber block 11 and the optical chip 12 are adhesively fixed, and the optical chip 12 and the electrical chip 13 are adhesively fixed.

When connecting the fiber block 11 and the optical chip 12, the area between the back surface of the extension of the lid 113 of the fiber block 11 and the back surface of the optical chip 12 (hereinafter referred to as the "lid/optical chip gap") is filled with adhesive (hereinafter referred to as the "lid support adhesive") 31 to fix (bond) the lid 113 and the optical chip 12.

Also, the area between the end face of the fiber block 11 including the optical fiber 111 and the end face of the optical chip 12 including the waveguide 121 (hereinafter referred to as the "optical path end face spacing") is filled with adhesive (hereinafter referred to as the "optical path adhesive") 15 to fix (bond) the fiber block 11 and the optical chip 12.

Here, different adhesives are used for the lid support adhesive 31 and the optical path adhesive 15. In detail, the wider of the lid/optical chip spacing and the optical path end face spacing is filled with an adhesive with a smaller elasticity modulus.

For example, if the lid/optical chip spacing is wider than the optical path end face spacing, the elastic modulus of the lid support adhesive 31 is smaller than the elastic modulus of the optical path adhesive 15. For example, if the lid/optical chip spacing is 10 times wider than the optical path end face spacing, the elastic modulus of the lid support adhesive 31 is set to 1/10 or less of the elastic modulus of the optical path adhesive 15.

In the optical element 30 according to this embodiment, as an example, since the elastic modulus of a normal silicone adhesive is smaller than that of an epoxy adhesive, a silicone adhesive is used for the wider of the lid/optical chip spacing and the optical path end face spacing, and an epoxy adhesive is used for the narrower one.

＜Effects＞
In the manufacturing process of the optical element according to the first embodiment, for example, due to manufacturing tolerances, the extension of the lid or the optical chip may become thinner than designed, and the lid/optical chip interval may become wider than the optical path end face interval. In this state, when the same type of adhesive is filled into the lid/optical chip interval and the optical path end face interval and the adhesive is cured, a large stress is applied to the portion with the narrow optical path end face interval, which may cause deformation or peeling of the portion with the optical path end face interval (fiber block or optical chip).

In the optical element according to this embodiment (third embodiment), an adhesive with a smaller elastic modulus is used for the wider of the lid/optical chip spacing and the optical path end face spacing, so that the stress on the narrower of the lid/optical chip spacing and the optical path end face spacing can be reduced, suppressing deformation and peeling in that area. This makes it possible to ease the manufacturing tolerances of the lid and optical chip.

For example, if the lid/optical chip spacing is wider than the spacing between the optical path end faces, the elastic modulus of the lid support adhesive is smaller than the elastic modulus of the optical path adhesive, so the stress on the area between the optical path end faces (fiber block or optical chip) can be reduced, and deformation or peeling in that area can be suppressed.

In this embodiment, the adhesive curing process can be changed by using a light-curing epoxy adhesive and a heat-curing silicone adhesive. In this case, after aligning the fiber block and the optical chip without using adhesive, the optical path adhesive and the lid support adhesive are applied (filled), and the alignment is re-done and the light-curing epoxy adhesive is cured by UV curing, and then the heat-curing silicone adhesive is cured by heat curing, thereby curing the entire adhesive portion and easily fixing the fiber block and the optical chip.

<Fourth embodiment>
An optical element according to a fourth embodiment of the present invention will be described with reference to FIGS.

<Configuration of optical element>
13, an optical element 40 according to this embodiment includes a fiber block (e.g., an optical fiber array) 11, an optical chip 12, and an electric chip 13. In the optical element 40, the fiber block 11 and the optical chip 12 are connected via an adhesive (hereinafter also referred to as a "lid/optical chip adhesive part") 15, and the optical chip 12 and the electric chip 13 are connected via an adhesive (hereinafter also referred to as a "lid/electrical chip adhesive part") 41.

The fiber block 11 and the optical chip 12 are bonded together by bonding the end face of the fiber block 11, which includes the optical fiber 111, to the end face of the optical chip 12, which includes the waveguide 121, and by bonding the back surface of the extension of the lid 113 of the fiber block 11 to the back surface of the optical chip 12.

Furthermore, in the optical element 40, the extension of the lid 113 of the fiber block 11 and the electrical chip 13 are bonded via an adhesive. As a result, the lid/electrical chip adhesive part 41 is formed in the vertical direction between the back surface of the extension of the lid 113 and the surface of the electrical chip 13.

In the manufacturing method of the optical element 40, for example as shown in FIG. 14, the lid 113 and the electrical chip are arranged so that there is an overlapping area when viewed from above, and after the optical fiber 111 and the waveguide 121 of the optical chip 12 are aligned, the lid 113 and the electrical chip 13 are adhesively fixed together.

At this time, the lid/electrical chip adhesive 41 is fixed with an adhesive having a low elastic modulus, and the optical chip 12 and the electrical chip 13 are fixed with an adhesive having a high elastic modulus. As an adhesive having a low elastic modulus is used for the lid/electrical chip adhesive 41, the stress applied to the connection between the optical chip 12 and the electrical chip 13 due to the hardening shrinkage of the adhesive can be reduced, and peeling or breakage of the connection (flip chip connection) 14 between the optical chip 12 and the electrical chip 13 can be suppressed. This makes it possible to reduce the manufacturing tolerance of the extension part of the lid.

Here, the lid/electrical chip adhesive 41 may or may not contact the side of the optical chip 12. However, if the lid/electrical chip adhesive 41 contacts the side of the optical chip 12, stress may be applied to the lid/electrical chip adhesive 41 due to the hardening shrinkage of the adhesive, which may cause the lid/electrical chip adhesive 41 to peel off or break, so it is preferable that the lid/electrical chip adhesive 41 not contact the side of the optical chip 12.

＜Effects＞
In the first embodiment, only the bonding area between the lid and the optical chip is increased, thereby increasing only the connection strength between the lid and the optical chip. However, gravity at the lid/optical chip bonding portion and tension from the optical fiber are applied to the flip chip connection between the optical chip and the electrical chip, which may cause the flip chip connection to peel off or break.

The optical element according to this embodiment (fourth embodiment) forms a lid/electrical chip adhesive in addition to a lid/optical chip adhesive, improving the connection strength of the flip chip connection between the optical chip and the electrical chip. As a result, peeling or breakage of the flip chip connection can be avoided.

In addition to improving the connection strength between the lid and the optical chip, the connection strength between the optical chip and the electrical chip can also be improved.

<Modification 2>
An optical element according to a second modification of the present embodiment will be described with reference to FIG.

<Configuration of optical element>
15, in an optical element 40_2 according to this modification, a lid/electrical chip connection portion 42 is formed in the vicinity of the end face of the optical chip 12 opposite to the end face connected to the optical fiber 111. The other configurations are substantially similar to those of the fourth embodiment.
＜Effects＞
In the fourth embodiment, a lid/electrical chip connection is formed near the side of the optical chip. In this configuration, if a lid/electrical chip connection is formed only on one of the two side surfaces of the optical chip, a difference in cure shrinkage occurs in one connection, so a force is applied to the fiber block to rotate it around the optical axis direction. In addition, if lid/electrical chip connection parts are formed at two locations on both sides and are asymmetrical, a difference in cure shrinkage occurs between one and the other connection, so a similar force is applied to the fiber block. Therefore, it becomes necessary to form lid/electrical chip connection parts symmetrically at two locations on both sides, which increases the number of steps, workload, etc.

With the optical element of this modified example, the lid/electrical chip connection portion only needs to be formed in one location near the side of the optical chip, simplifying the process.

In this modified example, as shown in FIG. 16, the amount of adhesive dispensed at the lid/electrical chip connection 43 may be increased to serve as the underfill for both the optical chip 12 and the electrical chip 13, thereby simplifying the underfill application process and the manufacturing process for the optical element.

In the embodiment of the present invention, examples have been shown in which the end faces of the optical fiber, V-groove substrate, and lid are flush with each other at the end face of the fiber block, the end faces of the optical fiber and V-groove substrate are flush with the end face of the lid being recessed, and only the end face of the optical fiber protrudes or recedes, but the present invention is not limited to these. At least one end face of the optical fiber, V-groove substrate, and lid may protrude from the other end faces at the end face of the fiber block.

In the embodiment of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration and manufacturing method of the optical element are shown, but the present invention is not limited to these. Anything that can exert the function and effect of the optical element can be used.

The present invention relates to optical elements and can be applied to optical communications and optical interconnections.

10 Optical element 11 Fiber block 111 Optical fiber 112 V-groove substrate 113 Lid 12 Optical chip 121 Waveguide

Claims (8)

a fiber block having a V-groove substrate, a lid, and an optical fiber fixed between the V-groove substrate and the lid;
an optical chip having a waveguide on a surface thereof;
an end face of the optical fiber and an end face of the waveguide are disposed opposite to each other;
an end surface of at least one of the V-groove substrate and the lid extends to cover a portion of a rear surface of the optical chip; Equipped with an electric chip,
2. The optical element according to claim 1, wherein a surface of the electrical chip is mounted opposite a surface of the optical chip. At the end surface of the fiber block to be adhesively fixed to the optical chip,
3. The optical element according to claim 1, wherein an end face of at least one of the optical fiber, the V-groove substrate, and the lid protrudes from the other end faces. 3. The optical element according to claim 1, further comprising a connection waveguide that connects the optical fiber and the waveguide. 3. The optical element according to claim 1, wherein at least one of the V-groove substrate and the lid is provided with a liquid-proof groove. 3. The optical element according to claim 1, characterized in that, in the adhesive filled in a first gap between the extended portion and a part of the back surface of the optical chip and a second gap between the end face of the optical fiber and the end face of the waveguide, the adhesive filled in the wider of the first gap and the second gap has a greater elastic modulus. 3. The optical element according to claim 2, wherein the extended portion and a surface of the electrical chip are adhesively fixed to each other. A method for manufacturing an optical element including a fiber block having a V-groove substrate, a lid, and an optical fiber fixed between the V-groove substrate and the lid, and an optical chip having a waveguide, comprising:
placing the optical fiber in a V-groove of the V-groove substrate;
adhesively fixing the lid to the V-groove substrate so as to press the optical fiber against the V-groove substrate;
aligning the optical fiber with the waveguide;
a step of providing an extended portion on one of the end faces of the V-groove substrate and the lid, the extended portion being disposed so as to cover a portion of a rear surface of the optical chip;
filling an adhesive between an end face of the optical fiber and an end face of the waveguide and/or between the extended portion and a back surface of the optical chip;
aligning the optical fiber and the waveguide again;
and curing the adhesive.

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