WO2022249313A1

WO2022249313A1 - Optical component

Info

Publication number: WO2022249313A1
Application number: PCT/JP2021/019925
Authority: WO
Inventors: 拓也田中; 光太鹿間
Original assignee: 日本電信電話株式会社
Priority date: 2021-05-26
Filing date: 2021-05-26
Publication date: 2022-12-01
Also published as: JPWO2022249313A1

Abstract

An optical component (1) according to present invention comprises: a fiber block (11), in which an optical fiber (13) is mounted between a V-groove component (14) and a press cover (15); a waveguide type optical component (12), an input-output end of which is made of SiO2; and a glass plate (16) which is disposed at a connection end surface of the waveguide type optical component (12) and on the upper surface in the vicinity of the connection end surface, wherein at least a portion of a connection end surface of the fiber block (11) has protrusions and recesses, at least a portion of the connection end surface of the waveguide type optical component (12) has protrusions and recesses, and the fiber block (11) and the waveguide type optical component (12) are fixed to each other by an adhesive (18) that fills a gap between the respective connection end surfaces.　The present invention thus can provide a small optical component without reducing adhesive strength between a fiber block and a waveguide type optical component.

Description

optical parts

The present invention relates to an optical component for connecting an optical fiber and a waveguide type optical device.

In recent years, in the field of optical communication and sensing, there has been a demand for miniaturization of optical devices due to high-density placement in equipment in which optical devices are mounted and space saving of the equipment itself. For example, as for the size of the optical transceiver, form factors such as QSFP56-DD and OSFP are applied, and further miniaturization is desired.

When a waveguide type optical device is used as the optical device, an optical fiber is connected to the waveguide chip. Here, since the waveguide chip made of silica-based glass (SiO2) has a refractive index of about 1.45, which is the same as the refractive index of the optical fiber, the fiber block is used to directly connect the optical fiber (butt joint connection). be done.

In this connection, the space between the fiber block and the SiO2-based waveguide chip is filled with an optical adhesive having a refractive index of about 1.45. Reflection of the guided light between the and the optical fiber is suppressed.

For example, silica-based glass waveguide (Planar Lightwave Circuit, PLC) devices have been used in communication networks as practical devices in the near-infrared wavelength band with wavelengths of 1.3 μm to 1.6 μm.

In the PLC device, an optical fiber is connected to the PLC chip via a fiber block, and a connector is formed in which the input/output end of the device is connected to the optical fiber. This connector connects the PLC device to another optical device (for example, a receiver), and the optical signal output from the PLC device is finally subjected to signal processing in an electrical stage.

In a conventional PLC device, a fiber block 31 is used to connect an optical fiber 33 to a PLC chip 32 with an interferometric circuit 37, as shown in FIGS.

In the fiber block 31, the optical fiber 33 has a core 33_1 and a clad 33_2, is mounted on the V-groove component 34, and is fixed by the restraining lid 35.

In the PLC chip 32, a waveguide core 32_1 and a waveguide clad 32_2 are formed on a Si substrate 32_3, and a glass plate 36 is arranged above the connecting portion with the fiber block 31.

When connecting the fiber block 31 and the PLC chip 32 , first, the glass plate 36 is fixed to the upper surface of the PLC chip 32 .

Next, the fiber block 31, the glass plate 36, and the PLC chip 32 are mirror-polished on the end faces (hereinafter referred to as "connection end faces") facing each other when connecting. Here, the smoothness of the mirror-polished surface is usually 1/100 or less of the wavelength of the guided light.

Finally, the optical fiber 33 of the fiber block 31 is aligned with the input waveguide of the interference circuit 37, the ultraviolet curable adhesive 38 is applied, and the adhesive 38 is cured by irradiating ultraviolet rays. Here, the input waveguide alignment method of the optical fiber 33 and the interference circuit 37 may be performed by using a dummy port such as an optical fiber for monitoring or a monitor waveguide instead of the port actually used.

When miniaturizing the above PLC device, it is necessary to miniaturize the fiber block and the PLC chip.

JP-A-8-313744

However, when the fiber block and the PLC chip are miniaturized, the bonding area between the fiber block and the PLC chip is reduced, and the tension from the optical fiber remains on the fiber block, so the bonding strength between the fiber block and the PLC chip is reduced. So it becomes a problem.

In order to solve the above-described problems, the optical component according to the present invention includes a fiber block in which an optical fiber is mounted between a V-groove component and a restraining lid, and a waveguide whose input and output ends are made of SiO2. and a glass plate disposed on a connection end surface of the waveguide type optical component and an upper surface in the vicinity of the connection end surface, at least a part of the connection end surface of the fiber block having unevenness, and the waveguide type optical component. At least a part of the connection end face of the waveguide type optical component has irregularities, and the fiber block and the waveguide type optical component are fixed with an adhesive filled between the respective connection end faces.

According to the present invention, a compact optical component can be provided without reducing the adhesive strength between the fiber block and the PLC chip.

FIG. 1 is a schematic diagram showing the configuration of an optical component according to the first embodiment of the invention. FIG. 2 is an enlarged schematic diagram of a connecting portion in the optical component according to the first embodiment of the present invention. FIG. 3A is a schematic diagram of a fiber block in the optical component according to the first embodiment of the invention; FIG. 3B is a schematic diagram of a PLC chip and a glass plate in the optical component according to the first embodiment of the present invention; FIG. 4A is a schematic diagram of a fiber block in an optical component according to a second embodiment of the invention; FIG. 4B is a schematic diagram of a PLC chip and a glass plate in the optical component according to the second embodiment of the present invention; FIG. 5 is a schematic diagram showing the configuration of a conventional optical component. FIG. 6 is an enlarged schematic diagram of a connecting portion in a conventional optical component.

<First Embodiment>
An optical component according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 3B.

<Configuration of optical components>
An optical component 1 according to this embodiment includes a fiber block 11 and a PLC chip 12 connected to the fiber block 11, as shown in FIG.

In the fiber block 11, the optical fiber 13 has a core 13_1 and a clad 13_2, is mounted on the V-groove component 14, and is fixed by the restraining lid 15. Thus, the optical fiber 13 is mounted between the V-groove part 14 and the holding lid 15 .

In the PLC chip 12, an interference circuit 17 is formed on the Si substrate 12_3. A waveguide in the interference circuit 17 is composed of a waveguide core 12_1 and a waveguide clad 12_2.

The light input to the optical component 1 is guided through the core 13_1 of the optical fiber 13 and the waveguide core 12_1 of the PLC chip 12 .

Also, a glass plate 16 is arranged on the upper surface near the connection end face including the end face (connection end face) connected to the fiber block 11 . Specifically, the glass plate 16 is arranged so that its connecting end surface is substantially on the same plane including the connecting end surface of the PLC chip 12 .

As shown in FIG. 2, the end face of the fiber block 11 faces the end faces of the PLC chip 12 and the glass plate 16, and an adhesive 18 is filled and connected (fixed) between the end faces. Here, an ultraviolet curable adhesive is used as the adhesive 18, but other adhesives may be used.

Here, the connection end faces of the fiber block 11 and the PLC chip 12 are uneven without being mirror-polished. Here, the “connection end face” refers to each end face facing each other when connecting the fiber block 11 and the PLC chip 12 .

Arithmetic mean roughness Ra of unevenness on the connection end surface of the fiber block 11 and the PLC chip 12 will be explained. The arithmetic mean roughness Ra is obtained by integrating the absolute value of the deviation from the average value of unevenness over the reference length and dividing the integrated value by the reference length, and corresponds to the average height of unevenness. Here, the spacing of the irregularities is of the same order as the height of the irregularities.

First, the distance between the end face of the optical fiber 13 in the fiber block 11 and the end face of the optical waveguide in the PLC chip 12 is 1 μm or more and 10 μm or less, and is appropriately determined according to the properties of the adhesive that is filled between the respective end faces. For example, the interval between the end faces is determined to be 1 to 10 times the wavelength of the guided light, and is 1 to 10 μm if the wavelength of the guided light is about 1 μm.

When the unevenness Ra is made smaller than 1/10 of the wavelength of the guided light, the smoothness of the end surface becomes equivalent to that of mirror polishing. Therefore, the effect of increasing the adhesion area due to small irregularities is reduced.

On the other hand, if the unevenness Ra is made larger than 10 times the wavelength of the guided light, it becomes longer than the interval between the end faces, and there is a possibility that the filling adhesive will be insufficient. In addition, curing shrinkage of the adhesive may cause stress in the connecting portion, which may reduce long-term reliability.

Therefore, it is desirable that the unevenness Ra be 1/10 or more and 10 or less times the wavelength of the guided light. Further, when the wavelength of guided light is about 1 μm, it is desirable that the unevenness Ra be 0.1 or more and 10 μm or less. Here, the height of the unevenness does not need to be uniform, and may be non-uniform.

The loss of guided light in the connection between the optical fiber 13 and the PLC chip 12 will be explained.

In the ordinary connection between the optical fiber 13 and the PLC chip 12, when at least a part of the connection end faces of the optical fiber 13 and the PLC chip 12 has unevenness and the gap between the connection end faces is filled with an adhesive, The amplitude and phase of the guided light incident on the adhesive from the optical fiber 13 and the guided light incident on the optical waveguide from the adhesive are distorted. At this time, the connection efficiency is the square of the absolute value of the overlap integral of the electric field of the incident light and the propagation mode of the waveguide.

Therefore, the difference between the amplitude and phase of the light incident on the optical waveguide and the propagation mode of the waveguide increases, and the connection loss increases.

On the other hand, in the connection between the optical fiber 13 and the PLC chip 12 in this embodiment, the amplitude and Phase distortion is suppressed and connection loss is reduced. Here, "substantially the same refractive index" includes the same refractive index, and includes a refractive index to the extent that distortion of the amplitude and phase of light guided through the connection is suppressed.

Further, in this embodiment, since the connection interface between the optical fiber 13 and the PLC chip 12 has unevenness, the difference between the refractive index of the optical fiber 13 and the optical waveguide made of silica glass and the refractive index of the adhesive 18 causes Diffuse reflection occurs on the connection end face having unevenness. For example, when guided light enters the PLC chip 12 from the optical fiber 13, the diffusely reflected light enters the optical fiber 13 and becomes return light.

This return light can be suppressed by inclining the end face of the optical fiber 13 or the optical waveguide with respect to a plane perpendicular to the traveling direction of the guided light. The inclination angle of the slanted end surface may be set to such an angle that most of the diffusely reflected light is not coupled to the mode of the optical fiber 13 . Since the angle of inclination of the end face of an angled physical connector (APC) that assumes mirror polishing is 8°, it is desirable that the angle of inclination is within 10° with respect to the plane perpendicular to the traveling direction of guided light.

<Method for manufacturing optical components>
An example of a method for manufacturing the optical component 1 according to this embodiment will be described. Here, the connection between the fiber block 11 and the PLC chip 12 in the optical component 1 will be mainly described.

First, as shown in FIG. 3A, the fiber block 11 is produced by fixing and mounting the optical fiber 13 between the V-groove component 14 and the holding lid 15 .

Next, the end faces (area P in the drawing) of the optical fiber 13, the V-groove component 14, and the holding lid 15 in the fiber block 11 are polished.

At this time, a liquid mixture of abrasive grains (polishing liquid) is poured onto the polishing surface plate, and the fiber block 11 is supported by a jig and pressed against the polishing surface plate for polishing. First, the optical fiber 13, the V-groove component 14, and the end face (area P in the figure) of the holding lid 15 are polished so that they are flush with each other. Here, "flush" means that there are no steps between a plurality of surfaces and the surfaces are flat.

As each end surface becomes smoother (flat), the polishing liquid is replaced to reduce the grain size of the abrasive grains.

Next, the polishing of the fiber block 11 is stopped when the Ra of the surface becomes approximately the wavelength of the guided light (approximately 1 μm).

On the other hand, in the PLC chip 12, as shown in FIG. 3B, the glass plate 16 is attached to the connection end surface of the PLC chip 12 and the upper surface in the vicinity thereof.

Next, in the same manner as described above, the PLC chip 12 and the glass plate 16 are polished so that they are flush with each other. region).

Finally, the optical fiber 13 of the fiber block 11 is aligned with the waveguide of the PLC chip 12, and the connection end surface of the fiber block 11 and the connection end surface of the PLC chip 12 and the glass plate 16 are connected with an ultraviolet curing adhesive 18. (stick).

As described above, in the present embodiment, polishing is stopped before the mirror surface is obtained, so the fiber block 11 can be connected to the PLC chip 12 in a simpler process than the conventional polishing process.

In addition, since the other steps are the same as the conventional steps, the optical component according to this embodiment can be produced without using additional steps.

According to the optical component according to the present embodiment, each can be miniaturized without reducing the bonding strength between the fiber block and the PLC chip.

In the present embodiment, an example in which the entire connection end surfaces of the fiber block, PLC chip, and glass plate are uneven has been shown, but the present invention is not limited to this. If at least a part of the connecting end faces of the fiber block, PLC chip, and glass plate has unevenness, the bonding strength can be improved compared to the case where the entire connecting end face is mirror-polished. Here, it is desirable that the area of the uneven portion is 1/4 or more of the total area of the connecting end face.

<Second Embodiment>
An optical component according to a second embodiment of the present invention will be described with reference to FIGS. 4A and 4B.

<Configuration of optical components>
The optical component according to the present embodiment differs from that of the first embodiment in the irregularities on the connection end surface between the fiber block and the PLC chip. Other configurations are the same as those of the first embodiment.

As shown in FIG. 4A, on the connection end face of the fiber block 21 according to the present embodiment, the core and clad of the optical fiber 23 and the end faces in the vicinity thereof are mirror-polished (region R in the figure). The end face (area P1 in the drawing) and the lower portion of the end face of the V-groove component 24 (area P2 in the drawing) have irregularities.

On the other hand, in the connection end face of the PLC chip 22, the end face of the portion of the waveguide core 22_1 and the waveguide clad 22_2 is mirror-polished (region S in the drawing), and the end face of the glass plate 26 (region Q1 in the drawing). And the end face (Q2 region in the figure) of the Si substrate 22_3 has unevenness.

In this way, since the end faces of the core and the clad through which light is guided are mirror-polished, the phase and amplitude of the light emitted from the end faces are not distorted. Therefore, the connection loss does not increase even if the refractive index of the optical adhesive filled between the fiber block 21 and the PLC chip 22 is not set to about the refractive index of SiO2 (1.45).

As a result, the selection range of adhesives that can be applied to connections in optical components can be expanded. For example, an adhesive having a refractive index different from 1.45 and having excellent adhesion strength and adhesion reliability can be applied.

<Method for manufacturing optical components>
An example of a method for manufacturing the optical component 2 according to this embodiment will be described. Here, the connection between the fiber block 21 and the PLC chip 22 in the optical component 2 will be mainly described.

First, a fiber block 21 is produced in the same manner as in the first embodiment. Further, in the quartz-based PLC chip 22, a glass plate 26 is attached to the connection end surface of the PLC chip 22 and the upper surface in the vicinity thereof.

Next, the end faces of the optical fiber 23, the V-groove part 24, and the holding lid 25 in the fiber block 21 are mirror-polished. Also, the end surfaces of the PLC chip 22 and the glass plate 26 are mirror-polished.

Next, by sandblasting, unevenness is selectively formed on each end surface.

Specifically, first, the areas where the mirror-polished state remains are masked. Here, the core and the clad of the optical fiber 23 and the end face of the vicinity thereof (region R in FIG. 4A) are masked. In addition, the end faces (region S in FIG. 4B) of the waveguide core 22_1 and waveguide clad 22_2 of the PLC chip 22 are masked.

Next, the exposed portions (areas P1 and P2 in FIG. 4A) that are not masked on the end face of the fiber block 21 and the exposed portions that are not masked on the end faces of the PLC chip 22 and the glass plate 26 (regions P1 and P2 in FIG. 4B). Concavities and convexities are formed by spraying an abrasive mixed with compressed air onto the regions Q1 and Q2.

In this way, the part where the unevenness is formed is processed and formed after mirror-polishing the entire surface, so it is recessed from the mirror-polished part.

Finally, the optical fiber 23 of the fiber block 21 is aligned with the waveguide of the PLC chip 22, and the connection end surface of the fiber block 21 and the connection end surface of the PLC chip 22 and the glass plate 26 are connected with an ultraviolet curable adhesive ( stick).

Alternatively, a selective polishing method can be used in the step of forming unevenness on the end face of the PLC chip 22 .

Specifically, Si is selectively polished by polishing using a polishing liquid that does not react with SiO2 but reacts with Si. As a result, on the end face of the PLC chip 22, the SiO2 of the waveguide core 22_1 and the waveguide clad 22_2 can be kept in a mirror state, and only the end face of the Si substrate 22_3 can be uneven.

Thus, when the selective polishing method is used, unevenness is formed only on the end surface of the Si substrate 22_3, but the bonding strength can be improved compared to the case where the entire connection end surface is mirror-polished.

As described above, according to the present embodiment, unevenness can be selectively formed on the connection end face of the fiber block 21 and the connection end face of the PLC chip 22 and the glass plate 26 by a simple process, and the fiber block 21 can be connected to the PLC chip 22. Can connect.

In addition, the height HR of the mirror-polished portion (R area in FIG. 4A) on the end face of the fiber block 21 is about 100 μm. Moreover, the height HS of the mirror-polished portion (region S in FIG. 4B) of the end surfaces of the PLC chip 22 and the glass plate 26 is also about 100 μm.

On the other hand, on the end face of the fiber block 21, the heights HP1 and HP2 of the uneven portions (areas P1 and P2 in FIG. 4A) are each about 1 mm. Further, the heights HQ1 and HQ2 of the uneven portions (regions Q1 and Q2 in FIG. 4B) on the end surfaces of the PLC chip 22 and the glass plate 26 are about 1 mm, respectively.

As described above, since most of the end face of the fiber block 21 and the end faces of the PLC chip 22 and the glass plate 26 have unevenness, the same level of connection strength as the case where the entire surface has unevenness (first embodiment) can be obtained. have.

Although the embodiment of the present invention shows an example of connecting a PLC chip to a fiber block, it is not limited to this. Besides the PLC chip, for example, a silicon photonics (SiPh) chip may be used. Silicon photonics is configured using Si for the waveguide core and silica glass (SiO2) for the waveguide clad, etc., and the waveguide mode of the guided light is expanded by a tapered Si waveguide (SSC: Spot Size Converter). , is finally output from an input/output end made of SiO2 (there is no Si waveguide). In this way, the components connected to the fiber block may be waveguide type optical components whose input and output ends are made of SiO2.

In this embodiment, the end surface of the restraining lid 25 (area P1 in the drawing), the lower portion of the end surface of the V-groove component 24 (area P2 in the drawing), and the PLC chip 22 are connected to the connection end surface of the fiber block 21. An example in which the end surface of the glass plate 26 (area Q1 in the figure) and the edge surface of the Si substrate 22_3 (area Q2 in the figure) have unevenness has been shown, but the present invention is not limited to this.

In the present embodiment, the connection end surfaces of the core and the clad of the optical fiber 23 and the waveguide core 22_1 and the waveguide clad 22_2 of the PLC chip 22 are mirror-polished. If there is unevenness, the bonding strength can be improved as compared with the case where the entire connection end surface is mirror-polished. Here, it is desirable that the area of the uneven portion is 1/4 or more of the total area of the connecting end face.

In the embodiment of the present invention, an example in which the PLC chip is provided with an interferometric circuit has been shown, but the PLC chip is not limited to this, and may be provided with an optical circuit with other functions.

In the embodiments of the present invention, examples of the structure, dimensions, materials, etc., of each constituent part have been shown in the optical connection structure and optical component structure, manufacturing method, etc., but the present invention is not limited to this. Any material may be used as long as it exhibits the functions of the optical connection structure and the optical component and produces an effect.

The present invention can be applied to the connection of optical devices, especially optical parts, used in the fields of optical communication and sensing.

1 optical component 11 fiber block 12 PLC chip 13 optical fiber 14 V groove component 15 holding lid 16 glass plate 17 interference circuit 18 adhesive

Claims

a fiber block in which an optical fiber is mounted between the V-groove component and the holding lid;
a waveguide type optical component whose input and output ends are made of SiO2;
a glass plate disposed on the connection end surface of the waveguide optical component and on the upper surface near the connection end surface;
at least a portion of the connection end surface of the fiber block has unevenness,
at least a part of the connection end face of the waveguide type optical component has unevenness,
An optical component, wherein the fiber block and the waveguide type optical component are fixed with an adhesive filled between their connecting end faces.
2. The optical component according to claim 1, wherein at least a part of the connection end face of said glass plate has unevenness.
The optical fiber has a core and a cladding,
The waveguide-type optical component has a waveguide core and a waveguide clad,
3. The optical component according to claim 1, wherein light is guided through the core and the waveguide core.
4. The optical component according to claim 3, wherein the arithmetic mean roughness of the unevenness is from 1/10 to 10 times the wavelength of the light.
The optical component according to claim 3 or 4, characterized in that the connection end surface is inclined with respect to a plane perpendicular to the traveling direction of the light.
At least a portion of the core and clad end faces of the optical fiber at the connection end face of the fiber block, and at least a part of the core and clad portion of the optical waveguide component at the connection end face of the optical waveguide component. and has unevenness,
6. The optical component according to any one of claims 1 to 5, wherein the refractive index of the adhesive is approximately equal to the refractive index of the SiO2.
The end face of the core and clad of the optical fiber at the connection end face of the fiber block and the end face of the core and clad portion of the optical waveguide component at the connection end face of the optical waveguide component are mirror-polished. The optical component according to any one of claims 1 to 5, characterized by:
8. The optical component according to claim 7, wherein the uneven portion is recessed from the mirror-polished portion.