JP2002023004A - Optical coupling structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical coupling structure that facilitates optical coupling between an optical fiber and a waveguide through a little adjustment of the optical axis and that also improves mechanical strength of the joint part. SOLUTION: The base plate 20 of the optical waveguide is formed with a first total reflection surface 24 on the end at an inclination of 45 deg. to the optical axis direction of the waveguide 21. The optical fiber 10 is formed with a second total reflection surface 12 at an inclination of 45 deg. similarly to its optical axis direction. The optical fiber 10 is arranged along the upper face of the base plate 20 of the waveguide and fixed so that the center position of the second total reflection surface 12 comes immediately above that of the first total reflection surface 24 of the waveguide 21. The light waves L1 made incident to the optical fiber 10, after totally reflected on the second total reflection surface, enter the first total reflection surface 24 of the waveguide 21. Then, the light waves L1 are totally reflected on the first total reflection surface 24 and propagated to the waveguide 21. Thus, the optical fiber 10 and the waveguide 21 are optically coupled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical coupling structure, and more particularly, to a structure for optically coupling an optical fiber and an optical waveguide.

[0002]

2. Description of the Related Art Conventionally, to configure an optical communication system,
Various optical elements such as a light emitting element, a light receiving element, an optical switch, an optical splitter / coupler, and an optical multiplexer / demultiplexer are required, and these optical elements need to be optically coupled. Early optical communication systems were configured by combining these optical elements with optical components such as lenses and prisms. However, an optical communication system in which optical components such as a lens and a prism are mounted is large in size, expensive, and it is difficult to secure mechanical stability required for the optical communication system. Therefore, it has been considered that a plurality of optical elements disposed on a substrate are optically coupled by an optical waveguide also provided on the substrate. This optical waveguide is made of a substance having a large refractive index, and light propagates through the inside. The optical waveguide is
Functions equivalent to various optical elements, such as forming an optical branching coupler by branching a part, or forming a lens or the like by changing the thickness, can be provided. Therefore, the optical waveguide is an optical component that has a possibility of multifunctionality and can cope with miniaturization, cost reduction and high performance of an optical circuit. On the other hand, as an optical communication transmission line, an optical fiber is usually used, so that the optical fiber and the optical waveguide are
It needs to be optically coupled. As a method of optically coupling an optical fiber and an optical waveguide, the end face coupling method is conventionally considered to be the most effective in practical use because of high efficiency and a simple structure.

FIG. 13 is a diagram showing an example of an optical coupling structure between an optical fiber and an optical waveguide connected by a conventional end face coupling method. 13A shows a view from above, and FIG. 13B shows a cross section e-
FIG. 4 shows a cross-sectional view of e ′ as viewed from a direction f. The optical coupling structure by the end face coupling method includes an optical fiber 100 mounted on a fiber support 60 and an optical waveguide substrate 20.
0. The optical fiber 100 includes a core 101 disposed at the center thereof and a clad 103 surrounding the core 101. The optical waveguide substrate 200 includes an optical waveguide 201 having a rectangular cross section provided thereon and a cladding layer 202 surrounding the optical waveguide 201. The end face of the core 101 of the optical fiber 100 is connected to directly face the end face of the optical waveguide 201. The optical fiber 100 is fixed to the optical waveguide substrate 200 with a suitable adhesive (not shown). Each end face of the core 101 and the optical waveguide 201 is in a state perpendicular to the traveling direction of the guided light. Since the optical waveguide 201 and the core 101 are in direct contact with each other, the guided light of the core 101 is directly
The light enters the optical waveguide 201. In order to further increase the coupling efficiency, a coupling lens is provided between the optical fiber 100 and the optical waveguide 201 so that the light emitted from the core 101 is transmitted to the optical waveguide 2.
In some cases, an optical coupling method is used in which the light is efficiently incident on the light emitting device 01.

[0004]

In the above-mentioned end face joining method, as shown in FIG. 13, the end face of the optical waveguide 201 and the core 101 of the optical fiber 100 are directly joined. Therefore, when considering the optical waveguide 201 as a reference, a total of four directions of the X-axis (horizontal) direction, the Y-axis (vertical) direction, the θx (X-axis rotation) direction, and the θy (Y-axis rotation) direction shown in FIG. It is necessary to adjust the optical axis of the optical fiber 100 with respect to the direction (hereinafter, the direction of the optical axis adjustment is described as the direction of adjusting the optical axis of the optical fiber with reference to the optical waveguide). The core 10
1 is on the order of μm, the optical waveguide 20
It is difficult to perform an accurate joining operation between the optical fiber 100 and the optical fiber 100, the operation efficiency is low, and it is not suitable for mass production. The optical fiber 100 is fixed to the optical waveguide substrate 200 with an appropriate adhesive (not shown). However, the optical fiber 100
Since the bonding area of the optical fiber 100 is small, the bonding strength of the optical fiber 100 is low, and the optical coupling portion between the optical fiber 100 and the optical waveguide substrate 200 may have insufficient mechanical stability.

On the other hand, for example, Japanese Patent No. 2946434 discloses another connection method. FIG. 14 is a side sectional view showing an example of an optical coupling structure between an optical waveguide and an optical fiber disclosed in Japanese Patent No. 2946434. Figure 1
In 4, the optical coupling structure includes optical fibers 100a and 100b and an optical waveguide substrate 300.
The optical fibers 100a and 100b are respectively composed of cores 101a and 101b arranged at the center and cores 1a and 1b.
01a and 101b. The optical waveguide substrate 300 includes an optical waveguide 301 having a rectangular cross section provided thereon, and a cladding layer 302 and a buffer layer 303 provided below the optical waveguide 301. The optical waveguide 3
01 is exposed to the outside. Optical fiber 100
The end faces of the cores 101a and 101b are cut obliquely, and the cut end faces of the cores 101a and 101b are connected to the upper surface of the optical waveguide 301. The optical fibers 100a and 100b are fixed to the optical waveguide substrate 300 with a suitable adhesive (not shown). According to this method, the X-axis (horizontal) direction, the θx (X-axis rotation) direction, the θy
(Y-axis rotation) direction and θz (Z-axis rotation) direction
As for the direction, the optical axes of the optical fibers 100a and 100b need to be adjusted. However, in the above optical coupling structure, the surface area of the end faces of the optical fibers 100a and 100b is large, so that the adjustment of the optical axes of the optical fibers 100a and 100b in the θx direction is eased as compared with the above-mentioned end face coupling method. Also, the optical fibers 100a and 1
Since the bonding area between the optical fiber 100a and the optical waveguide substrate 300 is increased, the bonding strength between the optical fibers 100a and 100b and the optical waveguide substrate 300 is improved.

However, in this conventional example, since the optical fibers 100a and 100b are connected on the optical waveguide 301, supporting components for supporting the optical fibers 100a and 100b, respectively, must be mounted on the optical waveguide 301. No. Further, the support component needs an optical fiber mounting surface corresponding to the mounting angle of each of the optical fibers 100a and 100b, and has a complicated shape. Therefore, it was difficult to attach and manufacture the above-mentioned supporting parts. In addition, when the above components are not attached, gravity and the like always act on the optical fibers 100a and 100b, so that a mechanical load is likely to be applied, and the optical coupling portion has an unstable structure. Also,
From the optical waveguide 301 to the optical fibers 100a and 100b
Since the light wave propagating to the optical waveguide 301 has a branching structure, only a part of the light wave guided to the optical waveguide 301 oozes out, and the optical coupling efficiency between the optical fibers 100a and 100b and the optical waveguide 301 is not good. Also, the optical fiber 100a
The angles of the end cuts of the optical fibers 100a and 100b are uniquely determined by the propagating wavelength.
No. 0b could not optically couple a plurality of wavelengths. Further, at the optical junction between the optical fibers 100a and 100b and the optical waveguide 301, the position of the end face of the optical fiber,
If the angle or the like is not set accurately, mode mismatch may occur. Further, since the upper part of the optical waveguide 301 is exposed to the outside, the light wave propagating in the optical waveguide 301 has an imbalance in light intensity distribution and optical waveguide mode distribution. Therefore, the optical waveguide 301 exposed to the outside is a cause of promoting the mode mismatch of the optical coupling portion.

Therefore, it is an object of the present invention to easily and optically couple an optical fiber and an optical waveguide with a small optical axis adjustment, to reduce optical coupling loss, and to connect an optical fiber to an optical waveguide substrate. It is an object of the present invention to provide an optical coupling structure that also improves the mechanical strength of the part.

[0008]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the present invention has the following features. A first invention is a structure for optically coupling two different types of light propagation media to each other, comprising: an optical waveguide substrate having an inclined surface at an end; First on the same plane as the inclined surface
An optical waveguide having a total reflection surface, and an optical fiber disposed on the optical waveguide substrate and having a second total reflection surface at an end thereof, the mutual positional relationship between the optical waveguide and the optical fiber, At least a portion of the light wave propagating in the optical waveguide and totally reflected by the first total reflection surface intersects the second total reflection surface, and propagates in the optical fiber to be reflected by the second total reflection surface. It is characterized in that the positional relationship is adjusted so that at least a part of the totally reflected light wave intersects the first total reflection surface.

According to the first aspect, when the directions of adjusting the optical axis of the optical fiber and the optical waveguide are considered as coordinate axes in three directions, that is, the horizontal direction, the vertical direction, and the optical axis direction, the optical fiber becomes an optical waveguide substrate. Since they are arranged along the upper side, it is not necessary to adjust the optical axis of the optical fiber in the vertical axis direction and the horizontal axis rotation direction. Further, even if the optical fiber is rotated in the vertical axis rotation direction about the center of the second total reflection surface as an axis, the optical coupling state of the optical fiber with the optical waveguide does not change. Becomes unnecessary. As a result, the optical axis adjustment of the optical fiber in a total of four directions, which was required in the optical coupling structure by the conventional end face connection method, is performed in three directions of the horizontal axis, the optical axis, and the optical axis rotation. Adjustment is enough. Therefore, the efficiency of the operation of adjusting the optical axis between the optical waveguide and the optical fiber is improved. In addition, since the optical fiber is arranged along the upper surface of the optical waveguide substrate, the mechanical stability of the optical coupling part is improved. Moreover, since the total reflection characteristic capable of reflecting light waves of all wavelengths is used, it is necessary to consider the inclination angles of the first total reflection surface and the second total reflection surface according to the wavelength of the propagating light wave. There is no. In addition, the optical coupling portion does not cause the optical waveguide mode mismatch.

A second invention is an invention according to the first invention, wherein the optical waveguide is surrounded by a cladding layer.

According to the second aspect, since the optical waveguide is surrounded by the cladding layer, the light wave propagates through the optical waveguide without generating an imbalance in the light intensity distribution and the optical waveguide mode distribution. be able to.

A third invention is an invention according to the first invention, wherein the angle α of the first total reflection surface with respect to the optical axis direction of the optical waveguide and the second total angle with respect to the optical axis direction of the optical fiber. The angle β of the reflecting surface is set by a relational expression α + β ≒ 90 °.

According to the third aspect, the light wave propagated from the optical fiber to the optical waveguide is incident substantially parallel to the optical axis direction of the optical waveguide. Can be combined. Further, since the light wave propagated from the optical waveguide to the optical fiber is also incident substantially parallel to the optical axis direction of the optical fiber, the optical fiber and the optical waveguide can be efficiently optically coupled.

A fourth invention is an invention according to the third invention, wherein the angle α of the first total reflection surface is set at 45 ° and the angle β of the second total reflection surface is 45 °. It is characterized by being set.

According to the fourth aspect, the light wave passes through the cladding of the optical fiber and the cladding layer of the optical waveguide substrate perpendicularly, so that the loss due to reflection at each layer can be reduced. Further, since the distance between the first total reflection surface and the second total reflection surface is shortest, the loss due to the spread of the light wave between the first total reflection surface and the second total reflection surface is minimized. Can be limited. Therefore, the optical fiber and the optical waveguide can be optically coupled with the highest efficiency.

A fifth invention is the invention according to the first invention, wherein the optical fiber is fixed on the optical waveguide substrate with an adhesive.

According to the fifth aspect, the optical fiber is arranged along the upper surface of the optical waveguide substrate, and is fixed with an adhesive. Therefore, the mechanical strength between the optical fiber and the optical waveguide substrate is improved.

A sixth invention is an invention according to the fifth invention, wherein the adhesive has the same refractive index as the cladding layer,
A space through which a light wave propagating between the optical fiber and the optical waveguide passes is filled with an adhesive.

According to the sixth aspect of the present invention, the space through which the light wave entering the optical waveguide from the optical fiber or the light wave entering the optical fiber from the optical waveguide passes has the same refractive index as the cladding layer. Filled with. Therefore, the light wave propagates through the same refractive index material, and does not suffer loss due to emission to the outside. Therefore, the optical coupling efficiency between the optical fiber and the optical waveguide is improved.

A seventh invention is an invention according to the first invention, wherein a groove is formed on the optical waveguide substrate, and the optical fiber is arranged along the groove. I do.

According to the seventh aspect, the optical fiber is disposed along the groove formed on the optical waveguide substrate in advance.
Therefore, the optical axis adjustment of the optical fiber in a total of three directions, which is required in the first invention, does not require the optical axis adjustment in the horizontal axis direction. Therefore, the efficiency of the operation of adjusting the optical axis of the optical fiber and the optical waveguide is further improved as compared with the first aspect.

An eighth invention is the invention according to the first or seventh invention, wherein the optical fiber is provided with an alignment surface for fixing a positional relationship between the optical waveguide and the optical fiber. It is characterized by.

According to the eighth aspect, the optical fiber is positioned on the optical waveguide substrate after being aligned by the jig for aligning the alignment surface of the optical fiber and the end of the optical waveguide substrate on the same plane. Be placed. Therefore, the optical axis adjustment of the optical fiber in a total of three directions, which is required in the first invention, does not require the adjustment of the optical axis in the optical axis direction. Therefore, the efficiency of the operation of adjusting the optical axis of the optical fiber and the optical waveguide is further improved as compared with the first aspect.

A ninth invention is an invention according to the first or seventh invention, wherein an alignment surface for fixing a positional relationship between the optical waveguide and the optical fiber is formed on the optical waveguide substrate. It is characterized by the following.

According to the ninth aspect, the optical fiber is positioned on the optical waveguide substrate after being aligned by the jig for aligning the alignment surface of the optical waveguide substrate with the end of the optical fiber on the same plane. Be placed. Therefore, the optical axis adjustment of the optical fiber in a total of three directions, which is required in the first invention, does not require the adjustment of the optical axis in the optical axis direction. Therefore, the efficiency of the operation of adjusting the optical axis of the optical fiber and the optical waveguide is further improved as compared with the first aspect.

A tenth invention is an invention according to the first invention, wherein the positional relationship between the optical fiber and the optical waveguide substrate is such that the light intensity at which the optical fiber and the optical waveguide are optically coupled is:
It is characterized in that the positional relationship is adjusted so as to provide an optimal light reduction amount.

According to the tenth aspect, by reducing the area where the optical fiber and the optical waveguide are optically coupled, the light intensity at which the optical fiber and the optical waveguide are optically coupled can be reduced. . That is, the positional relationship between the first total reflection surface and the second total reflection surface is changed,
The optical axis is adjusted when the optimum light intensity reduction amount is reached.
Therefore, after the optical axis of the optical fiber and the optical waveguide are adjusted to the optimum amount of reduction in light intensity, the optical fiber is disposed on the surface of the optical waveguide substrate, whereby an optical coupling structure having an optical attenuation function is provided. realizable.

An eleventh invention is an invention according to the first invention, further comprising a movable means for moving the optical fiber in an arbitrary direction with respect to the optical waveguide substrate.

According to the eleventh aspect, the optical fiber is moved by an arbitrary distance with respect to the optical waveguide, and the moving position of the optical fiber is controlled. Therefore, the amount of decrease in light intensity at which the optical fiber and the optical waveguide are optically coupled can be arbitrarily adjusted. Therefore, by controlling the position of the optical fiber so that the light intensity at which the optical fiber and the optical waveguide are optically coupled is the optimal amount of reduction of the light intensity, an optical coupling structure having a variable optical attenuation function is provided. realizable.

A twelfth invention is an invention according to the first invention, wherein another optical waveguide substrate is bonded to the inclined surface of the optical waveguide substrate via a semi-transmissive reflection film, Another optical waveguide substrate is characterized in that another optical waveguide that is optically coupled to the optical waveguide is formed.

A thirteenth invention is an invention according to the first invention, wherein an optical fiber is bonded to the optical waveguide substrate via a semi-transmissive reflection film on an inclined surface. .

A fourteenth invention is an invention according to the first invention, wherein a light receiving element is joined to the optical waveguide substrate via a semi-transmissive reflection film on an inclined surface. .

According to the twelfth to fourteenth aspects, another optical waveguide substrate, an optical fiber, or a light receiving element is bonded to the optical waveguide substrate via the semi-transmissive reflection film on the inclined surface. Since the semi-transmissive reflective film splits the light wave in the straight traveling direction and the total reflection direction, an optical coupling structure having a light branching function can be realized.

A fifteenth invention is an invention according to the first invention, wherein another optical waveguide substrate is bonded to the optical waveguide substrate via a wavelength separation filter on the inclined surface. Another optical waveguide optically coupled to the optical waveguide is formed on the optical waveguide substrate.

A sixteenth invention is a invention according to the first invention, wherein an optical fiber is bonded to the inclined surface of the optical waveguide substrate via a wavelength separation filter.

A seventeenth invention is an invention according to the first invention, wherein a light receiving element is joined to the optical waveguide substrate via a wavelength separation filter on an inclined surface.

According to the fifteenth to seventeenth aspects, another optical waveguide substrate, an optical fiber, or a light receiving element is joined to the optical waveguide substrate via the wavelength separation filter on the inclined surface. The wavelength separation filter allows light waves of wavelengths that can pass through to go straight and totally reflects light waves of other wavelengths, so that an optical coupling structure having an optical demultiplexing function can be realized.

An eighteenth invention is an invention according to the first invention, wherein the optical waveguide substrate having the inclined surface is formed by press molding using a mold provided with a predetermined inclination angle. It is characterized by.

According to the eighteenth aspect, an inclined surface having a predetermined inclination angle is provided in advance in a mold of the optical waveguide substrate, and the optical waveguide substrate material is put into the mold and press-molded. Therefore, the inclined surface of the optical waveguide substrate can be easily formed.

A nineteenth invention is an invention according to the second invention, wherein the upper clad layer of the optical waveguide is formed by dip coating, and the inclined surface of the optical waveguide substrate is formed by dip coating. And a protection film is formed at the same time.

According to the nineteenth aspect, the clad layer above the optical waveguide is formed on the optical waveguide substrate having the inclined surface formed in advance by dip coating. for that reason,
A cladding layer is also formed on the inclined surface at the same time. Therefore, it is possible to form a protective film on the inclined surface of the optical waveguide substrate without increasing the number of operation steps, and by this protective film, it is possible to prevent adhesion of foreign matter and dew condensation on the first total reflection surface. .

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 to 3
FIG. 1 is a diagram illustrating an optical coupling structure according to a first embodiment of the present invention. FIG. 1A is a front view of the optical coupling structure according to the first embodiment, and FIG. 1B is a side view of the optical coupling structure. FIG. 2 shows a cross section aa ′ of FIG.
It is sectional drawing seen from the b direction. FIG. 3 is a cross-sectional view of the cross section ii ′ of FIG. Hereinafter, the first embodiment will be described with reference to FIGS.

In FIG. 1, the optical coupling structure according to the first embodiment includes an optical fiber 10 and an optical waveguide substrate 20. The optical fiber 10 is bonded to the optical waveguide substrate 20 with an adhesive 70.
Fixed at. The optical fiber 10 includes a core 11 disposed at the center thereof, and a clad 13 surrounding the core 11. In FIG. 2, the optical waveguide substrate 20 includes an optical waveguide 21 having a rectangular cross section provided thereon, a cladding layer 22 surrounding the optical waveguide 21, and a buffer layer 23. The end of the optical waveguide substrate 20 is obliquely cut, and as a result, the optical waveguide substrate 20 has the first total reflection surface 24. The first total reflection surface 24 is cut at an angle α with respect to the optical axis direction of the optical waveguide 21.
α is set at 45 °. The end face of the optical fiber 10 is obliquely cut, and as a result, the second total reflection surface 1 is cut.
2 is provided. The second total reflection surface 12 is cut at an angle β with respect to the optical axis direction of the optical fiber 10, and is set at β = 45 ° here.

Next, a method of adjusting the optical axis of the optical fiber 10 will be described. In FIG. 1, the optical fiber 10 is arranged along the upper surface of the optical waveguide substrate 20 and keeps a line contact with the optical waveguide substrate 20. In FIG. 2, the optical fiber 10 is arranged such that the second total reflection surface 12 is at an angle of 45 ° with respect to the upper surface of the optical waveguide substrate 20, and the second total reflection surface 12 has a + Y axis. It is arranged so as to face the direction (that is, the direction opposite to the optical waveguide substrate 20). That is, the optical axis of the optical fiber 10 is adjusted in the θz (Z-axis rotation) direction. Further, the optical fiber 10 has a second
Are arranged so that the center position of the total reflection surface 12 is just above the center position of the first total reflection surface 24 of the optical waveguide 21.
That is, in the optical fiber 10, the center position of the second total reflection surface 12 and the center position of the first total reflection surface 24 of the optical waveguide 21 correspond to the X axis (horizontal) and the Z axis (optical axis). The optical axis is adjusted so that the directions match. Thereafter, the optical fiber 10 is fixed to the optical waveguide substrate 20 with an adhesive 70 having the same refractive index as the clad layer. An acrylic UV curable resin or an epoxy UV curable resin whose refractive index can be adjusted is used as the adhesive 70.

Next, the propagation of the light wave in the first embodiment will be described. 2 and 3, a light wave L1 incident on the optical fiber 10 and propagating through the core 11 is shown.
Are totally reflected by the second total reflection surface 12 of the core 11. Thereafter, the light wave L1 passes through the clad 13, the adhesive 70, and the clad layer 22, and passes through the first total reflection surface 24 of the optical waveguide 21.
Incident on. Next, the light wave L <b> 1 is totally reflected by the first total reflection surface 24 and propagates to the optical waveguide 21. In this way,
The optical fiber 10 and the optical waveguide 21 are optically coupled.

Here, a cladding layer 22 is provided between the optical fiber 10 and the optical waveguide 21 on the optical waveguide substrate 20.
Is provided. Compared to the state where the optical waveguide 21 is exposed to the outside, the clad layer 22 makes the light intensity distribution and the optical waveguide mode distribution of the light wave propagating through the optical waveguide 21 uniform.

Incidentally, as shown in FIG.
And the optical waveguide substrate 20 are in line contact with each other. For this reason,
Between the core 11 and the optical waveguide 21, the light wave L1 is
It will pass through the outside air. Therefore, at least the space through which the light wave L1 passes is completely filled with the adhesive 70 having the same refractive index as the clad layer. Therefore, the light wave L1 propagates through the same refractive index material, and does not suffer loss due to emission to the outside.

In the conventional end face coupling method shown in FIG. 13 described above, the optical fiber is used in a total of four directions of the X-axis direction, the Y-axis (vertical) direction, the θx (X-axis rotation) direction, and the θy (Y-axis rotation) direction. Optical axis adjustment was required. However, in the first embodiment, the optical fiber 10 is arranged along the upper surface of the optical waveguide substrate 20. Therefore, as shown in FIG.
The optical axis adjustment of the optical fiber 10 in the axial direction and the θx direction
It is unnecessary because it is uniquely determined. Further, even if the optical fiber 10 is rotated in the θy direction with the center of the second total reflection surface 12 as the rotation axis, the optical coupling state between the optical fiber 10 and the optical waveguide 21 does not change. Therefore, the optical fiber 1 in the θy direction
The optical axis adjustment of 0 becomes unnecessary. As a result, the optical axis adjustment direction of the optical fiber 10 in the first embodiment can be in three directions of the X axis, the Z axis, and the θz direction.
The work of adjusting the optical axis between the optical waveguide and the optical waveguide 21 becomes easy.

The side surfaces of the optical fiber 10 are arranged along the optical waveguide substrate 20, and both surfaces are fixed with an adhesive 70. Accordingly, the connection between the optical fiber 10 and the optical waveguide substrate 20 has increased stability and mechanical strength.

Further, since the total reflection characteristic capable of reflecting light waves of all wavelengths is used, the first total reflection surface 24 and the second total reflection surface 1 are changed depending on the wavelength of the propagating light wave.
There is no need to consider the angle of inclination with 2. Further, since the characteristic of totally reflecting the light wave is used, no mode mismatch occurs at the optical coupling portion between the optical fiber 10 and the optical waveguide 21, and the optical coupling efficiency is high. Further, the optical waveguide 21 is surrounded by the cladding layer 22. Therefore, the light wave can propagate through the optical waveguide 21 without causing an imbalance in the light intensity distribution and the optical waveguide mode distribution.

By the way, considering that the incident angle and the reflection angle are equal in relation to the reversibility of light and the incident angle and the reflection angle according to Snell's law, the optical waveguide 21 can be set on the light wave incident side. It goes without saying that the present invention can be applied with the same structure.

On the other hand, in the first embodiment, the optical fiber 10 is disposed so as to be parallel to the optical waveguide 21.
The optical fiber 10 and the optical waveguide 21 need not be parallel. Hereinafter, the optical fiber 10 and the optical waveguide 21
The optical coupling structure in the case of not being parallel will be described.

FIG. 4 is a diagram showing an optical coupling structure when the optical fiber 10 and the optical waveguide 21 are optically coupled at an angle γ. FIG. 4A is a perspective view of the optical coupling structure with a part thereof cut away, and FIG.
It is the top view of the said optical coupling structure seen from the v direction of (a). In FIG. 4B, components other than the optical fiber 10 and the optical waveguide 21 are omitted to simplify the description. Hereinafter, the optical structure will be described with reference to FIG.

As described above, the first total reflection surface 24 of the optical waveguide 21 has an angle α = α with respect to the optical axis direction of the optical waveguide 21.
Inclined at 45 °. Further, the second total reflection surface 12 of the optical fiber 10 is inclined at an angle β = 45 ° with respect to the optical axis direction of the optical fiber 10. In the first embodiment, since the optical fiber 10 is arranged parallel to the optical waveguide 21, the optical fiber 10 is arranged immediately above the optical waveguide 21. In FIG. 4, the optical fiber 10 is the optical waveguide 2
1 and at an angle γ. Also, in the optical fiber 10, similarly to the first embodiment, the center position of the second total reflection surface 12 is the same as the first total reflection surface 24 of the optical waveguide 21.
Are arranged directly above the center position of the. That is, the optical fiber 10 is arranged in a state where the optical fiber 10 is rotated by an angle γ in the θy direction from the position of the first embodiment with the center of the second total reflection surface 12 as an axis. The other parts are the same as those of the optical coupling structure according to the first embodiment. Therefore, the same parts are denoted by the same reference numerals and detailed description thereof will be omitted.

Next, the propagation of light waves will be described. FIG.
In the same manner as in the first embodiment,
Is totally reflected by the second total reflection surface 12. After that, the light wave L1 enters the first total reflection surface 24 of the optical waveguide 21. Next, the light wave L <b> 1 is totally reflected by the first total reflection surface 24 and propagates through the optical waveguide 21. Thus, the optical fiber 10 and the optical waveguide 21 are optically coupled. As described above, the present invention can be applied even when the optical fiber 10 and the optical waveguide 21 are not parallel.

In the optical coupling structure according to the first embodiment, the angle α of the first and second total reflection surfaces 24 and 12
And β were both set at 45 °. Therefore, the light wave L
1 is the clad 13 of the optical fiber 10 and the adhesive 70
And the cladding layer 21 of the optical waveguide substrate 20, so that the loss due to reflection at each layer can be reduced. Further, the distance between the first total reflection surface 24 and the second total reflection surface 12 is also minimized. Therefore, the loss due to the spread of the light wave L1 between the first total reflection surface 24 and the second total reflection surface 12 can be minimized. Therefore, when the angles α and β are 4
By setting the angle to 5 °, the optical fiber 10 and the optical waveguide 21
The optical junction with can be made as highly efficient as possible.

However, if the above advantages are not expected, the first and second total reflection surfaces 24 and 12
May be set to an angle other than 45 °. The optical coupling structure when the angles α and β of the first and second total reflection surfaces 24 and 12 are set to an angle other than 45 ° will be described below. FIG.
FIG. 3 is a detailed side sectional view of the optical coupling structure when the angle is set. Since the component configuration is the same as that of the above-described embodiment of FIG. 2, the same components are denoted by the same reference numerals, and detailed description thereof will be omitted. Hereinafter, with reference to FIG. 5, an optical coupling structure when the angle is set will be described.

In FIG. 5, the angle α of the first total reflection surface 24 is such that the refractive index of the optical waveguide 21 is n1, and the refractive index of the outside air is n.
Assuming that 2, cos α> n2 / n1 is set to a value that satisfies the following condition. Further, the second total reflection surface 12
Is set to a value satisfying cos β> n2 / n3, where n3 is the refractive index of the core 11. Further, the relationship between the angles α and β is α + β ≒ 90 °. The angles α and β are set so as to satisfy such a conditional expression.

Next, a method of adjusting the optical axis of the optical fiber 10 and the optical waveguide 21 will be described. In FIG. 5, the optical fiber 10 is arranged along the upper surface of the optical waveguide substrate 20 and keeps a line contact with the optical waveguide substrate 20.
The optical fiber 10 is disposed such that the second total reflection surface 12 is at an angle β with respect to the upper surface of the optical waveguide substrate 20 and the second total reflection surface 12 is in the + Y axis direction (that is, (The direction opposite to the waveguide substrate 20). Next, the optical fiber 10 has its second total reflection surface 12
Is located at a position displaced in the Z-axis direction by a distance w from directly above the center position of the first total reflection surface 24 of the optical waveguide 21. Here, assuming that the radius of the optical fiber 10 is r and the distance from the upper surface of the optical waveguide substrate 20 to the center of the optical waveguide 21 is h, the distance w is w = (r + h) / tan2α. However, the optical fiber 10 is shifted in the -Z-axis direction when the distance w is a positive value, and + when the distance w is a negative value.
They are displaced in the Z-axis direction.

In FIG. 5, a light wave L 1 that has entered the optical fiber 10 and has propagated through the core 11 is totally reflected by the second total reflection surface 12 of the core 11. After that, the light wave L1 is
After passing through the clad 13 and the clad layer 22, the optical waveguide 2
The first light enters the first total reflection surface 24. Next, the light wave L1
Are totally reflected by the first total reflection surface 24 and propagate to the optical waveguide 21. Thus, the optical fiber 10 and the optical waveguide 2
1 is optically coupled.

As described above, the first and second total reflection surfaces 2
Even when the angles α and β of 4 and 12 are set to angles other than 45 °, the present invention can be applied by adjusting the optical axis of the optical fiber 10 and the optical waveguide 21 as described above.

On the other hand, in the first embodiment, the optical fiber 1
In order to maximize the efficiency of optical coupling between the optical waveguide 10 and the optical waveguide 21, the optical fiber 10 is arranged such that the center position of the second total reflection surface 12 is the same as that of the first total reflection surface 24 of the optical waveguide 21. It was arranged just above the center position. Here, the optical fiber 1
The light intensity at which the optical fiber 10 and the optical waveguide 21 are optically coupled may be reduced by reducing the area where the optical waveguide 10 and the optical waveguide 21 are optically coupled. That is, the first
The positional relationship between the total reflection surface 24 and the second total reflection surface 12 is
The optical fiber 10 is moved in the X axis, the Z axis, or the θz direction to change the position from the position immediately above. Then, the optical fiber 10 is disposed at the position where the optimum light intensity reduction amount is obtained. As described above, after the optical axis of the optical fiber 10 and the optical waveguide 21 is adjusted to the optimal light intensity reduction amount,
The optical fiber 10 is fixed to the optical waveguide substrate 20 by the method described above, so that an optical coupling structure having an optical attenuation function can be realized.

Further, means for moving the optical fiber 10 by an arbitrary distance (for example, a stepper with a motor, a magnet,
(Not shown) and control means (not shown). That is, the optical fiber 10 is moved by an arbitrary distance with respect to the optical waveguide 21, and the moving position of the optical fiber 10 is controlled. Thus, the amount of decrease in light intensity at which the optical fiber 10 and the optical waveguide 21 are optically coupled can be arbitrarily adjusted. Thus, the optical fiber 10
By controlling the position of the optical fiber 10 so that the light intensity at which the light is optically coupled to the optical waveguide 21 is the optimum light intensity reduction amount, an optical coupling structure having a variable light attenuation function can be realized. .

(Second Embodiment) FIGS. 6 to 8 are views showing an optical coupling structure according to a second embodiment of the present invention. FIG. 6A is a front view of the optical coupling structure according to the second embodiment, and FIG. 6B is a side view of the optical coupling structure. FIG. 7 is a cross-sectional view of the cross section cc ′ of FIG. FIG. 8 shows the optical coupling structure.
It is the side view which showed the positioning method by a jig. Hereinafter, the second embodiment will be described with reference to FIGS.

In FIG. 6, in the second embodiment, an alignment surface 14 is formed at the tip of the second total reflection surface 12 of the optical fiber 10. In FIG. 8, a jig 80 is used for the optical coupling structure. The other components are the same as those of the first embodiment, and therefore, the same components are denoted by the same reference characters and will not be described in detail.

Next, the alignment surface 14 of the optical fiber 10 will be described. In FIG. 7, the tip of the second total reflection surface 12 of the optical fiber 10 is cut by the length s. Thus, an alignment surface 14 is formed at the tip of the optical fiber 10. The alignment surface 14 is provided to make the tip g of the first total reflection surface 24 and the alignment surface 14 coincide with each other on the same plane, thereby making it unnecessary to adjust the optical axis of the optical fiber 10 in the Z-axis direction. It is the face that was done. Therefore, the length s is equal to the alignment surface 1
The optical fiber 10 is set so that the optical axis of the optical fiber 10 is adjusted in the Z-axis direction when the tip 4 and the tip end g are aligned on the same plane. Here, assuming that the radius of the optical fiber 10 is r and the distance from the upper surface of the optical waveguide substrate 20 to the center of the optical waveguide 21 is h, the length s is: s = | (r / sin2β) − (h / sin2α) | When both the angles α and β are 45 °, s = | r−h |. Here, if r> h, the optical fiber 10
The tip of the second total reflection surface 12 is cut by polishing or the like by the length s calculated in this manner. Note that r <h
The case will be described later.

Next, the optical fiber 10 and the optical waveguide substrate 20
The method of positioning with will be described. In FIG.
The optical fiber 10 is arranged along the upper surface of the optical waveguide substrate 20. Next, the alignment surface 14 and the tip end g of the first total reflection surface 24 are made to coincide with the surface 81 of the jig 80 on the same plane by matching them in the Z-axis direction.
After that, the optical fiber 10 is connected to X as in the first embodiment.
The optical axis is adjusted in each direction of the axis and θz, and the optical axis is fixed to the optical waveguide substrate 20 with the adhesive 70.

Here, the length s is set so that the optical axis of the optical fiber 10 is adjusted in the Z-axis direction when the alignment surface 14 and the tip end g are made to coincide on the same plane. Therefore, when the alignment surface 14 and the tip end g are aligned on the same plane, the optical axis adjustment of the optical fiber 10 in the Z-axis direction becomes unnecessary. As a result, a total of 3 in the X-axis, the Z-axis and the θz direction required in the first embodiment are obtained.
The optical axis of the optical fiber 10 in the directions is adjusted in two directions, that is, the X axis and the θz direction. Therefore, the optical fiber 10
The work of adjusting the optical axis of the optical waveguide 21 and the optical waveguide 21 is easier than in the first embodiment.

In the above description, an example is shown in which the alignment surface 14 is provided on the second total reflection surface 12 of the optical fiber 10 on condition that r> h. On the other hand, when r <h, the length s is derived by the same calculation formula as described above, but the alignment surface is formed on the optical waveguide substrate 20 side. That is, in the optical waveguide substrate 20, the tip portion of the first total reflection surface 24 is cut perpendicularly to the optical waveguide 21 by the length s by polishing or press molding, and as a result, an alignment surface is provided. The optical fiber 10 is arranged along the upper surface of the optical waveguide substrate 20. Next, the front end of the second total reflection surface 12 and the alignment surface provided on the optical waveguide substrate 20 are aligned on the same plane on the surface 81 of the jig 80 in the Z-axis direction.
Thereafter, the optical fiber 10 is, like the first embodiment,
The optical axis is adjusted in each of the X-axis and θz directions, and is fixed to the optical waveguide substrate 20 with an adhesive 70. Thus, r
Even in the case of <h, it is not necessary to adjust the optical axis of the optical fiber 10 in the Z-axis direction.

(Third Embodiment) FIG. 9 and FIG.
It is a figure showing the optical coupling structure concerning a 3rd embodiment of the present invention. FIG. 9 is a side view of the optical coupling structure according to the third embodiment. FIG. 10 is a detailed front view of the optical coupling structure. Hereinafter, the third embodiment will be described with reference to FIGS. 9 and 10.

9 and 10, a groove 25 is provided above the optical waveguide substrate 20 at a portion where the optical fiber 10 and the optical waveguide substrate 20 are in line contact. Otherwise, the second embodiment is the same as the first embodiment, and therefore, the same components are denoted by the same reference characters and will not be described in detail.

Next, the groove 25 provided in the optical waveguide substrate 20 will be described. 9 and 10, the depth u of the groove 25 is different from the optical waveguide 21 to the optical waveguide substrate 20.
Is set smaller than the distance to the upper surface of the. That is, the depth u of the groove 25 is set to a depth at which the groove 25 does not interfere with the optical waveguide 21. Also, the optical waveguide substrate 20
The position of the groove 25 on the upper surface of the optical fiber 10 is adjusted by adjusting the optical axis of the optical fiber 10 with respect to the optical waveguide 21.
Is set on the line to be contacted. That is, the groove 25
Is formed immediately above the optical waveguide 21. Also, the groove 25
May be integrally formed in advance at the time of press-molding the optical waveguide substrate 20, or may be provided by etching or the like.

Next, the optical fiber 10 and the optical waveguide substrate 20
The method of positioning with will be described. In FIG. 10, the optical fiber 10 is arranged so as to fit into the groove 25. At this time, the optical fiber 10 is fitted into the groove 25 by the depth t. Thereafter, similarly to the first embodiment, the optical fiber 10 is arranged with the optical axis adjusted in each of the Z-axis and θz directions. Optical fiber 1
Numeral 0 is fixed to the optical waveguide substrate 20 with an adhesive 70. At this time, if there is a space between the optical fiber 10 and the groove 25, the space is completely filled with the adhesive 70.

Here, the groove 25 is formed so that the optical fiber 10 whose optical axis has been adjusted contacts the optical waveguide substrate 20.
It is provided in advance. Accordingly, when the optical fiber 10 is disposed so as to fit into the groove 25, the optical fiber 10
The optical axis adjustment in the X-axis direction becomes unnecessary. As a result, the optical axis adjustment of the optical fiber 10 in the X axis, the Z axis, and the θz direction, which is required in the first embodiment, is performed in two directions, the Z axis and the θz direction. As described above, the operation of adjusting the optical axis of the optical fiber 10 and the optical waveguide 21 is easier than in the first embodiment.

The distance between the optical fiber 10 and the optical waveguide 21 is determined by the depth t at which the optical fiber 10 fits into the groove 25.
And the loss due to the spread of light can be reduced, so that the efficiency of optical coupling is further improved as compared with the optical coupling structure according to the first or second embodiment.

In the third embodiment, as shown in FIG. 4, the optical fiber 10 may be arranged at an angle γ with respect to the optical axis direction of the optical waveguide 21. Also in this case, the position of the groove 25 on the upper surface of the optical waveguide substrate 20 is set on a line where the optical fiber 10 whose optical axis has been adjusted with respect to the optical waveguide 21 is to come into contact with the optical waveguide substrate 20. The invention can be applied.

Further, the optical coupling structure according to the second embodiment and the optical coupling structure according to the third embodiment may be combined. By combining these two embodiments, the optical axis adjustment of the optical fiber 10 can be performed only in the θx direction. First, the groove 2 in FIG.
The method of forming No. 5 is the same as that described above, and the description is omitted here. Next, a method for forming the alignment surface 14 in FIG. 7 will be described. The length s is calculated as follows. Let the radius of the optical fiber 10 be r and the optical waveguide substrate 20
If the distance from the upper surface of the optical waveguide 21 to the center of the optical waveguide 21 is h and the depth at which the optical fiber 10 fits into the groove 25 is t, the length s is s = (r / sin2β) − when r> h. {(Ht) / sin2α}
− (T / tan α). When both the angles α and β are 45 °, the length s is s = r−h. In the optical fiber 10, the tip of the second total reflection surface 12 is cut by polishing or the like by the length s calculated in this way, and as a result, an alignment surface 14 is provided. Note that the case of r <h will be described later.

Next, the optical fiber 10 is aligned with the optical waveguide substrate 20 as in the second embodiment.
That is, the alignment surface 14 and the tip end g of the first total reflection surface 24 of the optical waveguide substrate 20 are aligned on the same plane with the surface 81 of the jig 80 in the Z-axis direction. At the same time, the optical fiber 10 is arranged so as to fit into the groove 25.

Here, when the alignment surface 14 and the tip end g are aligned on the same plane,
The adjustment of the optical axis in the Z-axis direction becomes unnecessary. Optical fiber 1
When 0 is disposed so as to fit into the groove 25, the optical axis adjustment of the optical fiber 10 in the X-axis direction becomes unnecessary. Therefore, it is not necessary to adjust the optical axis of the optical fiber 10 in each of the X-axis and Z-axis directions. As a result, a total of 3 in the X-axis, the Z-axis and the θz direction required in the first embodiment are obtained.
The optical axis adjustment of the optical fiber 10 in the direction is an optical axis adjustment operation only in the θz direction.

In the above description, an example is shown in which the alignment surface 14 is provided on the second total reflection surface 12 of the optical fiber 10 on the condition that r> h. On the other hand, when r <h, the alignment surface is provided on the optical waveguide substrate 20 side. The length s in this case is: s = (h / sin2α) − {(rt) / sin2β}
− (T / tanβ). When both the angles α and β are 45 °, s = hr. In the optical waveguide substrate 20, a tip portion of the first total reflection surface 24 is cut by a length s perpendicular to the optical waveguide 21 by polishing or press molding, and as a result, an alignment surface is provided. After that, the optical fiber 10 is aligned with the optical waveguide substrate 20 as in the second embodiment. That is, the optical fiber 10 is placed on the surface 81 of the jig 80.
The front end of the second total reflection surface 12 and the alignment surface provided on the optical waveguide substrate 20 are aligned on the same plane by being aligned in the Z-axis direction. At the same time, the optical fiber 10 is arranged so as to fit into the groove 25. Thus, also in the case of r <h, the optical axis adjustment of the optical fiber 10 is an optical axis adjustment operation only in the θz direction.

(Fourth Embodiment) FIG. 11 is a view showing an optical coupling structure according to a fourth embodiment of the present invention. In addition,
FIG. 11 is a side sectional view of the optical coupling structure. Hereinafter, the fourth embodiment will be described with reference to FIG.

In FIG. 11, the optical coupling structure according to the fourth embodiment is obtained by adding an optical waveguide substrate 30 and a semi-transmissive reflective film 40 to the optical coupling structure according to the first embodiment. is there. In the fourth embodiment, the same parts as those in the optical coupling structure of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Next, the optical waveguide substrate 30 and the transflective reflection film 40 will be described. In FIG. 11, the optical waveguide substrate 30 has the same structure as the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment. That is, the optical waveguide substrate 30 includes an optical waveguide 31 having a rectangular cross section provided thereon, a clad layer 32 surrounding the optical waveguide 31, and a buffer layer 33. Also,
The end portion of the optical waveguide substrate 30 is obliquely cut, and as a result, a third total reflection surface 34 is provided. The third total reflection surface 34 is cut at an angle α with reference to the optical axis direction of the optical waveguide 31. Here, α is set to 45 °. Further, the first or third total reflection surface 2
A semi-transmissive reflective film 40 is provided on 4 or 34 by sputtering or the like. This transflective reflective film 40 is
It is a multilayer film of metal or dielectric, and has the property of partially transmitting / reflecting light waves. And the third total reflection surface 34 is
The optical waveguide 21 and the optical waveguide 31 are joined to the first total reflection surface 24 via the semi-transmissive reflection film 40 so as to be orthogonal to each other. Thereafter, the optical waveguide substrate 30 is placed on the first total reflection surface 2.
By applying an appropriate adhesive (not shown) to the outer peripheral portion of the joint surface with the optical waveguide 4, the optical waveguide substrate 20 is fixed to each other.

Next, light wave propagation in the fourth embodiment will be described. In FIG. 11, the optical fiber 10
The lightwave L1 incident on the core 11 and propagating through the core 11 is totally reflected by the second total reflection surface 12. Thereafter, the light wave L1 passes through the clad 13, the adhesive 70, and the clad layer 22, and is incident on the first total reflection surface 24 of the optical waveguide 21. Next, the light wave L1 is branched by the semi-transmissive reflection film 40 provided between the first total reflection surface 24 and the third total reflection surface 34. That is, the light wave L1 is branched into a light wave L2 which is totally reflected by the semi-transmissive reflective film 40 and propagates to the optical waveguide 21 and a light wave L3 which is transmitted through the semi-transmissive reflective film 40 and propagates to the optical waveguide 31.

As described above, by utilizing the total reflection surface of the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment, an optical waveguide having the same structure manufactured in the same manufacturing process as the optical waveguide substrate 20 is used. Using the waveguide substrate 30 and the transflective reflective film 40, an optical coupling structure having a light branching function can be realized.

Further, a wavelength separation filter may be provided instead of the transflective reflection film 40 provided in the optical coupling structure according to the fourth embodiment. This wavelength separation filter
It is provided by laminating high / low refractive index dielectric films. Here, a wavelength-selective transmission film that allows only the light wave of wavelength λ1 to pass is provided as a wavelength separation filter. Thus, as described above, when the lightwave L1 is incident on the optical fiber 10, the lightwave L3 becomes a lightwave having only the wavelength λ1, and the lightwaves of other wavelengths are totally reflected by the wavelength separation filter and split into the lightwave L2. That is, only the wavelength λ1 is propagated as the lightwave L3 to the optical waveguide 31, and the lightwave L2 other than the wavelength λ1 is propagated to the optical waveguide 21.

As described above, using the total reflection surface of the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment, the optical waveguide substrate 20 is manufactured in the same manufacturing process.
An optical coupling structure having an optical demultiplexing function can be realized by using the optical waveguide substrate 30 having the same structure and the wavelength separation filter.

In the above description, a wavelength-selective transmission film is used as a wavelength separation filter. However, a wavelength-selective reflection film may be used, or a long-wavelength transmission filter or a short-wavelength transmission filter may be used. It goes without saying that the invention can be applied.

The optical coupling structure according to the fourth embodiment has been described above. Instead of the optical waveguide substrate 30, an optical fiber or a light receiving element may be joined to the first total reflection surface 24. . In the same connection structure as described above, by joining an optical fiber or a light receiving element to the first total reflection surface 24 via a semi-transmissive reflective film or a wavelength separation filter, the light is branched into an optical fiber or a light receiving element. Alternatively, an optical coupling structure having a function of splitting light can be realized.

(Fifth Embodiment) In the fourth embodiment,
The optical fiber 10 has been described as the light wave incident side. Here, an optical coupling structure according to a fifth embodiment in which the optical waveguide 21 is on the light wave incident side will be described. FIG. 12 is a side sectional view of the optical coupling structure. Hereinafter, the fifth embodiment will be described with reference to FIG.

In FIG. 12, the optical coupling structure according to the fifth embodiment is obtained by adding an optical waveguide substrate 50 and a semi-transmissive reflection film 40 to the optical coupling structure according to the first embodiment. is there. In the fourth embodiment, the same parts as those in the optical coupling structure of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Next, the optical waveguide substrate 50 and the transflective reflection film 40 will be described. In FIG. 12, the optical waveguide substrate 50 has the same structure as the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment.
That is, the optical waveguide substrate 50 includes an optical waveguide 51 having a rectangular cross section provided thereon, a cladding layer 52 and a buffer layer 53 surrounding the optical waveguide 51. In addition, the optical waveguide substrate 50 has its end portion cut obliquely, and as a result, has the fourth total reflection surface 54. However, the fourth total reflection surface 54 is cut at an angle (180 ° −α) with respect to the optical axis direction of the optical waveguide 51, and is set at α = 45 ° here. Further, a semi-transmissive reflection film 40 is provided on the first total reflection surface 24 or the fourth total reflection surface 54 by sputtering or the like. The semi-transmissive reflective film 40 is a multilayer film of a metal or a dielectric, and has a characteristic of partially transmitting / reflecting a light wave.
Then, the fourth total reflection surface 54 is joined to the first total reflection surface 24 via the semi-transmissive reflection film 40 so that the optical waveguide 21 and the optical waveguide 51 are linearly arranged. . Thereafter, the optical waveguide substrate 50 is fixed to the optical waveguide substrate 20 by applying an appropriate adhesive (not shown) to the outer peripheral portion of the bonding surface with the first total reflection surface 24.

Next, the propagation of light waves in the fifth embodiment will be described. In FIG. 12, a light wave L4 incident on the optical waveguide 21 and propagating through the optical waveguide 21 is the first light wave L4.
Is incident on the semi-transmissive reflective film 40 provided between the total reflection surface 24 and the fourth total reflection surface 54. Next, the light wave L
4 is branched by a semi-transmissive reflective film 40. That is,
The light wave L4 transmits through the semi-transmissive reflective film 40 and passes through the optical waveguide 51.
, And a light wave L6 totally reflected by the transflective reflective film 40. The totally reflected light wave L6 passes through the clad layer 22, the adhesive 70, and the clad 13, and
Incident on the total reflection surface 12. After that, the light wave L6 is totally reflected by the second total reflection surface 12 of the core 11, and the optical fiber 10
Is propagated. Therefore, the light wave L4 is split by the semi-transmissive reflective film 40 into a light wave L5 propagating in the optical waveguide 51 and a light wave L6 propagating in the optical fiber 10.

As described above, by utilizing the total reflection surface of the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment, the optical waveguide substrate 50 and the transflective reflection film 40 are used. Thus, an optical coupling structure having an optical branching function can be realized.

Further, a wavelength separation filter may be provided instead of the transflective reflection film 40 provided in the optical coupling structure according to the fifth embodiment. This wavelength separation filter
It is provided by laminating high / low refractive index dielectric films. Here, a wavelength-selective transmission film that allows only the light wave of wavelength λ1 to pass is provided as a wavelength separation filter. Accordingly, as described above, when the lightwave L4 is incident on the optical waveguide 21, the lightwave L5 becomes a lightwave having only the wavelength λ1, and
Light waves of other wavelengths are totally reflected by the wavelength separation filter and split into light waves L6. That is, the lightwave L5 propagates only to the wavelength λ1 in the optical waveguide 51, and the lightwave L6 other than the wavelength λ1 propagates to the optical fiber 10.

As described above, by utilizing the total reflection surface of the optical waveguide substrate 20 provided in the optical coupling structure according to the first embodiment, the light splitting is performed by using the optical waveguide substrate 50 and the wavelength separation filter. An optical coupling structure having a wave function can be realized.

In the above description, a wavelength-selective transmission film is used as a wavelength separation filter. However, a wavelength-selective reflection film may be used, or a long-wavelength transmission filter or a short-wavelength transmission filter may be used. It goes without saying that the invention can be applied.

Although the optical coupling structure according to the fifth embodiment has been described above, an optical fiber or a light receiving element may be bonded to the first total reflection surface 24 instead of the optical waveguide substrate 50. . In the same connection structure as described above, by joining an optical fiber or a light receiving element to the first total reflection surface 24 via a semi-transmissive reflective film or a wavelength separation filter, the light is branched into an optical fiber or a light receiving element. Alternatively, an optical coupling structure having a function of splitting light can be realized.

Next, a method of manufacturing the optical coupling structure according to each of the above-described embodiments will be described. The total reflection surface of the optical fiber or the optical waveguide substrate used in each embodiment can be formed by obliquely polishing at a predetermined angle using a polishing machine or the like. However, a mold provided with an inclined surface whose side surface has a predetermined angle in advance is provided with SiO2 as an optical waveguide substrate material.
Glass or PMMA (polymethyl methacrylate)
Alternatively, a plastic such as fluorinated polyimide is put. Then, from the upper part of the mold, by pressing with another mold in which the groove for the optical waveguide is formed, the total reflection surface and the groove for the optical waveguide at a predetermined angle are simultaneously formed on the optical waveguide substrate. Can be formed. Moreover, by forming an inclined surface on the mold of the optical waveguide substrate, the optical waveguide substrate can be easily separated from the mold after pressing. Thereafter, a core material such as an ultraviolet curable resin is injected into the groove for the optical waveguide by spin coating or the like in a mold provided with the inclined surface to form an optical waveguide. Further, by forming the layer to be the upper clad by dip coating, a thin film is simultaneously formed on the optical waveguide substrate on the inclined surface including the total reflection surface at a predetermined angle. This thin film becomes a protective film of the same material as the upper clad layer. This protective film can prevent the total reflection surface of the optical waveguide from being exposed to the outside, and can prevent adhesion of foreign matter and dew condensation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an optical coupling structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line a-a ′ of FIG.

FIG. 3 is a sectional view taken along line i-i 'of FIG.

FIG. 4 is a diagram showing a structure in which an optical fiber and an optical waveguide are optically coupled at an angle γ.

FIG. 5 is a detailed side sectional view of a structure in which an optical fiber and an optical waveguide are optically coupled.

FIG. 6 is a diagram illustrating an optical coupling structure according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along line c-c 'of FIG.

FIG. 8 shows an optical coupling structure according to a second embodiment of the present invention.
It is a figure showing alignment by a jig.

FIG. 9 is a side view of an optical coupling structure according to a third embodiment of the present invention.

FIG. 10 is a detailed front view of an optical coupling structure according to a third embodiment of the present invention.

FIG. 11 is a diagram illustrating an optical coupling structure according to a fourth embodiment of the present invention.

FIG. 12 is a diagram illustrating an optical coupling structure according to a fifth embodiment of the present invention.

FIG. 13 is a view showing a structure of a conventional end face joining method.

FIG. 14 is a diagram showing an optical coupling structure disclosed in Japanese Patent No. 2946434.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Optical fiber 11 ... Core 12 ... 2nd total reflection surface 13 ... Cladding 14 ... Alignment surface 20, 30, 50 ... Optical waveguide board 21, 31, 51 ... Optical waveguide 22, 32, 52 ... Cladding layer 23, 33 53, buffer layer 24, first total reflection surface 25, groove 34, third total reflection surface 40, semi-transmissive reflection film 54, fourth total reflection surface 70, adhesive 80, jig

Claims (19)

[Claims] 1. A structure for optically coupling two types of different light propagation media to each other, comprising: an optical waveguide substrate having an inclined surface at an end; and an optical waveguide substrate formed near an upper surface of the optical waveguide substrate and having an end. An optical waveguide having a first total reflection surface on the same plane as the inclined surface, and an optical fiber disposed on the optical waveguide substrate and having a second total reflection surface at an end thereof, The mutual positional relationship between the optical waveguide and the optical fiber,
At least a part of the light wave that propagates in the optical waveguide and is totally reflected by the first total reflection surface intersects with the second total reflection surface, and propagates in the optical fiber to form the second wave. At least a part of the light wave totally reflected by the total reflection surface of the first
An optical coupling structure characterized in that the optical coupling structure is adjusted so as to intersect with the total reflection surface of the light emitting element. 2. The optical coupling structure according to claim 1, wherein the optical waveguide is surrounded by a cladding layer. 3. The relation α + β is defined as an angle α of the first total reflection surface with respect to the optical axis direction of the optical waveguide and an angle β of the second total reflection surface with respect to the optical axis direction of the optical fiber.
The optical coupling structure according to claim 1, wherein the optical coupling structure is set at ≒ 90 °. 4. The angle of the first total reflection surface is set at 45 °, and the angle β of the second total reflection surface is set at 45 °. Optical coupling structure. 5. The optical coupling structure according to claim 1, wherein the optical fiber is fixed on the optical waveguide substrate with an adhesive. 6. The adhesive has the same refractive index as the cladding layer, and a space through which a light wave propagating between the optical fiber and the optical waveguide passes is filled with the adhesive. The optical coupling structure according to claim 5, wherein 7. The optical coupling structure according to claim 1, wherein a groove is formed on the optical waveguide substrate, and the optical fiber is arranged along the groove. 8. The optical coupling according to claim 1, wherein an alignment surface for fixing the positional relationship between the optical waveguide and the optical fiber is formed on the optical fiber. Construction. 9. The optical waveguide substrate according to claim 1, wherein an alignment surface for fixing the positional relationship between the optical waveguide and the optical fiber is formed on the optical waveguide substrate.
Or the optical coupling structure according to 7. 10. The positional relationship between the optical fiber and the optical waveguide substrate is adjusted such that the light intensity at which the optical fiber and the optical waveguide are optically coupled has an optimal light reduction amount. The optical coupling structure according to claim 1, wherein: 11. The optical coupling structure according to claim 1, further comprising movable means for moving said optical fiber in an arbitrary direction with respect to said optical waveguide substrate. 12. The optical waveguide substrate, another optical waveguide substrate is bonded to the inclined surface via a semi-transmissive reflective film, and the other optical waveguide substrate is connected to the optical waveguide and the optical waveguide. The optical coupling structure according to claim 1, wherein another optical waveguide to be coupled is formed. 13. The optical coupling structure according to claim 1, wherein an optical fiber is bonded to the optical waveguide substrate via the translucent reflective film on the inclined surface. 14. The optical coupling structure according to claim 1, wherein a light receiving element is joined to the optical waveguide substrate via the transflective film on the inclined surface. 15. The optical waveguide substrate, another optical waveguide substrate is bonded to the inclined surface via a wavelength separation filter, and the other optical waveguide substrate is optically coupled to the optical waveguide. The optical coupling structure according to claim 1, wherein another optical waveguide is formed. 16. The optical coupling structure according to claim 1, wherein an optical fiber is bonded to the optical waveguide substrate on the inclined surface via a wavelength separation filter. 17. The optical coupling structure according to claim 1, wherein a light receiving element is joined to the optical waveguide substrate via the wavelength separation filter on the inclined surface. 18. The optical coupling structure according to claim 1, wherein the optical waveguide substrate having the inclined surface is formed by press molding using a mold provided with a predetermined inclination angle. . 19. The method of claim 19, wherein the cladding layer on the optical waveguide is formed by a dip coating method, and a protection film is formed on the inclined surface of the optical waveguide substrate by a dip coating method. The optical coupling structure according to claim 2.