JPS63226607A - Optical coupling structure - Google Patents

Abstract

PURPOSE:To simplify assembly and to improve mass productivity by fitting the front end part of an optical fiber worked to a small diameter into a small- diameter through-hole provided to a support. CONSTITUTION:An optical element 1 fixed to a mount 2 and the optical fiber 3 inserted into a receptacle 7 and a guide 5 are optically coupled. The through- hole 6 which is tapered and has the diameter at the front end smaller than the outside diameter of the optical fiber 3 is provided to this guide 5. The optical fiber 3 and the element 1 are coupled with high accuracy if the front end part 4 of the optical fiber 3 worked to the small diameter is fitted into the hole 6. The optical coupling structure is thus obtd. The optical coupling structure is, therefore, easily assembled and the mass productivity thereof is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical coupling structure suitable for easily realizing highly efficient optical coupling between an optical element and an optical fiber.

[Conventional technology]

In a conventional optical coupling structure, for example, as described in Japanese Patent Application Laid-Open No. 57-28392, a through-hole with an equal diameter larger than the outer diameter of the optical fiber is provided in an optical fiber support, and the optical fiber is inserted into this through-hole. The optical element was then fixed to perform optical coupling with the optical element.

[Problem that the invention seeks to solve]

In the above-mentioned conventional structure, since the diameter of one through hole is larger than the outer diameter of the optical fiber, it is not possible to accurately position the optical fiber by simply inserting the optical fiber into one through hole, so in one assembly process.

First, insert the optical fiber into the through hole provided in the support.

Next, the optical fiber is fixed to the support, the support is held by a fine movement device, the optical axes of the optical element and the optical fiber are aligned, and the support is fixed to the case containing the optical element.

Now, when optical devices are integrated into arrays in the future, with the conventional structure, it is necessary to perform complicated fine optical axis alignment work for each pair of optical devices and optical fibers, and in addition, it is necessary to perform support for each optical fiber. Because of the need for physical and working space, it has been impossible to miniaturize and integrate optical coupling structures. Furthermore, when the conventional structure is incorporated into an integrated optical module, it is extremely difficult to align the optical axis inside the narrow module.

An object of the present invention is to provide an optical coupling structure that is compatible with the integration of optical elements, has a simple assembly process, and can attach and detach optical fibers as needed, and is highly suitable for mass production. be. .

[Means for solving problems]

The above purpose is to provide a through hole in the support body that is smaller than the outer diameter of the optical fiber, process the tip of the optical fiber to reduce its diameter (for example, process the tip into a tapered shape), and pass the tip through the tip. This is achieved by fitting the device into the mouth and optically coupling the optical element and the optical fiber.

[Effect]

When the tip portion of the optical fiber is fitted into the through hole, the tip portion and the through hole come into contact with each other at a point, a line, or a plane, and the position of the tip portion is uniquely determined mechanically. Therefore, if the optical axis of the optical element is aligned with the through hole in advance, then all that is left to do is to fit the tip portion into the through hole, and highly efficient optical coupling between the optical element and the optical fiber can be easily realized.

According to this structure, even when optical elements are integrated into an array,
If the through-hole array is machined with high precision on one support, the optical axis alignment between the optical element array and the through-hole lower array only needs to be done once, and all that is left is to insert the optical fiber array into the through-hole lower array. - All you have to do is fit them together, which means the assembly process is extremely simple. Furthermore, since the support body becomes one, the size can be reduced, and the working space between arrays is not required, so that the optical coupling structure can be integrated.

By the way, even when the optical fiber is attached and detached from the through hole, the reproducibility of the optical coupling efficiency is sufficiently good, so there is no need to fix the optical fiber to the support.

It is also possible to separate the support and the optical fiber and connect them with a connector.

When incorporating this structure into an optical integrated module, the optical axis alignment work of the through-hole is performed outside the module, and inside the module, only the optical fiber needs to be fitted into the through-hole.In other words, inside the narrow module This eliminates the need for optical axis alignment.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram illustrating a first embodiment of the present invention, and is a sectional view of a basic optical coupling structure of a pair of optical elements and an optical fiber. FIG. 2 is an enlarged view of the main parts of the first embodiment.

In FIGS. 1 and 2, an optical element 1 is fixed on a mount 2. In FIGS. The optical fiber 3 and the optical element 1 are optically coupled and supported by a guide 5 and a receptacle 7. The optical fiber 3 is inserted into the through hole 8 of the receptacle 7, and the distal end portion 4 of the optical fiber 3 is tapered to have a smaller diameter, and is fitted into the tapered through hole 6 provided in the guide 5. There is. The mount 2 and the guide 5, and the guide 5 and the receptacle 7 are bonded by fixing materials 10.11, respectively. The optical fiber 3 is fixed in the opening 9 of the receptacle 7 by a fixing member 12 .

The optical element 1 is made of InGaAs5P/with an oscillation wavelength of 1.3 pm.
It is an I n P semiconductor laser. The optical element 1 was fixed to the mount 2 using solder (not shown). Electrodes and lead wires of the optical element 1 are omitted and not shown.

The optical fiber 3 is a single mode optical fiber with an outer diameter of 125 μm. A tapered spherical lens is formed at the distal end portion 4 of the lens. Tapered shape (taper angle θ) by precision grinding
= 25°), then heated and melted to reduce the radius R.
With the radius of the tip lens of this embodiment in which a minute tip lens of =17.5 μm is formed, optimal optical coupling is achieved when the distance between the optical element 1 and the tip lens is approximately 20 μm. The permissible positional deviation error in the optical axis direction is ±5 μm, and that in the direction perpendicular to the optical axis is ±1 μm. The surface of the optical fiber 3 other than the tip portion 4 was metallized with A u /N i for solder fixation.

The through hole 6 provided in the guide 5 is machined into a tapered shape by precision micro-drilling. The taper angle is 25@, and the minimum diameter of the through hole 6 is 50 μm, which is smaller than the outer diameter of the optical fiber 3, which is 125 μm.

The outer diameter of the through hole 8 of the receptacle 7 is 140 μm.

The opening 9 is provided so that the optical fiber 3 can be easily inserted into the through hole 8.

Kovar alloy, which has a small coefficient of thermal expansion, was selected as the material.

Their surfaces have A u/N i for solder fixation.
Plated. Solder was used for the fixing materials 10, 11, and 12.

Next, the assembly process of the first embodiment will be described with reference to FIG.

FIG. 3 shows a flowchart of the assembly process and a sectional view of the structure in each process.

(1) Optical element mounting process The optical element 1 is fixed to the mount 2 by solder (not shown). Depending on the processing accuracy of the through hole 6, the amount by which the tip portion 4 of the optical fiber 3 protrudes from the through hole 6 changes. It is also possible to adjust the fixed position of the optical element 1 by shifting it back and forth in the optical axis direction.

(2) Through-hole centering process After centering the through-hole 6 of the guide 5 and the through-hole 8 of the receptacle 7, the guide 5 and the receptacle 7 are fixed to each other with the fixing material 11.

(3) Through-hole optical axis adjustment process The optical axis of the through hole 6 with respect to the optical element 1 is adjusted.

After adjustment, the guide 5 is fixed to the mount 2 with a fixing member 10. Optical axis adjustment was performed using the following two methods. One method is to insert a standard optical fiber into the through holes 6 and 8 and actually optically couple it with the optical element 1 to align the optical axis, and then remove the standard optical fiber. ,8
In this method, the position of the guide 5 is adjusted so that the intensity of the light emitted from the optical element 1 passing through the optical element 1 is maximized.

(4) Optical fiber insertion process Insert the optical fiber 3 into the through hole 8, fit the tip portion 4 of the optical fiber 3 into the through hole 6, and connect the optical element 1 and the optical fiber 3.
optically couple.

(5) Optical fiber fixing step When the optical fiber 3 is permanently fixed, it is fixed in the opening 9 of the receptacle 7 with the fixing material 12. but,
If the optical fiber needs to be attached or detached, there is no need to fix it.

According to this embodiment, the tapered tip portion 4 of the optical fiber 3 and the tapered through hole 6 are in surface contact and fit together well, and the position of the tip portion 4 is accurately determined. If the assembly is completed up to step 3 in FIG. 3, the end portion 4 is guided to an appropriate position by the hour wheel operation in step 4, and high optical coupling efficiency can be easily obtained. That is, there is an effect that the assembly work becomes easier. Furthermore, even when the optical fiber 3 was repeatedly attached and detached in the state of step 4, the reproducibility of the optical coupling efficiency was sufficiently good (
(Fig. 4), 40±1 for 20 times of attaching and detaching the optical fiber 3.
%, a stable and high optical coupling efficiency has been obtained. This is ±
The fiber tip position accuracy can be estimated to be within 0.5 μm, indicating that the positioning performance of the present invention is excellent.

When this example was incorporated into an optical integrated module, steps up to step 3 were performed outside the module, and steps 4 and subsequent steps were performed inside the module. In this way, the single optical integrated module, which does not require difficult optical axis alignment work inside a narrow module as in the past, is used particularly for optical communications and operates stably for a long period of time.

The effects of the present invention are achieved because the position of the optical fiber tip is uniquely determined mechanically by point, line, or surface contact with the through hole, and the optical fiber tip is mechanically determined uniquely by point, line, or surface contact with the through hole. It doesn't depend on the method.

In this example, a semiconductor laser was selected as the optical element, but
Of course, other optical elements that are optically coupled to the optical fiber, such as light emitting/light receiving elements, optical functional elements, guiding waveguides, etc., may also be used.

In addition, although the tip of the optical fiber was tapered to make it smaller, it is also possible to use a different shape to make the diameter smaller.It is important that the minimum diameter of the through hole is smaller than the outer diameter of the optical fiber. However, if the shape of the tip of the optical fiber or the through hole changes, multiple point contacts will occur instead of a single surface contact as in this embodiment. Alternatively, the tip portion may be positioned by line contact.

In this case, the tip of the optical fiber and the through hole were created by precision machining, but it is also possible to use other microfabrication methods, such as chemical etching or dry etching. If you leave it there, the diameter will be reduced. When the (10G) plane of Si is anisotropically etched in a KOH aqueous solution, the (111) plane forms about 70mm inside the taper.
A 6' square pyramid-shaped through hole is obtained. Also, a through hole can be created by dry etching Si, 5ins, etc. using a fluorine gas. When etching is used, the processing accuracy of the through hole is determined by the pattern shape accuracy of the etching mask, and sufficient submicron accuracy can be obtained.

Moreover, batch processing allows processing with good reproducibility, which has the effect of improving mass productivity.

In this example, a pair of optical elements and optical fibers are used as the basic components of the optical coupling structure, but the effects of the present invention are even more remarkable when the optical elements and optical fibers are integrated into an array. be. Naturally, it can also be applied to optical switches and optical parallel processing computers. Typical application examples thereof are shown in the second and third embodiments.

FIG. 5 is a diagram illustrating a second embodiment of the present invention, and is a developed plan view of an optical coupling structure between an optical waveguide array and an optical fiber array.

In FIG. 5, an optical waveguide array 13 is optically coupled to an optical fiber array 16. The optical waveguide array 13 is fixed on a mount 25. The optical fibers 17 constituting the optical fiber array 16 are connected to the V-groove 2 of the support 19, respectively.
0, and the tip portion 1 of the optical fiber 17
8 fits into a through hole 22 provided in the support body 21. The support 19.21 and the mount 24 are fixed to each other. A spacer 23 is sandwiched between the support 21 and the optical waveguide array 13.

The optical waveguide array 13 is an input/output end portion of a multi-terminal optical device such as an optical switch. Four optical waveguides 15 are formed on a substrate 15 with an array interval of 160 μm. The substrate 15 is made of InP. The optical waveguide 15 has a waveguide width of 4μ.
It is a ridge-shaped InGaAsP optical waveguide with a thickness of 2 μm, and propagates light with a wavelength of 1.15 μm in a single mode. Semiconductor process technology was used to create the guide waveguide 15.

The optical fiber array 16 is composed of four optical fibers 17, and the array interval is 160 μm. The optical fiber 17 is a single mode optical fiber with an outer diameter of 125 μm. At the tip part 18.

Tapered (taper angle 30°) diameter reduction processing is applied,
A microscopic spherical lens is formed. The radius of the tip lens is 1
It is 5 μm. The distance between the tip portion 18 and the optical waveguide 15 was 20 μm. This interval can be adjusted by adjusting the thickness of the spacer 23. The allowable misalignment error of the tip portion 18 in the optical axis direction is ±5 μm, and that in the direction perpendicular to the optical axis is ±1 μm.

The material of the support 19.21 is Si. Support 19-4
The four V-grooves 20 and the four through holes 22 of the support 21 were all processed using anisotropic etching using a KoH aqueous solution on the 5i (100) plane. ■The angle of the groove 20 and the taper angle of the square pyramid-shaped through hole 22 are both 70.6 degrees. 13, if it is made equal to the pattern interval of the etching mask for creation.

(2) The array spacing of the grooves 20 and the array spacing of the through holes 22 are both exactly equal to the array spacing of the optical waveguide array 13, which is 160 μm, with an accuracy of submicron or less. In addition, according to the anisotropic etching process, the accuracy of the shape of the groove 20 and the through hole 22 is also very good. within range. Therefore, it is expected that the variation in optical coupling efficiency will be very small. Note that the support 19
and 21 are joined to each other and are integrated. First, a glass film was vapor-deposited on one surface to be bonded, and after adjusting the position, a high voltage was applied between the supports 19 and 21 to perform Si-glass-Si bonding and integrate them.

The material of the mounts 24 and 25 is Kovar alloy, and the surface is plated with Au/Ni.

Optical waveguide array 13 and mount 25. Integrated support 19.21 and mount 24, mount 24 and mount 2
5 were all adhesively fixed with solder. A u
/Ni/Ti were metalized. Since the spacer 23 is for adjusting the distance, it may or may not be fixed, but if it is fixed, solder is used.

Next, an outline of the assembly process of the second embodiment will be explained. The assembly process is basically the same as that of the first embodiment. First, the optical waveguide array 13 is fixed to the mount 25. Next, the integrated support body 19.21 is fixed to the mount 24. At this time, the fixing position is adjusted by the spacer 23. The mount 24 is held by a fine movement device, and the mounts 24 and 25, which align the optical axes of the array of through holes 22 and the optical waveguide array 13, are fixed. The optical fiber array 16 is inserted and fitted into the array of through holes 22. The tip portion 18 is 4
It contacts the through hole 22 at a point and is positioned with high precision, so that highly efficient optical coupling between the light source waveguide array 13 and the optical fiber array 16 is performed.

Now, according to this embodiment, the complicated fine-movement optical axis alignment work that was conventionally performed for each set of optical waveguides 15 and optical fibers 17 can be completed by a single batch optical axis alignment process for the arrays. .

In other words, there is an effect that one assembly process becomes extremely simple. Furthermore, even if the guide waveguides 15 are further integrated into an array, the support bodies 19 and 21 can be miniaturized accordingly, and the optical coupling structure can be integrated.

Furthermore, as in the case of the first embodiment, since the optical fiber array 13 can be attached and detached, the work for assembling the optical integrated module is also simple. In this example, despite the single mode optical coupling, the variation in the optical coupling efficiency between the four sets of optical waveguides and optical fibers was very small at ±2%. Therefore, the reliability of this example is high.

Incidentally, a conventional optical coupling structure using a V-groove of Si is also known. It has a structure similar to that of the second embodiment except that one support member 21 is removed. In this structure, the outer periphery of the optical fiber is supported by the groove, so the dimensional accuracy of the outer diameter of the optical fiber and the eccentricity of the core directly affect the displacement of the tip of the optical fiber. Therefore, the position of each optical fiber in the optical axis direction is not determined.In contrast, in the present invention, the optical fiber is supported at a location close to the optical axis, so the influence of the outer diameter dimensional accuracy and core eccentricity is partially suppressed. As a result, variations in optical coupling efficiency are suppressed to a minimum. On top of that,
The position in the optical axis direction is also stably determined by fitting.

Although the effects of this embodiment have been described above, these effects are not limited to the component parts or the processing method.
It goes without saying that this embodiment can be applied to other optical functional element arrays instead of the optical waveguide array, and the number of arrays can be changed from 4 to 8, or even dielectric optical waveguides such as 5. Of course, it is also possible to increase the number of optical wiring to 16 and improve the performance of multi-terminal optical devices.1 For example, if this embodiment is used in an optical switch exchanger, it will be possible to replace a large number of optical wiring with a small device, and the performance will be improved. Although this example is a one-dimensional array, there is no problem in extending this to a two-dimensional array.As an example of this two-dimensional array, a third example will be shown next.

FIG. 6 is a diagram illustrating a third embodiment of the present invention.

Pan view ((a)) and partially enlarged view ((b) of the optical coupling structure between the two-dimensional microlens array and the two-dimensional fiber array.
)).

An outline will be explained with reference to FIG. A two-dimensional microlens array 26 is optically coupled to a two-dimensional optical fiber array 27. The optical fibers 28 each have a through hole 35 in the support 34.
The distal end portion 29 is inserted into the through hole 3 of the support body 32.
3 is fitted.

The two-dimensional microlens array 26 was created by performing electric field ion exchange on a glass substrate in molten salt. Lens diameter 1
．． There are 3 lenses, a focal length of 1.5+m, and a lens pitch of 2 lenses.

The optical fiber 28 is a silica-based single mode optical fiber, and consists of a core 30 and a cladding 31. The tip portion 29 is tapered to have a smaller diameter, and the tip of the core 30 is vertically polished.

The support body 32 is made of Si, and the through holes 33 are processed by anisotropic etching, and the distance between the through holes 33 is two degrees.

The accuracy of the spacing can be controlled by the pattern accuracy of the etching mask.

The support 34 is made of metal, and the adhesive surfaces of the supports 32 and 34 are metallized and then fixed by soldering.The assembly process of this embodiment was carried out in the same manner as in the first and second embodiments.

Now, according to this embodiment, collective optical coupling of two-dimensional optical fiber arrays can be performed. Moreover, high optical coupling efficiency can be easily obtained just by mating, and the variation in optical coupling efficiency is so small that it does not become a problem.This embodiment is further combined with a two-dimensional optical element array such as an all-optical optical bistable device. If so, optical parallel processing can be performed. Naturally, it is also possible to increase the number of two-dimensional arrays from 4x4 to 8x8 or 16x16 to improve parallel processing performance, and this embodiment can become an important component of an optical computer.

FIG. 7 is a diagram illustrating a fourth embodiment of the present invention.

A perspective view ((a)) of an optical coupling structure of a laminated optical circuit.

A partially enlarged view ((b)).

In the figure, a stacked two-dimensional optical logic element array (43, 45, 47) and a two-dimensional fiber tube are coupled to form a stacked optical circuit as a whole. Each of the optical fibers 37 is inserted into a through hole 40 of the support 39 , and the tip portion 38 of the optical fiber 37 is fitted into the through hole 38 of the support 41 . Optical fiber 37 and two-dimensional optical logic element array 4
The optical logic elements 44, 46, and 48 of 3, 45, and 47 are optically coupled to each other, and input and output of optical logic operations is performed through the optical fiber 37.

Optical fiber 37 is a single mode optical fiber.

In order to integrate a two-dimensional array, the outer diameter of the array was smaller than usual. A tapered spherical lens (see the first embodiment) is formed at the tip portion 38 to increase the coupling efficiency.

The optical logic elements 44, 46, and 48 are semiconductor elements exhibiting optical bistable characteristics. This allows switching of input and output light.

Regarding the assembly process of the supports 39 and 41 and the main structure, please refer to Part 3.
This is similar to the example.

According to the laminated optical circuit of this example, logical operations can be performed in parallel processing, which has the effect of increasing the calculation speed.6 In this example, the number of arrays is 4 x 4, but this number can be increased. Even in this case, the coupling efficiency between the optical fiber and the optical logic element was sufficiently good, indicating that the optical coupling structure according to the present invention has high positioning performance.

In this embodiment, a semiconductor element is used as the optical logic element, but other dielectric elements such as an electro-optic control element or a magneto-optical control element may be used. Although we did so, it is also possible to perform analog operations using holograms instead of logic elements. In addition to wet etching, dry etching (reactive ion etching, ion beam etching, etc.) with good microfabrication properties may be used to process the through hole into which the optical fiber is fitted. The number of layers of optical circuits can be further increased.

FIG. 8 is a diagram illustrating a fifth embodiment of the present invention, and is a perspective view of an example in which the optical coupling structure is applied to optical interconnection.

In the figure, a large-scale electronic integrated circuit (LSI) 47 and the outside thereof are connected by optical wiring using an optical fiber 55. Light is emitted on LSI47.

A plurality of light receiving elements 48 are formed. This emitting/light receiving element 48 mutually converts the electrical signal of the LSI 47 into an optical signal.The emitting/light receiving element 48 is coupled to an optical fiber 55. The optical fiber 55 connects the LSI 47 and the outside by optical signals. The optical fiber 55 is inserted into the through hole 54 of the support body 53, and its tip portion 56 is fitted into the through hole 52 of the support body 51. A through hole 50 is formed in the spacer 49, which allows the optical fiber 5 to pass through.
5 and the light emitting/receiving element 4B is maintained optimally. A tip spherical lens is formed at the tip portion 56 in order to increase the efficiency of optical coupling with the light emitting/receiving element 48 .

According to this embodiment, an arbitrary position on the LSI and the outside can be three-dimensionally connected by optical wiring. Therefore, the problem of signal delay due to the capacitance of electrical wiring is solved, and LSI
signal processing speed is increased. Additionally, unlike electrical wiring, optical wiring does not cause mutual signal interference, and since electrical wiring can be omitted, the degree of freedom in LSI design increases, and a zero-wire optical coupling structure enables high-density integration. Programmable optical distribution mIR as optical fiber can be attached and detached
This embodiment has the advantage of being able to form an LS.
It has a revolutionary effect on increasing the speed, integration, and functionality of I.

〔Effect of the invention〕

According to the present invention, the assembly process of the optical coupling structure is simplified, mass productivity is improved, and miniaturization and integration of arrays are possible, which has the effect of significantly increasing the parallel transmission of optical information through optical fibers. be.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the first embodiment of the present invention, Figure 2 is an enlarged view of the main parts of the first embodiment, Figure 3 is an assembly process diagram of the first embodiment, and Figure 4 is the first embodiment. FIG. 5 is a diagram showing the second embodiment, FIG. 6 is a diagram showing the third embodiment, and FIG.
The figure shows the fourth embodiment■ 1 Figure 3 Figure 4 Moonlight fly 48゛ Attachment/detachment circle tip No. O (0L) (b)
Core 27 2D each Ibaa L 3/7ri γ
Driver 23 Hikari Driver 32, 34 Branch J dispute 29 Leading forces IF now SS, ASII Kuchitomi 7
Figure (b)

Claims (1)

[Claims] 1. In an optical coupling structure consisting of an optical element, an optical fiber, and a support, the support has a through hole smaller than the outer diameter of the optical fiber, and the tip of the optical fiber has a small diameter. 1. An optical coupling structure characterized in that an optical element and an optical fiber are optically coupled by applying a chemical processing and fitting the tip portion into the through hole. 2. The optical coupling structure according to claim 1, wherein the tip end portion of the optical fiber is subjected to a tapered diameter reduction process. 3. The optical coupling structure according to claim 1, wherein the through hole has a tapered shape, and the minimum diameter of the through hole is smaller than the outer diameter of the optical fiber. 4. The optical coupling structure according to claim 1, wherein the through hole is processed by etching. 5. The optical coupling structure according to claim 1, wherein the optical element, the optical fiber, and the through hole form an array.