JP6788436B2 - Optical module - Google Patents

Description

The present invention relates to an optical module in which an optical waveguide and an optical fiber are connected, and more specifically, light in the visible region to the ultraviolet region (wavelength range 700 nm or less), or light of extremely strong power (specifically, a number). The present invention relates to an optical module that suppresses a time-dependent increase in connection loss when using light with a power of 100 mW to several watts.

Optical fibers and optical waveguides that have advanced for optical communication are being developed in the visible region and the ultraviolet region in order to expand their application range. In recent years, semiconductor lasers (LDs) having an applicable range from the visible region to the ultraviolet region have been put on the market. The range of application of light emitting diodes used for LD has reached the vacuum ultraviolet region, and as for optical fibers, single-mode fibers in the visible region to the ultraviolet region have become commercially available, and quartz-based waveguides are also visible. Something that can be used in the ultraviolet region is being created. In the near future, it is expected that optical fibers will be able to propagate light in the vacuum ultraviolet region, and it is thought that visible and ultraviolet light will be applied to a wide range of displays, microscopes, biotechnology, and so on.

Further, with the progress of fiber lasers and wavelength conversion lasers, light having a power of several watts and very strong light has come to pass through fibers and waveguides at wavelengths such as 780 nm, 850 nm, and 060 nm other than visible light.

Until now, light or high-power light output from the LD that covers the visible and ultraviolet regions is taken out as a spatial beam and passed through optical elements such as a polarizing beam splitter, mirror, filter, and diffraction grating for handling. It was often (branched, reflected, spectroscopic, attenuated, etc.). Specifically, the above-mentioned optical element is mounted on a platen for fixing the spatial arrangement of the optical element, light is reflected by a mirror, light is collected by a lens, and light is divided into a plurality by a beam splitter. Laser light was handled by dividing it. Here, if the light output from the LD is taken out by an optical fiber and these processes (branching, reflection, attenuation, polarization control, phase control, spectroscopy, branching, combined wave, etc.) can be performed by the optical fiber or the optical waveguide, it will be fixed. No board is required, and these processes are much easier.

FIG. 1 shows the structure of a conventional waveguide-fiber connection as shown in Patent Document 1. FIG. 1 includes an optical fiber array 10 having a plurality of optical fibers, a fiber block 20 for aligning and fixing the optical fiber array 10, an optical waveguide circuit 30, and an adhesive layer 40. The fiber block 20 is a glass for pressing a V-groove substrate 21 in which a V-groove for arranging the optical fibers of the optical fiber array 10 is formed and an optical fiber arranged and arranged in the V-groove of the V-groove substrate 21. It has a substrate 22 and. The optical waveguide circuit 30 has an optical waveguide 33 including a waveguide core 31 and a waveguide clad 32. The fiber block 20 and the optical waveguide circuit 30 are connected to each other via an adhesive layer 40, whereby the optical fiber array 10 fixed to the fiber block 20 and the optical waveguide 33 of the optical waveguide circuit 30 are coupled. ..

When the optical fiber is connected to the optical waveguide 33 provided in the optical waveguide circuit 30, the optical fiber array 10 is fixed to the fiber block 20 so that the end face of the optical fiber array 10 is flush with the end face of the fiber block 20. , It is usual to attach an adhesive to the connecting end face of the optical waveguide 33 and the fiber block 20 to bond and fix it. The fiber block 20 is provided with a PD or the like on the output end side of the optical fiber 10, the fiber block 20 is provided on a fine movement table, and fine movement is performed while passing light through the optical fiber 10 so that the light receiving intensity of the PD is maximized. Adjust to the optimum position on the table. By applying the adhesive to the end face, the adhesive penetrates into the gap of several μm between the connection end faces of the optical fiber array 10 and the optical waveguide 33 due to the capillary phenomenon, and spreads over the entire connection end face. By irradiating the adhesive on the connection end face with UV, the fiber block 20 and the optical waveguide 33 are adhesively fixed by the adhesive layer 40. As the material of the adhesive layer 40, in consideration of workability, a UV-curable adhesive is often used rather than a thermosetting adhesive, and an epoxy-based adhesive may be used in addition to the acrylic-based adhesive. is there.

Japanese Unexamined Patent Publication No. 8-313744 Japanese Unexamined Patent Publication No. 9-159860 Japanese Unexamined Patent Publication No. 10-221559

In the conventional communication wavelength band (wavelength 1.3 μm to 1.55 μm), even if 1 W of high-power light is put into the optical fiber, the connection loss between the optical fiber and the optical waveguide increases even after several thousand hours have passed. There is no such thing. However, the inventor has found that when light in the wavelength range from the visible region to the ultraviolet region of 700 nm or less is used, the loss increases sharply in several tens of minutes when the optical waveguide and the optical fiber are connected by the conventional connection method. Found.

In order to investigate the cause of this increase in loss, the loss in the fiber, waveguide, connector, and LD was measured by the cutback method, and the part where the loss increased was investigated. As a result, it was found that the loss increased most at the connecting end face of the optical fiber array 10 and the optical waveguide 33. This is because high-energy visible light with a very high power density is incident on the adhesive layer 40, so that the material of the adhesive layer 40 is denatured and the refractive index is locally greatly reduced or increased, resulting in light conduction. It was found that the wave structure (confinement of light) collapsed and the light escaped to the outside of the optical waveguide 33.

FIG. 2 shows the result of simulating the state of light propagation in the fiber-wavelength-fiber when the refractive index of a part of the adhesive layer is locally lowered by 0.05 due to visible light having a wavelength of 405 nm. Specifically, FIG. 2A shows the fiber-waveguide-fiber structure used in the simulation of FIG. 2, and FIG. 2B shows the simulation result. In this simulation, the optical fiber has a mode field system: 3 μm, the specific refractive index difference: 0.2% (refractive index 1.45 and refractive index 1.4529), and the same applies to the optical waveguide. As shown in FIG. 2B, it can be seen that light leaks at the connecting end face of the optical fiber and the optical waveguide, and the loss increases.

FIG. 3 shows the change with time of the transmittance when the optical fiber is fixed to the waveguide with a conventional acrylic adhesive and 10 mW of light having a wavelength of 405 nm, 488 nm, 559 nm, or 640 nm is input. As shown in FIG. 3A, with blue light of 405 nm, a loss of several tens of dB occurs in several hours. This result is the same for epoxy adhesives, and although the life is extended by using a relatively transparent silicone adhesive, a loss of several dB still occurs in 1000 hours.

Further, as shown in FIGS. 3 (a) to 3 (c), the life is extended as the wavelength becomes longer, but the loss may be greatly increased in the light having a wavelength of 640 nm or less shown in FIG. 3 (c). Understand. At wavelengths of 559 nm and 488 nm, a phenomenon was observed in which the loss increased once and then recovered a little. Therefore, in the case of 10 mW input, if the light has a wavelength of 700 nm or less, the adhesive deteriorates and the loss increases. For example, in the case of light having a wavelength of 640 nm, the loss increases sharply around 1000 hours.

Furthermore, we tried to inject various adhesives and liquids between the fiber end face and the waveguide end face, but when light with a wavelength of 405 nm and 10 mW was input, the loss increased regardless of which adhesive was used. Was done.

Further, in recent years, the output of semiconductor lasers, wavelength conversion lasers, and fiber lasers has become extremely high, and 1W to 10W class lasers have also been developed. Similarly, when these high-power laser beams are propagated to the optical fiber and joined to the optical waveguide, there is a problem that the connection loss at the adhesive connection portion becomes very large due to the deterioration of the adhesive. The same problem occurs when not only the wavelength in the visible region but also light having a wavelength slightly shorter than the communication wavelength band such as 780 nm, 850 nm, and 060 nm is used.

Therefore, the present invention suppresses a time-dependent increase in connection loss when using light in the visible to ultraviolet wavelength region of 700 nm or less or high-power light of several hundred mW or more in the wavelength region of 700 nm to 1300 nm. The purpose is to provide an optical module.

In order to achieve such an object, one aspect of the optical module of the present invention is to bond a capillary in which one optical fiber is inserted and fixed, and an optical waveguide circuit having at least one optical waveguide. An optical module including an agent layer, which is provided at a portion where light does not pass through the connection end face of the capillary and the connection end face of the optical waveguide circuit, which is an end face connecting the capillary and the optical waveguide circuit. By connecting the capillary and the optical waveguide circuit via the adhesive layer, the optical fiber fixed to the capillary and the optical waveguide of the optical waveguide circuit are coupled, and the connection of the capillary. A counterbore groove is provided on the end surface, the tip of the optical fiber is in direct contact with the optical waveguide of the optical waveguide circuit without using the adhesive, and the capillary is one in the longitudinal direction. The optical fiber is provided with a cut-out portion in which half of the radial direction is cut off, and the optical fiber is pressed against the optical waveguide circuit and buckled at the cut-out portion .

Another aspect of the present invention is a top Symbol optical module, the optical fiber, the tip portion is ground to a trapezoidal shape, the distal end surface of the trapezoidal shape is square outline with respect to the traveling direction of the light It is a feature.

According to the present invention, when using light in the wavelength region from the visible region to the ultraviolet region of 700 nm or less, or when using light with a high output power of 100 mW to several W in the wavelength region of 700 nm to 1300 nm, the connection is made. It is possible to realize an optical module in which an optical waveguide and an optical fiber are connected, which suppresses an increase in loss over time.

It is a figure which shows the structure of the connection part of the conventional waveguide-fiber. It is a figure which shows the simulation result which shows the state of the light propagation of a fiber-a waveguide-fiber when the refractive index of an adhesive layer is locally lowered by visible light. It is a figure which shows the time-dependent change of the transmittance of a fiber-wavelength path in light of each wavelength. It is a figure which illustrates the optical module which concerns on Example 1 of this invention. It is a figure which illustrates the appearance that the adhesive is blocked by the adhesive blocking groove in the optical module according to the first embodiment of the present invention. It is a figure which shows the example which provided the adhesive blocking groove in the arrangement direction of an optical fiber array in the optical module which concerns on this invention. It is a figure which illustrates the optical module which concerns on Example 2 of this invention. It is a figure which shows the time-dependent change of the transmittance when light is input to the optical module which concerns on Example 2 of this invention. It is a figure which illustrates the optical module which concerns on Example 3 of this invention. It is a figure which illustrates the optical module which concerns on Example 4 of this invention. It is a figure which shows the relationship between the thickness and loss of a void layer with respect to light of each wavelength. It is a figure which illustrates the optical module which concerns on Example 5 of this invention. It is a figure which illustrates the optical module which concerns on Example 6 of this invention. It is a figure for demonstrating the optical module which concerns on Example 7 of this invention. It is a figure which shows the time-dependent change of the output when the buckling fiber and the optical waveguide circuit are connected in the optical module which concerns on Example 7 of this invention. It is a figure for demonstrating the optical module which concerns on Example 8 of this invention. It is a figure for demonstrating the optical module which concerns on Example 8 of this invention. It is sectional drawing of the connection part of the optical waveguide circuit and a capillary in the optical module which concerns on Example 8 of this invention. It is a figure which shows the air-cooling effect of a fiber block when the material of a fiber block is made of glass or Si.

<Example 1>
FIG. 4 illustrates an optical module according to a first embodiment of the present invention. FIG. 4 shows an optical fiber array 110 having a plurality of optical fibers, a fiber block 120 for aligning and fixing the optical fiber array 110, an optical waveguide circuit 130 having a plurality of optical waveguides, and an adhesive layer 140. The provided optical module is shown. The fiber block 120 and the fiber block 120 are provided via an adhesive layer 140 provided at a portion of the connection end surface of the fiber block 120 and the connection end surface of the optical waveguide circuit 130, which is an end surface connecting the fiber block 120 and the optical waveguide circuit 130. By connecting the optical waveguide circuit 130, the optical fiber array 110 fixed to the fiber block 120 and each optical waveguide of the optical waveguide circuit 130 are coupled. The fiber block 120 is arranged so as to sandwich the optical fiber array 110 outside the optical fibers at both ends in the arrangement direction (hereinafter referred to as "arrangement direction") of the optical fiber array 110 of the optical fiber array 110 aligned and fixed. Two adhesive damming grooves 121 are provided in a direction approximately perpendicular to the direction and the traveling direction of light (hereinafter, referred to as "vertical direction").

In the optical module according to the first embodiment of the present invention, in order to prevent an increase in loss due to deterioration of the adhesive layer due to irradiation of the adhesive layer between the optical waveguide and the optical fiber with light in the visible region to the ultraviolet region. , Adhesive is not used on the connection end face of the fiber block 120 and the connection end face of the optical waveguide circuit 130, but is used only on the part where light does not pass, and the fiber block 120 and the optical waveguide circuit 130 are bonded and fixed. To do. In order to easily realize the structure, in the present invention, the fiber block 120 is provided with the adhesive damming groove 121. By providing the adhesive damming groove 121, the adhesive is prevented from entering the portion where light is transmitted on both connection end faces, and the adhesive layer 140 is provided only on the portion where light is not transmitted on both connection end faces. However, the fiber block 120 and the optical waveguide circuit 130 can be bonded and fixed. The adhesive damming groove 121 may have a width of 100 μm or more and a depth of 100 μm or more.

FIG. 5 illustrates a state in which the adhesive is blocked by the adhesive blocking groove in the optical module according to the first embodiment of the present invention. As shown in FIG. 5A, the adhesive is applied to the outside of the two adhesive damming grooves 121 in the fiber block 120. Light of 640 nm is passed through each optical fiber of the optical fiber array 110, the connection end face of the fiber block 120 is brought close to the connection end face of the optical waveguide circuit 130, and the light is aligned so as to be incident on the optical waveguide of the optical waveguide circuit 130. The distance between the end face of the fiber block 120 and the end face of the optical waveguide circuit 130 is about 1 μm to 5 μm.

As shown in FIG. 5B, when the end face of the fiber block 120 and the end face of the optical waveguide circuit 130 come close to each other, the adhesive tries to spread over both end faces due to the capillary phenomenon, but the adhesive blocking groove. The adhesive is blocked by 121, and the adhesive does not reach the portion of the connecting end face through which light passes. When the connection end face of the fiber block 120 and the connection end face of the optical waveguide circuit 130 are sufficiently close to each other, as shown in FIG. 5 (c), the adhesive of the fiber block 120 separated by the adhesive blocking groove 121 Spreads in a square shape on both sides. After that, the adhesive spread on the connection end face of the fiber block 120 and the connection end face of the optical waveguide circuit 130 is irradiated with UV, and the connection end face of the fiber block 120 and the connection end face of the optical waveguide circuit 130 are adhesively fixed as the adhesive layer 140. To do.

Here, in this embodiment, the structure in which the adhesive blocking groove 121 is provided in the fiber block 120 is shown, but the adhesive blocking groove may be provided in the optical waveguide circuit 130. Further, in this embodiment, two adhesive damming grooves are provided in the vertical direction, but two may be provided in the arrangement direction as shown in FIG. In this case as well, the adhesive may be applied to the outside of the two adhesive damming grooves 121. The same applies to the following examples.

<Example 2>
FIG. 7 illustrates an optical module according to a second embodiment of the present invention. FIG. 7 shows an optical module according to the second embodiment in which the connection end face is obliquely polished. If there is no adhesive layer in the portion of the connection end face through which light is transmitted, light will come out directly into the space from each connection end face of the fiber block and the optical waveguide circuit. When each connection end face of the fiber block and the optical waveguide circuit is perpendicular to the traveling direction of light, the reflection at each connection end face becomes large, so that the output of the laser may fluctuate due to the return light. In order to reduce reflection, in the optical module according to the second embodiment, as shown in FIGS. 7A and 7B, the fiber block 220 and the optical waveguide circuit 230 each have their connection end faces diagonally polished. The obliquely polished end faces 222 and 231 formed by the above can be obtained. The obliquely polished end faces 222 and 231 can have an oblique polishing angle that is inclined by, for example, 7 ° or more with respect to the traveling direction of light.

FIG. 8 shows the time course of the transmittance when light having a wavelength of 405 nm and 10 mW is input to the optical module according to the second embodiment. The loss is greatly increased when there is an adhesive layer in the portion where light passes through the connection end face as in the conventional case, but there is no adhesive layer in the portion where light passes in the connection end face according to the second embodiment of the present invention. In the optical module, the loss hardly increases as shown in FIG.

Similarly, when high-power (1 W) light having wavelengths of 780 nm, 850 nm, and 1063 nm is put into an optical fiber and connected to an optical waveguide, an increase in loss can be similarly prevented.

<Example 3>
FIG. 9 illustrates an optical module according to a third embodiment of the present invention. FIG. 9 shows an optical module in which a non-reflective coating 350 is provided at a portion through which light passes on both connection end faces of the fiber block 320 and the optical waveguide circuit 330. According to the optical module according to the third embodiment, the reflection at each connection end face can be reduced by forming the non-reflective coating 350 in the portion through which the light passes.

<Example 4>
FIG. 10 illustrates an optical module according to a fourth embodiment of the present invention. When a gap layer is present between both connection end faces of the fiber block and the optical waveguide circuit, there is a problem that the loss increases as the thickness of the gap layer increases. Further, if there is a void layer, there is a problem that the loss becomes large due to the reflection of this connecting portion and the light returns to the input side due to the reflected return light. In order to solve the problem caused by the void layer, in the optical module shown in FIG. 10, the portions of the fiber block 420 and the optical waveguide circuit 430 where light is transmitted are in direct contact with each other.

FIG. 11 shows the relationship between the thickness and loss of the void layer in the optical module when light having wavelengths of 400 nm, 559 nm, 640 nm, and 1550 nm is used. FIG. 11 shows a case where the void layer is filled with an adhesive and a case where the void layer is not filled. As shown in FIGS. 11A to 11D, the shorter the wavelength, the larger the loss. Further, when the void layer is not filled with the adhesive, the loss is about twice as much as when the void layer is filled with the adhesive. Therefore, the loss can be reduced by making the void layer as small as possible. In order to reduce the loss to 0.1 dB or less, which is within the measurement error of the connection loss of the optical waveguide, the thickness of the void layer is preferably 5 μm or less.

According to the optical module according to the fourth embodiment, the reflection of light on the connection end faces can be eliminated by directly contacting both connection end faces.

<Example 5>
FIG. 12 illustrates an optical module according to a fifth embodiment of the present invention. FIG. 12 shows an optical module including an optical fiber array 510, a fiber block 520 for aligning and fixing the optical fiber array 510, an optical waveguide circuit 530, and an adhesive layer 540. In this embodiment, the fiber block 520 is not provided with an adhesive blocking groove as in the above embodiment, and the optical waveguide circuit 530 is provided with optical waveguides at both ends of the optical waveguide circuit 530 in the arrangement direction. An adhesive damming groove 531 is provided in the vertical direction so as to sandwich the all-optical waveguide on the outside of the. The fiber block 520 and the optical waveguide circuit 530 are connected via an adhesive layer 540.

In Examples 1 to 4, an adhesive blocking groove is provided in the fiber block in order to prevent the adhesive from adhering to the optical fiber and the end face of the optical waveguide. However, as in the fifth embodiment, the optical waveguide circuit 530 An adhesive damming groove 531 can be provided on the connecting end surface of the above. In this case, the adhesive may be applied to the outside of the two adhesive blocking grooves 531 in the optical waveguide circuit 530.

In the fifth embodiment as in the first to fourth embodiments, the connection end faces may be diagonally polished or a non-reflective coating may be provided on the connection end faces in order to reduce the reflection between the two connection end faces. The end faces may be brought into direct contact.

<Example 6>
FIG. 13 illustrates an optical module according to a sixth embodiment of the present invention. FIG. 13 shows an optical module including an optical fiber array 610, a fiber block 620 for aligning and fixing an optical fiber array 610, an optical waveguide circuit 630, and a yatoi plate 650 made of glass. The yatoi plate 650 is provided on the optical waveguide circuit 630 so that its end face is flush with the connection end face of the optical waveguide circuit 630. The optical waveguide circuit 630 and the yatoi plate 650 are connected to the fiber block 620 via an adhesive layer 640 provided on the optical waveguide circuit 630 and the yatoi plate 650, respectively. Further, the optical waveguide circuit 630 and the yatoi plate 650 are provided with adhesive damming grooves 631 and 651 in the arrangement direction so as to sandwich the optical waveguide of the optical waveguide circuit 630.

In this way, by providing the Yatoi plate 650 on the optical waveguide circuit 630 and providing the adhesive blocking groove 651 in the arrangement direction, the adhesive blocking groove 631 is provided in the arrangement direction on the connection end surface of the optical waveguide circuit 630. It becomes possible to provide.

In the sixth embodiment as in the first to fourth embodiments, the connection end faces may be diagonally polished or a non-reflective coating may be provided on the connection end faces in order to reduce reflection between the two connection end faces. The connection end faces may be brought into direct contact with each other.

In Examples 5 and 6 above, an experiment was conducted in which 10 mW of light having a wavelength of 405 nm, 488 nm, 559 nm, and 640 nm was input, but the loss did not increase over time even with light in the ultraviolet region. For example, in Examples 5 and 6, the loss between the optical fiber and the optical waveguide increases with time, whether the light has a wavelength of 370 nm from the blue LD or the light having a wavelength of 266 nm from the wavelength conversion laser. Was not seen.

<Example 7>
The optical module according to the seventh embodiment of the present invention will be described with reference to FIG. FIG. 14A shows the configuration of the fiber block of the optical module according to the seventh embodiment. FIG. 14A shows an optical fiber array 710 and a fiber block 720 that aligns and fixes the optical fiber array 710. As shown in FIG. 14A, the fiber block 720 is composed of a V-groove substrate provided on the lower side and an upper substrate provided on the upper side, and is an optical fiber for inserting the optical fiber array 710. The array direction and light so as to sandwich the optical fiber array 710 outside the optical fibers at both ends of the array V-groove 721, the spacer V-groove 722 for inserting the spacer fiber 711, and the optical fiber array 710 in the arrangement direction. It has two adhesive damming grooves 723 provided in the direction perpendicular to the traveling direction of the above.

In the optical fiber array 710, the rear side of the fiber is adhesively fixed on the V-groove 721 for the optical fiber array with an adhesive 724, and the optical fiber is buckled by being pressed against the optical waveguide circuit. The diameter of the spacer fiber 711 can be made equal to, for example, the diameter of the optical fiber of the optical fiber array 710, and the spacer V-groove 722 is provided at both ends of a plurality of V-grooves for aligning the optical fiber array 710. ..

In the optical module according to the fourth embodiment described above, the end face of the optical fiber and the end face of the optical waveguide are in physical contact with each other. However, it is difficult to continuously physically completely contact the end face of the optical waveguide with the end face of the fiber block. For example, when connecting an optical fiber using a connector, the end face of the optical fiber is polished into a trapezoidal shape so that the core portion of the optical fiber at the center thereof physically contacts, for example, in the case of an FC connector. Is physically contacted by tightening with a screw, and in the case of an SC connector, it is physically contacted by a spring. However, it is technically difficult to polish the optical waveguide and the fiber block into a trapezoidal shape in this way and physically contact them by tightening them with screws or using a spring.

Therefore, as shown in FIG. 14A, in the fiber block 720 provided with the adhesive blocking groove 723, the optical fiber array 710 is inserted into the V groove so that the optical fiber itself moves back and forth, and further. The end face of the optical fiber is polished into a trapezoidal shape, and the rear side of the optical fiber is adhesively fixed with an adhesive 724 so that the tip of the optical fiber protrudes from the fiber block 720 by several tens of μm.

As shown in FIG. 14B, the tip surface of the optical fiber is approximately perpendicular (90 ± 0.3 °) to the traveling direction of light, and the side surface is further polished into a trapezoidal shape to make the tip thin. By doing so, for example, the portion in contact with the end face of an optical waveguide circuit such as a PLC (Planar Lightwave Circuit) is set as the minimum area. As a result, the force due to contact is concentrated on the tip portion of the optical fiber, and the adhesion between the optical fiber and the optical waveguide circuit can be improved, so that connection loss can be suppressed.

As shown in FIG. 14C, a laser beam is introduced into the optical fiber in a state where the tip portion of the optical fiber protrudes from the fiber block 720 by several tens of μm to align the optical waveguide circuit with the optical waveguide. At this time, the optical fiber is physically brought into contact with the optical waveguide core. The adhesive 725 is applied to the adhesive application areas on both sides of the fiber block 720, and the fiber block 720 is further pushed in the direction of the waveguide to bond the fiber block 720 and the optical waveguide circuit by UV curing. The optical fiber is arranged in the V-groove, the tip portion is not adhesively fixed, and the optical fiber can easily move back and forth. As shown in FIG. 14D, the tip of the optical fiber is pushed back to the fiber block 720, but the buckling of the optical fiber pushes the tip of the optical fiber against the end face of the waveguide. The buckling stress is optimized by setting the buckling length to 5-10 mm.

Conventionally, a fiber or fiber waveguide connector using such a buckling stress has already been developed (see, for example, Patent Documents 2 and 3). However, there is no example in which a physical contact using such buckling stress is realized in a connector that connects and fixes an optical fiber and an optical waveguide instead of the removable connector as shown in Patent Documents 2 and 3.

In this way, the optical fiber-optical waveguide circuit-optical fiber was connected, a 405 nm light source 70 mW was input, and the change over time in the output was examined. The results are shown in FIG. As shown in FIG. 15, light of 50 mW or more could be passed through for 1000 hours or more.

Here, in this embodiment, the adhesive 724 is directly applied to the back side of the optical fiber to bond and fix it. However, the optical fiber is inserted into the capillary and the capillary and the optical fiber are adhered to the V-groove substrate. It may be fixed with. Thereby, the adhesive fixing between the fiber block 720 and the optical fiber can be further strengthened.

<Example 8>
The optical module according to the eighth embodiment of the present invention will be described with reference to FIGS. 16 to 18. FIG. 16 shows an optical fiber 810 and a capillary 820 with the upper half partially cut off. The tip of the optical fiber 810 is polished, and the capillary 820 is, for example, a capillary having a hole of 126 μmφ. The capillary 820 has a capillary counterbore groove 821 provided at the tip of the capillary 820, and first and second cutout portions 822 and 823 from which the upper half of the capillary 820 is cut off. The first cutout portion 822 is provided on the tip end side of the capillary 820, and the second cutout portion 823 is provided on the rear end side of the capillary. In the first cutout portion 822, the optical fiber 810 is buckled, and in the second cutout portion 823, the optical fiber 810 is adhesively fixed by the adhesive 824. In the seventh embodiment, the optical fiber can be moved back and forth by using the V-groove formed in the fiber block 720. However, as in the eighth embodiment, the capillary 820 is used instead of the fiber block having the V-groove. It may be used for.

FIG. 17 shows a process of inserting an optical fiber into a capillary and abutting the tip of the fiber against the end face of an optical waveguide circuit to buckle the optical fiber. As shown in FIG. 17A, the optical fiber 810 is inserted into the capillary 820, and as shown in FIG. 17B, the tip of the optical fiber 810 protrudes from the capillary 820 by several tens of μm, and the tip of the capillary 820 is formed. It is adhesively fixed with an adhesive 824 at a position of about 5-10 mm. After that, as in Example 7, as shown in FIG. 17C, the adhesive 825 is applied to the adhesive application area of the capillary 820, and the capillary 820 is further pushed in the waveguide direction to buckle the optical fiber 810. After that, the capillary 820 and the optical waveguide circuit are bonded by UV curing of the adhesive. Since the adhesive has a counterbore groove 821 for blocking, the adhesive does not penetrate between the optical fiber and the end face of the optical waveguide. As a result, the optical waveguide and the optical fiber are always in physical contact due to the stress caused by buckling.

FIG. 18 is a cross-sectional view of a connection portion between an optical waveguide circuit and a capillary in the optical module according to the eighth embodiment of the present invention. As shown in FIG. 18A, since the capillary counterbore groove 821 for preventing the adhesive from flowing into the optical fiber 810 is provided at the tip of the capillary 820, the capillary 820 and the optical waveguide circuit are fixed. The adhesive 825 for this purpose flows into the capillary counterbore groove 821 and does not reach the optical fiber 810.

<Example 9>
In the first embodiment, the adhesive damming creates a gap between the optical fiber and the optical waveguide. In the visible region, this structure can almost suppress the increase in loss, but when light near ultraviolet light of 450 nm or less is passed through, the increase in loss is still observed. This is because the core portion of the optical fiber pops out into the gap due to the light of this wavelength. In order to suppress this, physical contact was made in Examples 7 and 8.

On the other hand, when passing light of such a wavelength, it was discovered that the temperature of the connection between the optical waveguide and the optical fiber has risen, and by cooling this connection, the increase in loss can be greatly reduced. discovered.

In the ninth embodiment, in order to air-cool the connection portion, a fiber block is manufactured using a Si substrate having higher heat dissipation than glass instead of conventional glass, a V groove is formed on the Si substrate, and quartz is formed on the fiber block. The optical fiber was fixed by covering with glass.

FIG. 19 shows the air cooling effect of the fiber block when the material of the fiber block is made of glass or Si. In FIG. 19, input light having a wavelength of 405 nm and 40 mW is used. As shown in FIGS. 19A and 19B, when the material of the fiber block is made of Si, the attenuation time of the transmittance is longer than that of the case where the material of the fiber block is made of glass. There is. In this way, by changing the material of the fiber block from glass to Si, the life can be extended by 2 to 3 times.

In the ninth embodiment, the configuration in which Si is used as the material of the fiber block is illustrated, but any material having higher heat dissipation than glass can be applied in the present invention.

Fiber Optic Array 10, 110, 210, 310, 410, 510, 610, 710
Fiber blocks 20, 120, 220, 320, 420, 520, 620, 720
V-groove substrate 21
Glass substrate 22
Optical waveguide circuit 30, 130, 230, 330, 430, 530, 630
Waveguide core 31
Waveguide clad 32
Optical waveguide 33
Adhesive layer 40, 140, 240, 340, 440, 540, 640
Adhesive damming groove 121, 221, 321, 421, 531, 631, 651, 723
Diagonal polishing end face 222, 231
Non-reflective coat 350
Yatoi board 650
Spacer fiber 711
V-groove 721 for optical fiber array
V-groove for spacer 722
Adhesive 724,725,824,825
Optical fiber 810
Capillary 820
Capillary counterbore groove 821
Capillary cutouts 822, 823

Claims (2)

A capillary in which one optical fiber is inserted and fixed,
An optical waveguide circuit having at least one optical waveguide,
With the adhesive layer,
It is an optical module equipped with
The capillary and the optical waveguide are provided through the adhesive layer provided at the connection end surface of the capillary, which is the end surface connecting the capillary and the optical waveguide circuit, and the portion of the connection end face of the optical waveguide circuit through which light does not pass. By connecting the circuit, the optical fiber fixed to the capillary and the optical waveguide of the optical waveguide circuit are coupled.
A counterbore groove is provided on the connecting end face of the capillary.
The tip of the optical fiber is in direct contact with the optical waveguide of the optical waveguide circuit without using the adhesive .
The capillary is provided with a cutout portion in which a half in the radial direction is cut off in a part in the longitudinal direction.
An optical module characterized in that the optical fiber is pressed against the optical waveguide circuit and buckled at the cutout portion . The optical module according to claim 1, wherein the tip portion of the optical fiber is polished into a trapezoidal shape, and the tip surface of the trapezoidal shape is approximately perpendicular to the traveling direction of light.