JP2007309967A - Method of manufacturing optical component or optical module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical component or an optical module, wherein a thermosetting and UV-curing adhesive can be used even when the component is formed of an alkaline and UV non-transmitting material, and positional deviation and property deterioration are less during adhesive fixation, and long-term stability is excellent. <P>SOLUTION: In the optical module manufacturing method, an optical isolator element 23 is fixedly adhered to the end face of a ferrule 21 with a built-in optical fiber using an optical adhesive (adhesive 25), wherein the optical isolator element is composed of a planar glass polarizer and a Faraday rotator fixedly adhered thereto with the optical adhesive. In this method, before the adhesive fixation of the isolator element 23, a non-alkaline dielectric film 24 having a refractive index nearly comparable to that of the adhesive 25 is formed on the joining face of the optical isolator element 23 to be joined through the adhesive 25. Also, a similar non-alkaline dielectric film 22 is formed on the end face of the ferrule 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical component or an optical module used in an optical communication device or the like.

  In general, as optical components and optical modules used for optical communication, optical connectors, optical isolators, LD modules for transmitting optical signals, and PD modules for receiving optical signals are known. In particular, in the case of an optical information processing system that requires large capacity, high speed, and long-distance relay communication functions, a DFB laser having excellent dispersion characteristics is used as an LD. Is very sensitive, and there is a problem that the characteristics become unstable when the reflected light from the coupling end face to the optical fiber or other discontinuous interface returns. Therefore, in such a case, in order to prevent the reflected light from returning to the light emitting element, a one-way transmission function of light between the light emitting element and the optical fiber (transmits light in the forward direction and transmits light in the reverse direction). An optical isolator module such as that shown in Patent Document 1 is used.

  A schematic cross-sectional view of an example of this optical isolator module is shown in FIG. In general, when configuring an optical module that combines optical components such as optical connectors and optical isolators, an optical fiber is required to obtain sufficient mechanical strength to protect and fix the end face of the optical fiber when it is integrated with the component. The tip of is fixed to the ferrule. In FIG. 4, the tip portion of the optical module of the optical fiber 100 is formed by removing the optical fiber coating material to form an optical fiber 101, which is cylindrical, zirconia having an optical fiber insertion hole at the center, glass, metal, or the like. It is inserted and fixed in a ferrule 102 made of the above material.

  In FIG. 4, the end surface 103 of the ferrule 102 is polished integrally with the end surface of the optical fiber 101, and the polished end surface is slanted to prevent the reflected light from being coupled back in the light transmission direction. Yes. The optical isolator element 104 is directly bonded and fixed to the end face 103. The optical isolator element 104 here is configured by installing and fixing a Faraday rotator between an incident side polarizer and an output side polarizer having a relative angle of about 45 degrees, and arranging a cylindrical magnet 105 around the Faraday rotator. The Faraday rotator has the action of rotating the plane of polarization of the optical signal by the magnetic field applied from the magnet, and the entrance side polarizer and the exit side polarizer have the action of passing only polarized light in a certain direction. Have. In FIG. 4, the magnet 105 is installed and fixed on the end face of a cylindrical metal tube 106 that holds the ferrule 102.

  Here, methods such as adhesion, welding, and solder are usually used for manufacturing or fixing optical components constituting the optical module. Among these, the manufacturing method or fixing method by bonding is most often used because it is not limited to the material of the component parts, the degree of freedom of the shape of the fixed object and the fixed object is large, and it is inexpensive. However, in fixing by adhesion, there are problems such as displacement of component parts due to shrinkage during curing of the adhesive, deviation of characteristics due to application of stress to the component parts after heat curing, deterioration, and long-term stability.

  Therefore, epoxy adhesives that are small in shrinkage at the time of adhesive curing, have no influence of heat distortion, and have a high stability such as an ultraviolet curable type or a thermosetting property have been used recently. That is, instead of curing the entire adhesive with ultraviolet rays, a part of the adhesive is cured and temporarily fixed by irradiation with ultraviolet rays, and the cured portion serves as a trigger, and the remaining portion is completely cured by subsequent heating. (Ultraviolet assisted adhesive) is also used as an adhesive having low shrinkage and high stability. Since thermosetting is imparted, it can also be applied to adhesion of sites where ultraviolet irradiation is impossible.

JP 2006-11019 A

  One of the problems with UV curable adhesives with the above thermosetting properties is that an acidic polymerization initiator is essential for curing, i.e., polymerization of the main agent of the adhesive. In some cases, the application of thermosetting was severely limited. One method for solving this problem is to use the ultraviolet assist method described in the previous section. However, in order to be able to use this ultraviolet assist method, it is necessary to sufficiently irradiate ultraviolet rays to the portion where the adhesive is applied. However, the glass polarizer used for the optical isolator element 104 is not only based on alkali glass but also has an ultraviolet transmittance of about 10% or less, so that it is difficult to perform sufficient ultraviolet irradiation. It is. Furthermore, the magneto-optic garnet that constitutes the Faraday rotator is also a material that does not transmit ultraviolet rays. Therefore, it is difficult to apply the ultraviolet assist method to fix the optical isolator element 104 and the end face 103 of the ferrule 102, and only the thermosetting property must be used.

  However, if the glass polarizer based on alkali glass and the ferrule end face are to be bonded and fixed only by thermal curing, it is essential to sufficiently polymerize the main agent before the acidic curing initiator reacts with alkali glass. As a result, it is essential to instantaneously raise the temperature to a very high temperature. For this reason, in the case of curing only by thermal curing, there is a problem that reliability of some components is impaired by raising the temperature to a temperature exceeding the heat resistance temperature of some components. Furthermore, if only the thermosetting property is used, the polymerization initiator reacts with the alkali before the polymerization sufficiently proceeds and is depleted, resulting in insufficient curing.

  As described above, in the conventional method for manufacturing an optical component or optical module, there is a significant limitation on the use of a UV curable adhesive imparted with thermosetting properties, and in particular, the manufacture of a bonded optical isolator element or a ferrule. Fixing the optical isolator element to the end face solves the problem that due to the factors that hinder thermosetting, the UV curing epoxy adhesive has no inherent cure shrinkage and excellent moisture resistance. It has not been.

  Accordingly, an object of the present invention is to provide an optical element produced by bonding and fixing planar optical elements to each other, and an optical module manufacturing method in which a flat optical element is bonded and fixed to a ferrule end face containing an optical fiber. Even if the material is alkaline and does not transmit UV rays, it is possible to use UV-curing adhesives that impart thermosetting, and have excellent long-term stability with little misalignment and deterioration of properties during adhesive fixing. Another object of the present invention is to provide a method for manufacturing an optical component or an optical module.

  The method for manufacturing an optical component or an optical module according to the present invention includes an optical component obtained by bonding and fixing planar optical elements with an optical adhesive, or a planar optical element or a ferrule incorporating an optical fiber for the optical component. In the method of manufacturing an optical component or an optical module for producing an optical module bonded and fixed to an end surface with an optical adhesive, one of the bonding surfaces to be bonded via the optical adhesive prior to the bonding and fixing. At least one non-alkaline dielectric film having a refractive index substantially equal to that of the optical adhesive is formed on the surface or more. By doing so, it is possible to eliminate the curable inhibition factor of the optical adhesive.

  The planar optical element includes a Faraday rotator or a glass polarizer having a magneto-optic garnet thick film. Further, the ferrule is made of zirconia, glass or metal.

  In the optical component or optical module manufacturing method of the present invention, as described above, at least one layer of dielectric film not showing alkalinity having a refractive index substantially equal to that of the optical adhesive is provided on the joint surface or ferrule end surface of each optical element. By forming the dielectric film as a bonding surface in contact with the adhesive, even if the component is a material having alkalinity and does not transmit ultraviolet rays, a thermosetting UV-curable epoxy system It is possible to provide a method for manufacturing an optical component or an optical module, which can use an adhesive, has little positional deviation and property deterioration at the time of adhesive fixation, and is excellent in long-term stability.

  Hereinafter, embodiments of the present invention will be described based on examples. However, this invention is not limited to Examples 1-3.

  As the Faraday rotator used in the present invention, a magneto-optical garnet produced by a liquid phase epitaxial growth method is preferable. Examples of the polarizer / analyzer that transmits only light of a specific polarization plane include an absorptive glass polarizer such as Polar Core (registered trademark) manufactured by Corning or CUPO (registered trademark) manufactured by HOYA. Examples of the magnet used in the present invention include a ferrite magnet and a samarium-cobalt magnet.

  An optical component is produced by bonding and fixing the above planar optical elements with an optical adhesive. Also, an optical module is manufactured by bonding and fixing the above planar optical element or the optical component to an end face of a ferrule containing an optical fiber with an optical adhesive. At this time, prior to the adhesive fixing, at least one non-alkaline dielectric film having a refractive index substantially equal to that of the optical adhesive is formed on one or more surfaces to be bonded via the optical adhesive. . The specific method is as in the following examples.

  FIG. 1 is a manufacturing process diagram for explaining an embodiment of an optical component manufacturing method according to the present invention. FIG. 1 (a) is a diagram for explaining a pre-processing process including dielectric film formation. 1 (b) is a view for explaining an adhesion process. The optical component is composed of three planar optical elements, two absorbing glass polarizers and one 45 degree Faraday rotator composed of a magneto-optic garnet. This optical element has an external magnet for saturating the Faraday rotator or a magnet effect on the Faraday rotator itself by a hard magnetic garnet, and the transmission polarization direction of the two glass polarizers is changed to the polarization plane of the Faraday rotator. It functions as an optical isolator by selecting appropriately with respect to the rotation direction.

First, an antireflective film for air made by laminating a SiO ₂ film and a Ta ₂ O ₅ film on the light incident surface of the first glass polarizer 1 on the light incident side is formed by sputtering, and then A dielectric film 2 (SiO ₂ film) having a thickness of about 200 nm was formed on the surface of the first glass polarizer 1 on the side of the Faraday rotator 5 by a sputtering method. Similarly, a dielectric film (SiO ₂ film) 4 having a film thickness of approximately 200 nm was formed on the surface of the second glass polarizer 3 on the light emitting side on the side of the Faraday rotator 5 by sputtering. Further, an antireflection film for air was formed on the surface of the second glass polarizer 3 on the light emitting side. Next, a SiO ₂ film and a Ta ₂ O ₅ film, which are anti-reflection films for the adhesive, were laminated on both surfaces of the Faraday rotator 5 by sputtering.

  Subsequently, these three optical elements were bonded to produce an optical component that becomes the core of the optical isolator. That is, the optical adhesive 6 is applied to the surfaces of the first and second glass polarizers 1 and 3 on the Faraday rotator side and both surfaces of the Faraday rotator 5, the surfaces coated with the adhesive are combined, and the first The pressure was applied so that the thickness of the adhesive was about 10 μm by appropriately controlling the polarization planes of the second glass polarizers 1 and 3. Subsequently, the block composed of the combined three optical elements was placed in an oven, heated to about 120 ° C., and held for about 30 minutes, whereby the adhesive was thermally cured to complete the optical component. The obtained optical component had sufficient optical characteristics and reliability.

  Here, as the optical adhesive, the thermosetting imparting type ultraviolet curing adhesive (optical adhesive capable of ultraviolet curing and thermal curing) described above was used. This optical adhesive is an epoxy-based airtight adhesive resin that has a refractive index similar to that of glass and can be cured by both UV and heat. It has low moisture permeability, high Tg (glass transition temperature), high It has adhesiveness and is known as an optimum adhesive for fixing an optical fiber to a V-groove in an optical fiber component. Once cured, it has been found that it exhibits very high moisture resistance against common epoxy or acrylic optical adhesives. However, this optical adhesive has the problem that it is inferior in the adhesiveness of the material which has alkalinity as the only fault.

  The reason why this optical adhesive is inferior in adhesiveness of a material having alkalinity is that it is essential that an acidic polymerization initiator intervenes in order to initiate the polymerization of the main agent. This is because sufficient polymerization initiator is not supplied due to the reaction between the polymerization initiator and the alkaline material. This is because prior to the production of the optical component according to the first embodiment, a similar optical component was attempted without forming a dielectric film on the Faraday rotator side surfaces of the first and second glass polarizers. This is also demonstrated from the results of the following comparative examples.

  Manufacture of an optical component as a comparative example prior to Example 1 was performed according to the following procedure. That is, in the process shown in FIG. 1, it was exactly the same except that the dielectric film was not formed on the surfaces of the first and second glass polarizers on the Faraday rotator side. Although this optical component was held at about 120 ° C. for about 30 minutes, the adhesive on the surface to be bonded was uncured, and both the optical properties and the reliability were insufficient. Since the adhesive was uncured, the joint surface could be easily removed. When the uncured adhesive was observed with a Fourier transform infrared spectrophotometer (FTIR), it was found that only the peak of the polymerization initiator disappeared compared to the adhesive before the reaction. The disappeared polymerization initiator is considered to have reacted with alkali glass which is the base material of the glass polarizer.

  On the other hand, as described above, the optical component manufactured in Example 1 has sufficient optical characteristics and reliability. When the optical component manufactured in exactly the same manner was destroyed and the joint surface was observed, an adhesive was obtained. Was confirmed to be completely cured. This is because the effect of the polymerization initiator is impaired by isolating the alkali glass that is the base material of the glass polarizer from the adhesive by interposing the dielectric film on the surface that meets the adhesive of the present invention. It is considered that the curing of the adhesive progressed without any problems.

  FIG. 2 is a manufacturing process diagram for explaining an embodiment of the manufacturing method of the optical module according to the present invention, and is a diagram showing the bonding process which is a part of the manufacturing process of the optical isolator module. FIG. 2A is a diagram for explaining the pretreatment process, and FIG. 2B is a diagram for explaining the bonding process and the magnet fixing process. In FIG. 2, the components and the like are shown in a cross-sectional view of only the cut surface, but hatching is omitted. This optical isolator module is a so-called pigtail fiber with an isolator, and has a structure having an optical isolator on the end face of the ferrule and various optical connectors on the opposite side of the optical fiber having a fixed length.

In the pretreatment process of FIG. 2A, a dielectric film (SiO ₂ film) 22 is formed by sputtering on the optical element side end face of the ferrule 21 that is made of zirconia, metal, glass, etc. and has a cylindrical optical fiber built in the center. It is formed to a thickness of about 300 nm. This is because the ferrule end face is polished through various polishing steps including polishing with a strong alkaline polishing agent in order to form a clean and smooth end face of the built-in optical fiber, and after polishing, for example, a strong alkaline detergent As it is, the alkali component is not completely removed as it is, and there is a high possibility of affecting the thermosetting of the thermosetting UV curable optical adhesive. Because.

  Subsequently, an optical isolator element 23, which is an optical component to be bonded to the ferrule end face on which the dielectric film was formed, was manufactured in a process based on Example 1. The only difference is that a dielectric film similar to the surface on the Faraday rotator side is used instead of forming an antireflection film for air on the surface on the light emitting side of the second glass polarizer bonded to the ferrule end face. 24 is formed.

  Next, in the bonding step of FIG. 2B, an appropriate amount of the first embodiment is applied to the surface on which the dielectric film 24 to be bonded to the ferrule end face of the optical isolator element 23 is formed and the ferrule end face on which the dielectric film is similarly formed. The same adhesive 25 was applied, and an isolator element (same as the optical isolator element) was pressed against the ferrule to apply pressure. Further, the magnet 26 was pressed against the outer periphery of the isolator element after applying the adhesive. Then, the adhesive was heat-cured by heating the ferrule end face to about 120 ° C. and holding it for about 30 minutes using a small contact heater 27 capable of local heating. The reason for the local heating is that the heat resistance of the optical connector or the optical fiber coating is taken into consideration.

  The optical isolator module manufactured by the above method has sufficient optical properties and reliability, and the ferrule, the isolator element, and the adhesive on the joint surface of the magnet were completely cured. On the other hand, as a comparative example, an optical isolator module manufactured without forming a dielectric film on the ferrule end face or the ferrule side end face of the isolator element is insufficient in terms of reliability and cannot be adopted as a mass production technique. It has been found.

  The optical isolator module manufactured as the comparative example is the following three types. (1) those having no dielectric film on both the ferrule end face and the isolator element end face; (2) those having a dielectric film on the ferrule end face but having no dielectric film on the end face of the isolator element; 3) The end face of the isolator element has a dielectric film, but the end face of the ferrule does not have a dielectric film.

  The manufacturing process of these three types of optical isolator modules was exactly the same as in Example 2 except for the presence or absence of a dielectric film. None of the results were perfect in terms of reliability, but 10 out of 100 were particularly reliable for those without a dielectric film on both the ferrule side and the end face of the isolator element. Was insufficient. Further, in the case where the dielectric film was formed only on the ferrule end face, 6 out of 100 were insufficient in reliability. Further, in the case where the dielectric film was formed only on the end face of the isolator element, 2 out of 100 were insufficient in reliability.

  When the joint surface between the ferrule and the isolator element of these modules with insufficient reliability was broken and observed, it was confirmed that the adhesive was partially uncured. On the other hand, in the module according to Example 2, as described above, the adhesive was completely cured. That is, it is considered that the adhesive could be completely cured by isolating the substance that inhibits the curing of the adhesive by covering the surface that meets the adhesive with a dielectric.

  FIG. 3 is a view for explaining another embodiment of the method for manufacturing an optical module according to the present invention, and FIG. 3A is a schematic cross-sectional view of a receptacle type optical isolator module for which this embodiment 3 is intended to be manufactured. FIG. 3B is an explanatory view showing an optical isolator element bonding step which is a part of the manufacturing process. However, in the schematic sectional view of FIG. 3A, the main part of the present invention is not shown. Further, FIG. 3 shows only the cut surface of the cross section, and hatching is omitted.

  As shown in FIG. 3 (a), the receptacle-type optical isolator module is made of zirconia, metal, glass, or the like, and has a cylindrical shape, and a ferrule 31 that is fixed by inserting and fixing an optical fiber strand into a central insertion hole. An optical isolator element 33 is bonded and fixed to the end face 32. The other end face 34 of the ferrule 31 is polished flat, and the ferrule portion of the optical fiber terminal or optical connector having the same flat end-polished ferrule to be optically coupled is inserted into the metal holder 35 of the receptacle. The end surfaces of both ferrules are abutted against each other. Reference numeral 37 denotes a magnet.

The bonding process of the optical isolator element 33 of the third embodiment is basically the same as the process of FIG. That is, a dielectric film (SiO ₂ film) 38 is formed to a thickness of about 400 nm on the end surface of the ferrule 31 made of zirconia, metal, glass or the like and having a cylindrical shape and containing an optical fiber at the center by sputtering. This is because, in the receptacle manufacturing process as well as the pigtail fiber, the ferrule end face is subjected to various polishing processes including polishing with a strong alkaline polishing agent in order to form a clean and smooth end face of the built-in optical fiber. After polishing, and after polishing, it has undergone various cleaning steps including, for example, a cleaning step with a strong alkaline detergent, and as it is, the alkali component has not been completely removed, and a thermosetting UV curable optical system This is because there is a high possibility of affecting the heat curing of the adhesive.

  Subsequently, an optical isolator element 33 which is an optical component to be bonded to the ferrule end face on which the dielectric film was formed was manufactured by a process based on Example 1. That is, in the same manner as in Example 2, instead of forming an antireflection film for air on the surface on the light emitting side of the second glass polarizer bonded to the ferrule end surface, the same as the surface on the Faraday rotator side A dielectric film 39 was formed.

  Next, in the bonding step of FIG. 3B, an appropriate amount of the first embodiment is applied to the surface on which the dielectric film 39 to be bonded to the ferrule end surface of the optical isolator element 33 is formed and the ferrule end surface on which the dielectric film 38 is similarly formed. The same adhesive 40 was applied, and the isolator element was pressed against the ferrule to apply pressure. Further, a magnet 37 was applied to the outer periphery of the isolator element after being applied with an adhesive. Thereafter, the receptacle for holding the isolator element was heated to about 120 ° C. or higher in an oven and held for about 30 minutes or longer, whereby the adhesive was thermally cured. FIG. 3B shows only the optical element bonding step, and does not show the entire module having the structure shown in FIG.

  The receptacle type optical isolator module manufactured by the above method has sufficient optical characteristics and reliability, and the ferrule, the isolator element, and the adhesive on the joint surface of the magnet are completely cured. On the other hand, the optical isolator module manufactured without forming a dielectric film on the ferrule end face or the ferrule side end face of the isolator element in the same manner as the comparative example described in the second embodiment is also insufficient in terms of reliability. It has been found that it cannot be adopted as a mass production technology. The cause was also the same as that described in Example 2.

  When the joint surface between the ferrule and the isolator element of the module with insufficient reliability was broken and observed, it was confirmed that the adhesive was partially uncured. On the other hand, in the module according to this example, as described above, the adhesive was completely cured. That is, it is considered that the adhesive could be completely cured by isolating the substance that inhibits the curing of the adhesive by covering the surface that meets the adhesive with a dielectric.

  As described above, according to the present invention, even if the component is a material that does not transmit ultraviolet light or is difficult to transmit ultraviolet light, and is an alkaline substance that inhibits thermal curing, the thermosetting imparted ultraviolet curing adhesive It is possible to use an agent, and it is possible to manufacture an optical component or an optical module that is excellent in long-term stability with little misalignment and characteristic deterioration during adhesion fixation.

In the embodiment of the present invention, the dielectric film is a SiO ₂ film, but the refractive index is about 1.5, that is, almost the same as the refractive index of the optical adhesive and does not show alkalinity. Any dielectric material can be used. For example, a mixture of SiO ₂ and other dielectrics, so-called multicomponent glass may be used. In addition, as a method for forming the dielectric film, the sputtering method is used in the embodiments, but an ion-assisted vapor deposition method, an ion beam sputtering method, and the like are also applicable. Further, the dielectric film may be a film having two or more layers.

The manufacturing process figure for demonstrating one Example of the manufacturing method of the optical component by this invention. FIG. 1A is an explanatory diagram of a pretreatment process including dielectric film formation, and FIG. 1B is an explanatory diagram of an adhesion process. The manufacturing process figure for demonstrating one Example of the manufacturing method of the optical module by this invention. FIG. 2A is an explanatory diagram of a pretreatment process, and FIG. 2B is an explanatory diagram of an adhesion process and a magnet fixing process. The figure for demonstrating the other Example of the manufacturing method of the optical module by this invention. FIG. 3A is a schematic cross-sectional view of a receptacle-type optical isolator module, and FIG. 3B is an explanatory diagram of an optical isolator element bonding step. A typical sectional view of an optical isolator module.

Explanation of symbols

1, 3 Glass polarizer 2, 4, 22, 24, 38, 39 Dielectric film 5 Faraday rotator 6 Optical adhesive 21, 31, 102 Ferrule 23, 33, 104 Optical isolator element 25, 40 Adhesive 26, 37 , 105 Magnet 27 Contact type heater 32 End face 34 obliquely polished The other end face 35 Metal holder
36 Sleeve 100 Optical fiber 101 Optical fiber strand 103 End face
106 Metal tube

Claims (3)

  An optical component formed by bonding and fixing planar optical elements with an optical adhesive, or an optical module formed by bonding and fixing a flat optical element or the optical component to an end face of a ferrule containing an optical fiber with an optical adhesive In the method of manufacturing an optical component or an optical module for manufacturing an optical component, a refractive index substantially equal to that of the optical adhesive is applied to one or more surfaces to be bonded via the optical adhesive prior to the adhesive fixing. A method for producing an optical component or an optical module, comprising forming a non-alkaline dielectric film having at least one layer.  2. The method of manufacturing an optical component or an optical module according to claim 1, wherein the planar optical element includes a Faraday rotator or a glass polarizer having a magneto-optic garnet thick film.   3. The method of manufacturing an optical component or an optical module according to claim 1, wherein the ferrule is made of zirconia, glass, or metal.

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