JP2008277547A - Method for manufacturing optical amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical amplifier which can actualize the optical amplifier having low connection loss with high precision by a comparatively easy technique. <P>SOLUTION: The method for manufacturing an optical amplifier 10 includes a step to arrange a light hardening material in which optical amplification material is mixed in the vicinity of end surface of an optical fiber 20, and a step to propagate a laser light to the optical fiber 20 and to harden the light hardening material by the irradiation of the laser light emitted from the end surface of the optical fiber 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical amplifier using a self-written waveguide technique.

  Conventionally, in the field of optical communication, an optical amplifier (EDFA: Erbium Doped Fiber Amplifier) using transition of Er (erbium) ions added to glass has been widely adopted.

  However, since the number of Er atoms (Er concentration) that can be contained in this EDFA is low, the total length of the fiber amplifier needs to be several meters or more in order to obtain a practical gain. Therefore, it is not suitable for small applications, for example, application to optical integrated circuits.

  Semiconductor optical amplifiers have also been developed as an alternative to EDFAs. The semiconductor optical amplifier can be easily downsized, but it is difficult to perform the non-reflective coating on the end face, and the alignment between the waveguide of the optical amplifier and the fiber is poor, so that the packaging is difficult.

  On the other hand, since optical amplifiers using organic dyes can be expected to be small and have high gain, optical amplifiers as shown in Patent Documents 1 to 4 below have been proposed.

JP 2004-256393 A JP 2004-214571 A Japanese Patent Laid-Open No. 9-240482 JP 2006-222403 A JP 2004-246335 A IEEE Photonics Technology Letters, Vol. 17, No. 4, pp.786-788, 2005

  In the above-mentioned patent document, materials such as organic dyes and phosphors that can be used as an optical amplifier are mentioned, but the actual connection method with an optical waveguide such as an optical fiber, which is a problem in practical use, is completely described. There is no mention.

  In the future, when optical amplifiers using organic dyes or phosphors are put into practical use, connection technology between optical waveguides such as optical fibers and optical amplifiers will be extremely important.

  An object of the present invention is to provide an optical amplifier manufacturing method capable of realizing an optical amplifier having high accuracy and low connection loss by a relatively simple method.

In order to achieve the above object, an optical amplifier manufacturing method according to the present invention includes a step of disposing a photocurable material mixed with an optical amplification material in the vicinity of an end face of an optical waveguide;
And propagating a laser beam to the optical waveguide, and curing the photocurable material by irradiating the laser beam emitted from the end face of the optical waveguide.

Further, the method of manufacturing an optical amplifier according to the present invention includes a step of causing the first end surface of the first optical waveguide to face the second end surface of the second optical waveguide;
Disposing a photocurable material mixed with a light amplification material in the vicinity of the first end face and the second end face;
Laser light is incident on one or both of the first optical waveguide and the second optical waveguide, and laser light is emitted from one or both of the first end surface and the second end surface to cure the photocurable material; and It is characterized by including.

  In the present invention, the photocurable material is preferably a monomer or oligomer composed of an acrylic acid compound containing a photopolymerization initiator, a cationic polymerizable epoxy compound, a polyimide compound, a silicone compound, or the like, or a mixture of a monomer and an oligomer. .

  In the present invention, the light amplification material is preferably at least one selected from the group consisting of a low molecular weight organic dye, a light emitting polymer and a rare earth ion compound.

  In the present invention, the optical waveguide may be an optical fiber.

  According to the present invention, laser light is propagated to an optical waveguide to be connected to an optical amplifier, and the photocurable material is cured by irradiation of the laser light emitted from the end face of the optical waveguide. The body of the optical amplifier can be formed in a self-aligned manner along the axis. Therefore, there is almost no optical axis deviation between the optical waveguide and the optical amplifier, and an optical amplifier having high accuracy and low connection loss can be easily realized.

  FIG. 1 is a perspective view showing an example of a method for manufacturing an optical amplifier according to the present invention. After a light amplifying material is mixed with a photocurable material to obtain a light amplifying composition 2, an appropriate amount is dropped onto a substrate 1 such as a glass plate.

  Next, the optical fiber 20 is used as an optical waveguide to be connected to the optical amplifier, and the tip of the optical fiber 20 is immersed in the optical amplification composition 2. At this time, the optical fiber 20 is floated from the substrate 1 and is kept substantially parallel to the main surface of the substrate 1 so that a sufficient amount of the optical amplification composition 2 exists in the vicinity of the end surface of the optical fiber 20.

  Next, a laser oscillator 40 that generates a laser beam Lc having a wavelength at which the photocurable material is cured, for example, an Ar laser having a wavelength of 488 nm is operated by CW, and the laser beam Lc is collected using a condensing optical system 30 such as a lens Is incident from the other end of the optical fiber 20. When the laser light Lc propagates through the optical fiber 20 and is emitted from the end face of the optical fiber 20, the photocurable material existing near the end face is irradiated locally. In the portion of the photocurable material that has been irradiated with the laser beam Lc, a curing reaction such as photopolymerization starts, and is cured linearly along the optical axis of the laser beam Lc. On the other hand, the part which is not irradiated with the laser beam Lc remains uncured.

  When the cured linear portion reaches a desired length, the irradiation with the laser beam Lc is stopped, and the optical amplifier 10 is obtained by removing from the composition for optical amplification and washing.

  FIG. 2 is an explanatory diagram showing the state of curing at the end of the optical fiber 20. First, as shown in FIG. 2A, an optical amplification composition is disposed in the vicinity of an end portion of an optical fiber 20 having a core 20a and a clad 20b.

  Next, as shown in FIG. 2B, when the laser beam Lc is incident on the optical fiber 20, a curing reaction starts at a portion in contact with the end face of the core 20a. As shown in FIG. 2C, the cured portion gradually grows as the irradiation time of the laser beam Lc elapses.

  Next, as shown in FIG. 2D, the irradiation of the laser beam Lc is stopped when the cured portion has a required length.

  At this time, when the optical fiber 20 is a step index type multimode fiber, the laser light is emitted from the end face of the optical fiber 20 in a beam shape of a plurality of spots. Therefore, the cured portion of the optical amplification composition may have a complicated shape. On the other hand, when the optical fiber 20 is a graded index type multimode fiber or a single mode fiber capable of single mode propagation for the laser light Lc, the laser light has a single spot beam shape from the end face of the optical fiber 20. Exit. Therefore, the cured portion of the optical amplification composition has a single rod shape. Therefore, in order to reduce insertion loss, the optical fiber 20 to be used is preferably a graded index type multimode fiber or a single mode fiber capable of single mode propagation for the laser light Lc.

  FIG. 3 is an explanatory view showing another example of a method of manufacturing an optical amplifier according to the present invention. Here, an example in which an optical amplifier is formed between two optical fibers will be described.

  First, as shown in FIG. 3A, optical fibers 21 and 22 having cores 21a and 22a and clads 21b and 22b, respectively, are used as optical waveguides to which optical amplifiers are to be connected. Position so as to face each other with a gap. At the time of positioning, the centers of the cores 21a and 22a are accurately matched using a V-shaped groove jig or other alignment tool. In this state, an appropriate amount of the above-described optical amplification composition is dropped into the gap between the two, and is disposed in the vicinity of each end face of the optical fibers 21 and 22.

  Next, as shown in FIG. 3B, when the laser light Lc is incident on the optical fiber 21, a curing reaction starts at a portion in contact with the end face of the core 21a, and as the irradiation time of the laser light Lc elapses. Hardened part grows gradually. Then, the irradiation of the laser beam Lc is stopped just before the leading end of the cured portion reaches the end face of the other optical fiber 22, and the curing reaction is stopped.

  Next, as shown in FIG. 3C, this time, the laser beam Lc is incident on the optical fiber 22, and a curing reaction is started at a portion in contact with the end face of the core 22a. Then, when the entire shape of the cured portion becomes substantially bilaterally symmetric, the irradiation of the laser beam Lc is stopped and the curing reaction is stopped. Thus, a single rod-shaped optical amplifier 10 is obtained.

  Next, as shown in FIG. 3 (d), after the optical amplification composition adhering to the surfaces of the optical amplifier 10 and the optical fibers 21 and 22 is washed, a curable material for cladding is disposed around the optical amplifier 10. To do. Then, the optical amplifier 10 integrated with the optical fibers 21 and 22 is obtained by curing the curable material for cladding.

  The clad curable material may be the same photocurable material as the optical amplification composition, may be a different photocurable material, or may be a material utilizing a different kind of curing reaction, for example, a thermosetting material. Absent. In general, from the viewpoint of adhesion between the core and the clad, it is preferable to use the same photocurable material as the optical amplification composition as the clad curable material.

  Moreover, when hardening the composition for optical amplification, the case where the laser irradiation from the optical fiber 21 and the laser irradiation from the optical fiber 22 are performed at different timings has been described, but both laser irradiations may be performed simultaneously. Alternatively, only one of the laser irradiations may be performed.

  FIG. 4A is a side view showing an example of an optical amplifier obtained by the method shown in FIG. It can be seen that a coaxial rod-shaped optical amplifier extends from the end face of the optical fiber.

  FIG. 4B is a side view showing an example of an optical amplifier obtained by the method shown in FIG. FIG. 4c is an enlarged view corresponding to FIG. FIG. 4d is an enlarged view corresponding to FIG. It can be seen that an optical amplifier formed coaxially between the two optical fibers connects the end faces of the optical fiber. Further, since the length of the optical amplifier also changes according to the gap between the optical fibers, it is easy to make it exactly match the design length of the optical amplifier.

  In the optical amplifier manufacturing method described above, the photocurable material used as a base material is a monomer or oligomer made of an acrylic acid compound containing a photopolymerization initiator, a cationic polymerizable epoxy compound, a polyimide compound, a silicone compound, or the like, or a monomer Among them, an acrylic acid compound is preferable. For example, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, epoxy acrylic acid, epoxy acrylic acid ester, urethane acrylic acid, urethane acrylic acid ester and the like can be used. Specific products such as PAK-01 ( Toyo Gosei) and DF-803N (Nippon Kayaku).

  Examples of the photopolymerization initiator added to the photocurable material include benzoin and benzoin alkyl ethers, acetophenones, aminoacetophenones, anthraquinones, thioxanthones, ketals, benzophenones, and xanthones.

  The light amplifying material mixed with the photocurable material is preferably at least one selected from the group consisting of a low molecular weight organic dye, a light emitting polymer and a rare earth ion compound.

  For example, rhodamine 6G, rhodamine B, coumarin 153, coumarin 307, and the like can be used as the low molecular organic dye. In addition, perchlorate dyes (for example, NK-2807 (Hayashibara Biochemical Research Institute)) and iodides can be used. System dyes (for example, NK-125 (Hayashibara Biochemical Research Institute)) and the like can be used.

  As the light-emitting polymer, polyphenylene vinylene or a derivative thereof (for example, CN-PPV) can be used.

  As the rare earth ion compound, those soluble in an organic base material such as an organic rare earth complex or a rare earth metal composite alkoxide can be used.

  Regarding the combination of the base material and the light amplification material, from the viewpoint of solubility, a combination of DF-803N and NK-125, a combination of PAK-01 and rhodamine 6G, rhodamine B, coumarin 153, coumarin 307 or CN-PPV, methyl methacrylate And a combination of NK-2807, methyl methacrylate and an organic rare earth complex or a rare earth metal composite alkoxide.

  FIG. 5 is a configuration diagram showing an example of a method for measuring the emission spectrum of the optical amplifier. The optical amplifier 10 uses a composition for light amplification in which a photocurable monomer (product name: DF-803N) and a luminescent dye NK-125 are mixed by solvent replacement using ethanol, and the self-forming method as described above. Produced. The optical amplifier 10 was prepared with waveguide lengths of 0.83 mm, 0.96 mm, 1.18 mm, 1.20 mm, and 1.32 mm.

  The optical amplifier 10 formed on the end face of the optical fiber 20 is fixed on the stage 50, the other end of the optical fiber 20 is optically connected to the spectrometer 51, and the emission spectrum of the optical amplifier 10 is measured by a PC (personal computer) 52. Analyzed.

  A dye laser 60 having a wavelength of 723 nm was oscillated as excitation light, and the optical amplifier 10 was irradiated from the side through an ND filter 61 and a cylindrical lens 62.

  FIG. 6A is a graph showing an example of the emission spectrum of the optical amplifier 10. The vertical axis represents light intensity (arbitrary unit), and the horizontal axis represents wavelength (nm). The waveguide length of the used optical amplifier 10 is 1.32 mm.

When the intensity of the pumping light was changed to 162, 270, 324, 378, 432, 486, 540 (μJ / cm ² ), the emission intensity of the optical amplifier 10 gradually increased, and in particular, 486 (μJ / cm ² ) to 540 (μJ / cm ² ), the emission intensity in the vicinity of the wavelength of 770 nm increases abruptly, and it can be seen that amplified spontaneous emission light (ASE) is generated.

FIG. 6B is a graph showing the relationship between the emission intensity and the excitation light intensity in the optical amplifier 10. The vertical axis represents normalized emission intensity, and the horizontal axis represents excitation light intensity (μJ / cm ² ). The curves correspond to the waveguide lengths 0.83 mm, 0.96 mm, 1.18 mm, 1.20 mm, and 1.32 mm of the optical amplifier 10, respectively.

As can be seen from the graph, in the optical amplifier 10 having a short waveguide length, the light emission intensity monotonously increases with respect to the excitation light intensity. It can be seen that when the light intensity exceeds 486 (μJ / cm ² ), the emission intensity rapidly increases and amplified spontaneous emission light (ASE) is observed.

  FIG. 7 is a configuration diagram illustrating an example of a method for measuring a gain spectrum of an optical amplifier. The optical amplifier 10 has the same configuration as that used in FIG. The optical amplifier 10 is interposed between the optical fiber 21 and the optical fiber 22. As signal light, CW light having a wavelength of 770 nm was generated from an LD (semiconductor laser) 70 and incident on the front end face of the optical fiber 21 via the lens 71. The rear end face of the optical fiber 22 was optically connected to a spectrometer 51, and the gain spectrum of the optical amplifier 10 was analyzed by a PC (personal computer) 52.

  As excitation light, a dye laser 60 having a wavelength of 723 nm was pulse-oscillated with a pulse width of 1 ns, and the optical amplifier 10 was irradiated from the side through a cylindrical lens 62.

  FIG. 8 is a graph showing an example of the optical amplification action of the optical amplifier 10. The vertical axis represents light intensity (arbitrary unit), and the horizontal axis represents wavelength (nm). A curve a indicates a transmission spectrum of signal light that is integrated for 0.1 seconds with the excitation light irradiation stopped. A curve b shows a spectrum obtained by subtracting ASE from the total of ASE and signal light in a state where 1 ns of excitation light is irradiated with one pulse during time integration of 0.1 seconds.

Comparing curve a and curve b shows that a gain of about 1.2 times is obtained near the wavelength of 770 nm. This corresponds to 1.7 × 10 ⁷ (72.3 dB) in terms of gain at the time of pulse irradiation for 1 ns.

  In the above description, an example in which an optical fiber is used as a connection target of an optical amplifier is shown. However, in the present invention, an optical amplifier may be provided so as to connect waveguides formed on a substrate. Application to circuits is also possible.

  The present invention is extremely useful industrially in that an optical amplifier having high accuracy and low connection loss can be realized by a relatively simple method.

It is a perspective view which shows an example of the manufacturing method of the optical amplifier which concerns on this invention. It is explanatory drawing which shows the state of hardening in the edge part of an optical fiber. It is explanatory drawing which shows the other example of the manufacturing method of the optical amplifier which concerns on this invention. It is a side view which shows an example of the optical amplifier obtained by the method shown in FIG. It is a side view which shows an example of the optical amplifier obtained by the method shown in FIG. FIG. 4 is an enlarged view corresponding to FIG. FIG. 4 is an enlarged view corresponding to FIG. It is a block diagram which shows an example of the measuring method of the emission spectrum of an optical amplifier. FIG. 6A is a graph showing an example of the emission spectrum of the optical amplifier, and FIG. 6B is a graph showing the relationship between the emission intensity and the excitation light intensity. It is a block diagram which shows an example of the measuring method of the gain spectrum of an optical amplifier. It is a graph which shows an example of the gain spectrum of an optical amplifier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Composition for optical amplification 10 Optical amplifier 20, 21, 22 Optical fiber 20a, 21a, 22a Core 20b, 21b, 22b Clad 30 Condensing optical system 40 Laser oscillator 50 Stage 51 Spectrometer 52 PC (personal computer)
60 Dye laser 61 ND filter 62 Cylindrical lens

Claims (5)

Arranging a photocurable material mixed with a light amplification material in the vicinity of an end face of the optical waveguide;
And a step of propagating the laser beam to the optical waveguide and curing the photocurable material by irradiation of the laser beam emitted from the end face of the optical waveguide. Opposing the first end face of the first optical waveguide and the second end face of the second optical waveguide;
Disposing a photocurable material mixed with a light amplification material in the vicinity of the first end face and the second end face;
Laser light is incident on one or both of the first optical waveguide and the second optical waveguide, and laser light is emitted from one or both of the first end surface and the second end surface to cure the photocurable material; and An optical amplifier manufacturing method comprising:   3. The method of manufacturing an optical amplifier according to claim 1, wherein the photocurable material is a monomer or an oligomer made of an acrylic acid compound containing a photopolymerization initiator, or a mixture of a monomer and an oligomer.   3. The method of manufacturing an optical amplifier according to claim 1, wherein the light amplification material is at least one selected from the group consisting of a low molecular organic dye, a light emitting polymer, and a rare earth ion compound.   3. The method of manufacturing an optical amplifier according to claim 1, wherein the optical waveguide is an optical fiber.