JP2009200348A - Material for optical doping, and optical amplifying medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the thermal resistance of a material for optical doping used for an optical amplifier using an organic polymer. <P>SOLUTION: Rare earth metal salt and a carboxylic acid compound are mixed in an organic solvent and/or water. In a combination of the salt of rare earth metal and carboxylic acid compound, the rare earth metal is preferably erbium and the carboxylic acid compound is preferably fluoride or chloride of benzoic acid, or fluoride or chloride of aliphatic carboxylic acid with C2-10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical doping material used for an optical amplifier that amplifies the intensity of signal light by pump light. In particular, in optical communication, optical interconnection, etc., the pump light and / or signal light is light. The present invention relates to an optical doping material used for an optical amplifier that propagates a fiber, an optical waveguide, and the like, and an optical amplification medium using the same.

  The role of optical communication technology in the advanced information society is very important, and the optical communication network covers the whole world, such as the Internet, domestic trunk lines, metro networks, and FTTH (Fiber To The Home). In the 1990s, with the introduction of an arrayed waveguide grating (hereinafter also referred to as “AWG”), wavelength division multiplexing (Wavelength multiplexing) that simultaneously transmits a large number of optical signals of different wavelengths in one optical fiber. Division Multiplexing (hereinafter also referred to as “WDM”) transmission system has been commercialized, and the construction of a large-capacity high-speed information communication network has been accelerated.

  One of the elemental technologies that has enabled commercialization of such a WDM transmission system is an optical amplification technology in a low-loss wavelength region (1.55 μm band) of a silica-based optical fiber. A technology for amplifying signal light in a wavelength band of 1550 nm using a semiconductor laser having a wavelength of 980 nm or 1480 nm as excitation light has already been commercialized. At this time, rare earth metal is doped in the optical fiber in which the signal light and the excitation light propagate, and the rare earth metal is excited by the excitation light, and then emitted in the 1550 nm band is superimposed on the signal light. It compensates for the signal light intensity that attenuates in the long-distance transmission process. As the rare earth metal doped in such an optical fiber, erbium is best known and widely used as an erbium-doped optical fiber amplifier. In addition to erbium, optical amplifiers using rare earth metals such as praseodymium and thulium are being actively developed according to the signal light wavelength band to be used.

  Generally, rare earth metals are doped in a silica-based optical fiber at a concentration of about 500 to 1000 ppm. Doping at a higher concentration causes the rare earth metals to agglomerate, and the energy of the rare earth metals excited by the excitation light moves to the adjacent rare earth metal before emitting the light corresponding to the signal light wavelength, and the desired light emission is achieved. It is known that a phenomenon that cannot be obtained occurs. This is called “concentration quenching” and affects the limit of doping rare earth metal into a silica-based optical fiber (see, for example, Non-Patent Document 1). For this reason, in order to amplify the signal light to a practically necessary intensity by the pumping light, a long optical fiber of about 100 m is required, which is a factor that hinders downsizing of the optical amplifier.

  On the other hand, with the aim of further increasing the functionality and cost, studies are underway to replace the quartz base material of the optical amplifier with an organic polymer base material. In general, rare earth metal-containing phosphors can be cited as rare earth metals that can be doped into organic polymers. Here, the phosphor is composed of three components: a host material, an activator, and an active assistant, and an oxide crystal or an ionic compound crystal is used as the host material. That is, the rare earth metal having fluorescence itself as an activator component is not directly doped into the organic polymer, but the rare earth metal is yttrium aluminum garnet (hereinafter also referred to as “YAG”) or the like. The purpose is achieved by once doping the oxide crystal and then crushing the crystal and mixing it into the organic polymer. However, when such a method is used, it is necessary to perform baking at a high temperature of about 1400 ° C. in order to form a YAG crystal, which increases the process cost. In addition, the particle size of the pulverized rare earth metal-containing phosphor is generally 1000 nm (1 μm) or more, and when dispersed at a high concentration for the purpose of application to an optical amplifier, the transparency decreases due to light scattering. It will not function as an optical transmission line. Therefore, there is a limit to the concentration at which the organic polymer can be doped with a rare earth metal-containing phosphor in a host material such as a crystal, and the optical amplifier is downsized as the doping amount increases, and an organic material is used as an optical transmission medium. It is impossible to achieve economic improvement by doing.

  As a technique for doping rare earth metals directly into organic polymers, (a) organic polymers formed by forming organic complexes of rare earth metals with organic ligands such as pyridines, phenanthrolines, quinolines, β-diketones, etc. An organic-inorganic composite synthesis method has been proposed, for example, in which a rare earth metal is dispersed therein, or (b) a material in which a rare earth metal is incorporated in an organic inclusion compound is dispersed in an organic polymer (for example, Patent Document 1, 2, refer to Non-Patent Document 2).

  The methods shown in the above (a) and (b) have the feature that the control range of the kind and concentration of rare earth metals can be expanded. Further, since the rare earth metal-containing dispersed phase thus obtained is in the molecular order, even if this dispersed phase is somewhat aggregated, it can be suppressed to a size of several nanometers to 20 nm. It has a feature that it can be doped at a high concentration without deteriorating the properties. However, when these methods are used, the excited state energy of the rare earth metal excited by the excitation light is directly linked to the rare earth metal by the Frank-Condon principle known in quantum mechanics. There is a problem that the light emission process inherent to the rare earth metal is inhibited (quenched).

  As means for solving such a problem, the excitation energy level of the rare earth metal is obtained by fluorinating or deuterating the CH group of the organic ligand or organic inclusion compound or organic polymer of the rare earth metal complex. There has been proposed a technique for suppressing quenching so that excitation energy levels in organic ligands and organic inclusion compounds do not overlap (see, for example, Patent Documents 3, 4, 5, 6, and Non-Patent Document 3). ).

  The method of fluorinating the CH group is effective in suppressing quenching while enabling the rare earth metal to be dissolved and dispersed in an organic medium at a high concentration. However, the fluoride or deuteride used as a raw material is effective. Since it is unreasonably expensive, it cannot bring about the effect of improving the economic efficiency of the optical transmission network expected by putting an optical amplifier using an organic polymer as a base material into practical use.

As a method for effectively doping a rare earth metal material into an organic polymer, a method using a rare earth metal-containing organic-inorganic composite has been proposed (for example, see Patent Document 7).
Japanese Patent Laid-Open No. 05-088026 JP 2000-208551 A US Pat. No. 6,292,292 US Pat. No. 6,538,805 JP 2000-256251 A Japanese Patent Laid-Open No. 6-1914 JP 2006-222403 A Shoichi Sudo et al. "Optical fiber and optical fiber amplifier" Kyoritsu Shuppan (2006), page 172 C. Koeppen et al., "Journal of Optical Society of America, B", Vol. 14, 155 (1997) LH Slooff et al., Journal of Applied Physics, 91, 3955 (2002)

  On the other hand, if the heat resistance of the rare earth metal is low, an organic-inorganic composite containing the rare earth metal is generated due to heat generated during molding and / or microfabrication of the organic polymer or heat generated when used as an optical amplifier such as an optical waveguide amplifier. There is a concern that the expected amplification effect cannot be obtained. In the case where an organic polymer is doped with a rare earth metal as a light doping material, various studies have been made on concentration quenching and vibration quenching, but no studies have been made from the viewpoint of heat-resistant light doping materials.

  As described above, methods for synthesizing organic-inorganic composites in which rare earth metal materials are doped into organic polymers by various methods have been proposed. However, there are no known materials that have high heat resistance and can be applied to optical amplifiers. .

  This invention is made | formed in view of the above situations, The objective is to provide the material for optical doping with high heat resistance.

  As a result of intensive studies to solve the above problems, the present inventors have found that a light doping material obtained by mixing a rare earth metal salt and a carboxylic acid compound in an organic solvent and / or water is heat resistant. It was found to be excellent.

  That is, the present invention is as follows.

(1) A light doping material obtained by mixing a rare earth metal salt and a carboxylic acid compound in an organic solvent and / or water.

(2) A material for optical doping obtained by mixing and dissolving a carboxylic acid compound in a solution in which a salt of a rare earth metal is dissolved in an organic solvent and / or water, and then removing the organic solvent and / or water. .

(3) Obtained by removing the organic solvent and / or water and by-products after mixing and dissolving the carboxylic acid compound in a solution in which the salt of the rare earth metal is dissolved in the organic solvent and / or water. Photodoping material.

(4) The light doping material according to any one of (1) to (3), wherein the rare earth metal is erbium.

(5) The material for optical doping as described in any one of (1) to (4) above, wherein the carboxylic acid compound is a fluorinated carboxylic acid compound.

(6) The above-mentioned (1) to (4), wherein the carboxylic acid compound is either a fluoride or chloride of benzoic acid and a fluoride or chloride of an aliphatic carboxylic acid having 2 to 10 carbon atoms. The material for optical doping as described in any one.

(7) The above (1), wherein the carboxylic acid compound is any one of trifluoroacetic acid, pentafluoropropanoic acid, undecafluoropropanoic acid, tetradecafluoroheptanoic acid, difluoroacetic acid, trichloroacetic acid, and pentafluorobenzoic acid. The material for optical doping as described in any one of (4).

(8) The light doping material as described in any one of (1) to (7) above, wherein the hue does not change when heated at 200 ° C. for 30 minutes.

(8) An optical amplifying medium in which an organic polymer having transparency at the excitation light wavelength and the signal light wavelength is doped with the light doping material according to any one of (1) to (8) above.

  The light doping material of the present invention has improved heat resistance.

  The optical amplification medium of the present invention can effectively exhibit optical amplification.

<Optical doping material>
The light doping material of the present invention is obtained by mixing a rare earth metal salt and a carboxylic acid compound in an organic solvent and / or water, and has heat resistance.

  Although it does not specifically limit as said rare earth metal salt, For example, nitrate, sulfate, carbonate, chloride, formate, oxalate, acetate, chromium salt, etc. of rare earth metals can be used. Considering reduction of anionic impurities, organic acid salts such as formate, acetate and oxalate are preferred. More preferably, acetate is used. The rare earth metal acetate usually contains water of crystallization and can be used as it is, depending on the type of other metal to be coordinated, but it is preferable to perform a dehydration treatment before the reaction. The rare earth metal salt other than acetate is also preferably dehydrated at 110 to 120 ° C. for about 1 to 2 hours.

  The rare earth metals are lanthanides (lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), Terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu)), scandium and yttrium. In the present invention, praseodymium (Pr ), Neodymium (Nd), erbium (Er) and thulium (Tm) are useful and preferred. In particular, erbium is preferable because it emits light having a wavelength of 1550 nm used for optical communication after being excited. In application to an optical amplifier in a wavelength region called 1.5 μm band (S band 1460-1530 nm, C band 1530-1565 nm, L band 1565-1625 nm) in optical communication, erbium, in particular, is a fluorescence having a central wavelength of 1533 nm. Since it has a light emission level, it is preferable.

  As a combination of the rare earth metal salt and the carboxylic acid compound used for constituting the light doping material of the present invention, the rare earth metal is preferably erbium, and the carboxylic acid compound is a fluorinated carboxylic acid compound. Preferably, it is a fluorinated aromatic carboxylic acid compound or a fluorinated aliphatic carboxylic acid compound. The carboxylic acid compound is preferably either a benzoic acid fluoride or chloride and an aliphatic carboxylic acid fluoride or chloride having 2 to 10 carbon atoms. More preferably, erbium and trifluoroacetic acid, erbium and pentafluoropropanoic acid, erbium and undecafluoropropanoic acid, erbium and tetradecafluoroheptanoic acid, erbium and difluoroacetic acid, erbium and trichloroacetic acid, erbium and pentafluorobenzoic acid And the like.

  A light doping material having high heat resistance can be obtained when these combinations are used. Here, heat resistance means that there is no change in hue even when heated at a constant temperature for 30 minutes. More preferably, the light doping material of the present invention has a combination of heat resistance of 200 ° C. or higher (erbium and trifluoroacetic acid, erbium and pentafluoropropanoic acid, erbium and undecafluoropropanoic acid, erbium and tetradecafluoroheptane Acid, erbium and difluoroacetic acid), and combinations (erbium and trichloroacetic acid, erbium and pentafluorobenzoic acid, etc.) that are 350 ° C. or higher. The light doping material used for the optical amplifier is preferably higher in heat resistance so as not to be decomposed by heat when it is filled in an organic polymer and molded and / or finely processed. Preferably it is 150 degreeC or more, More preferably, it is 200 degreeC or more, Most preferably, it is 350 degreeC or more. That is, it is preferable that the hue does not change even when heated at 150 ° C. for 30 minutes, more preferably the hue does not change even if heated at 200 ° C. for 30 minutes, and even if heated at 350 ° C. for 30 minutes, the hue is changed. More preferably, there is no change.

  The heat resistance in the present invention was measured as follows. In the heat resistance measurement, it is possible to measure with a tool shown below that can easily evaluate whether a heat resistant temperature is higher than a certain temperature (for example, 200 ° C. in the present invention). Specifically, a hot plate capable of raising the temperature of the photodoping material of the present invention as a measurement sample to a certain temperature (for example, 200 ° C.) or higher and a temperature adjusting means capable of adjusting the hot plate to a predetermined temperature are provided. Use the provided hot plate type measuring instrument. As a measurement method, for example, a measurement sample is placed in a powder state on a hot plate, temperature adjusting means is set so that the temperature of the hot plate becomes a certain temperature (for example, 200 ° C.), and the sample is heated at 200 ° C. for 30 minutes. . In the case of a light doping material containing erbium, the measurement sample exhibits a pink color in an active state, and when it is decomposed by heat, it turns black brown. Therefore, when the hot plate is at a certain temperature (for example, 200 ° C.), if there is no change from pink after 30 minutes, the thermal decomposition temperature can be determined to be higher than a certain temperature (for example, 200 ° C.), and the color changes from pink to black brown When it does, it can be judged that the heat-resistant temperature is below a certain temperature (for example, 200 ° C.).

  The mixing ratio of the carboxylic acid compound to the salt of the rare earth metal is not particularly limited, but is preferably 1 equivalent or more with respect to 1 mole of the metal of the rare earth metal. More preferably, it is 2 equivalents or more with respect to 1 mole of the metal of the rare earth metal. By setting the mixing ratio within this range, it is possible to expect further improvement in heat resistance.

  The organic solvent and / or water used when mixing the rare earth metal salt and the carboxylic acid compound is not particularly limited, and the light doping material can be dispersed in the organic polymer, and the rare earth metal salt and Any material that is soluble in the chelating agent may be used. Examples of such an organic solvent include primary alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol; polyvalent resins such as ethylene glycol, propylene glycol, and glycerin. Alcohol: ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol-α-monomethyl ether, propylene glycol-α-monoethyl ether, etc. glycol ether; acetone, methyl ethyl ketone, etc. ketone; tetrahydrofuran, dioxane Cyclic ethers such as methyl acetate, ethyl acetate, propyl acetate, etc .; acetonitrile; aromatic compounds such as benzene, toluene, xylene; penta And hydrocarbon compounds such as hexane, hexane, heptane, cyclohexane; dimethylacetamide (DMAc) and the like. Examples of water include distilled water and ion exchange water. Also, a mixed aqueous solution with an organic solvent that is compatible with water and in which the rare earth metal salt is dissolved can be used.

  The light doping material is obtained by mixing the rare earth metal salt and the carboxylic acid compound in an organic solvent and / or water. The method and conditions for mixing the rare earth metal salt and the carboxylic acid compound are not particularly limited.

  In addition, a carboxylic acid compound may be mixed and dissolved in a solution in which a rare earth metal salt is dissolved in an organic solvent and / or water, and then used as a light doping material while containing the organic solvent and / or water. However, the organic solvent and / or water may be removed, and it is more preferable to remove by-products.

<Optical amplification medium>
It is also preferable to use a combination of different rare earth metals as the optical doping material used for the optical amplification medium.

  The optical amplification medium of the present invention is obtained by doping an organic polymer having transparency at the excitation light wavelength and the signal light wavelength with the light doping material of the present invention.

  The organic polymer in the present invention is not particularly limited as long as it has transparency at the excitation light wavelength and the signal light wavelength, and can be dispersed without aggregating the light doping material. Those having substantial transparency in the wavelength band in which the expression of the optical function is utilized, particularly in the excitation light wavelength and the signal light wavelength, are used. Here, the wavelength band in which the expression of the optical function is used is not limited to the visible band from purple to red, but from ultraviolet rays and X-rays having a wavelength shorter than purple having a wavelength of about 400 nm, and red having a wavelength of about 750 nm. Alternatively, an infrared band having a long wavelength may be used.

  Examples of such an organic polymer include polymethyl methacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate, polyphenyl methacrylate, polycarbonate, polyethylene terephthalate, polystyrene, polytetrafluoroethylene, poly-4-methylpentene-1, polyvinyl alcohol, Examples include polyethylene, polyacrylonitrile, styrene-acrylonitrile copolymer, polyvinyl chloride, polyvinyl carbazole, styrene-maleic anhydride copolymer, polyolefin, polyimide, epoxy resin, polysiloxane, polysilane, polyamide, and cyclic olefin resin. However, it is not limited to these. Moreover, these organic polymers may be used independently and can also be used in combination of 2 or more type.

  Those organic polymers dissolved in a solvent or melted by heating or the like can be mixed with the above-mentioned optical doping material and processed into a desired optical amplification medium. In addition, monomers, oligomers, and the like that are precursors of the desired organic polymer are selected as appropriate, and polymerized in the process of processing into the form of an optical amplifying medium using a mixture of the above-described materials for light doping as a starting material. You can also

  Furthermore, these organic polymers may have a functional group that promotes a reaction such as addition, crosslinking, or polymerization by light or heat in the main chain or side chain. Examples of such a functional group include a hydroxyl group, a carbonyl group, a carboxyl group, a diazo group, a nitro group, a cinnamoyl group, an acryloyl group, an imide group, and an epoxy group. By having these functional groups in the organic polymer, it is possible to improve the adhesion to a substrate or the like, and to perform an addition reaction with an organic material having functionality other than the optical doping material.

  The organic polymer may contain additives such as stabilizers such as plasticizers and antioxidants, surfactants, dissolution accelerators, polymerization inhibitors, and colorants such as dyes and pigments. Furthermore, in order to improve molding processability such as coating properties, organic polymers are made of organic solvents such as solvents (water, alcohols, glycols, cellosolves, ketones, esters, ethers, amides, hydrocarbons). Solvent).

  When the light doping material is dispersed in the organic polymer, the light doping material is preferably present with a diameter of 20 nm or less so as not to cause scattering.

  The optical amplification medium of the present invention can be used for an optical waveguide of an optical waveguide amplifier, a micro optical element of an optical amplifier or a laser, a temperature sensor material, or the like.

<Evaluation of optical characteristics>
The light doping material of the present invention can be evaluated for optical properties by the following method.

  First, an optical waveguide as a measurement sample used for evaluation of optical characteristics is manufactured. As shown in FIG. 1A, the optical waveguide as a measurement sample is a substrate 1 such as a silicon wafer, quartz, or polyimide (the material is not limited as long as it can withstand heating at 350 ° C.), preferably silicon with an oxide film. On the substrate 1 of a wafer, more preferably a silicon wafer having a total thickness of 1 mm having an oxide film having a thickness of 1 μm, and a surface treatment agent for improving adhesion, and if necessary, the present invention is applied at a wavelength of 1.5 microns. An organic polymer having a refractive index lower than that of the optical amplification medium is applied by spin coating or the like (preferably 5 μm or more), and cured (drying, condensation / polymerization / crosslinking reaction) with heat or ultraviolet rays to form a lower clad layer or adhesion assist A film 2 to be a film is formed. The adhesion auxiliary film here is, for example, a surface modified layer using a silane coupling agent or a layer made of a material having a good affinity for the material used for the core layer 3, It is a film | membrane for improving the adhesiveness of. In particular, a material having a refractive index smaller than that of the core layer 3 serves as a lower cladding layer ((b) in FIG. 1). Next, a solution containing an optical amplifying medium is applied on the lower clad layer or the film 2 serving as an adhesion auxiliary film by a spin coat method or the like, and similarly cured by heat or ultraviolet rays (drying, condensation / polymerization / crosslinking reaction), The core layer 3 is formed ((c) of FIG. 1).

  Next, using a dicing saw (manufactured by DISCO Corporation, automatic dicing saw DAD-522, etc.), an excess portion is cut so as to leave the core layer 3 having a width of 10 to 20 μm ((d) in FIG. 1). Preferably, it is better to cut the substrate 1 such as a silicon wafer in order to make the side surface vertical. Subsequently, cutting is performed at a predetermined length (which becomes the waveguide length) in a direction perpendicular to the direction of the optical waveguide to obtain an optical waveguide measurement sample 4. As shown in FIG. 6, optical characteristic evaluation is performed using the optical waveguide measurement sample 4. Details will be described later with reference to FIG.

  In addition, regarding the film in which peeling is observed at the time of cutting due to an adhesive problem, for example, in the case of a polyimide film, cutting is performed after drying only at a temperature before imidization at about 200 ° C., and then 350 ° C. The problem of peeling can be solved by adopting a method of imidizing in such a manner.

  2 shows a cross-sectional view of FIG.

  Using the optical waveguide measurement sample obtained above, optical characteristic evaluation is performed as shown in FIG. As a light source for exciting the rare earth element, a semiconductor laser having a wavelength of 980 nm or 1480 nm is used in the case of erbium. As the signal light source, a wavelength tunable laser that can be arbitrarily selected between wavelengths of 1460 to 1625 nm is used. The light emitted from the signal light source is coupled to a single mode optical fiber, and is passed through an optical isolator that transmits light only in one direction in order to eliminate the influence on the stability of the light source due to the return light from the end face of the optical fiber. The light emitted from the excitation light source is similarly coupled to the single mode optical fiber. Subsequently, the excitation light and the signal light are multiplexed into one single mode optical fiber by a WDM (wavelength division multiplexing) coupler. Subsequently, the combined excitation light and signal light are coupled to the optical waveguide manufactured by the above-described method. The outgoing light from the optical waveguide is similarly coupled to the single mode optical fiber and is demultiplexed by the WDM coupler. The demultiplexed signal light passes through different optical isolators, is coupled to a spectroscope, a detector, and the like, and a fluorescence emission spectrum and a signal light intensity change are measured.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1
<Production Example 1 of Photodoping Material>
10 g of erbium nitrate pentahydrate was placed in a 100 mL eggplant flask, dried and dehydrated under conditions of 110 ° C./vacuum (7 mmHg) for 2 hours to obtain 8 g of erbium nitrate. Under a nitrogen atmosphere, 37.5 mL of dimethylacetamide (DMAc) was added to the obtained erbium nitrate with stirring and dissolved. Subsequently, 44.3 g of a dimethylacetamide solution (concentration 25% by mass) of trichloroacetic acid was added so that 3 equivalents of trichloroacetic acid was added per 1 mol of erbium nitrate.

  Thereafter, the reaction was carried out by stirring at room temperature (20 ° C.). As a result, a transparent solution was maintained. After 2 hours, the reaction solution was stored in a freezer at 5 ° C. for about 20 hours for recrystallization. The crystals were isolated by suction filtration and then dried at 110 ° C. under a constant pressure of 7 mmHg to obtain erbium chloroacetate. The amount of crystals obtained was 12 g. This crystal was used as a light doping material 1 (pink crystal).

<Evaluation of thermal decomposition temperature of photo-doping material>
The thermal decomposition start temperature of the obtained material 1 for photodoping was measured using a heat resistance measuring device (product name: TG / DTA6300, manufactured by Seiko Instruments Inc.). As a result, a temperature of 160 ° C. and 30 ° C. higher than the thermal decomposition starting temperature of 130 ° C. of erbium nitrate as a starting material was obtained.

  The conditions for measuring the pyrolysis temperature are as follows.

  Using Tg / DTA6300 manufactured by Seiko Instruments Inc., 5 mg of a measurement sample was put in a platinum sample container, heated to 600 ° C. at a temperature rising rate of 10 ° C./min at an air flow rate of 400 sccm, and a change in mass was measured. The reference sample was an empty platinum sample container. The temperature at which the mass decreased by 5% was defined as the thermal decomposition temperature.

<Evaluation of heat resistance of material for photodoping>
About 0.1 g of the powder of the light doping material 1 obtained in Preparation Example 1 is weighed on a glass plate and placed on a hot plate heated to 200 ° C. or 350 ° C. in advance. The change in hue was visually observed. As a result, there was no change in hue after heating at any temperature for 30 minutes.

(Example 2)
<Production Example 2 of Photodoping Material>
In a 25 mL flask, 4.0 g of erbium acetate tetrahydrate was weighed and dried at 110 ° C./vacuum (7 mmHg) in a constant temperature vacuum apparatus for about 2 hours. The mass after drying was 3.3 g. 2.0 g of dried erbium acetate was weighed into a 25 mL two-necked flask, 7.5 g of dimethylacetamide was added and dissolved at room temperature with stirring. After visually confirming that it was dissolved, 6.7 g of pentafluorobenzoic acid was added and dissolved while stirring. Thereafter, the same conditions were maintained at room temperature for about 2 hours. During this time, the pink transparent solution was maintained. Thereafter, this was placed in an oil bath, and the solvent was removed at about 7 mmHg while gradually heating from 60 ° C. After confirming that the solvent was almost removed and became powdery, it was cooled to room temperature. To this was added 10 g of toluene, and the mixture was stirred at 40 ° C. to dissolve excess pentafluorobenzoic acid and remaining dimethylacetamide in the toluene layer. The powdery rare earth metal complex is insoluble in toluene. After stirring for about 20 minutes, the stirring was stopped and toluene was removed by decantation. Then, 10 g of toluene was further added and the same operation was repeated, and then a powdered solid was separated by suction filtration. The obtained powdery solid was dried at 7 mmHg for 20 hours in a constant temperature vacuum apparatus at 40 ° C. to obtain the target light doping material 2. The mass of the obtained light doping material 2 was 7.5 g.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C and 350 ° C.

(Example 3)
<Production Example 3 of Photodoping Material>
The same procedure as in Example 2 was performed except that 3.6 g of trifluoroacetic acid was used instead of 6.7 g of pentafluorobenzoic acid.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

Example 4
<Production Example 4 of Photodoping Material>
The same procedure as in Example 2 was conducted except that 5.2 g of pentafluoropropanoic acid was used instead of 6.7 g of pentafluorobenzoic acid.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

(Example 5)
<Production Example 5 of Photodoping Material>
The same procedure as in Example 2 was performed except that 9.9 g of undecafluoropentanoic acid was used instead of 6.7 g of pentafluorobenzoic acid.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

(Example 6)
<Production Example 6 of Photodoping Material>
The same procedure as in Example 2 was performed except that 13.1 g of tetradecafluoroheptanoic acid was used instead of 6.7 g of pentafluorobenzoic acid.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

(Example 7)
<Production Example 7 of Photodoping Material>
The same procedure as in Example 2 was performed except that 3.1 g of difluoroacetic acid was used instead of 6.7 g of pentafluorobenzoic acid.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

(Example 8)
<Production Example 8 of Photodoping Material>
The same method as in Example 2 except that 2.2 g of trifluoroacetic acid was used instead of 6.7 g of pentafluorobenzoic acid and 7.5 g of distilled water was used instead of 7.5 g of dimethylacetamide as a solvent. I went there.

<Evaluation of heat resistance of material for photodoping>
Evaluation of heat resistance was performed in the same manner as in Example 1. It was confirmed that there was no change in hue at 200 ° C.

Example 9
<Preparation of optical amplification medium and its evaluation>
An example of an optical amplification medium in which a fluorinated polyimide precursor varnish is used as an organic polymer and the optical doping material 2 produced in Example 2 is doped is shown below.

  A fluorinated polyimide precursor varnish was synthesized as follows.

  Using a 1-liter glass four-necked flask, while passing dry nitrogen at a flow rate of 30 ml / min, 95.7 g of 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 4, After charging and dissolving 6.7 g of 4'-diaminodiphenyl ether and 375 g of N, N-dimethylacetamide having a water content of 0.008% by mass, 2,2-bis (3,4-dicarboxyphenyl) hexafluoro was added. After adding 147.6 g of propane dianhydride and stirring in an ice bath for 1 hour, 375 g of N, N-dimethylacetamide was added and stirred for 12 hours to obtain a fluorine-containing polyimide precursor solution having a viscosity of 800 poise. . After adding water 3.0g to this solution, it stirred at 65 degreeC for 3 hours, and obtained the fluorinated polyimide precursor varnish 1 with a viscosity of 70 poise. The water content of this solution was 0.4% by mass.

  The erbium concentration with respect to the solid content of the fluorinated polyimide precursor varnish 1 is oxidized with 10 g (solid content 25%) of the fluorinated polyimide precursor varnish 1 obtained above by using the photo-doping material 2 prepared in Example 2. After adding in an amount of 16% by mass in terms of product and stirring at room temperature for 30 minutes, a varnish A which is a uniform and transparent pink liquid was obtained. Varnish A was uniformly dispersed and gelation did not occur.

  Subsequently, the obtained varnish A was applied on a 1 μm oxide-coated silicon substrate using a spin coater and cured under conditions of 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 350 ° C. for 2 hours, and a thickness of 4 μm. A film A was prepared. Thereafter, the refractive indexes of the obtained film A at wavelengths of 632.8 nm and 1550 nm were measured by a prism coupler (manufactured by Metricon Corporation, prism coupler 2010). As a result, they were 1.5540 and 1.5278, respectively.

  When a beam having a wavelength of 632.8 nm (He—Ne laser) is coupled to the film A prepared above via a prism by the prism coupler method, the light wave shows a good streak and propagates linearly. Was observed. Further, good m-line was observed through the output prism. From this, it was confirmed that the photodoping material 1 was uniformly dispersed in the varnish A using fluorinated polyimide as a matrix.

  Next, a ridge type optical waveguide was manufactured as an optical waveguide amplifier. A silane coupling agent (manufactured by Shin-Etsu Chemical: KBM-573) was applied to a silicon wafer having a total thickness of 1 mm having an oxide film having a thickness of 1 μm by a spin coating method (1000 rpm, 30 seconds) and dried at 120 ° C. for 10 minutes. . Subsequently, the varnish A obtained above was applied by spin coating (1000 rpm, 30 seconds), heated (100 ° C. for 1 hour, then 200 ° C. for 1 hour, then 350 ° C. for 2 hours) and cured. The film thickness was measured by a probe-type surface level meter (DEKTAK) and found to be about 9 μm. Next, using a dicing saw (manufactured by DISCO Corporation, automatic dicing saw DAD-522, etc.), an excess portion was cut so as to leave the film with a width of 20 μm. Thus, a ridge type optical waveguide having a cross section of 9 μm × 20 μm was obtained.

  Next, the fluorescence characteristics and optical characteristics of the ridge type optical waveguide obtained above were evaluated.

  Prior to fluorescence measurement, an absorption spectrum was measured using an optical spectrum analyzer (manufactured by Ando Electric, product name: AQ6315A). As a result, absorptions derived from erbium were confirmed at wavelengths of 980 nm and 1530 nm.

  In the optical characteristic evaluation system shown in FIG. 3, the optical waveguide obtained above is cut in a direction perpendicular to the dicing direction so as to have a length of 2 mm, and a linear InGaAs (indium gallium arsenide) array detector is used as a detector. As a result of measuring the fluorescence intensity using (manufactured by Nippon Roper, product name: OMA-V), as shown in FIG. 4, fluorescence having a peak at a wavelength of 1530 nm was confirmed at an intensity of 82.9 mW. . A sharp peak at a wavelength of 1480 nm is signal light.

  Subsequently, the amplification characteristics were evaluated using the same array detector. As a result, as shown in FIG. 5, the signal increase at the wavelength of 1530 nm tended to become remarkable as the excitation light intensity increased. In addition, at an excitation light intensity of 82.9 mW, a signal increase of 3 dB or more was confirmed in the wavelength region of 1500 nm to 1550 nm.

  The light doping material of the present invention is suitably used for an optical amplifier that amplifies the intensity of signal light with pumping light. An example of such an optical amplifier is an EDFA that has already been commercialized using a quartz-based inorganic material as a base material. However, the present invention enables the quartz-based inorganic material to be replaced with an organic polymer, thereby reducing the cost. To do.

  Further, since rare earth metal ions that can be doped only in the range of about 50 to 100 ppm can be doped by 10 mass% (100,000 ppm) or more, it is possible to reduce the size of an optical amplifier that can only be realized with a long length, and heat resistance is improved. Since it is high, a stable amplification effect can be expected without being decomposed by heat. For this reason, not only long-distance trunk optical fiber networks that have been used in the past, but also subscriber optical communication networks, etc. The effect can be demonstrated even in.

  Furthermore, in the optical interconnection field where research is going on to break down the bottleneck of information processing capacity and speed by using inter-board transmission between computers and intra-board transmission instead of conventional electronics. In addition, the effect of the present invention can be exhibited.

  The optical amplifying medium using the optical doping material of the present invention can be used not only for optical amplifier amplifiers but also for optical amplifiers, laser micro-optical elements, temperature sensor materials, and the like.

The figure of the measurement sample used for the evaluation method of the optical characteristic of the optical amplification medium of this invention is shown. Sectional drawing of the measurement sample used for the evaluation method of the optical characteristic of the optical amplification medium of this invention is shown. The figure explaining the evaluation method of the optical characteristic of the optical amplification medium of this invention is shown. The fluorescence characteristic of the optical amplification medium using the material for optical doping (Example 2) of this invention is shown. The optical amplification characteristic of the optical amplification medium using the optical doping material of the present invention (Example 2) is shown. The figure explaining the evaluation method of the optical characteristic of the optical amplification medium of this invention is shown.

Explanation of symbols

1 substrate 2 film (lower clad layer or adhesion auxiliary film)
3 Core layer 4 Optical waveguide measurement sample

Claims (9)

  An optical doping material obtained by mixing a rare earth metal salt and a carboxylic acid compound in an organic solvent and / or water.   A light doping material obtained by mixing a carboxylic acid compound in a solution obtained by dissolving a salt of a rare earth metal in an organic solvent and / or water and then dissolving the carboxylic acid compound, and then removing the organic solvent and / or water.   Photodoping obtained by mixing and dissolving a carboxylic acid compound in a solution in which a rare earth metal salt is dissolved in an organic solvent and / or water, and then removing the organic solvent and / or water and by-products. Materials.   The material for optical doping according to claim 1, wherein the rare earth metal is erbium.   The material for optical doping according to any one of claims 1 to 4, wherein the carboxylic acid compound is a fluorinated carboxylic acid compound.   5. The carboxylic acid compound is any one of benzoic acid fluoride or chloride and an aliphatic carboxylic acid fluoride or chloride having 2 to 10 carbon atoms. Material for optical doping.   The carboxylic acid compound is any one of trifluoroacetic acid, pentafluoropropanoic acid, undecafluoropropanoic acid, tetradecafluoroheptanoic acid, difluoroacetic acid, trichloroacetic acid, and pentafluorobenzoic acid. The light doping material according to claim 1.   The material for light doping according to any one of claims 1 to 7, wherein there is no change in hue when heated at 200 ° C for 30 minutes.   The optical amplification medium which doped the organic polymer which has transparency in an excitation light wavelength and a signal light wavelength with the material for optical doping as described in any one of Claims 1-8.

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