JP3968355B2 - Optical fiber for deep ultraviolet light transmission and manufacturing method thereof - Google Patents

Description

  The present invention relates to an optical fiber for deep ultraviolet light transmission and a method for manufacturing the same, and more particularly to an optical fiber for deep ultraviolet light transmission useful for transmitting deep ultraviolet light having a wavelength of 300 nm or less and a method for manufacturing the same. .

  Recently, an optical fiber for deep ultraviolet light transmission is used in an apparatus that dislikes deterioration of a fiber due to ultraviolet irradiation, such as a semiconductor lithography apparatus, an ultraviolet laser processing machine, or an ultraviolet optical measuring instrument.

  Conventionally, a deep ultraviolet optical fiber using fluorine-doped silica (hereinafter referred to as “fluorine-doped silica fiber”) is known as an optical fiber for this type of deep ultraviolet light transmission (see, for example, Patent Document 1).

  According to the fluorine-doped silica fiber having such a configuration, it is possible to improve the transmittance in the deep ultraviolet region and reduce the deterioration of the transmittance due to ultraviolet light irradiation.

  However, the fluorine-doped silica fiber having such a configuration has the following difficulties.

  First, in a thin fiber having a fiber diameter of about 200 μm, there is a problem that the transmittance is lowered and the durability is deteriorated depending on the spinning conditions. This is because, as will be described later, oxygen deficiency defects (ODC (II)) and E ′ centers are generated by heating and drawing during the spinning process.

  FIG. 7 shows a change diagram of ultraviolet transmittance immediately after spinning of fibers having different fiber diameters. In the figure, a solid line L1 indicates an ultraviolet transmittance with a fiber diameter of 200 μm, and a dotted line L2 indicates an ultraviolet transmittance with a fiber diameter of 500 μm.

  From the figure, in the thin fiber (solid line L1), absorption of transmittance due to the generation of the E ′ center is observed near the wavelength of 216 nm, and absorption of transmittance due to the generation of ODC (II) is observed near the wavelength of 246 nm. However, it can be seen that the fiber having a large diameter (dotted line L2) shows no absorption of transmittance due to the occurrence of such E ′ center or ODC (II). From the above measurement results, it can be seen that the occurrence of defects in the spinning process varies depending on the fiber diameter, and that E ′ center and ODC (II) are likely to occur particularly in a fiber having a small diameter.

  Second, the fluorine-doped silica fiber containing such defects has a drawback that the E ′ center can be eliminated by applying hydrogen treatment, but ODC (II) cannot be eliminated.

  FIG. 8 shows a change diagram of transmittance before and after hydrogen treatment in a fiber including defects. In the figure, the solid line L3 indicates the ultraviolet transmittance immediately after spinning, and the dotted line L4 indicates the ultraviolet transmittance after the hydrogen treatment. Here, the conditions for the above hydrogen treatment are: temperature: 150 ° C., pressure: 15 MPa, and the number of days left in a hydrogen atmosphere: 2 days.

  From the figure, the E ′ center (solid line L3) in the fiber just after spinning that occurs in the vicinity of the wavelength of 216 nm disappears by hydrogen treatment, and the transmittance is recovered (dotted line L4), but it occurs in the vicinity of the wavelength of 246 nm. It can be seen that there is almost no change in the absorption of ODC (II) (solid line L3). This indicates that ODC (II) does not disappear by hydrogen treatment at about 150 ° C. Here, it is possible to extinguish ODC (II) by performing a hydrogen treatment at a temperature exceeding 150 ° C. However, if the temperature is increased, there is a possibility of damaging the protective coating layer existing on the cladding. Therefore, it is not practical.

  Third, the fluorine-doped silica fiber containing ODC (II) has a drawback that its transmittance is deteriorated by irradiation with ultraviolet light such as ArF excimer laser.

FIG. 9 is a diagram showing a change in transmittance due to ultraviolet light irradiation in a fiber containing ODC subjected to hydrogen treatment, FIG. 9A is a diagram showing a change in transmittance before and after irradiation with an ArF excimer laser, and FIG. The transmittance | permeability change in the 193 nm wavelength during ArF excimer laser irradiation is shown. In FIG. 9A, the dotted line L5 indicates the transmittance before irradiation, and the solid line L6 indicates the transmittance after irradiation. Here, the ArF excimer laser irradiation conditions are a repetition frequency of 50 Hz, a pulse number of 10 ⁵ shots, and an ArF excimer laser power density of 20 mJ / cm ² .

  From FIG. 9A, the fluorine-doped silica fiber (dotted line L5) containing ODC (II) has a transmittance due to irradiation with ultraviolet light such as an ArF excimer laser as shown by the solid line L6 and FIG. 9B. It can be seen that it has deteriorated by about 10%, but this is caused by the fact that ODC (II) changes to the E ′ center due to ultraviolet light irradiation, and the absorption position changes from around 245 nm to around 215 nm. It is understood.

  Such a deterioration in transmittance of about 10% is very small compared to a conventional fiber containing a lot of OH groups, but depending on the application, a deterioration in transmittance of about 10% is a practical problem. It may become.

JP 2002-214454 A (paragraph number “0043”, FIG. 1)

  An object of the present invention is to provide an optical fiber for deep ultraviolet light transmission with little deterioration in transmittance by eliminating ODC (II) in a fluorine-doped silica fiber and a method for manufacturing the same.

An optical fiber for deep ultraviolet light transmission according to a first aspect of the present invention includes a core made of silica glass containing 100 to 1000 ppm of fluorine and 1000 to 7000 ppm of fluorine or 2000 to 10,000 ppm of boron provided on the core. And a thin fiber having a fiber diameter of about 200 μm having a clad made of silica glass containing a protective layer and a protective coating layer provided on the clad. The fiber has a temperature of 80 to 150 ° C. and a pressure of 10 to 15 MPa. The oxygen treatment is allowed to stand in an oxygen atmosphere for substantially 7 days , and then the hydrogen treatment is allowed to stand in a hydrogen atmosphere at a temperature of 15 to 150 ° C. and a pressure of 5 to 15 MPa for substantially 2 days .

  According to a second aspect of the present invention, in the optical fiber for deep ultraviolet light transmission according to the first aspect of the present invention, the clad includes a plurality of hollow holes parallel to the optical axis.

  A method for producing an optical fiber for deep ultraviolet light transmission according to a third aspect of the present invention includes a core made of silica glass containing 100 to 1000 ppm of fluorine, 1000 to 7000 ppm of fluorine or 2000 to 2000 provided on the core. A thin fiber having a fiber diameter of about 200 μm having a clad made of silica glass containing 10000 ppm boron and a protective coating layer provided on the clad, in an oxygen atmosphere at a temperature of 80 to 150 ° C. and a pressure of 10 to 15 MPa. It is allowed to stand for 7 days and then left in a hydrogen atmosphere at a temperature of 15 to 150 ° C. and a pressure of 5 to 15 MPa for substantially 2 days.

  According to a fourth aspect of the present invention, in the method for manufacturing an optical fiber for deep ultraviolet light transmission according to the third aspect of the present invention, the clad includes a plurality of hollow holes parallel to the optical axis.

According to the deep ultraviolet light transmission optical fiber of the first aspect or the second aspect of the present invention, the ODC (II) concentration in the fiber is obtained by subjecting the fluorine-doped silica fiber to oxygen treatment under a predetermined condition. Can be reduced to 10 ¹² / cm ³ or less, and this fiber is subjected to hydrogen treatment under predetermined conditions, so that deep ultraviolet light transmission excellent in durability that hardly causes deterioration due to ultraviolet light irradiation. An optical fiber can be provided. Moreover, according to the method for manufacturing an optical fiber for deep ultraviolet light transmission according to the third to fourth aspects of the present invention, the oxygen treatment and the hydrogen treatment are performed at a temperature of 150 ° C. or lower. It is possible to provide an optical fiber for deep ultraviolet light transmission that is excellent in durability and hardly deteriorates with respect to ultraviolet light irradiation without damaging the existing protective coating layer.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments to which an optical fiber for ultraviolet light transmission and a manufacturing method thereof according to the invention are applied will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of an optical fiber for ultraviolet light transmission according to the present invention, and FIGS. 2 and 3 are cross-sectional views of another embodiment of the optical fiber for ultraviolet light transmission according to the present invention. 2 and 3, the same reference numerals are given to the portions common to FIG.

  In FIG. 1, an optical fiber for ultraviolet light transmission according to the present invention includes an optical fiber 3 having a clad 2 provided on the outer periphery of a core 1, a protective coating layer 4 provided on the outer periphery of the optical fiber 3, and a protection if necessary. And an outer protective layer 5 provided on the outer periphery of the coating layer 4, and the optical fiber 3 having the protective coating layer 4 is subjected to oxygen treatment and hydrogen treatment by methods described later.

  The core 1 is made of silica glass containing 100 to 1000 ppm of fluorine. Such fluorine has been conventionally doped in the clad as a material for reducing the refractive index. In the present invention, a predetermined amount of fluorine is contained in the silica glass forming the core 1 so that the optical fiber contains the fluorine. The transmittance of ultraviolet light that transmits light can be increased. Here, the reason why the content of fluorine with respect to the silica glass is set to 100 ppm or more is that when the content is less than 100 ppm, the transmittance of ultraviolet light transmitted through the optical fiber is reduced. The reason why the content is set to 1000 ppm or less is that considering the content of fluorine contained in the clad described later. Moreover, as a silica glass whose fluorine content is 100-1000 ppm, it is preferable to contain OH group in the range of 4-7 ppm from a viewpoint of preventing the deterioration of the optical fiber resulting from ultraviolet light irradiation. Here, the range of the OH group is set to 4 to 7 ppm, if it is less than 4 ppm, it is not possible to prevent a reduction in the transmittance of ultraviolet light transmitted through the optical fiber, and if it exceeds 7 ppm, This is because the transmittance is reduced.

  The clad 2 is made of silica glass containing 1000 to 7000 ppm of fluorine, or silica glass containing 2000 to 10000 ppm of boron. Thus, by containing a predetermined amount of fluorine or boron in silica glass, it is possible to prevent a decrease in the transmittance of light transmitted through the optical fiber. Here, the content of fluorine with respect to the silica glass is set to 1000 ppm or more in consideration of the content of fluorine contained in the core 1, and the content of 7000 ppm or less in consideration of the saturation amount of fluorine with respect to the silica glass. It is a thing. Moreover, the content of boron with respect to the silica glass is 2000 to 10000 ppm. If the content is less than 2000 ppm, it is possible to prevent a decrease in the transmittance of light transmitted through the optical fiber from the relationship with the refractive index of the core 1. The reason why it is difficult to set it to 10000 ppm or less is that considering the saturation amount of boron with respect to silica glass.

  As described above, in the above-described embodiment, the clad 2 made of silica glass containing a predetermined amount of fluorine or boron is provided on the outer periphery of the core 1. As described above, a clad 2 a made of an ultraviolet transmitting resin may be formed on the outer periphery of the core 1. As such an ultraviolet transmissive resin, a fluororesin is preferable, and from the viewpoint of light transmittance, an amorphous fluororesin is preferable. Since the fluororesin having crystallinity decreases in transmittance due to light scattering, the crystallinity of the fluororesin is preferably 30% or less when used as the clad 2a. In the case of an amorphous fluororesin, the crystallinity is preferably 20% or less. As such a fluororesin, a fluoropolymer having an aliphatic ring structure in the main chain, for example, an amorphous perfluoro resin (trade name: Cytop (Asahi Glass Co., Ltd.)) is preferably used.

  Further, as shown in FIG. 3, instead of the clad 2, a clad 2 b having a large number of hollow holes H may be formed on the outer periphery of the core 1. The hollow hole H is formed in parallel with the optical axis of the optical fiber, and the total cross-sectional area thereof is provided to be about 10 to 60% with respect to the cross-sectional area of the optical fiber. The numerous hollow holes H are provided so as to be arranged uniformly with respect to the core 1.

  In this embodiment, due to the presence of air in the hollow hole H, the refractive index can be lowered to optimize the light transmission with respect to the refractive index of the core 1.

  The protective coating layer 4 is provided to mechanically protect the core 1 and the clads 2, 2a, and 2b and protect them from the environment. As the protective coating layer 4, silicone resin, polyimide resin, urethane resin, acrylate resin, or the like is used. An outer protective layer 5 may be further provided on the outer periphery of the protective coating layer 4 in order to increase the strength of the optical fiber as necessary. The outer protective layer 5 can be formed by melting nylon resin or the like, extruding it from the die onto the outer periphery of the optical fiber, and cooling it.

  The optical fiber having such a configuration has a 200 μm clad 2, 2 a, 2 b for a 150 μm core 1, and a 1000 μm clad 2, 2 a, 2 b for an 800 μm core 1. have. On the other hand, the protective coating layer 4 is provided with a thickness of 100 to 250 μm, and the external protective layer 5 is provided with a thickness of 400 to 600 μm. Here, when the thickness of the protective coating layer 4 is less than 100 μm, the core 1 and the clads 2, 2 a, and 2 b cannot be sufficiently protected, and when the thickness of the external protection layer 5 is less than 400 μm, This is because sufficient strength cannot be obtained.

Next, the manufacturing method of the optical fiber for ultraviolet light transmission of this invention is demonstrated.
Create core
In order to create a core portion, a predetermined amount of SiO ₂ particles are deposited on quartz glass and vitrified by flame hydrolysis to create a direct vitrification method or a so-called sintering process. A core rod having a diameter of about 20 mm can be produced by a soot method or the like.
[Production of optical fiber having silica glass clad containing a predetermined amount of fluorine or boron]
In order to manufacture an optical fiber having a silica glass clad containing a predetermined amount of fluorine or boron, the VAD method (gas phase axial method), the OVD method (external method), the MCVD method (internal method), etc. It is possible to create a preform by forming a hollow dope tube having an outer diameter of about 30 mm from silica glass containing a predetermined amount of fluorine or boron, and inserting the core rod formed previously. it can.

This preform is spun to produce an optical fiber. Spinning can be performed by heating and melting the preform in a furnace and adjusting the winding speed with a winder so as to obtain a predetermined diameter. Further, in order to form a protective layer, the resin for forming the protective layer is extruded from the die to the periphery of the clad in the downstream of the furnace, and the resin is heat-crosslinked by a crosslinking apparatus or UV-irradiated to be solidified or solution is formed Remove to form a protective layer. In this case, when a silicone resin or a polyimide resin is used as the protective layer, heat crosslinking is performed, and when a urethane resin or acrylate resin is used, UV irradiation crosslinking is performed.
[Manufacture of an optical fiber having a clad of ultraviolet ray transmitting resin]
The core rod formed by the above-mentioned method is heated and melted in a furnace, the winding speed is adjusted by a winder so that a predetermined diameter is obtained, the ultraviolet transmitting resin is extruded from a die, and the UV of the ultraviolet transmitting resin is obtained by a crosslinking device. Perform cross-linking. Further, as in the case of the protective layer described above, a predetermined amount of the resin that forms the protective layer is extruded from the die to the outer periphery of the UV transmissive resin, and the resin is heat-crosslinked or UV-irradiated by a cross-linking device to form a protective layer. A fiber can be manufactured.
[Manufacture of optical fiber having hollow holes in cladding]
Similar to the production of the core, a direct vitrification method in which a predetermined amount of SiO ₂ particles are deposited on quartz glass and vitrified by flame hydrolysis, or a so-called soot method in which it is produced by another sintering process. Etc. to produce a quartz rod having a diameter of about 30 mm. At this time, the silica rod can be made of the same silica glass as the core material. Note that the quartz rod is not necessarily a hexagonal prism, and a circular tube can also be used. A hole is made in the center of the quartz rod. A quartz rod provided with a hole is drawn to a diameter of about 1 mm, and a core rod serving as a core is assembled at the center of the drawn quartz rod. The one incorporating the core rod is covered with a quartz pipe to form a preform having an outer diameter of about 30 mm. Thereafter, the preform is spun to obtain an optical fiber for ultraviolet light transmission having a predetermined aperture. The protective layer can be formed by the same method as described above.
[Oxygen treatment and hydrogen treatment]
The fluorine-doped silica fiber produced as described above is subjected to the following oxygen treatment and hydrogen treatment. First, the oxygen treatment is performed to eliminate ODC (II). The oxygen treatment is performed by leaving the fluorine-doped silica fiber in an oxygen atmosphere at a pressure of 10 to 15 MPa and a temperature of 80 to 150 ° C. for 7 days. Here, the pressure is set to 10 to 15 MPa because if the pressure is less than 10 MPa, the amount of oxygen impregnated in the fiber is insufficient, and a sufficient effect cannot be expected. On the other hand, even if it exceeds 15 MPa, there is no difference in effect, and 15 MPa is sufficient. The reason why the temperature is set to 80 to 150 ° C. is that when the temperature is less than 80 ° C., the impregnated oxygen does not react with ODC (II), and ODC (II) cannot be sufficiently removed. This is because if the temperature exceeds ℃, the fiber coating resin is damaged. Furthermore, the reason for leaving in an oxygen atmosphere for 7 days is that if it is less than 7 days, the impregnation of oxygen and the reaction between oxygen and ODC (II) are insufficient. This is because you cannot see. The oxygen treatment does not cause any particular inconvenience even if it is left for 7 days or longer, but if the optical fiber diameter is large, it needs to be left in an oxygen atmosphere for a longer time (about one month).

  As described above, after the oxygen treatment is performed on the fluorine-doped silica fiber, the hydrogen treatment is performed. The reason why the hydrogen treatment is performed is to reduce the E ′ center. The hydrogen treatment is performed by leaving the oxygen-treated fluorine-doped silica fiber in a hydrogen atmosphere at a pressure of 5 to 15 MPa and a temperature of 15 to 150 ° C. for 2 days. Here, the pressure was set to 0.5 to 15 MPa because if the pressure is less than 0.5 MPa, the effect of enhancing durability due to insufficient hydrogen amount is insufficient, and even if the pressure exceeds 15 MPa, the effect is different. This is because the effect is sufficient at 15 MPa. Moreover, the temperature was set to 15 to 150 ° C. because when the temperature was less than 15 ° C., the amount of hydrogen impregnated in the fiber was insufficient, and the effect of enhancing the durability was insufficient. This is because the fiber coating resin is damaged. Further, the reason for leaving in a hydrogen atmosphere for 2 days is that if it is less than 2 days, sufficient effects of preventing deterioration of ultraviolet irradiation cannot be obtained. The hydrogen treatment can be performed for a long time, for example, 50 hours or more. However, a treatment effective for preventing deterioration of the optical fiber due to ultraviolet irradiation can be obtained by the treatment for 50 hours or more.

[Create protective coating]
After the fluorine-doped silica fiber is subjected to oxygen treatment and hydrogen treatment, a protective coating layer is provided. The protective coating layer can be formed by melting nylon resin or the like, extruding it from the die onto the outer periphery of the optical fiber, and cooling it.

  Thereafter, the end processing of the optical fiber is performed to complete the final product. End processing is performed according to demands, such as polishing of the end faces and attachment of connectors and the like.

  A fluorine-doped silica glass (trade name: AQX, manufactured by Asahi Glass Co., Ltd.) having a fluorine content of 100 to 200 ppm and an OH group content of 4 to 7 ppm was used as a core, and a silica glass clad having a fluorine content of 2000 ppm was formed. The core diameter was 180 μm and the cladding diameter was 200 μm. After the oxygen treatment, the transmittance of the fiber before and after irradiation with ultraviolet light was measured using an ArF excimer laser.

FIG. 4 is a diagram showing a change in transmittance of an untreated fiber, an oxygen-treated fiber, an oxygen-treated fiber, and a hydrogen-treated fiber. FIG. 4A shows the transmittance of the untreated fiber at 150 ° C. FIG. 4B is a graph showing a change in transmittance of an untreated fiber at 20 ° C. FIG. 4B is a diagram showing a change in transmittance of a fiber subjected to oxygen treatment, FIG. The change figure and the change figure of the transmittance | permeability of the fiber which performed oxygen treatment are shown. Here, the solid line L7 is the transmittance of the untreated fiber, the thin line L8 is the transmittance of the fiber treated with oxygen, the dotted line L9 is the transmittance of the fiber treated with oxygen and hydrogen, and the solid line L10 is the untreated fiber. The dotted line L11 indicates the change in transmittance of the fiber subjected to oxygen treatment.
Further, FIG. 5 shows a change in transmittance before and after ArF excimer laser irradiation in an oxygen-treated fiber, FIG. 5A shows a change in transmittance before and after irradiation, and FIG. 5B shows a 193 nm wavelength during irradiation. The change figure of the transmittance | permeability in is shown. Here, the solid line L12 indicates the transmittance before irradiation, and the dotted line L13 indicates the change in the transmittance after irradiation.

  4 and 5, when the fluorine-doped silica fiber containing ODC (II) is left in an oxygen atmosphere at a pressure of 15 MPa and a temperature of 150 ° C. for 7 days, as shown by a thin line L8, a significant decrease in ODC (II) is observed. Be looked at. Then, when the fluorine-doped silica fiber subjected to oxygen treatment is left in a hydrogen atmosphere at a pressure of 15 MPa and a temperature of 150 ° C. for 2 days, a decrease in E ′ center is observed as shown by a dotted line L9.

  However, as shown by the dotted line L11, it can be seen that there is not much decrease in ODC (II) in the fiber that has been oxygen-treated at a pressure of 15 MPa and a temperature of 20 ° C. for 7 days.

  From the above results, it can be seen that it is effective to treat the fiber with oxygen at about 150 ° C. in order to eliminate ODC (II).

  By the way, the irradiation durability of the fiber is not sufficient only by eliminating ODC (II) by oxygen treatment. This is because, as indicated by the dotted line L13, in the fiber subjected only to the oxygen treatment, E ′ center is generated by irradiation and the transmittance is lowered.

  FIG. 6 shows a result of ArF excimer laser irradiation of a fiber that has been subjected to oxygen treatment and then subjected to hydrogen treatment. FIG. 6A shows a change in transmittance before and after the irradiation, and FIG. ) Shows the change in transmittance at a wavelength of 193 nm during irradiation. Here, the solid line L14 indicates the transmittance before the ultraviolet light irradiation, and the dotted line L15 indicates the change in the transmittance after the irradiation.

  As shown in the dotted line L15 and FIG. 6 (b), in the fiber subjected to oxygen treatment for 7 days at a pressure of 15 MPa and a temperature of 150 ° C. and then subjected to hydrogen treatment for 2 days at a pressure of 15 MPa and a temperature of 150 ° C., It turns out that it is not seen. In other words, (b) ODC, which is a precursor of E ′ center, can be extinguished by subjecting fluorine-doped silica fiber to oxygen treatment, and (b) hydrogen treatment of oxygen-treated fluorine-doped silica fiber. By applying, it is possible to repair the E ′ center that is being generated by irradiation, and as a result of these two effects, it becomes possible to produce a fiber that does not deteriorate with respect to irradiation.

  From the above, the durability against ultraviolet irradiation can be enhanced by subjecting the fluorine-doped silica fiber to oxygen treatment and hydrogen treatment.

Sectional drawing which shows one Example of the optical fiber for deep ultraviolet light transmission of this invention. Sectional drawing of the optical fiber for deep ultraviolet light transmission in the other Example of this invention. Sectional drawing of the optical fiber for deep ultraviolet light transmission in the other Example of this invention. FIG. 4A is a diagram showing a change in transmittance of an untreated fiber, an oxygen-treated fiber, and an oxygen-treated and hydrogen-treated fiber. FIG. 4A shows an untreated fiber and an oxygen-treated fiber at 150 ° C. FIG. 4B is a diagram showing a change in the transmittance of a fiber subjected to oxygen treatment and hydrogen treatment. FIG. 4B is a diagram showing a change in the transmittance of an untreated fiber and a fiber subjected to oxygen treatment at 20 ° C. FIG. 5A is a change diagram of the transmittance before and after the ArF excimer laser irradiation in the oxygen-treated fiber, FIG. 5A is a change diagram of the transmittance before and after the irradiation, and FIG. 5B is a graph of the transmittance at the 193 nm wavelength during the irradiation. Change diagram. FIG. 6A is a result of ArF excimer laser irradiation of an oxygen-treated and hydrogen-treated fiber, FIG. 6A is a transmittance before and after irradiation, and FIG. 6B is a change diagram of transmittance at a 193 nm wavelength during irradiation. The change figure of the ultraviolet region transmittance | permeability immediately after spinning in the fiber from which a fiber diameter differs. The change figure of the transmittance | permeability before and behind hydrogen treatment in the fiber containing a defect. FIG. 9 (a) shows a change in transmittance before and after ArF excimer laser irradiation, and FIG. 9 (b) shows an ArF excimer laser irradiation. The change figure of the transmittance | permeability in 193 nm wavelength inside.

Explanation of symbols

1a, 1b, 1c ... Core 2a, 2b, 2c ... Cladding 3c ... Hollow hole

Claims (4)

A core made of silica glass containing 100 to 1000 ppm of fluorine, a clad made of silica glass containing 1000 to 7000 ppm of fluorine or 2000 to 10000 ppm of boron provided on the core, and provided on the clad A thin fiber having a diameter of about 200 μm having a protective coating layer,
The fiber is subjected to an oxygen treatment which is allowed to stand in an oxygen atmosphere at a temperature of 80 to 150 ° C. and a pressure of 10 to 15 MPa for substantially 7 days. An optical fiber for deep ultraviolet light transmission, which is subjected to hydrogen treatment that is allowed to stand for 2 days .   The optical fiber for deep ultraviolet light transmission according to claim 1, wherein the clad includes a plurality of hollow holes parallel to the optical axis.   A core made of silica glass containing 100 to 1000 ppm of fluorine, a clad made of silica glass containing 1000 to 7000 ppm of fluorine or 2000 to 10000 ppm of boron provided on the core, and provided on the clad A thin fiber having a diameter of about 200 μm and having a protective coating layer is allowed to stand in an oxygen atmosphere at a temperature of 80 to 150 ° C. and a pressure of 10 to 15 MPa for substantially 7 days, and then at a temperature of 15 to 150 ° C. and a pressure A method for producing an optical fiber for deep ultraviolet light transmission, characterized by being allowed to stand in a hydrogen atmosphere of 5 to 15 MPa for substantially 2 days.   4. The method of manufacturing an optical fiber for deep ultraviolet light transmission according to claim 3, wherein the clad includes a plurality of hollow holes parallel to the optical axis.

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