JP6502286B2 - Method of manufacturing single crystal fiber - Google Patents

Description

  The present invention relates to a method of manufacturing a titanium-doped sapphire single crystal fiber used for a laser device or the like.

A titanium sapphire laser has attracted attention because of its ability to generate ultrashort pulses. The titanium-sapphire laser is used for the study of ultrashort pulses and the associated non-linear phenomena due to the above characteristics. A titanium-sapphire laser is a type of solid-state laser, and sapphire (titanium) -doped sapphire is used as a laser medium. Titanium is present in sapphire in the form of trivalent ions (Ti ³⁺ ).

In the manufacture of a sapphire single crystal fiber to which Ti ³⁺ is added, which is used for the above-mentioned laser medium etc., one end of the base material is heated and melted by a carbon dioxide gas laser in an atmosphere containing argon and hydrogen to It is moved in contact with the melting portion and moved upward (see Non-Patent Document 1). The base material is formed by machining from bulk Ti ³⁺ -added sapphire single crystal manufactured by the Czochralski method or the like.

This will be briefly described using the flowchart of FIG. 4. In step S201, a base material portion is manufactured by forming bulk Ti ³⁺ -added sapphire single crystal by machining. As shown in FIG. 5, a columnar base material portion 201 is produced.

Next, in step S202, for example, one end of the base material is heated and melted by a carbon dioxide gas laser in an atmosphere containing argon and hydrogen, and the single crystal fiber is pulled up from one end of the molten base material portion. As shown in FIG. 6, the end portion of the base material portion 201 is irradiated with CO ₂ laser light 231 in an atmosphere containing argon and hydrogen, heated and melted to form a melted portion 202. Here, the seed crystal 210 is brought into contact from above in the axial direction, and the single crystal fiber 203 is pulled up. The base material portion 201 is lifted from below in the vertical direction toward the melting portion 202 (laser irradiation portion), and the single crystal fiber 203 produced in the upward direction from the melting portion 202 is pulled up.

In the melting portion 202, a part of Ti ³⁺ is oxidized to change into a tetravalent titanium ion (Ti ⁴⁺ ), so the produced single crystal fiber 203 contained Ti ⁴⁺ . It becomes a state. It is known that this Ti ⁴⁺ causes absorption at around 0.8 μm of the oscillation wavelength, and it is necessary to reconvert Ti ⁴⁺ to Ti ³⁺ . In the prior art, in order to ^convert Ti ⁴⁺ to Ti ³⁺ , heat treatment at about 1800 ° C. is performed in a reducing atmosphere for 3 days in step S203.

L. Wu et al., "Growth and laser properties of Ti: sapphire single crystal fibres", Electronics Letters, vol. 31, no. 14, pp. 1151-1152, 1995. L. G. DeSh et al., "Tunable Titanium Doped Sapphire Fiber Laser", Proceedings of SPIE, vol. 843, pp. 118-122, 1987.

However, in the above-described technique, first, heating at the time of pulling the fiber is performed in an atmosphere containing hydrogen, and there is a problem that the operation is not easy. In addition, heat treatment for ^converting Ti ⁴⁺ to Ti ³⁺ requires a long time, and this also causes a problem that the operation is not easy.

The present invention has been made to solve the problems as described above, and it is an object of the present invention to more easily manufacture a sapphire single crystal fiber to which Ti ³⁺ is added.

  The method for producing a single crystal fiber according to the present invention comprises a first step of preparing a columnar portion made of sapphire, and a titanium reduction layer comprising at least one layer of titanium monoxide, titanium or aluminum on the side surface of the columnar portion And the second step of forming an aluminum oxide layer made of aluminum oxide covering the titanium reduction layer to form a base material portion, and one end of the base material portion is melted by a laser melting pedestal growth method to add titanium ions to aluminum oxide Forming a molten portion, and pulling up a fiber made of sapphire to which trivalent titanium ions are added from the molten portion.

  In the method of manufacturing a single crystal fiber, in the second step, a titanium oxide layer composed of titanium trioxide may be formed between the titanium reduction layer and the columnar part or between the titanium reduction layer and the aluminum oxide layer. . In this case, the titanium oxide layer may be formed in a cylindrical shape surrounding the side surface of the columnar portion.

  In the method of manufacturing a single crystal fiber, in the second step, the titanium reduction layer may be formed in a tubular shape surrounding the side surface of the columnar portion.

  In the method of manufacturing a single crystal fiber, the columnar portion may be made of sapphire which does not contain tetravalent titanium ions.

As described above, according to the present invention, an excellent effect can be obtained that a sapphire single crystal fiber to which Ti ³⁺ is added can be manufactured more easily.

FIG. 1 is a flow chart for explaining a method of manufacturing a single crystal fiber according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the base material portion 100. As shown in FIG. FIG. 3 is an explanatory view showing a state in which the single crystal fiber 106 is pulled up from the base material portion 100 by the laser melting pedestal growth method. FIG. 4 is a flow chart for explaining a method of manufacturing a conventional Ti ^{3+ -doped} single crystal fiber. FIG. 5 is a cross-sectional view showing the configuration of the base material portion 201 in the conventional method of manufacturing Ti ^{3 + -doped} single crystal fiber. FIG. 6 is an explanatory view showing a state in which the single crystal fiber 203 is pulled up from the base material portion 200 in the conventional method of manufacturing a single crystal fiber to which Ti ³⁺ is added.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart for explaining a method of manufacturing a single crystal fiber according to an embodiment of the present invention.

  First, in the first step S101, a columnar portion made of sapphire is prepared. The columnar portion may be formed in, for example, a cylinder having a diameter of about 240 μm. The cross-sectional shape of the columnar part is not limited to a circle, and may be a triangle, a tetragon, a pentagon, a hexagon, an octagon, an oval or the like.

Next, in a second step S102, an aluminum oxide (Al ₂ O ₃₎ covering a titanium reduction layer and a titanium reduction layer consisting of at least one layer of titanium monoxide (TiO), titanium, or aluminum on the side surface of the above-mentioned columnar part ) To form a base material portion. The titanium reduction layer may be composed of only a titanium layer or only a TiO layer, or may be a laminated structure of a titanium layer and a TiO layer. Alternatively, an alloy layer of titanium and aluminum may be used. In this step, a titanium oxide layer composed of titanium trioxide (Ti ₂ O ₃ ) may be formed between the titanium reduction layer and the columnar part, or between the titanium reduction layer and the aluminum oxide layer.

For example, as shown in FIG. 2, the base material portion 100 is made of a cylinder 101 made of sapphire which is a single crystal (corundum) of aluminum oxide and Ti ₂ O ₃ formed in a state surrounding the side surface of the cylinder 101 The titanium oxide layer 102, the titanium layer (titanium reduction layer) 103 formed to surround the outer side surface of the titanium oxide layer 102, and the aluminum oxide layer 104 formed to surround the outer side surface of the titanium layer 103; Prepare. The titanium oxide layer 102, the titanium layer 103, and the aluminum oxide layer 104 are cylindrically formed.

  Each layer described above can be formed by, for example, an electron beam evaporation method, a sputtering method, or the like. The titanium oxide layer 102 may have a thickness of 0.11 μm, the titanium layer 103 may have a thickness of 0.22 μm, and the aluminum oxide layer 104 may have a thickness of 0.2 μm. The cylinder 101 may be made of sapphire which does not contain tetravalent titanium ions. In addition, it is preferable that the cylinder 101 (columnar portion) does not contain other additive elements that inhibit laser oscillation and the like. In addition, there is no problem at all even if the cylinder 101 (columnar portion) contains trivalent titanium ions.

  Next, in the third step S103, one end of the base material is melted by laser melting pedestal growth to form a melted portion in which titanium ions are added to aluminum oxide, and trivalent titanium ions are added from the melted portion. Pull out a sapphire single crystal fiber.

For example, as shown in FIG. 3, the end portion of the base material portion 100 is irradiated with CO ₂ laser light 151 and heated in an atmosphere of an inert gas such as argon to melt and form a melted portion 105. Here, the seed crystal 131 is brought into contact from above in the axial direction, and the single crystal fiber 106 made of sapphire is pulled up (see Non-Patent Document 2). In the pulled single crystal fiber 106, trivalent titanium ions are added. Note that FIG. 3 shows a cross section parallel to the axial direction of the base material portion 100 and the single crystal fiber 106 in a cutaway view.

The heating temperature is about 2040 ° C. in order to melt the sapphire in the above-described pulling of the fiber. The melting point of aluminum oxide constituting the outermost aluminum oxide layer is approximately equal to 2030 ° C., which is the melting point of sapphire. On the other hand, the melting point of titanium (metallic titanium) is 1660 ° C. The melting point of titanium oxide (Ti ₂ O ₃ ) is 1900 ° C. The melting point of TiO is 1730 ° C.

Therefore, the titanium oxide layer 102 made of the titanium layer 103 and Ti ₂ O ₃ is melted before reaching the melting portion 105 and reaches the melting portion 105. On the other hand, the aluminum oxide layer 104 reaches the melting portion 105 in the solid phase and melts. In the melting portion 105, the components of the cylinder 101, and the components of the titanium oxide layer 102, the titanium layer 103, and the aluminum oxide layer 104 are mixed in a liquid (melt) state. Therefore, in addition to Ti ³⁺ produced from Ti ₂ O _3, divalent titanium ions (Ti ²⁺ ) produced from metallic titanium are mixed in the fusion zone 105. When the titanium reduction layer is a TiO layer, Ti ²⁺ produced ^therefrom is included.

When the seed crystal 131 is brought into contact with the melted portion 105 in this state and the seed crystal 131 is moved upward, the single crystal fiber 106 is obtained from the melted portion 105. Here, even if a part of Ti ³⁺ is oxidized in the melting portion 105 to become Ti ⁴⁺ , it is reduced by the action of metallic titanium produced from the titanium layer 103 and returns to Ti ³⁺ . The same applies to using a TiO layer instead of a titanium layer. Further, Ti ² produced from metal titanium or TiO is oxidized to become Ti ³ . As a result, Ti ⁴⁺ is not contained in the finally obtained single crystal fiber 106. For this reason, hydrogen is not necessary for the atmosphere in the third step S103. Further, the heat treatment of the formed single crystal fiber 106 is not necessary. The Ti ³⁺ concentration in the single crystal fiber 106 is about 0.18 at%.

The columnar part is not limited to non-doped sapphire but may be added with Ti ³⁺ . For example, the columnar portion may be formed by machining a Ti ³⁺ -added sapphire single crystal manufactured by a bulk crystal growth method such as the Czochralski method. Moreover, you may produce and use the columnar part made into a thinner columnar (fiber) from the Ti ^<3+> addition sapphire single crystal mentioned above by the laser melting pedestal growth method. Thus, when using Ti ³⁺ -doped sapphire, there is no need to form a titanium oxide layer of Ti ₂ O ₃ .

Note that the columnar portion, also contain Ti ^4+, the thickness of the titanium reduction layer, by setting as appropriate to the growth conditions of single crystal fibers, by reducing the Ti ⁴⁺ contained Ti It can be ³⁺ . However, the columnar portion, it does not contain Ti ⁴⁺ is, it is easy to manufacture the single crystal fiber that do not contain Ti ^4+.

As described above, according to the present invention, since a titanium reduction layer made of titanium monoxide, titanium or aluminum is formed on the side surface of the columnar portion made of sapphire to form the base material portion, Ti ³ can be more easily made. A sapphire single crystal fiber doped with ⁺ can be manufactured without including Ti ^{4 +} .

  The present invention is not limited to the embodiments described above, and many modifications and combinations can be made by those skilled in the art within the technical concept of the present invention. It is clear. For example, it goes without saying that the titanium reduction layer and the aluminum oxide layer may be formed by other methods such as sol-gel method, polycrystalline sintering method, ion plating method, etc. .

DESCRIPTION OF SYMBOLS 100 ... Base material part, 101 ... cylinder, 102 ... titanium oxide layer, 103 ... titanium layer (titanium reduction layer), 104 ... aluminum oxide layer, 105 ... fusion part, 106 ... single crystal fiber, 131 ... seed crystal, 151 ... CO ₂ laser light.

Claims (5)

A first step of preparing a columnar portion made of sapphire;
A second step of forming a titanium reduction layer consisting of at least one layer of titanium monoxide, titanium or aluminum and an aluminum oxide layer consisting of aluminum oxide covering the titanium reduction layer on the side surface of the columnar part to form a base material part When,
One end of the base material is melted by laser melting pedestal growth to form a melted portion in which titanium ions are added to aluminum oxide, and a fiber made of sapphire to which trivalent titanium ions are added is pulled up from the melted portion. And a third step of manufacturing a single crystal fiber. In the method of manufacturing a single crystal fiber according to claim 1,
In the second step, a titanium oxide layer composed of titanium trioxide is formed between the titanium reduction layer and the columnar part, or between the titanium reduction layer and the aluminum oxide layer. Fiber manufacturing method. In the method of manufacturing a single crystal fiber according to claim 2,
In the second step, the titanium oxide layer is formed in a cylindrical shape surrounding a side surface of the columnar portion. In the method of manufacturing a single crystal fiber according to any one of claims 1 to 3,
In the second step, the titanium reduction layer is formed in a cylindrical shape surrounding a side surface of the columnar portion. In the method of manufacturing a single crystal fiber according to any one of claims 1 to 4,
The method for manufacturing a single crystal fiber, wherein the columnar portion is made of sapphire which does not contain tetravalent titanium ions.

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