JPH04280891A - Method for growing single crystal fiber - Google Patents

Abstract

PURPOSE:To realize the optimum crystal growing condition of a single crystal fiber over a wide crucible temperature range in a pull-out process by adjusting the protruded length of an insertion member protruded from a molten liquid pull-out port. CONSTITUTION:A fiber 7 is grown by pulling out a molten raw material 4 from a crucible 1 through a pull-out port 2 opened at a part of the crucible 1 by using a pull-out driving shaft 8 holding a seed crystal 5 at the tip end. In the above process, an insertion member 3 is protruded from the pull-out port 2, the molten liquid 4 is extruded through the gap between the insertion member 3 and the pull-out port 2 and guided along the surface of the insertion member 3 to the seed crystal, and the extruded liquid is crystallized at the seed crystal 5 and pulled out with the driving shaft 8. The protrusion length of the insertion member 3 is made to be long when the crucible temperature is high and to be short when the temperature is low. A solid-liquid interface 6 satisfying the crystallization condition can be formed at the tip end of the insertion member by this process.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for growing single crystal fiber from a raw material melt.

0002

[Prior Art] Fiber waveguides confine light and achieve high optical power density inside, so in the field of nonlinear optics, where the effect is dependent on the light intensity, the use of single crystal fibers There is a growing interest in

Laser pedestal method and micro-Czochralski method (Onishi: Japanese Patent Application No. 61-24763, Japanese Patent Application No. 1983)
No. 1-24763) has been published.

[0004] Conventionally, however, for fibers such as metals and halogen compounds, a basic method (hereinafter referred to as the drawing method) of drawing out the raw material melt from a drawing port or nozzle of a desired diameter provided in a crucible has been known. there were.

In this method, as shown in FIG. 2, a raw material melt 4 in a crucible 1 is pulled out while being single-crystallized by the seed crystal 5 using a pull-out drive shaft 8 having a seed crystal 5 at its tip. This method produces single crystal fibers, and is attracting attention as a method that is technically simple and has many advantages, regardless of the form of the raw material.

[0006]

[Problems to be solved by the invention] However, in order to apply this drawing method to the production of nonlinear optical fibers,
The required fiber diameter is small, 100 microns or less, and there are problems specific to nonlinear optical fibers, such as controlling the melt temperature to achieve this.

That is, most of the main nonlinear optical crystals that are currently useful are high-melting-point oxide crystals, and it is difficult to obtain metals for crucibles that can withstand use at the growing temperature and atmosphere and can be processed finely. Moreover, most of the nonlinear optical crystals are made of lithium (Li), sodium (Na), potassium (K),
), which is a multi-component crystal containing easily evaporated elements such as narrow.

[0008] In the extraction method, high frequency heating, resistance heating,
The crucible itself is heated by a heating method such as infrared heating, and the heat for melting the raw materials and growing the fibers is all supplied by the heat generated by the crucible 1, and the temperature during fiber growth is controlled by controlling the crucible temperature.

Considering now that an ideal solid-liquid interface 6 is formed in the opening and the fiber 7 is growing steadily [FIG. 3(a)], the temperature near the crucible is the highest thermally. The temperature of the raw material portion far from the crucible wall is below the melting point and is in the solid state 9, and only the raw material portion in contact with the crucible is in the melt state 10.

When the fiber 7 is grown in this thermal environment,
Since only the raw material 10 in a molten state in contact with the crucible 1 is consumed during fiber growth, a space 11 is created between the crucible 1 and the unmelted raw material 9, which prevents heat transfer and prevents further melting. As a result, the melt supply is interrupted and fiber growth cannot be continued [Figure 3(b)].

On the other hand, when all the raw materials 4 filled in the crucible 1 are heated until they are melted, the temperature of the melt at the outlet 2 is too high for fiber growth because the outlet 2 is provided in the crucible wall. The height is too high to form an optimal solid-liquid interface, resulting in disadvantages such as melt breakage being more likely to occur and the inability to obtain a desired diameter.

[0012] Therefore, in order to grow high-melting-point crystal fibers using the conventional drawing method, it is necessary to attach a pipe or nozzle to the drawing port to guide the melt to a lower temperature area, or to extremely slow down the fiber growth speed. This makes the cultivation technique itself difficult.

Furthermore, when the temperature of the melt is high, as shown in FIG. 4, a phenomenon often occurs in which the melt 12 seeping out from the draw-out port spreads while wetting the crucible bottom 13, which causes disadvantages such as changes in the fiber diameter. Problems are also likely to occur. This invention was made to solve these problems.

[0014]

[Means for Solving the Problems] Therefore, in the present invention, as shown in FIG. In a fiber growing method in which the raw material melt 4 in the crucible 1 is pulled out from the opening 2, the insertion body 3 is protruded into the extraction opening 2 provided in a part of the crucible 1,
On the other hand, the raw material melt 4 is made to seep out from the gap between the insertion body 3 and the draw-out port 2, is guided through the surface of the insertion body 3 to the seed crystal 5, and is drawn out by the drive shaft 8 while being crystallized by the seed crystal 5. This paper proposes a method for growing single crystal fibers.

[0015]

[Operation] That is, according to the present invention, the protrusion length of the inserter 3 is increased when the crucible temperature is high, and the protrusion length is shortened when the crucible temperature is low. It becomes possible to form a solid-liquid interface 6 that satisfies the crystal conditions.

Therefore, in this invention, by adjusting the protruding length of the tip of the insertion member 3 from the drawer opening 2,
Optimal crystal growth conditions for single crystal fibers can be achieved over a relatively wide range of crucible temperatures.

Furthermore, in this invention, the raw material melt 4 is guided to the seed crystal 5 through the surface of the inserter 3 protruding from the outlet 2, so that the crucible temperature can be set sufficiently higher than the temperature of the solid-liquid interface. , the raw material melt 4 is sufficiently supplied, and it is possible to grow long fibers, and at the same time, the fiber diameter, which was determined by the diameter of the draw-out port 2 in the conventional method, can be selected to a certain extent with this invention, and it is possible to grow thin fibers. This makes it easier to grow diameter fibers.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments. FIG. 5 shows a concrete example of implementing the contents of the invention. In this embodiment, an electrically heated crucible 14 is used as the crucible, and the melting of the raw material and the temperature of the melt are all controlled by the amount of heat generated by the crucible, that is, the amount of current.

[0019] The crucible 14 used here has a size of 8 × 4 ×
A platinum plate of about 0.1 mm in diameter is bent and welded on both sides, processed as shown in Fig. 5, and a conductive wire 15 is attached to this.
Provide a hole for drawing out the micron melt.

As the insertion member 3, a platinum wire of 100 to 300 microns is used, one end of which is fixed to the crucible wall, and the other end is inserted into the drawer opening so that the protruding portion is 300 to 500 microns.
It was adjusted and cut to a micron size.

[0021] After the crucible thus processed is filled with raw materials such as lithium niobate (LiNbO3) and barium/sodium niobate (Ba2NaNb5O15), the crucible is heated by directly applying electricity. When the raw material melts, the melt oozes out from the gap between the opening and the insertion body and wets the surface of the insertion body, so the fiber 7 is grown by pulling down this melt at the tip of the insertion body using a seed crystal.

FIG. 6 shows an example in which a hollow pipe is used as the insertion member. In this case, the pipe 16 has an outer diameter of 500 microns and an inner diameter of about 350 microns, and the fibers are grown using the same procedure as in the previous example, but the melt is in the hollow pipe 16.
A hollow single-crystal fiber 17 can be grown by setting the solid-liquid interface 6 at a point drawn hollow from the end face of the fiber.

FIG. 7 shows a pipe 18 whose tip is divided into two to be used as an insertion body. By using this type of pipe as an insertion body, the melt flowing on the surface is divided into two at the end of the pipe. By pulling this down using a seed crystal as in the previous example, two fibers can be grown at the same time.

[0024] Due to the action of the surface tension of the melt, the cross section of the fiber becomes approximately circular regardless of the shape of the end face.

[0025]

As described above, according to the present invention, the shape of the melt and the solid-liquid interface can be controlled by protruding the insert from the melt outlet and adjusting the length of the protruding portion. Fiber growth conditions can be satisfied over a wide range of crucible temperatures.

Furthermore, in the present invention, since the melt is guided to the seed crystal by passing through the insertion member, it becomes easy to make the grown fibers longer, thinner, and more uniform.

Furthermore, according to the present invention, special fiber growth such as simultaneous growth of hollow fibers or a plurality of fibers is possible by devising the cross-sectional shape of the end of the insertion body.

[Brief explanation of the drawing]

[Figure 1] Schematic diagram showing the principle of this invention

[Figure 2] Illustration of the conventional withdrawal method

[Figure 3] A diagram explaining the inconveniences that occur when growing high-temperature crystal fibers.
FIG. 3(a) is a diagram illustrating the state before the withdrawal operation, and FIG. 3(b) is a diagram illustrating the state after the withdrawal operation.

[Figure 4] Illustration of fiber diameter variation at high temperatures

[Figure 5]
A diagram showing an embodiment of this invention

[Fig. 6] A diagram showing another embodiment for growing hollow fibers in this invention.

[Figure 7] Diagram of the tip shape of the insertion body that grows two fibers simultaneously in this invention

[Explanation of symbols]

1 Crucible 2 Drawer opening 3 Insert body 4 Raw material melt 5 Seed crystal 7. Growing fiber 8 Drive shaft for drawer 16 Hollow pipe 17. Grown hollow fiber 18　Tip 2-split pipe

Claims (4)

[Claims] Claim 1: A fiber growing method in which a raw material melt in a crucible is drawn out from a draw-out port provided in a part of the crucible using a pull-out drive shaft having a seed crystal at its tip. The insertion body is made to protrude into a draw-out port provided in the part, and the raw material melt is allowed to ooze out from the gap between the insertion body and the draw-out port, travels along the surface of the insertion body, and is guided to the seed crystal. A method for growing a single crystal fiber, characterized in that it is drawn out by the drive shaft while being crystallized. 2. The method for growing a single crystal fiber according to claim 1, wherein the length of the insertion member protruding from the outlet is adjusted depending on the temperature inside the crucible. 3. The method for growing a single crystal fiber according to claim 1, wherein a hollow pipe is used as the insertion member. 4. The method for growing a single crystal fiber according to claim 1, wherein a hollow pipe with a split tip is used as the insertion member.