JPS61174199A - Method for growing tellurium dioxide single crystal - Google Patents

Abstract

PURPOSE:To obtain the titled high-quality crystal without any optical defect and to obtain an optical element for a <001> type A-O modulator in high yield by orienting the <100> axis in the pulling direction when the tellurium dioxide single crystal is grown by the pull method. CONSTITUTION:The raw material is charged. for example, into a gold crucible having 50mm internal diameter and depth, and melted at about 733 deg.C by high-fre quency heating. A tellurium dioxide single crystal having 25mm diameter and 60mm length is grown from the melt at 2.0mm/Hr pulling velocity and at 25rpm rotational speed of the crystal by using the <100> axis as the pulling aixs. Consequently, the crystal without any air bubbles, striae, and impurities at the inside and having the same high quality as the crystal obtained by the conventional <110> axis pulling method can be obtained. When the optical element for an acoustooptic (A-O) modulator used for transmitting the longitudi nal wave of a ultrasonic wave in the <001> direction is cut out, a hexahedral optical element surrounded by a (001) face, a (100) face, and a (010) face must be used. When the size is regulated to <001> axis = <100> axis = <010> axis, three elements 2 of maximum 17mm square can be cut out, and four elements 1 of 14mm square can be cut out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for growing tellurium dioxide single crystals suitable for use in optical elements for modulating laser light applied to, for example, laser facsimiles.

This invention relates to a method for growing tellurium dioxide single crystals by a pulling method.

[Conventional technology]

Tellurium dioxide single crystals with a melting point of 733° C. are grown by charging a raw material into a crucible made of a noble metal such as platinum, heating and melting the crucible, and then using a pulling method. In this case, conventionally <110>
Alternatively, high-quality crystals can be obtained by growing with the pulling axis in an equivalent direction.

When using a tellurium dioxide single crystal as an optical element for a modulator, a type that propagates ultrasonic transverse waves in the <110> direction,
Two types are useful: and a type in which longitudinal waves of ultrasound are propagated in the <001> direction.

[Problem that the invention seeks to solve]

Of these two types, in the case of the type in which the longitudinal waves of ultrasound propagate in the <001> direction, the optical element is surrounded by the (001) plane and the (Zoo) plane because the Rede light propagates in the <100> direction. It must be a hexahedron.

Conventionally, this type of optical element is cut out from a crystal.

This is because the pulling axis direction of the crystal is the <110> axis direction.

The crystal must be cut in the (001) plane at an angle of 45° to the pulling axis <110> axis, resulting in a decrease in yield when cutting optical elements from the crystal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for growing a tellurium dioxide single crystal that eliminates the above-mentioned drawbacks and allows a tellurium dioxide optical element for a modulator to be cut out at a high yield.

[Means for solving problems]

According to the present invention, there is obtained a method for growing a tellurium dioxide single crystal, which is characterized in that when growing a tellurium dioxide single crystal by a pulling method, the <100> axis is set as the pulling axis direction.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

After charging the raw material into a metal crucible with an inner diameter and depth of 50 cm, the raw material was melted at about 733° C. by high-frequency heating.

The molten liquid was pulled up at a rate of 2.0 m+/Hr.

A tellurium dioxide single crystal with a diameter of 25 m5 and a length of 60 mm was grown under the growth conditions of a crystal rotation speed of 25 rpm, with the <100> axis as the pulling axis. As a result, there were no bubbles, striae, or impurities inside the crystal, and a high-quality crystal equivalent to that obtained by the conventional method of <110) axial pulling was obtained.

Ultrasonic longitudinal waves from the crystal thus obtained are <00
When cutting out an optical element for an acousto-optic (A-0) modulator that propagates in the 1> direction, the optical element has (oo i ) plane, (
It needs to be a hexahedron surrounded by (Zoo) plane and (010) plane. For example, the dimensions of this optical element are <001>axis=<
If the 100> axis = the <010> axis, then three elements 2 with a maximum size of 17W square can be cut out, as shown in FIG. 1, and four elements can be cut out if the element 1 is 14cm square.

If the crystal has the same dimensions as the conventional method of <110> axis pulling, the pulling axis <1 in the (001) plane as shown in Figure 2.
Since the 45° direction relative to 10> is the <100> axis direction, a similar optical element can only be cut into three 14m square elements at most, and even one 17mm square element cannot be cut out due to the size of the crystal. I can't cut it out.

Furthermore, Table 1 shows the volume yield of optical element crystals when optical elements for <001> type A-0 modulators are cut out from tellurium dioxide single crystals with <100> axis pulling and <110> axis pulling. . Crystal dimensions are diameter 25mφ and length 6.
0■, the dimensions of the optical element are 10 mm square and 12 mm, respectively.
The angle was set to 14 dark angle.

Table 1 As can be seen from Table 1, the <100> axis pulling according to the present invention always has a higher yield of <00> than the conventional <110> axis pulling K, depending on the size of the optical element.
An optical element for a 1> type modulator can be cut out.

〔Effect of the invention〕

As described above, according to the present invention, when a tellurium dioxide single crystal is grown by a pulling method, the <100> axis is set as the pulling axis direction, thereby producing a high quality crystal without optical defects inside the crystal. is obtained.

Furthermore, it has become possible to provide a method for growing tellurium dioxide single crystals which has the advantage of allowing optical elements for <001> type A-0 modulators to be obtained at a high yield.

[Brief explanation of drawings]

Figure 1 shows a <100> axis pulled crystal obtained by the present invention, and Figure 2 shows a <11> axis pulled crystal obtained by the conventional method.
FIG. 2 is a diagram showing a 0>axis-pulled crystal. In the figure 1: Optical element for <001> type modulator (14 square) 2
: Optical element for <001> type modulator (17th corner) N Gai

Claims (1)

[Claims] 1. A method for growing a tellurium dioxide single crystal, which is characterized in that when growing a tellurium dioxide single crystal by a pulling method, the <100> axis is set as the pulling axis direction.