JPH06256096A - Production of cdmnhgte single crystal - Google Patents

Abstract

PURPOSE:To provide a CdMnHgTe single crystal which is a light isolator material capable of carrying out LD modulation used in 0.98-1.02mum wavelength band-exciting light amplifier. CONSTITUTION:In a method for producing a CdMnHgTe single crystal, the CdMnHgTe single crystal is produced using a CdMnTe sintered body and a HgTe sintered body instead of simple substances of Cd, Mn, Hg and Te as starting raw materials. Since the vapor pressure in Hg simple substance is not applied, a crucible for growing the crystal can be prevented from cracking. Further, segregation of Hg is suppressed to provide the objective single crystal having uniform composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical isolator material, and particularly to a 0.98 .mu.m band to 1.02 .mu.m.
The present invention relates to a method for manufacturing a CdMnHgTe single crystal which is an optical isolator material essential for a band pump optical amplifier.

[0002]

2. Description of the Related Art A 1.5 μm band traveling wave type optical amplifier using an optical fiber doped with erbium (Er) is highly efficient, has no polarization dependence, and is excellent in compatibility with a transmission system.
Therefore, for its practical use, 0.98 μm and 1.4
Excitation using an 8 μm band laser diode (LD) has been actively studied. Among them, the signal light gain and noise characteristics in each wavelength band were experimentally studied, and 0.98 μm
It has been confirmed that the band excitation has higher efficiency and lower noise characteristics than the 1.48 μm band excitation. However, optical devices used for optical amplifiers (optical isolators, etc.)
However, although it has been put to practical use in the 1.48 μm band,
Since the 0.98 μm band has not been put to practical use yet, the development of the 0.98 μm band is currently delayed.

On the other hand, an optical fiber to which praseodymium (Pr) is added is 1.3 μm when light with a wavelength of 1.02 μm is transmitted.
Since it has a function of amplifying m light, it is expected to be used as a light source for an optical amplifier in 1.3 μm band optical communication.

Further, a 1.02 μm band laser was developed in 1992, and further development of an optical amplifier for the 1.3 μm band is expected.

At present, a terbium gallium garnet (TGG) single crystal is used as an optical isolator for the 0.98 to 1.02 μm band.

[0006]

However, the terbium-gallium-garnet (TGG) single crystal described above is much larger than the laser diode (LD) and can be used in the future. Not a thing. The bulk yttrium-iron-garnet (YIG) and Bi-substituted garnet are 0.98-
Since the absorption is large in the 1.02 μm band, the transmission loss becomes 3 to 5 dB, which is not practical.

On the other hand, the inventors of the present invention have found that Cd in CdTe having a ZnS type crystal structure is partially replaced with Mn.
_1-x Mn _x Te was developed, but this Cd _1-x Mn _x Te
Is a material having a large Verdet constant, and its practical performance as an optical isolator material for visible light wavelengths of 0.85 to 0.63 μm has been confirmed. {Onodera, Oikawa: Proceedings of the 15th Annual Meeting of the Japan Society for Applied Magnetics 30aB-7,
(1991)} However, this Cd _1-x Mn _x Te
However, in the 0.98 to 1.02 μm band, the Verdet constant is too small, and full-scale practical application in these bands was difficult.

As described above, 0.98 μm to 1.02 μ
At present, there is no magneto-optical material that is practically excellent as an optical isolator for the m band.

Therefore, 0.98 μm band excitation / 1.02
At present, there is no optical isolator that can be used as an LD module for a μm-band pumping optical amplifier, and this is one of the factors behind the delay in the practical development of the 0.98 μm-1.02 μm band pumping optical amplifier described above. Met.

An object of the present invention is to have a wavelength of 0.98 to 1.02.
An object of the present invention is to provide a method of manufacturing an optical isolator material that can be used as an LD module for a μm band pumping optical amplifier. The method for producing a CdMnHgTe single crystal according to the present invention makes it possible to provide a high-quality optical isolator material having practical characteristics of extinction ratio:> 35 dB and light transmission loss: 0.5 dB.

[0011]

As described above, ZnS
Cd _1-x Mn _x Te, which is obtained by substituting a part of Cd of CdTe having a type crystal structure with Mn, is generally a material having a large Verdet constant, and is an optical isolator for visible light wavelength of 0.85 to 0.63 μm. Practical performance has been confirmed as a material, but practical performance was not obtained in the 0.98 to 1.02 μm band due to the small Verdet constant. This is because the Verdet constant is large near the absorption edge of light. Therefore, in order to obtain practical performance using this material, consideration should be given to adjusting the bandgap energy of the material and selecting the Mn composition so as to increase the absolute value of the Verdet constant. To shift the band gap energy to the 0.98 to 1.02 μm band,
Part of Cd may be replaced with Hg. In order to increase the absolute value of the Verdet constant, Mn with a higher concentration may be replaced. Ultimately, bulk crystallinity has a large effect. Therefore, the optimum crystal composition is determined in consideration of the crystallinity.

However, the CdMnHgTe single crystal has problems that the vapor pressure of the components is high and the segregation of Hg is too large. Therefore, it is difficult to obtain a good quality crystal satisfying the practical characteristics. .

Therefore, according to the method for producing a CdMnHgTe single crystal according to the present invention, a HgTe sintered body and a CdM are produced.
A CdMnHgTe polycrystal is obtained by melting the nTe sintered body as a starting material and then rapidly cooling it. The obtained polycrystalline body becomes a raw material bar having a uniform composition. Next, the raw material rod is sliced into a quartz crucible only at its tip to be used as a charging raw material and loaded into the growing crucible. The growing crucible has a seed crystal at the tip and CdMnHgTe as the first raw material.
Minimize Hg segregation by loading a small amount of polycrystalline material and placing a raw material rod of uniform composition on top to pressurize it in a heating device to melt the raw material rod of uniform composition while producing crystals. To do. As a result, 0.98 μm band
A method of manufacturing an optical isolator material satisfying the practical characteristics essential for a 1.02 μm pump optical amplifier can be obtained.

[0014]

Operation: That is, the above-mentioned visible light wavelength of 0.85 to 0.63
The practical performance has been confirmed as an optical isolator material for the μm band. The Verdet constant of Cd _1-x Mn _x Te in which a part of Cd of CdTe having a ZnS type crystal structure is replaced with Mn becomes large near the light absorption edge. By utilizing the characteristics, it is possible to shift the bandgap energy to the 0.9 μm band by replacing a part of Cd with Hg. Further, in order to increase the absolute value of the Verdet constant, Mn with a higher concentration is replaced. Ultimately, the crystallinity of the bulk has a great influence, and the crystal composition is determined in consideration of the crystallinity.

Regarding the problems such as the above-mentioned CdMnHgTe single crystal having a high vapor pressure of components and a large segregation of Hg, there is a factor that the vapor pressure becomes high by using the HgTe sintered body and the CdMnTe sintered body as starting materials. Suppress and synthesize polycrystals of uniform composition. Thereafter, the polycrystalline body is cut in the quartz crucible only at its tip and placed on the upper part of the growing crucible. The diameter of the lower part of the growing crucible is made small so that the quartz crucible containing the polycrystal does not fall. The reason why the raw material for charging is used in the state of the quartz crucible containing the polycrystal is that it is difficult to hold the polycrystal in a state without cracking. By continuously charging a uniform polycrystal, crystals having a uniform composition can be obtained.

As a result, CdMnHg having practical characteristics of extinction ratio:> 35 dB and light transmission loss: 0.5 dB.
A method for manufacturing a Te single crystal is obtained.

[0017]

EXAMPLES Hereinafter, CdMnHg according to one example of the present invention
A method for manufacturing a Te single crystal will be described in detail with reference to the drawings.

First, in order to make the understanding of the present invention easier, a conventional manufacturing method will be described as a comparative example with reference to FIGS. 3 and 4, and then a manufacturing method of this embodiment will be described with reference to FIGS. Will be explained.

In the conventional manufacturing method, as shown in FIGS.
As shown in (a), first, the raw material 5 (Cd, Mn, Hg,
Te) with a predetermined composition ratio Cd0.8Mn0.1Hg0.1
Weigh it so that it becomes Te, and the quartz crucible 2 (20φ × 120
Lmm) was blended in an amount of 30 g and was vacuum sealed. Incidentally, FIG.
In (a), 5a is Te, 5b is Mn, and 5c is H.
g and 5d represent Cd.

Subsequently, the quartz crucible 2 was placed in a pressurizable Bridgman furnace 6 as shown in FIG. 4 (b), and the raw material 5 was heated and melted using the electric furnace 1.

Further, after holding the melt of the raw material 5 for about 5 hours, the melt in the quartz crucible 2 is single-crystallized at a speed of 4 mm / h, as shown in FIGS. 3 and 4 (b). Single crystal 4 was obtained. At this time, as shown in FIG. 4C, the temperature inside the electric furnace 1 becomes higher from the top to the center, and the elevating device 3 is used to move the quartz crucible 2 in the electric furnace 1 at a constant speed. The melt of the raw material 5 in the quartz crucible 2 is solidified from below by manufacturing the single crystal 4 by lowering the melt.

However, in most cases, the quartz crucible 2 was cracked due to the presence of Hg having a high vapor pressure of the compound constituents, which made crystal growth impossible. This is because the quartz crucible 2 is cracked when the dissolution is insufficient due to the high vapor pressure of the compound constituents.

Even if the quartz crucible 2 can be grown without cracking, the grown single crystal 4 has a uniform composition because the segregation of mercury (Hg) as a compound constituent is too large. No crystals were obtained.

On the other hand, in the manufacturing method of this embodiment,
Before growing the crystal, a polycrystal of Cd0.8Mn0.2Te and a polycrystal of HgTe are respectively synthesized, and these sintered bodies are used as starting materials. These sintered bodies are HgT
e and CdMnTe in a vacuum system with a vacuum degree <1 ×
Each quartz crucible was loaded under 10 ⁻⁶ Torr, heated gas was discharged, and vacuum sealing was performed. Then, each quartz crucible was heated to dissolve HgTe and CdMnTe in each crucible, and then rapidly cooled to prepare. To do.

That is, in the manufacturing method of this embodiment, as shown in FIG. 1, first, CdMnTe and HgTe are separately weighed. Next, the weighed CdMnTe and HgTe are respectively used to synthesize a CdMnTe polycrystal crucible and HgTe.
It is vacuum sealed in a crucible for synthesizing polycrystals. Then, the crucible for synthesizing the CdMnTe polycrystal and the crucible for synthesizing the HgTe polycrystal were put in a Bridgman furnace capable of pressurization similar to that in FIG. The melt is held at the melt temperature as it is for a predetermined time and then rapidly cooled.

In this way, a sintered body of CdMnTe and a sintered body of HgTe were obtained, weighed so as to have a predetermined composition ratio Cd0.8Mn0.1Hg0.1Te corresponding to the wavelength used, and the starting materials were blended. To do.

Further, in the manufacturing method of this embodiment, the starting raw material manufactured as described above is used as a quartz crucible 7 (2) for synthesizing CdMnHgTe polycrystals as shown in FIG. 2 (a).
0φ × 120 Lmm) vacuum degree <1 ×
30 g was compounded and loaded under 10 ⁻⁶ Torr, heated gas was discharged, and vacuum sealed. The quartz crucible 7 for synthesizing the CdMnHgTe polycrystal was placed in a pressurizable Bridgman furnace 6 (see FIG. 4B), heated and melted, and then rapidly cooled to synthesize a crystal raw material 8A for charging. The crystal raw material 8A for charging thus obtained has a uniform composition. This charge crystal raw material 8A was not taken out from the CdMnHgTe polycrystal synthesizing quartz crucible 7, and the tip thereof was sliced.

On the other hand, the crystal-growing quartz crucible 2'used in the manufacturing method of this embodiment has a raw material supply section 2'A on the upper side thereof, as shown in FIGS. The crystal growth portion 2'B is provided on the lower side thereof. A quartz crucible 7 was housed in the raw material supply part 2'A, as shown in FIG. The raw material supply part 2'A was formed to have a diameter of 25φ x 80 Lmm, and the crystal growth part 2'B was formed to have a diameter of 20φ x 100 Lmm. That is, the raw material supply unit 2'A has a diameter slightly larger than the diameter of the quartz crucible 7 so that the quartz crucible 7 can be stored. The crystal growth part 2'B was loaded with a small amount of a starting material 8B made of a CdMnHgTe polycrystal and a seed crystal 8C.

As shown in FIG. 2 (b), this quartz crucible 2'is put into a Bridgman furnace 6 which can be pressurized so that the crystal raw material 8A for charging having a uniform composition is located above, and after heating and melting. After holding for about 5 hours, the melt in the quartz crucible 2'was single-crystallized at a speed of 4 mm / h to obtain a single crystal 4 '.

As described above, in the manufacturing method of the present embodiment, HgTe is used as the starting material because it is CdMn.
This is to prevent vapor pressure of Hg simple substance from being applied to the quartz crucible 7 for synthesizing the HgTe polycrystal and the quartz crucible 2'for crystal growth. This is because the vapor pressure of Hg simple substance, which is a component of the compound, reaches ˜300 atm near the melting temperature, whereas the vapor pressure of HgTe is ˜100 atm. By the way, Cd0.
The vapor pressure calculated from the molar fraction of Hg at a weight of 8Mn0.1Hg0.1Te (30 g) is -25 atm.
Is. Therefore, the external pressure corresponding to this internal pressure causes the pressure applied to the quartz crucible 2'to be apparently zero.

Further, in the manufacturing method of this embodiment, the idea of deformation zone melting is applied in order to obtain a uniform composition. The idea is to continuously supply the crystal raw material corresponding to the single crystallized portion while keeping the melt depth constant. That is, as described above, when the melt in the quartz crucible 2'is single-crystallized at a predetermined speed,
As shown in (a) and (b), the single crystal 4'is grown while melting and dropping the charging crystal raw material 8A having a uniform composition. Therefore, by continuously charging the CdMnHgTe polycrystal having a uniform composition, the segregation of Hg is suppressed to the minimum, and the single crystal 4 ′ having a uniform composition can be obtained.

In this case, it is necessary to devise so that the raw material lot to be supplied can be charged with a constant amount. Here, the crystal raw material for charge 8A having a uniform composition was once synthesized, and the crystal raw material for charge 8A was not taken out from the quartz crucible 7, but the tip thereof was cut into slices. The reason is that once the charge crystal raw material 8A is taken out,
This is because it is difficult to maintain the temperature. During the growth, the charge crystal raw material 8A drops into the melt together with the lot, which causes a rapid temperature change near the solid-liquid interface and traps impurities during crystallization. This is because good quality crystals cannot be obtained.

In the manufacturing method of this embodiment, unlike the conventional Bridgman method, since the melt amount is small, the substantial vapor pressure can be set low and the temperature fluctuation during crystal growth can be suppressed to a minimum. is there.

The characteristics of the single crystal 4'obtained as described above as an optical isolator material were examined.
As a result, the segregation of mercury (Hg), which is a constituent component of the compound, is extremely small, and the characteristics (extinction ratio> 30 dB, insertion loss <0.
5 dB) was satisfied. Further, in the manufacturing method of the present embodiment, unlike the conventional manufacturing method as a comparative example,
The quartz crucible 2'was not cracked to make crystal growth impossible.

[0035]

As described above, the CdMn of the present invention is
According to the method for producing an HgTe single crystal, it is possible to provide a high-quality optical isolator material having both practically sufficient characteristics in both extinction ratio and light transmission loss.

That is, a method for producing a CdMnHgTe single crystal which is an optical isolator material satisfying the practical characteristics indispensable for the 0.98 μm band / 1.02 μm band pumping optical amplifier can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of a CdMnHgTe single crystal of the present invention.

FIG. 2 is a diagram for explaining a method for producing a CdMnHgTe single crystal of the present invention, (a) is a diagram showing the structure of the quartz crucible, and (b) is a diagram showing the structure of the single crystal producing apparatus. It is a figure and (c) is a figure which shows the temperature distribution in the electric furnace.

FIG. 3 is a diagram showing a manufacturing process of a conventional CdMnHgTe single crystal.

FIG. 4 is a diagram for explaining a conventional method for producing a CdMnHgTe single crystal, (a) is a diagram showing the structure of the quartz crucible, and (b) is an example of the structure of the single crystal producing apparatus. It is a figure which shows, and (c) is a figure which shows the temperature distribution in the electric furnace.

[Explanation of symbols]

1 Heating Device (Electric Furnace) 2, 2'Crystal Crucible for Crystal Growth 2'A Raw Material Supply Section 2'B Crystal Growth Section 3 Lifting Device 4, 4'Single Crystal 5 Crystal Growth Raw Material (Melt) 5a Te 5b Mn 5c Hg 5d Cd 6 Bridgman furnace capable of pressurizing 8A Crystal raw material for charging (CdMnHgT
e polycrystal) 8B initial raw material (CdMnHgTe polycrystal) 8C seed crystal

Claims (6)

[Claims] 1. A method for producing a CdMnHgTe single crystal by a Bridgman method, a step of producing a CdMnTe sintered body and a HgTe sintered body, and the CdMnTe
Using CdMnH as a starting material from the sintered body and the HgTe sintered body
A method for producing a CdMnHgTe single crystal, comprising the step of producing a gTe single crystal. 2. The method for producing a CdMnHgTe single crystal according to claim 1, wherein each of the sintered bodies is loaded with CdMnTe and HgTe in their respective crucibles, and then the respective crucibles are heated to melt CdMnTe and HgTe. CdMnHgT characterized by being rapidly quenched afterwards
e A method for producing a single crystal. 3. The method for producing a CdMnHgTe single crystal according to claim 1, wherein in the step of producing the CdMnHgTe single crystal, the CdMnTe sintered body and the HgTe sintered body are used as starting materials in a crucible for synthesizing a polycrystalline body. At CdM
a step of synthesizing nHgTe polycrystal, and said CdMnHg
And a step of growing a CdMnHgTe single crystal in a crucible for crystal growth using a Te polycrystal as a crystal growth raw material, a method for producing a CdMnHgTe single crystal. 4. The method for producing a CdMnHgTe single crystal according to claim 3, wherein the CdMnHgTe polycrystal synthesizing crucible is cut into round slices and loaded into the crystal-growing crucible to obtain the CdMnHgTe polycrystal. A method for producing a CdMnHgTe single crystal, wherein the body is used as a raw material for charging. 5. The method for producing a CdMnHgTe single crystal according to claim 4, wherein the crucible for crystal growth is the C
It has a raw material supply part in which a crucible for synthesizing dMnHgTe polycrystal is loaded, and a crystal growth part for growing the CdMnHgTe single crystal, and the crystal growth part has a diameter smaller than that of the raw material supply part. CdMnHgT characterized by
e A method for producing a single crystal. 6. The method for manufacturing a CdMnHgTe single crystal according to claim 1, wherein the crystal growth raw material in the crucible for crystal growth is made into a melt by using a pressurizable heating device, and the heating device and the heating device are combined. A method for producing a CdMnHgTe single crystal, characterized in that the melt is solidified from below to produce a single crystal by continuously changing the relative positional relationship of the crucible for crystal growth at a predetermined speed.