JP5377785B1 - Bismuth-substituted rare earth iron garnet single crystal and method for producing the same - Google Patents

Abstract

There is a need for a RIG that has a low content of both Pb and Pt, excellent crystallinity, and little environmental impact.
A bismuth-substituted rare earth iron garnet single crystal grown by a liquid phase epitaxial method, wherein 0.010 or more and 0.100 or less of Ca per composition formula, Pb greater than 0 and 0.005 or less per composition formula, And a bismuth-substituted rare earth iron garnet single crystal comprising more than 0 and less than 0.010 Pt per composition formula.
[Selection] Figure 1

Description

  The present invention relates to a bismuth-substituted rare earth iron garnet single crystal used for a Faraday rotator such as an optical isolator or an optical circulator, and a method for producing the same.

  In recent years, the development of optical fiber communication and optical measurement has been remarkable. In this optical fiber communication and optical measurement, a semiconductor laser is often used as a signal source. However, if there is reflected return light that is reflected from the end face of the optical fiber and returns to the semiconductor laser itself, the semiconductor laser tends to be unstable. Therefore, an optical isolator is provided on the emission side of the semiconductor laser to block the reflected return light and stabilize the oscillation of the semiconductor laser.

  The optical isolator mainly includes a polarizer, an analyzer, a Faraday rotator, and a permanent magnet for magnetically saturating the Faraday rotator. For the Faraday rotator that plays a central role in the optical isolator, a bismuth-substituted rare earth iron garnet (hereinafter abbreviated as RIG) single crystal grown by a liquid phase epitaxial (hereinafter abbreviated as LPE) method is used. It is common.

In the growth of RIG single crystals using the LPE method, PbO—B ₂ O ₃ —Bi ₂ O ₃ is generally used as a flux component, and this flux and the RIG component rare earth oxide, iron oxide (Fe A melt obtained by mixing ₂ O ₃ ) or the like and dissolved in a Pt crucible is used.

  The RIG single crystal can be grown from the single crystal substrate immersed in the melt after the melt is heated to the saturation temperature or higher, stirred, cooled to the supersaturation temperature at which the RIG single crystal is deposited. it can.

  Lead oxide (PbO) is generally used as a flux component because of its low melting point and low viscosity. However, when a RIG single crystal is grown using a flux containing PbO, Pb is incorporated as an impurity in the RIG grown crystal.

  Pb is a substance that can cause central nervous system dysfunction and cancer and has an environmental impact. For example, it is specified in the RoHS Directive “European Parliament and Council Directive on Restriction of Use of Specific Hazardous Substances in Electrical and Electronic Equipment” It is a substance, and its maximum allowable amount is defined as 0.1% by mass.

  On the other hand, in order to suppress the amount of Pb mixed in RIG to a small amount, a grown RIG single crystal can be obtained by using a flux with a small Pb component ratio or, alternatively, by adding calcium oxide (CaO) to the melt. A method for suppressing the mixing of lead (Pb) into the body has been proposed (Patent Document 1). Patent Document 1 shows that in order to reduce the Pb content, the larger the amount of CaO added to the melt composition, the better.

  In addition, platinum (Pt) crucibles are generally used in the growth of RIG single crystals by the LPE method.

JP 2007-153696 A

  Since Pt has a high melting point and can increase the strength by adding a small amount of Zr or the like, as described above, as a crucible material used for growing RIG single crystals in the LPE method, It is used.

  Conventionally, if the flux has a high Pb component ratio, even if Pt dissolved in the flux is taken into the RIG, there has been no particular problem. However, according to the study by the present inventors, it has been found that if a flux with a small amount of Pb is used to reduce the amount of Pb mixed in the grown RIG, crystal defects called pits are likely to occur in the RIG grown crystal. Furthermore, as a result of earnest investigation on the cause, Pt, which is a component of the Pt crucible, can be dissolved into the melt and mixed into the RIG-grown crystal. However, when using a flux with a small amount of Pb, this mixed Pt Was found to cause pits in the RIG-grown crystal.

  Even if the pits are polished after the RIG crystal growth, the pits cannot be completely removed. In particular, pits starting from Pt are likely to occur at the initial stage of RIG crystal growth and have a large shape. Therefore, the portion where the pits are generated is not suitable for use as an optical component.

  If an Au crucible is used in place of the Pt crucible, the effect of Pt can be eliminated. However, if an Au crucible is used when a flux with a small amount of Pb is used, pits starting from Au are likely to occur, which is more affected than Pt. Was found to be large. In addition, the Au crucible is weaker than the Pt crucible and easily deforms, and the melt cannot be raised above the melting point of Au, 1064 ° C. In fact, the saturation temperature of the melt is higher than the melting point. There is a restriction that it must be considerably low. Therefore, a Pt crucible is generally used.

  On the other hand, when the Ca content of the RIG grown crystal is increased in order to reduce the amount of Pb mixed in the RIG grown crystal, the amount of tetravalent Fe increases in the RIG grown crystal and the light absorption increases. It has also been found that the insertion loss increases.

  As described above, in the RIG single crystal grown by the LPE method, it is difficult to stably reduce the contents of both the Pb amount and the Pt amount, and it is possible to obtain an RIG single crystal having little environmental influence and excellent crystallinity. It was difficult.

  The present inventors have conducted intensive research in view of the above problems, and have found a RIG single crystal having a low Pt and Pb content, little environmental impact, and excellent crystallinity.

The present invention is a bismuth-substituted rare earth iron garnet single crystal grown by a liquid phase epitaxial method,
0.010 to 0.100 Ca per composition formula, Pb greater than 0 and 0.005 or less per composition formula, and Pt greater than 0 and less than 0.010 per composition formula,
Bismuth-substituted rare earth iron garnet single crystal.

The present invention also heats and melts a melt raw material containing a flux component containing lead oxide, calcium oxide, bismuth oxide, and boron oxide and a garnet single crystal component containing rare earth oxide and iron oxide in a Pt crucible. A single crystal substrate is brought into contact with the melt, and a bismuth-substituted rare earth iron garnet single crystal is grown on the single crystal substrate by a liquid phase epitaxial method,
The amount of calcium oxide added is an amount selected from 0.007 to 0.070 mass% based on the total amount of the melt raw material constituting the melt,
The amount of lead oxide added is an amount selected from 7 to 14% by mass based on the total amount of the melt raw material constituting the melt,
Growing a bismuth-substituted rare earth iron magnetic garnet single crystal at a melt temperature selected from the range of 860 ° C. to 905 ° C .;
Is a manufacturing method.

  According to the present invention, it is possible to provide a RIG single crystal having low Pt and Pb contents, little environmental impact, and excellent crystallinity.

It is an infrared-microscope observation photograph of the RIG growth crystal | crystallization in an Example. It is an infrared microscope observation photograph of the RIG growth crystal in a comparative example.

  The present invention is a bismuth-substituted rare earth iron garnet (RIG) single crystal grown by a liquid phase epitaxial method, wherein 0.010 or more and 0.100 or less of Ca per composition formula, and more than 0 and 0.005 or less per composition formula Rb single crystal containing Pb and Pt of greater than 0 and less than 0.010 per composition formula.

  The upper limit of the amount of Pb contained in the RIG single crystal according to the present invention is 0.010 or less, preferably 0.005 or less, more preferably 0.004 or less per composition formula. The lower limit of the amount of Pb is a range larger than 0 per composition formula, and is not particularly limited otherwise, but is, for example, 0.001 or more, 0.002 or more, or 0.003 or more. When the amount of Pb contained in the RIG single crystal is in the above range, it is possible to provide a RIG single crystal with few crystal defects, good crystallinity, and low environmental load.

  The amount of Pt contained in the RIG single crystal according to the present invention is less than 0.010, preferably 0.006 or less, more preferably 0.005 or less per composition formula. When Pt contained in the RIG single crystal is in the above minute range, an RIG single crystal having few crystal defects and excellent crystallinity can be obtained. The lower limit of the amount of Pt is in a range larger than 0 per composition formula, and the others are not particularly limited, but for example, 0.001 or more, 0.002 or more, or 0.004 or more.

  In addition, when the amount of Pt contained in the RIG single crystal is within the above range, it is possible to obtain a RIG single crystal with little light absorption and low insertion loss. This is because the amount of divalent Fe in the RIG single crystal is reduced by reducing the content of tetravalent Pt in the RIG single crystal.

  Furthermore, since the amount of Pt contained in the RIG single crystal is in the above range, the temperature change of the Faraday rotation angle can be suppressed to be small, and the performance of the optical component using the Faraday rotator can be maintained in a wide temperature range. Can do. This is presumably because the amount of Pt mixed in the RIG single crystal is small, the amount of substitution of iron ions by Pt is suppressed, and the temperature change of the Faraday rotation angle becomes small.

  The RIG single crystal according to the present invention contains Ca. When the RIG single crystal contains Ca, the amount of Pb mixed in the RIG single crystal can be reduced. In addition, by including Ca in the RIG single crystal, generation of divalent Fe can be suppressed and light absorption of the RIG single crystal can be reduced.

  As the Ca content in the RIG grown crystal increases, the amount of Pb mixed in the RIG single crystal can be reduced. However, if the Ca content in the RIG grown crystal is too large, the crystallinity of the grown RIG decreases. It's easy to do. If the crystallinity of the grown RIG is low, the RIG may crack or break during processing after crystal growth, such as cutting or mirror polishing.

  Therefore, the amount of Ca contained in the RIG single crystal according to the present invention is preferably 0.010 or more and 0.100 or less, more preferably 0.010 or more and 0.050 or less, more preferably 0.015 or more per composition formula. It is 0.040 or less, still more preferably 0.015 or more and 0.030 or less.

  The RIG single crystal according to the present invention contains bismuth (Bi). In the RIG single crystal, Bi replaces rare earth elements and has the effect of increasing the Faraday effect. In the RIG single crystal according to the present invention, the amount of Bi per composition formula is preferably 0.8 or more. The above range is preferable because the Faraday effect can be enhanced as the amount of bismuth substitution increases, and the required film thickness can be reduced. However, if the amount of Bi is too large, the difference in lattice constant from the single crystal substrate on which the RIG is grown increases, and the stress applied to the grown RIG increases, so 1.4 or less is preferable.

  The RIG single crystal according to the present invention contains a rare earth element. The rare earth element can be selected in consideration of the optical characteristics and magnetic characteristics of the RIG single crystal and the suitability of the lattice constant with the growth substrate. The rare earth element preferably includes at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. More preferably, it may contain at least one element selected from the group consisting of Gd, Tb, Ho, and Yb. In the RIG single crystal according to the present invention, the rare earth element amount per composition formula is preferably 3- (Bi amount + Ca amount + Pb amount) per composition formula.

  The RIG single crystal according to the present invention may contain a nonmagnetic element that substitutes for an Fe site, if desired. The element substituting for Fe is preferably at least one element selected from the group consisting of Ga, Al, Ge, and Si, and more preferably at least one element selected from Ga and Al. . By substituting Fe with the above element, the saturation magnetic field of RIG can be lowered. However, when the amount of Fe-substituted element exceeds 1.0, the temperature change of Faraday rotation tends to increase, and the amount of Fe-substituted element is 1.0 The following are preferred. Further, from the viewpoint of reducing pits in the grown crystal, the smaller the amount of Fe-substituted element, the more preferable, 1.0 or less is preferable, 0.5 or less is more preferable, 0.1 or less is further preferable, and substantially 0. Even more preferred.

  The RIG single crystal according to the present invention contains Fe. The amount of Fe contained in RIG is preferably 5- (Fe-substitution element amount + Pt amount) per composition formula.

The RIG single crystal according to the present invention preferably has the general formula:
_{(R 3-xab Bi x Ca} a Pb b) (Fe 5-yc M y Pt c) O 12
(In the formula, R is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Is at least one element selected from Ga, Al, Ge, and Si, and 0.8 ≦ x ≦ 1.4, 0 ≦ y ≦ 1.0, 0.010 ≦ a ≦ 0.100 , 0 <b ≦ 0.005, and 0 <c <0.010).

  In addition, as the growth thickness of the RIG single crystal increases, the size of crystal defects caused by Pt tends to increase, and the influence of the crystal defects on performance degradation as an optical element increases. In particular, when growing a crystal having a thickness of 100 μm or more necessary as a Faraday rotator for optical communication wavelengths, a crystal defect caused by Pt is required when manufacturing a general RIG product having a thickness of about 300 μm to 600 μm. Was newly found to be problematic.

  The thickness of the RIG single crystal according to the present invention is preferably 100 μm or more, more preferably 300 μm or more, and even more preferably 500 μm or more. Since the RIG single crystal according to the present invention has a thickness in the above range, it can function well as a Faraday rotator for optical communication wavelengths. The upper limit of the thickness of the RIG single crystal is not particularly limited, but is, for example, 1000 μm or less, 800 μm or less, or 600 μm or less because of the necessity as an optical element when the RIG single crystal is used as a product.

  The present invention also heats and melts a melt raw material containing a flux component containing lead oxide, calcium oxide, bismuth oxide, and boron oxide and a garnet single crystal component containing rare earth oxide and iron oxide in a Pt crucible. A single crystal substrate is brought into contact with the melt and a bismuth-substituted rare earth iron garnet single crystal is grown on the single crystal substrate by liquid phase epitaxy, and the amount of calcium oxide added constitutes the melt The amount selected from 0.007 to 0.070 mass% based on the total amount of the melt raw material to be added, and the amount of lead oxide added is based on the total amount of the melt raw material constituting the melt, Growing a bismuth-substituted rare earth iron magnetic garnet single crystal at a melt temperature selected from a range of 860 ° C. to 905 ° C. in an amount selected from 7 to 12% by mass. Of interest.

The melt used in the method according to the present invention includes lead oxide (PbO), bismuth oxide (Bi ₂ O ₃ ), boron oxide (B ₂ O ₃ ), calcium oxide (CaO), and iron oxide (Fe ₂ O _3). ), And can be prepared in a Pt crucible using a melt raw material containing a rare earth oxide.

  The weighed melt raw material components are put in a Pt crucible, and the melt raw material is heated to a saturation temperature or higher, for example, 1000 ° C. or higher to form a melt and sufficiently stirred to form a melt.

  The addition amount of calcium oxide (CaO) is 0.007 to 0.070 mass%, preferably 0.007 to 0.022 mass%, more preferably based on the total amount of the melt raw material constituting the melt. It is 0.007-0.013 mass%. By adding an amount of CaO in this range to the melt raw material, it is possible to obtain an RIG having excellent crystallinity while favorably reducing the amount of Pb mixed in the RIG to be grown. By containing, the generation of divalent Fe can be suppressed and the light absorption of RIG can be reduced.

  The amount of lead oxide (PbO) added is 7 to 14% by mass, preferably 7 to 12% by mass, more preferably 8 to 11% by mass, and still more preferably based on the total amount of the melt raw material constituting the melt. Is 8 to 10% by mass. By adding an amount of PbO in this range to the melt raw material, it is possible to grow a RIG single crystal with few crystal defects and good crystallinity and low environmental load.

In the production method according to the present invention, the melt raw material contains bismuth oxide (Bi ₂ O ₃ ). The addition amount of bismuth oxide (Bi ₂ O ₃ ) is preferably 41 to 91% by mass based on the total amount of the melt raw material constituting the melt. For example, the Bi amount per composition formula in the growing RIG is The amount can be in the range of 0.8 to 1.4.

In the production method according to the present invention, the melt raw material contains boron oxide (B ₂ O ₃ ). The amount of boron oxide (B ₂ O ₃ ) added is preferably 0.5 to 3.5% by mass based on the total amount of the melt raw material constituting the melt.

  In the production method according to the present invention, the melt raw material contains a rare earth oxide. The rare earth oxide is preferably an oxide of at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is. The addition amount of the rare earth oxide can be appropriately adjusted according to the kind of the rare earth oxide and the required RIG characteristics. For example, the amount of the rare earth element per composition formula in the grown RIG is 3- (Bi amount). + Ca amount + Pb amount).

  In the production method according to the present invention, the melt raw material may include an oxide of a nonmagnetic element that substitutes the iron site of the RIG single crystal as desired. The addition amount of the nonmagnetic element oxide can be appropriately adjusted according to the kind of the nonmagnetic element oxide and the required RIG characteristics. For example, the amount of the nonmagnetic element per composition formula in the growth RIG is 0. The amount can be within the range of 1.0 or more and 1.0 or less.

In the production method according to the present invention, the melt raw material contains iron oxide (Fe ₂ O ₃ ). The amount of Fe ₂ O ₃ added is preferably 4.2 to 8.4% by mass based on the total amount of the melt raw material constituting the melt. For example, the amount of Fe per composition formula in the growing RIG is The amount can be set to 5- (nonmagnetic element amount + Pt amount).

  In the LPE method, crystals are grown at a supercooling temperature lower than the saturation temperature. In the method according to the present invention, although the reason is not clear, Pt mixing into RIG can be suppressed by increasing the crystal growth temperature.

  Accordingly, the crystal growth temperature is 860 ° C. or higher, preferably 865 ° C. or higher, more preferably 880 ° C. or higher, still more preferably 890 ° C. or higher, and even more preferably 895 ° C. or higher. On the other hand, since the thermal expansion coefficients of the single crystal substrate and the grown RIG are different, the heat of the single crystal substrate and the grown RIG increases in the process of returning to room temperature as the crystal growth temperature is higher and the thickness of the grown RIG is larger. Since the growth crystal is stressed by the difference in expansion coefficient and defects such as cracks and cracks may occur, the crystal growth temperature is preferably 905 ° C. or lower, more preferably 900 ° C. or lower, and even more preferably 895 ° C. or lower.

  By growing the RIG single crystal in the above temperature range, it is possible to reduce defects while suppressing the mixing of Pt into the RIG.

  The crystal growth temperature is the temperature of the surface of the melt and can be measured using an R thermocouple, a radiation thermometer, or the like.

  In the process of growing the RIG single crystal, the component of the RIG in the melt may be taken into the grown crystal, and the component of the melt may change. The crystal may be grown while being lowered.

  After cooling to the crystal growth temperature, the RIG single crystal can be grown by using the nonmagnetic garnet single crystal as a single crystal substrate and in contact with the liquid surface.

  According to the method of the present invention, since Pt mixing into RIG can be suppressed, crystal defects are unlikely to occur, and the crystal growth rate can be increased.

  Therefore, the crystal growth rate is preferably 0.20 μm / min or more, more preferably 0.25 μm / min or more, further preferably 0.30 μm / min or more, even more preferably 0.35 μm / min or more, and even more preferably. Is 0.40 μm / min or more. A larger crystal growth rate is preferable because it is advantageous in terms of cost. However, if it is too large, crystal defects are likely to occur.

As the single crystal substrate that can be used in the method of the present invention, a known substrate can be used. For example, a non-magnetic garnet [(GdCa) having a lattice constant of 1.2490 nm to 1.2515 nm that is commercially available as an SGGG substrate. ) ₃ (GaMgZr) ₅ O ₁₂ ] substrate or the like can be used.

  During crystal growth, the single crystal substrate is preferably rotated, and more preferably rotated at 40 to 120 rpm. By rotating the single crystal substrate at this rotational speed, the melt can be diffused more uniformly. Further, the rotation direction of the single crystal substrate may be periodically changed.

  After the RIG single crystal is grown by the LPE method, it is gradually cooled to room temperature and taken out. However, the thermal expansion coefficient of the single crystal substrate used in the LPE method is different from the thermal expansion coefficient of the grown RIG. Depending on the difference in expansion coefficient, warping of the growing RIG and internal stress may occur.

  Therefore, after growing the RIG single crystal, the grown RIG may be cut into a predetermined size, for example, a size of about 11 mm square, the single crystal substrate is scraped, and mirror-polished to a required film thickness.

After both surfaces of the RIG-grown crystal are mirror-polished, an antireflection film can be arranged to produce a RIG product. The antireflection film is a dielectric multilayer film, and can be, for example, Ta ₂ O ₅ / SiO ₂ , TiO ₂ / SiO ₂ , or Al ₂ O ₃ / SiO ₂ .

  The manufactured RIG product can be cut into a desired size and used in an optical component such as an optical isolator.

  The RIG single crystal grown by the method according to the present invention may be heat-treated in a reducing atmosphere of nitrogen, hydrogen, or a mixed gas thereof. By heating the RIG single crystal grown by the method according to the present invention in a reducing atmosphere, tetravalent Fe can be further reduced and insertion loss of the RIG single crystal can be further reduced. Preferably the reducing atmosphere comprises hydrogen and optionally nitrogen.

Example 1
In a Pt crucible, 80% by mass of bismuth oxide (Bi ₂ O ₃ ), 0.9% by mass of boron oxide (B ₂ O ₃ ), 9.7% by mass of oxidation based on the total amount of the melt raw material Lead (PbO), 0.013% by mass of calcium oxide (CaO), 7.8% by mass of iron oxide (Fe ₂ O ₃ ), 0.67% by mass of gallium oxide (Ga ₂ O ₃ ), 0.65 Mass% terbium oxide (Tb ₄ O ₇ ) and 0.27 mass% ytterbium oxide (Yb ₂ O ₃ ) were added to prepare a melt raw material.

The prepared Pt crucible containing the melt raw material was placed in a precision vertical tubular electric furnace, heated and melted to 1000 ° C., and thoroughly mixed to form an RIG growth melt. Next, the temperature of the melt is lowered to 890 ° C. below the saturation temperature (905 ° C.), and the surface of the melt has a disc shape, a diameter of 3 inches, a thickness of 760 μm, and a lattice constant of 1.2497 nm (111 ) One side of a garnet single crystal [(GdCa) ₃ (CaMgZr) ₅ O ₁₂ ] substrate was brought into contact.

  In the air atmosphere, the single crystal substrate was rotated at 60 rpm, and the RIG single crystal was grown by performing epitaxial growth for 24 hours while reversing the rotation direction periodically at intervals of 2 minutes. The grown RIG single crystal had a diameter of 3 inches and a film thickness of 530 μm. The crystal growth rate was 0.260 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, eight crystal defects were confirmed, but no damage such as cracks was found in the RIG. The number of crystal defects was recorded for those having a diameter of 100 μm or more. The same applies hereinafter.

  The grown RIG single crystal was cut into 11 mm square, the single crystal substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope for an 11 mm square RIG single crystal that had been mirror-polished, no crystal defect was observed. An infrared microscope observation photograph is shown in FIG.

As a result of analyzing the composition of the mirror-polished RIG single crystal by fluorescent X-ray analysis using an X-ray fluorescence analyzer (manufactured by JEOL Ltd., JXA-8100), the composition was Tb _1.2 Yb _0.53 Bi _1.2 Ca _0.015 Pb _0.004 Fe _4.3 was Ga _0.7 Pt _0.005 O _12.

In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film (Ta ₂ O ₅ / SiO ₂ ) on the mirror-polished RIG single crystal, it was 45 degrees at a wavelength of 1550 nm.

(Example 2)
The test was performed under the same conditions as in Example 1 except that the RIG single crystal was grown at 880 ° C.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 530 μm. The crystal growth rate was 0.260 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, nine crystal defects were confirmed, but no damage such as cracks was found in the RIG.

  The grown RIG single crystal was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope for an 11 mm square RIG single crystal that had been mirror-polished, no crystal defect was observed.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _1.2 Yb _0.55 Bi _1.2 Ca _0.015 Pb _0.005 Fe _4.3 Ga _0.7 Pt _0.005 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

(Example 3)
The test was performed under the same conditions as in Example 1 except that the RIG single crystal was grown at 865 ° C.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 530 μm. The crystal growth rate was 0.260 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, ten crystal defects were confirmed, but no damage such as cracks was found in the RIG.

  The grown RIG single crystal was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope for an 11 mm square RIG single crystal that had been mirror-polished, no crystal defect was observed.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _1.2 Yb _0.56 Bi _1.2 Ca _0.015 Pb _0.005 Fe _4.3 Ga _0.7 Pt _0.005 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

(Comparative Example 1)
Except that 0.022% by mass of calcium oxide (CaO) was added based on the total amount of the melt raw material, and the RIG single crystal was grown at 790 ° C., the same conditions as in Example 1 were performed.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 540 μm. The crystal growth rate was 0.265 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, no damage such as cracks was found in the RIG, but 75 crystal defects were confirmed.

  The grown RIG single crystal was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 440 μm.

  When the internal pits (crystal defects) of the 11 mm square RIG single crystal that had been mirror-polished were observed with an infrared microscope, three crystal defects with V-shaped swirls were observed. An infrared microscope observation photograph is shown in FIG.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _1.2 Yb _0.57 Bi _1.2 Ca _0.029 Pb _0.004 Fe _4.2 Ga _0.8 Pt _0.030 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

(Comparative Example 2)
Except that 38% by mass of lead oxide (PbO) was added based on the total amount of the melt raw material, and the RIG single crystal was grown at 765 ° C., the same conditions as in Example 1 were performed.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 540 μm. The crystal growth rate was 0.265 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, two crystal defects were confirmed, but no damage such as cracks was found in the RIG.

  The grown RIG was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope for an 11 mm square RIG single crystal that had been mirror-polished, no crystal defect was observed.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _1.2 Yb _0.46 Bi _1.2 Ca _0.019 Pb _0.037 Fe _4.2 Ga _0.8 Pt _0.067 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

(Comparative Example 3)
The process was performed under the same conditions as in Example 1 except that no CaO was added to the melt raw material and a RIG single crystal was grown at 800 ° C.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 530 μm. The crystal growth rate was 0.260 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, 22 crystal defects were confirmed, but no damage such as cracks was found in the RIG.

  The grown RIG single crystal was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope with respect to a mirror-polished 11 mm square RIG single crystal, one crystal defect was observed.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _0.9 Yb _0.91 Bi _1.2 Pb _0.020 Fe _4.1 Ga _0.9 Pt _0.038 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

(Comparative Example 4)
The process was performed under the same conditions as in Example 1 except that the RIG single crystal was grown at 790 ° C.

  The grown RIG single crystal had a diameter of 3 inches and a film thickness of 530 μm. The crystal growth rate was 0.260 μm / min. When the entire surface of the grown RIG single crystal was observed with a microscope, no damage such as cracks was found in the RIG, but 49 crystal defects were confirmed.

  The grown RIG single crystal was cut into 11 mm square, the substrate was removed by grinding, and both surfaces were mirror-polished using a chemical mechanical polishing (CMP) method to obtain a RIG single crystal having a thickness of 450 μm.

  When an internal pit (crystal defect) was observed with an infrared microscope with respect to a mirror-polished 11 mm square RIG single crystal, two crystal defects were observed.

As a result of analyzing the composition of the mirror-polished RIG single crystal by X-ray fluorescence analysis, the composition was Tb _1.2 Yb _0.50 Bi _1.2 Ca _0.015 Pb _0.010 Fe _4.3 Ga _0.7 Pt _0.036 O ₁₂ .

  In addition, as a result of measuring the Faraday rotation angle by disposing a double-sided anti-reflection film on the mirror-polished RIG single crystal, the angle was 45 degrees at a wavelength of 1550 nm.

  By the amount of Pt, Pb, and Ca per composition formula of the RIG single crystal grown in Examples 1 to 3 and Comparative Examples 1 to 4, the number of crystal defects observed by microscopic observation of the RIG surface, and an infrared microscope Table 1 shows the number of internal pits observed.

Claims (4)

A bismuth-substituted rare earth iron garnet single crystal grown by a liquid phase epitaxial method,
Composition 0.010 or more per equation 0.100 of Ca, the composition more than 0 0.005 following Pb per formula, and Pt of greater than 0.010 than 0 per formula seen including,
Bismuth-substituted rare earth iron garnet single crystal having a thickness of 100 μm or more . The bismuth-substituted rare earth iron garnet single crystal has the general formula:
_{(R 3-xab Bi x Ca} a Pb b) (Fe 5-yc M y Pt c) O 12
(In the formula, R is at least one element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; Is at least one element selected from Ga, Al, Ge, and Si, and 0.8 ≦ x ≦ 1.4, 0 ≦ y ≦ 1.0, 0.010 ≦ a ≦ 0.100 The bismuth-substituted rare earth iron garnet single crystal according to claim 1, wherein 0 <b ≦ 0.005 and 0 <c <0.010. In a melt obtained by heating and melting a melt raw material containing a flux component containing lead oxide, calcium oxide, bismuth oxide and boron oxide, and a garnet single crystal component containing rare earth oxide and iron oxide in a Pt crucible, A method of growing a bismuth-substituted rare earth iron garnet single crystal on the single crystal substrate by liquid phase epitaxial method by contacting the single crystal substrate,
The amount of calcium oxide added is an amount selected from 0.007 to 0.070 mass% based on the total amount of the melt raw material constituting the melt,
The amount of the lead oxide added is an amount selected from 7 to 14% by mass based on the total amount of the melt raw material constituting the melt,
Growing a bismuth-substituted rare earth iron magnetic garnet single crystal to a thickness of 100 μm or more at a melt temperature selected from a range of 860 ° C. to 905 ° C .;
Manufacturing method. The production method according to claim 3 , comprising growing a bismuth-substituted rare earth iron magnetic garnet single crystal at a growth rate of 0.25 μm / min or more.