JPH10186296A - Magneto-optical element material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain a magneto-optical element material having the small dependence of a Faraday rotating angle on temps. at a wavelength 1550nm band and having a large Faraday rotation coefft. and to embody a wide-band optical isolator having small dependence of the Faraday rotating angle on wavelengths. SOLUTION: This material consists of the magnetic garnet single crystal of the compsn. formula expressed by R3-x Bix Fe5-v-w-y Mav Mbw COy O12 (where, R is a rare earth element including yttrium, Ma is a trivalent element, Mb is a quadrivalent element, 0.6<=x<=0.9, 0.01<=y<=0.47, 260y-88x+45<=0.500y-30x+37>=0, 0<=v<=1.0, 0<=w<=0.35) and is used in the wavelength 1550nm band. The magnetic garnet single crystal may be produced by liquid epitaxial growth on a nonmagnetic garnet substrate. When 0.01<=y<=0.28, 800y-130x+45<=0 are set, the dependence on the wavelengths is lowered and the material suitable for a wider band is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to Bi (bismuth)
And Co consists rare-earth iron garnet single crystal was replaced with (cobalt), relates to a magnetic optical element material to be used in the 1550nm band, More particularly, R _3-x Bi _x Fe
_5-vwy Ma _v relates Mb _w Co _y O magneto-optical element material comprising a magnetic garnet single crystal represented by ₁₂ a composition formula. This material has a small temperature dependence of the Faraday rotation angle and can be formed by liquid phase epitaxial (hereinafter abbreviated as “LPE”) growth. In some of the composition regions, the wavelength dependence of the Faraday rotation angle is extremely small,
It is useful for a broadband optical isolator used in the used wavelength band of 1550 nm.

[0002]

2. Description of the Related Art In recent years, the wavelength used in optical fiber communication has become mainstream in the 1550 nm band with the practical use of erbium-doped fiber amplifiers (EDFA). As a magnetic garnet single crystal used in this wavelength band, for example, Tb
An LPE film having a composition of _1.85 Bi _1.15 Fe _4.75 Al _0.25 O ₁₂ (corresponding to Comparative Example 1 described later) is known. One of the criteria for evaluating the characteristics of such a magnetic garnet single crystal is a Faraday rotation coefficient θ _F (deg / cm). The larger the absolute value of the Faraday rotation coefficient is, the more the film thickness for obtaining the required Faraday rotation angle can be reduced, so that the Faraday rotation coefficient is preferable because it is easy to manufacture. Another criterion for evaluating the properties of magnetic garnet single crystals is the temperature dependence of the Faraday rotation angle.
The smaller the temperature dependence, the smaller the change in the Faraday rotation angle even when the external environment temperature changes. Here, LP
The reason for using the E film is that the LPE method is excellent in mass productivity (the time required for growth is short), the manufacturing cost is low, and the replacement of Bi that dramatically increases the Faraday rotation angle to a negative value is easily performed. It depends on what can be done.

Recently, wavelength multiplex transmission is expected to realize large-capacity optical communication in the 1550 nm band. To perform wavelength division multiplexing transmission, a broadband optical isolator is required. A characteristic required for a magnetic garnet single crystal to be a Faraday rotator of this broadband optical isolator is that the wavelength dependence of the Faraday rotation coefficient is small. Further, it is desired that the magnetic garnet single crystal can be formed into a film by the LPE method.

In recent years, various types of Bi-substituted iron garnet single crystals for broadband, which have been variously developed, are described in, for example, J. Appl. Phys.
70 (8), 15 Octorber 1991, JP-A-4-118623, JP-A-5-88126, JP-A-5-8812
No. 7, JP-A-8-91998 and the like.

[0005]

Generally, in a magneto-optical element material, the Faraday rotation angle changes depending on the external environment temperature. Therefore, even if the Faraday rotator is set so that the polarization plane rotates just 45 degrees at room temperature, when the temperature changes, the rotation angle of the polarization plane in the Faraday rotator deviates from 45 degrees. As a result, the degree of erasure of the light incident in the opposite direction is reduced, so that the isolation of the optical isolator is deteriorated. For example, the aforementioned L having a composition of Tb _1.85 Bi _1.15 Fe _4.75 Al _0.25 O ₁₂
In the case of the PE film (Comparative Example 1), when the external environment temperature greatly changes, the isolation is considerably deteriorated, and the performance cannot always be sufficiently satisfied.

[0006] The Faraday rotation angle of the magneto-optical element material also depends on the wavelength. Therefore, even if the Faraday rotator is set to rotate the polarization plane by exactly 45 degrees with respect to light of a specific wavelength of the light source, when the wavelength of the light source changes, the rotation angle of the polarization plane in the Faraday rotator becomes 45 degrees. Deviates from the degree. As a result, the degree of erasure of the light incident in the opposite direction decreases, so that the isolation of the optical isolator deteriorates.

In the wavelength division multiplexing transmission expected as a large-capacity optical communication in the 1550 nm band as described above, the optical isolator is, for example, ± 20 nm around 1550 nm, that is, 15 nm.
It is necessary to exhibit good isolation in a wide wavelength band of 30 to 1570 nm. For example, in the magneto-optical element material of Comparative Example 1, the wavelength dependence of the Faraday rotation coefficient is considerably large, and such a broadband optical isolator is required. Was unsuitable.

[0008] As materials for broadband optical isolator 1550nm band, J.Appl.Phys.70 (8), Bi substituted terbium iron having a composition of _{Tb 3-x Bi x Fe 5} O 12 disclosed in 15Octorber 1991 The garnet single crystal has a very small absolute value of the Faraday rotation coefficient, and requires a thickness of about 1.5 to 2 mm to constitute a Faraday rotator for an optical isolator, which has a disadvantage of increasing the size. The magnetic garnet single crystal was produced by a flux method. However, the flux method cannot provide a composition having a uniform composition, requires a long time for production, and is not suitable for mass production. The magnetic garnet single crystals described in JP-A-4-118623, JP-A-5-88126, and JP-A-5-88127 also show examples in which the flux method has a relatively large Faraday rotation coefficient. But LP
According to the E method, the absolute value of the Faraday rotation coefficient is small. Further, in the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-91998,
It is disclosed that the mass productivity is improved by preparing a magnetic garnet having a similar composition by a solid-phase reaction method, but it still requires a thickness of about 1.5 to 2 mm, which is an obstacle to miniaturization. Become.

An object of the present invention is to provide a magneto-optical element material having a small temperature dependence of a Faraday rotation angle and a large Faraday rotation coefficient. Another object of the present invention is to provide a broad band of 1550 nm band (specifically, for example, 153 nm band).
(1 to 1570 nm), and to provide a magneto-optical element material having a small wavelength dependence of the Faraday rotation angle. Still another object of the present invention is to provide a magneto-optical element material which can be formed by the LPE method and is suitable for mass production, thereby realizing the miniaturization and low cost of the broadband optical isolator.

[0010]

According to the present invention, a composition formula is represented by R
_{3-x Bi x Fe 5-} vwy Ma v Mb w Co y O 12 where
R is a rare earth element containing yttrium, Ma is a trivalent positive element, Mb is a tetravalent positive element, 0.6 ≦ x ≦ 1.9 0.01 ≦ y ≦ 0.47 260y-88x + 45 ≦ 0 500y-30x + 37 It is composed of a magnetic garnet single crystal represented by ≧ 00 ≦ v ≦ 1.00 ≦ w ≦ 0.35, and has a wavelength of 155
This is a magneto-optical element material used in the 0 nm band. Here, the wavelength 1550 nm band means a wide band (for example, about 1530 nm to 1570 nm) having a certain width capable of performing wavelength multiplex transmission with respect to the center wavelength 1550 nm when used only in the vicinity of the center wavelength 1550 nm. Means. When used in a wide band, 0.01 ≦ y ≦ 0.2
8 and 800y-130x + 23 ≦ 0. The magnetic garnet single crystal is a liquid-phase epitaxially grown LP on a non-magnetic garnet substrate.
E films are preferred.

For the magneto-optical device material used in the 1550 nm band, the present inventors have found that the rare earth iron garnet single crystal simultaneously substituted with Bi and Co is farader than the conventional rare earth iron garnet single crystal substituted with Bi. It has been experimentally found that the temperature dependence and the wavelength dependence of the rotation become extremely small, and the present invention has been completed. The rare earth iron garnet single crystal containing cobalt divalent ions is described in JP-A-62-78194, but the rare earth iron garnet single crystal simultaneously substituted with Bi and Co is not disclosed. .

[0012] Isolation in an optical isolator is the ratio of the insertion loss in the forward direction to the insertion loss in the reverse direction. An extinction ratio of 50 dB or more is obtained with a polarizer and an analyzer made of a rutile single crystal. From this, it can be said that the isolation of the optical isolator is determined by the extinction ratio of the Faraday rotator. Therefore, in the present invention, in order to evaluate the temperature dependency of the magneto-optical element material, the following evaluation method is adopted in consideration of the above matters. This is because the iron garnet single crystal in each example (comparative example and experimental example) described below had 45 dB even at the smallest isolation at 1550 nm and 25 ° C.
When the isolation K ₀ of the 45-degree rotator at 50 nm and room temperature (25 ° C.) is 45 dB, 0 ° C. to 50 ° C.
(At room temperature 25 ° C. ± 25 ° C.) to determine the minimum value of isolation K _{T min} and compare with the conventional magneto-optical element material ”.

In practice, K is given by the following formula:
_{Find T min} . The temperature of the LPE film is T ₀ (= room temperature 25 ° C.)
In when the film thickness of 45 degree Faraday rotation, when the temperature is changed to temperature T at room temperature T _0, usually, the Faraday rotation angle comes deviates from 45 degrees. Here Δθ the angle difference of the Faraday rotation angle at room temperature T ₀ phrase temperature T _T, RT T ₀
It is known that if the isolation at K is K ₀ and the isolation at a certain temperature T is K _T , the following equation holds. K _T = −10 × log (10 ^{−K0 / 10} + sin ² Δθ _T ) (1) By using this equation, the isolation K _T at a certain temperature T can be calculated from Δθ _T and K ₀ . Here, Δθ _T is calculated from the measured value of the temperature dependence of the Faraday rotation coefficient.
The smallest value among the calculated isolations K _T is defined as K _{T min} .

In the above-mentioned conventional TbBi-based iron garnet single crystal, K ₀ = 45 dB and K _{T min} = 32 dB.
In contrast, in the present invention, K _{T min} ≧ 33 dB is obtained. K _{T min} ≧ 33 dB is because at least 33 dB is required as the isolation of the optical isolator. The composition range of the present invention is a region surrounded by a dotted line in FIG. The reason why the Bi amount x is required to be 0.6 (/ fu) or more is that the LPE film can generally be grown only up to a thickness of about 500 μm. This is because the Faraday rotation coefficient of one LPE film needs to be 500 (deg / cm) or more in absolute value. Faraday rotation coefficient is 500 (de
g / cm) or more because the Bi content is 0.6 (/ fu) or more in the film composition of the present invention. The Bi amount is 1.9 (/ fu) or less because the Bi amount is too large for LP.
This is because the thermal expansion coefficient of the E film increases, the thermal expansion difference with the substrate increases, and a large stress is generated between the E film and the substrate during the temperature decrease after the growth, and the film is broken, so that the film cannot be grown substantially. .

As a result of the experiment, the rare-earth iron garnet single crystal of the above composition region in which Co and Bi are simultaneously and appropriately substituted can reduce the temperature dependence of the Faraday rotation angle and can achieve the minimum isolation K _{T min} of 33 dB or more. There was found. In this case, there is an example in which the wavelength dependence of the Faraday rotation angle is large, but in applications where the wavelength is limited to 1550 nm, it can be used without any problem.

By the way, recent wavelength division multiplexing transmission experiments have been performed within a wavelength range of 40 nm or less centered on a wavelength of 1550 nm. This is because the range of wavelength that can be amplified by the erbium-doped fiber amplifier is about 1530 to 1570 nm. Therefore, an optical isolator used in such a wavelength division multiplexing transmission system is required to exhibit high isolation in this wavelength region in addition to low temperature dependency.

In the present invention, in order to evaluate the wavelength dependence of the magneto-optical element material, the following evaluation method similar to the case of the temperature dependence is employed. It is "wavelength 1550
When the isolation K ₀ of the 45-degree rotator at 45 nm (room temperature 25 ° C.) is 45 dB, the wavelength multiplexing transmission is performed in the 1550 nm band, that is, the wavelength range that can be amplified by the erbium-doped fiber amplifier, 1530 to 157.
A minimum value K _WLmin of the isolation between 0 nm is determined, and comparison with a conventional magneto-optical element material is performed. "

In practice, K is given by the following formula:
_{Find WLmin} . The center wavelength λ ₀ (= 1550)
nm), the film thickness at which 45 degree Faraday rotation occurs
When the wavelength changes from 1550 nm to a certain wavelength λ, the Faraday rotation angle usually deviates from 45 degrees. Here, the difference between the center wavelength λ ₀ and the Faraday rotation angle at a certain wavelength λ is Δ
If θ _WL , the extinction ratio at the center wavelength λ ₀ is K ₀ , and the isolation at a certain wavelength λ is K _WL , the following equation holds. K _WL = −10 × log (10 ^{−K0 / 10} + sin ² Δθ _WL ) (2) Using this equation, the isolation K _WL at a certain wavelength λ can be calculated from Δθ _WL and K ₀ . Here, Δθ _WL is calculated from the measured value of the wavelength dependence of the Faraday rotation coefficient.
The smallest value of the calculated isolation K _WL is K _WLmin .

In the aforementioned conventional TbBi-based iron garnet single crystal, K ₀ = 45 dB and K _WLmin = 33 dB.
On the other hand, in the present invention, 0 ≦ y ≦
If 0.28 and 800y−130x + 23 ≦ 0, K _WLmin ≧ 35 dB is obtained. The composition range at that time is a region indicated by hatching in FIG.

It is considered that the reason why the wavelength dependence of the Faraday rotation angle is reduced by the appropriate substitution of Co is as follows. The Journal of the Japan Society of Applied Magnetics 13, 157-162 (1989) shows the wavelength dependence of the Faraday rotation coefficient of YIG (yttrium iron garnet) single crystals substituted with Co ²⁺ and Co ³⁺ , respectively. According to it, Co ²⁺ is 1
440 nm and Co ³⁺ have a peak of the Faraday rotation coefficient at 1400 nm. The Faraday rotation coefficient in these 1550 nm bands is positive. In the 1550nm band,
The wavelength dependence of the Faraday rotation coefficient has a negative slope. On the other hand, in the case of a Bi-substituted rare earth iron garnet single crystal, according to J. Appl. Phys. 70 (8), 15 October1991, B
If i is substituted about 0.3 (/ fu) or more, 1
The Faraday rotation coefficient in the 550 nm band is negative. In the 1550 nm band, the wavelength dependence of the Faraday rotation coefficient has a positive slope. In the present invention, 1550
Co ²⁺ and Bi, Co ³⁺ and B, which have the effect that the slopes of the wavelength dependence of the Faraday rotation coefficient in the nm band are opposite to each other.
It is considered that the simultaneous substitution of i or Co ²⁺ or Co ³⁺ and Bi cancels the effects of both, thereby substantially reducing the wavelength dependence of the Faraday rotation coefficient.

The determination of whether Co ions in garnet are divalent or trivalent is disclosed in the Journal of the Japan Society of Applied Magnetics, 12,171-174 (1988), and is described below. (A) When charge compensation is not performed with a tetravalent cation, C
The o ion is Co ³⁺ . (B) When charge compensation is performed with tetravalent cations,
The ions are Co ²⁺ by the concentration of tetravalent cations, and the remaining Co ions are Co ³⁺ . Therefore, by controlling the addition amount of Mb (ie, tetravalent positive element), the divalent and trivalent of Co ^ions , that is, the ratio of Co ²⁺ to Co ³⁺ is adjusted, and the wavelength of the Faraday rotation coefficient in the 1550 nm band is adjusted. The negative slope of dependence can be adjusted. This adjusted negative slope of the wavelength dependence of the Faraday rotation coefficient cancels out the positive slope of the wavelength dependence of the Faraday rotation coefficient due to the addition of Bi, so that wavelength characteristics without wavelength dependence can be realized.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to R _3-x Bi _x Fe
_5-vwy Ma _v consists Mb _w Co _y O ₁₂ in the magnetic garnet single crystal represented a magneto-optical element material for use in the wavelength 1550nm band. Here, since 0 ≦ v and 0 ≦ w, the following four types are included in the embodiment. R free of Ma and _{Mb 3-x Bi x Fe 5} -y Co y O
R contains only _{12 Ma 3-x Bi x Fe} 5-vy Ma v Co y
O containing only _{12 Mb R 3-x Bi x} Fe 5-wy Mb w Co y
O ₁₂ includes both Ma and _{Mb R 3-x Bi x Fe} 5-vwy M
a _v Mb _w Co _y O ₁₂

The above embodiment is the most basic one.
R is Y (yttrium), La (lanthanum),
One or more rare earth elements selected from Lu (lutetium), Tb (terbium), and Gd (gadolinium) are used. As a trivalent positive element Ma, Al,
One or two or more selected from Ga and In are used. 4
Ge, Sn, Ti,
One or more selected from Zr and Si are used. 3
Substitution with a valence positive element is mainly performed in order to match the lattice constant with the substrate during film formation by the LPE method. The substitution with the tetravalent positive element is for controlling the valence of Co. Co changes from trivalent to divalent by the amount replaced with the tetravalent positive element, and the wavelength dependence of the Faraday rotation coefficient by Co. Is controlling the negative slope. In the composition region where the wavelength dependence is reduced, the amount w of the tetravalent positive element may be 0 ≦ w ≦ 0.23.

The most preferred example is (CaGd) ₃
Tb _1.86 Bi _1.14 Fe liquid phase epitaxially grown on non-magnetic garnet substrate (MgZrGa) ₅ O _12
4.67 A magnetic garnet single crystal having a composition of Al _0.24 Co _0.09 O ₁₂ or (CaGd) ₃ (MgZrGa) ₅ O ₁₂
There is a magnetic garnet single crystal having a composition of Tb _2.40 Bi _0.60 Fe _4.97 Co _0.03 O ₁₂ which is liquid phase epitaxially grown on a non-magnetic garnet substrate.

[0025]

EXAMPLE An experiment was conducted in which magnetic garnet single crystals of various compositions were formed on a nonmagnetic garnet substrate by the LPE method. All fluxes were Bi ₂ O ₃ -B ₂ O ₃ -Pb
O was used. The thickness of the formed magnetic garnet single crystal is 4
It was 0 to 470 μm. For each magnetic garnet single crystal, the isolation K ₀ (dB) at a wavelength of 1550 nm and room temperature (25 ° C.), 0 ° C. to 50 ° at a wavelength of 1550 nm
Faraday rotation coefficient θ _F (deg / cm) between ℃ and 153
Faraday rotation coefficient θ _F at room temperature between 0 and 1570 nm
(Deg / cm) was measured. The minimum value of isolation K _{T min} (dB) in the temperature range of 0 ° C. to 50 ° C. is calculated by the above formula (1) using the Faraday rotation coefficient θ _F (deg / cm) measured in the temperature range of 0 ° C. to 50 ° C. ) Was substituted for Δθ _T obtained by normalizing the Faraday rotation angle at 25 ° C. to 45 degrees. In practice, Δθ _T is 4 degrees Faraday rotation at 25 ° C.
In film thickness is 5 degrees, there Faraday rotation angle in the Faraday rotation angle theta _T and 25 ° C. at a temperature T difference (45 degrees) (i.e. _{Δθ T = | θ T -45 |} ) is. 1530
The minimum value of the isolation K _WLmin (dB) in the wavelength range of １５1570 nm is 1530〜15 in the above formula (2).
Faraday rotation coefficient θ measured in the wavelength range of 70 nm
The Faraday rotation angle from _F (deg / cm) to 1550 nm is 4
The calculation was performed by substituting Δθ _WL obtained by normalizing to 5 degrees.
Actually, Δθ _WL is 1550 nm and the Faraday rotation is 45
The difference between the Faraday rotation angle θ _WL at a certain wavelength λ and the Faraday rotation angle (45 degrees) at 1550 nm (that is, Δθ _WL = | θ _WL −45 |) at a film thickness of a degree. The following are the results, the composition of the magnetic garnet single crystal, the type of the non-magnetic garnet substrate (its lattice constant), and the measured values.
Faraday rotation coefficient θ at room temperature (25 ° C.) at 50 nm
_F (deg / cm), the isolation K ₀ (dB), the calculated minimum value K _{T min} (dB) and the minimum value K _WLmin (dB) of the _isolation are listed in this order. Here, the comparative example is a case where Co is not contained, and the experimental examples are all Co
Is included. For each experimental example containing Co, B
The quality of the characteristics was determined with respect to the i amount x and the Co amount y, and is mapped in FIG. From this map, the composition range of the present invention is determined. The numbers in FIG. 1 correspond to the numbers of the experimental examples.

(Comparative Example 1) Composition: Tb _1.85 Bi _1.15 Fe _4.75 Al _0.25 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496 °) Measurement value: θ _F = -1060 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 32 dB / K _WLmin = 33 dB (Comparative Example 2) Composition: Tb _1.60 Bi _1.40 Fe _4.00 Ga _1.00 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant) = 12.500 °) Measured value: θ _F = -1130 deg / cm / K ₀ = 46 dB Calculated value: _{KT min} = 32 dB / K _WLmin = 33 dB

(Experimental example 1) Composition: Tb _1.86 Bi _1.14 Fe _4.67 Al _0.24 Co _0.09 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496 °) Measurement value: θ _F = −802 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 36 dB / K _WLmin = ₄₄ dB (Experimental Example 2) Composition: Tb _2.19 Bi _0.81 Fe _4.83 Ge _0.08 Co _0.09 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496 °) Measured value: θ _F = −548 deg / cm / K ₀ = 47 dB Calculated value: K _{T min} = 41 dB / K _WLmin = 37 dB (Experimental Example 3) Composition: Tb _2.40 Bi _0.60 Fe _4.97 Co _0.03 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.469 °) Measured value: θ _F = −512 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 43 dB / K _WLmin = 4 dB (Experimental Example 4) _{Composition: Tb 2.30 Bi 0.70 Fe 4.94 Co} 0.06 O 12 _{substrate: (CaGd) 3 (MgZrGa)} 5 O 12 ( lattice constant = 12.476A) _{measurement: θ F = -506deg / cm /} K ₀ = 46 dB Calculated value: K _{T min} = 43 dB / K _WLmin = 41 dB (Experimental Example 5) Composition: Tb _1.30 Bi _1.70 Fe _4.54 Ge _0.23 Co _0.23 O ₁₂ Substrate: Nd ₃ Ga ₅ O ₁₂ (lattice constant = 12.527 °) ) Measured value: θ _F = -973 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 43 dB / K _WLmin = 35 dB (Experimental example 6) Composition: Tb _1.90 Bi _1.10 Fe _4.83 Ge _0.05 Co _0.12 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.500 °) Measured value: θ _F = −755 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 40 dB / K _WLmin = 41 dB (Experimental Example 7) ) Composition: T _{2.10 Bi 0.90 Fe 4.80 Sn 0.10 Co} 0.10 O 12 _{substrate: (CaGd) 3 (MgZrGa)} 5 O 12 ( lattice constant = 12.494Å) _{measurement: θ F = -626deg / cm /} K 0 = 46dB Calculated: K _{T min} = 40 dB / K _WLmin = 38 dB (Experimental Example 8) Composition: Tb _1.90 Bi _1.10 Fe _4.82 Ti _0.09 Co _0.09 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.498 °) Measured value : Θ _F = −911 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 40 dB / K _WLmin = 35 dB (Experimental Example 9) Composition: Tb _2.10 Bi _0.90 Fe _4.82 Zr _0.09 Co _0.09 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496A) _{measurement: θ F = -667deg / cm /} K 0 = 45dB _{calculated: K T min = 42dB / K} WLmin = 37dB ( experimental example 10) composition _{Tb 1.80 Bi 1.20 Fe 4.82 Si 0.09} Co 0.09 O 12 _{substrate: (CaGd) 3 (MgZrGa)} 5 O 12 ( lattice constant = 12.496Å) _{measurement: θ F = -1033deg / cm /} K 0 = 46dB Calculated: K _{T min} = 38 dB / K _WLmin = 35 dB (Experimental Example 11) Composition: Tb _2.00 Bi _1.00 Fe _4.81 Al _0.05 Ge _0.05 Co
_0.09 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.490 °) Measured value: θ _F = −752 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 40 dB / K _WLmin = 40 dB (Experimental Example 12) Composition: Y _1.80 Bi _1.20 Fe _4.70 Co _0.30 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.480 °) Measured value: θ _F = −335 deg / cm 2 / K ₀ = 46 dB Calculated value: K _{T min} = 41 dB / K _WLmin = 0 dB (Experimental Example 13) Composition: Lu _1.45 Y _0.95 Bi _0.60 Fe _4.85 Co _0.15 O ₁₂ Substrate: Gd ₃ Ga ₅ O ₁₂ (lattice constant = 12.383Å) ) Measured value: θ _F = −117 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 38 dB / K _WLmin = 9 dB (Experimental example 14) Composition: La _0.30 Y _1.80 Bi _0.90 Fe _4.75 Co _0.25 O ₁₂ substrate: (CaGd) ₃ ( gZrGa) ₅ O ₁₂ (lattice constant = 12.490A) _{measurement: θ F = -156deg / cm /} K 0 = 45dB _{Calculated: K T min = 31dB / K} WLmin = 12dB ( Experimental Example 15) Composition: Lu _0.75 Y _0.35 Bi _1.90 Fe _4.40 Ge _0.30 Co
_0.30 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.497 °) Measured value: θ _F = 1136 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 42 dB / K _WLmin = 31 dB (Experimental Example 16) Composition: Tb _2.10 Bi _0.90 Fe _4.75 Ga _0.24 Co _0.01 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.484 °) Measured value: θ _F = −804 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 36 dB (Experimental Example 17) Composition: Tb _1.50 Bi _1.50 Fe _4.30 Al _0.50 Co _0.20 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ ( lattice constant = 12.498A) _{measurement: θ F = -705deg / cm /} K 0 = 46dB _{calculated: K T min = 40dB / K} WLmin = 35dB ( experimental example 18) composition: Tb _1.70 Bi _1.30 Fe _3.88 G _1.00 Co _0.12 O _{12 substrate: (CaGd) 3 (MgZrGa)} 5 O 12 ( lattice constant = 12.501Å) _{measurement: θ F = -535deg / cm /} K 0 = 46dB Calculated: K _{T min} = 42dB / K _WLmin = 35 dB (Experimental Example 19) Composition: Tb _1.80 Bi _1.20 Fe _4.70 In _0.15 Co _0.15 O ₁₂ Substrate: Nd ₃ Ga ₅ O ₁₂ (lattice constant = 12.527 °) Measured value: θ _F = −731 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 42 dB / K _WLmin = 35 dB (Experimental example 20) Composition: Tb _0.90 Bi _2.10 Fe _4.96 Co _0.04 O ₁₂ substrate: Gd ₃ Sc ₂ Ga ₃ O ₁₂ (lattice constant = 12.56)
1)) An attempt was made to grow on the substrate by the LPE method, but growth was not possible due to cracks and the like. (Experimental Example 21) Composition: Tb _1.40 Bi _1.60 Fe _4.46 Al _0.50 Co _0.04 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.499 °) Measurement value: θ _F = 1428 deg / cm 2 K ₀ = 46 dB Calculated value: K _{T min} = 33 dB / K _WLmin = 35 dB (Experimental Example 22) Composition: La _0.16 Y _0.94 Bi _1.90 Fe _4.52 Co _0.48 O ₁₂ Substrate: Gd ₃ Sc ₂ Ga ₃ O ₁₂ (lattice constant = 12.56
1Å) Measured value: θ _F = −476 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 38 dB / K _WLmin = 3 dB (Experimental example 23) Composition: Y _1.60 Bi _1.40 Fe _4.64 Co _0.36 O ₁₂ substrate: CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.498 °) Measured value: θ _F = −357 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 39 dB / K _WLmin = 3 dB (Experimental example 24) Composition: Lu _0.60 Y _0.80 Bi _1.60 Fe _4.60 Co _0.40 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.497Å) Measured value: θ _F = −438 deg / cm / K ₀ = 46 dB Value: K _{T min} = 41 dB / K _WLmin = 0 dB (Experimental Example 25) Composition: Y _1.60 Bi _1.40 Fe _4.62 Co _0.38 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.499 °) Measurement value: θ _F = 290deg / cm / K ₀ = 45dB _{Calculated: K T min = 33dB / K} WLmin = 10dB ( Experimental Example 26) _{Composition: Tb 1.40 Bi 1.60 Fe 4.72 Ge} 0.14 Co 0.14 O 12 substrate: Nd ₃ Ga ₅ O ₁₂ (grating Constant = 12.527 °) Measured value: θ _F = 1337 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 37 dB / K _WLmin = 36 dB (Experimental Example 27) Composition: Lu _0.05 La _0.05 Y _1.20 Bi _1.70 Fe _4.64 Co
_0.36 O ₁₂ substrate: Nd ₃ Ga ₅ O ₁₂ (lattice constant = 12.527 °) Measured value: θ _F = −687 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 37 dB / K _WLmin = 17 dB (Experimental example) 28) Composition: La _0.17 Y _0.93 Bi _1.90 Fe _4.53 Co _0.47 O ₁₂ Substrate: Gd ₃ Sc ₂ Ga ₃ O ₁₂ (lattice constant = 12.56
1Å) Measured value: θ _F = −512 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 40 dB / K _WLmin = 2 dB (Experimental Example 29) Composition: Tb _1.60 Bi _1.40 Fe _4.70 Co _0.30 O ₁₂ Substrate: Nd ₃ Ga ₅ O ₁₂ (lattice constant = 12.527 °) Measured value: θ _F = −532 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 41 dB / K _WLmin = _{16 dB} (Experimental example 30) Composition: Tb _2.00 Bi _1.00 Fe _4.84 Co _0.16 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.498 °) Measured value: θ _F = −525 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 38 dB / K _WLmin = 27 dB (Experimental Example 31) Composition: Lu _0.75 Y _0.35 Bi _1.90 Fe _4.30 Ge _0.35 Co
_0.35 O ₁₂ substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.497 °) Measured value: θ _F = −959 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 25 dB (Experimental Example 32) Composition: Tb _1.84 Bi _1.16 Fe _4.68 Al _0.24 Co _0.08 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496 °) Measured value: θ _F = −962 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 36 dB / K _WLmin = 36 dB (Experimental Example 33) Composition: La _0.40 Y _1.80 Bi _0.80 Fe _4.87 Co _0.13 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ ( lattice constant = 12.490A) _{measurement: θ F = -285deg / cm /} K 0 = 45dB _{calculated: K T min = 35dB / K} WLmin = 31dB ( experimental example 34) _{composition: Y 1.60 Bi 1.40 Fe 4.82 Co} 0.18 _{12 substrate: (CaGd) 3 (MgZrGa)} 5 O 12 ( lattice constant = 12.492Å) _{measurement: θ F = -798deg / cm /} K 0 = 47dB _{Calculated: K T min = 35dB / K} WLmin = 42dB ( Experimental Example 35) Composition: Y _1.70 Bi _1.30 Fe _4.80 Co _0.20 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.485 °) Measurement value: θ _F = −580 deg / cm / K ₀ = 46 dB calculated value: K _{T min} = 35 dB / K _WLmin = 34 dB (Experimental Example 36) Composition: La _0.20 Y _0.90 Bi _1.90 Fe _4.72 Co _0.28 O ₁₂ Substrate: Gd ₃ Sc ₂ Ga ₃ O ₁₂ (lattice constant = 12.56)
1Å) Measured value: θ _F = −913 deg / cm / K ₀ = 45 dB Calculated value: _{KT min} = 35 dB / K _WLmin = 35 dB (Experimental Example 37) Composition: Tb _1.10 Bi _1.90 Fe _4.44 Al _0.50 Co _0.06 O ₁₂ substrate : (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.510 °) Measured value: θ _F = 1646 deg / cm / K ₀ = 45 dB Calculated value: _{KT min} = 33 dB / K _WLmin = 35 dB (Experimental example) 38) Composition: Tb _2.00 Bi _1.00 Fe _4.49 Ga _0.50 Co _0.01 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.486 °) Measured value: θ _F = −929 deg / cm / K ₀ = 47 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 36 dB (Experimental example 39) Composition: Tb _1.50 Bi _1.50 Fe _4.87 Co _0.13 O ₁₂ Substrate: Nd ₃ Ga ₅ O ₁₂ (Lattice constant = 12.527 °) Measured value: θ _F -1184deg / cm / K ₀ = 45dB _{Calculated: K T min = 35dB / K} WLmin = 42dB ( Experimental Example 40) _{Composition: La 0.20 Y 1.70 Bi 1.10 Fe} 4.85 Co 0.15 O 12 substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.491 °) Measured value: θ _F = −1441 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 37 dB (Experimental example 41) Composition: Tb _1.50 Bi _1.50 Fe _4.45 In _0.50 Co _0.05 O ₁₂ substrate: Gd ₃ Sc ₂ Ga ₃ O ₁₂ (lattice constant = 12.56
1Å) Measured value: θ _F = -1273 deg / cm / K ₀ = 4
5 dB Calculated value: K _{T min} = 33 dB / K _WLmin = 36 dB (Experimental Example 42) Composition: Tb _1.10 Bi _1.90 Fe _3.96 Al _1.00 Co _0.04 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12) .487 °) Measured value: θ _F = 1360 deg / cm / K ₀ = 45 dB Calculated value: _{KT min} = 33 dB / K _WLmin = 35 dB (Experimental example 43) Composition: Tb _1.60 Bi _1.40 Fe _3.99 Ga _1.00 Co _0.01 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.496 °) Measured value: θ _F = −1082 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 33 dB / K _WLmin = 35 dB (Experiment Example 44) Composition: Lu _1.20 Bi _1.80 Fe _4.85 Co _0.15 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant = 12.486 °) Measured value: θ _F = 1457 deg / cm / K ₀ = 46 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 40 dB (Experimental example 45) Composition: Lu _0.60 Gd _1.10 Bi _1.30 Fe _4.90 Co _0.10 O ₁₂ Substrate: (CaGd) ₃ (MgZrGa) ₅ O ₁₂ (lattice constant) = 12.497 °) Measured value: θ _F = -1055 deg / cm / K ₀ = 45 dB Calculated value: K _{T min} = 35 dB / K _WLmin = 36 dB

In Experimental Example 14, K _{T min} is less than 33, which is not preferable. Experimental Example 12～14,22～25,33 is not preferred because the Faraday rotation coefficient theta _F is less than 500deg / cm. In Experimental Example 20, since the amount of Bi was too large, LP
E film cannot be formed. On the other hand, in particular, Experimental Example 1,
3, 4, 6, 11, 34, 39 and 44 are K _{T min}
Is 35 dB or more and K _WLmin is 40 dB or more, exhibiting extremely good characteristics.

Comparison results of the wavelength dependence of the Faraday rotation angle between the magnetic garnet single crystal containing no Co (Comparative Example 1) and the magnetic garnet single crystal containing Co (Experimental Example 1) (product of the present invention) are shown. As shown in FIG. As can be seen from FIG.
The product of the present invention in which Co and Bi are appropriately replaced at the same time has a small change in the Faraday rotation angle with respect to the wavelength change, and
It can be seen that in the range of １５1570 nm, almost flat wavelength characteristics are exhibited. This means that as long as the device is used in this wavelength band, the Faraday rotation angle remains at 45 degrees even if the wavelength changes, so that the isolation does not deteriorate when the optical isolator is configured. I have.

[0030]

The present invention provides a magneto-optical device material comprising a rare earth magnetic garnet single crystal in a characteristic composition region which is simultaneously and appropriately substituted with Bi and Co so that the ratio of the Bi amount and the Co amount falls within a constant relationship. Therefore, the optical isolator using the Faraday rotator in the Faraday rotator has a small temperature change in the Faraday rotation angle even when the external environment temperature changes, and can maintain high isolation. In addition, since a Faraday rotator having a larger Faraday rotation coefficient can be realized as compared with a conventional TbBi-based iron garnet single crystal, the Faraday rotator can be made thinner and downsized. In particular, since the magneto-optical element material of the present invention is suitable for the LPE method, mass production is improved by forming the film by the LPE method, and the cost of the broadband optical isolator can be reduced.

By setting the substitution amount of Bi and Co within a more appropriate range, the wavelength dependence of Faraday rotation can be minimized in a wide band of 1550 nm. This gives 1
A Faraday rotator that can be used for wavelength multiplex transmission in the 550 nm band can be configured, and a wideband optical isolator can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the range of the composition of the present invention determined from characteristics with respect to Bi amount x and Co amount y.

FIG. 2 is a graph showing the wavelength dependence of the Faraday rotation angle in Comparative Example 1 and Experimental Example 1.

Claims (9)

[Claims] 1. A composition formula _{R 3-x Bi x Fe 5} -vwy Ma
_v Mb _w Co _y O ₁₂ where the rare earth element R, including yttrium, Ma is a trivalent positive element, Mb is a tetravalent positive element, 0.6 ≦ x ≦ 1.9 0.01 ≦ y ≦ 0. 47 260y−88x + 45 ≦ 0 500y−30x + 37 ≧ 0 0 ≦ v ≦ 1.00 ≦ w ≦ 0.35 The magnetic garnet single crystal represented by the following formula:
Magneto-optical element material used in the 0 nm band. 2. When 0.01 ≦ y ≦ 0.28 and 800
2. The magneto-optical element material according to claim 1, wherein y-130x + 23≤0. 3. The method according to claim 1, wherein R is one or more rare earth elements selected from Y, La, Lu, Tb and Gd.
Or the magneto-optical element material according to 2. 4. The magneto-optical element material according to claim 1, wherein Ma is one or more trivalent elements selected from Al, Ga, and In. 5. Mb is Ge, Sn, Ti, Zr, Si
3. The magneto-optical element material according to claim 1, wherein the material is one or two or more tetravalent elements selected from the group consisting of: 6. The magneto-optical element material according to claim 1, wherein a magnetic garnet single crystal is grown by liquid phase epitaxial growth on a nonmagnetic garnet substrate. 7. (CaGd) ₃ (MgZrGa) ₅ O ₁₂
Tb _1.86 Bi _1.14 Fe _4.67 Al _0.24 Co _0.09 liquid phase epitaxially grown on a non-magnetic garnet substrate
O ₁₂ composed of a magnetic garnet single crystal of the composition, the wavelength 1
Magneto-optical element material used in the 550 nm band. 8. (CaGd) ₃ (MgZrGa) ₅ O _12
Composed of a magnetic garnet single crystal having a composition of Tb _2.40 Bi _0.60 Fe _4.97 Co _0.03 O ₁₂ grown by liquid phase epitaxial on a non-magnetic garnet substrate having a wavelength of 1550 nm.
Magneto-optical element material used in the belt. 9. The magneto-optical device material according to claim 2, wherein the material is used in a 1550 nm band which is between 1530 nm and 1570 nm.