JPH11236296A - Bismuth-substituted garnet thick film material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject garnet thick film material that is used as a substitute material for a Tb-Bi based garnet thick film material having essential absorption in an about >=1.6 μm wavelength band region and has improved insertion loss (improved transmissivity) and an improved θf/ T (temp. coefficient of Faraday rotation angle (θf ) value in a >=1.5 μm wavelength band region in which an unfavorable influence on the absorption spectrum due to Th ions is caused, and also to provide the production of this material. SOLUTION: This film material is a bismuth-substituted garnet thick film material which is produced by an LPE(liquid phase epitaxy) method with NGG (neodymium gallium garnet, Nd3 Ga5 O12 ) as the substrate and has a composition represented by the chemical formula Gd3-x-y-2 Yx Yby Biz Fe5-a Ala O12 (wherein: each of (x) and (y) is a numerical value of 0 to 0.2 and when any one of (x) and (y) is 0, the other is not 0; (z) is a numerical value of 0.8 to 1.4; and (a) is a numerical value of 0.2 to 0.7) and also contains 0 to 3.7 wt.% B2 O3 . The material is subjected to heat treatment while maintaining the material at 950 to 1,130 deg.C in an atmosphere having a >=5% oxygen concn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bismuth-substituted garnet thick film material and a method of manufacturing the same among optical garnet materials having a Faraday rotation effect, and more particularly, to a film grown by liquid phase epitaxy (Gd, Y, Gd). Y
b, Bi) ₃ (Fe, Al) ₅ O ₁₂ garnet (hereinafter referred to as
GdYYbBi-based garnet) and a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, in optical communications, devices utilizing Faraday rotation have been developed and put into practical use. In optical communication using a semiconductor laser, when reflected light from an optical fiber cable, a connector, or the like returns to the semiconductor laser, oscillation becomes unstable or causes noise. therefore,
2. Description of the Related Art An optical isolator is used to block return light to a semiconductor laser and secure a stable oscillation state.

[0003] Bismuth-substituted rare earth iron garnet (hereinafter referred to as Bi-based garnet) having a large Faraday rotation angle is grown by a liquid phase epitaxial method (hereinafter referred to as an LPE method), a flux method or the like, and is used as an isolator in the near infrared region. in use. In particular, the LPE method is excellent in productivity, and therefore, most garnet thick films currently in practical use are produced by this method.

At present, long-distance communication using fiber cables uses wavelength bands of 1.31 μm and 1.55 μm. In addition, about 1.6 for monitoring optical communication networks, etc.
Wavelengths in the range 〜2 μm are used.

Conventionally, a TbBi-based garnet thick film and a GdBi-based (Ga, Al-substituted) garnet thick film manufactured by the LPE method have been put to practical use as a material for a Faraday rotator for near infrared rays. The TbBi-based garnet thick film has a temperature coefficient θ of Faraday rotation angle θ _f (hereinafter simply referred to as θ _f ).
_{f / T} (hereinafter simply referred to as θ _{f / T} ) is about 0.04 to 0.06 deg
(Degrees) / ° C., but the saturation magnetic field Hs is about 800
Since it is as high as ~ 1200 Oe, a strong permanent magnet is required. The TbBi garnet thick film has a magnetization reversal temperature of about −50 ° C. or less, and can be used in a wide temperature range.

On the other hand, a GdBi-based (Ga, Al-substituted) garnet thick film has a relatively large θ _{f / T} of about 0.08 deg / ° C. but a low saturation magnetic field Hs of about 300 Oe. Further, the magnetization reversal temperature is as high as about −10 ° C. Accordingly, market demands are concentrated on TbBi-based garnet thick films having good temperature characteristics.

[0007]

However, TbB
Regarding i-based garnets, Journal of Applied Physics # 3
Vol. 8, No. 3, p. 1038, shows an absorption spectrum related to Tb ions in the region where the wavelength exceeds 1.6 μm. Therefore, it is estimated that the TbBi-based garnet thick film may lose its practical function due to light absorption in this wavelength band.

[0008] The object of the present invention is, therefore, to be about 1.6 μm.
TbBi showing intrinsic absorption in the wavelength band above m
Garnet thick film material with improved insertion loss and θ _{f / T} in a wavelength band of 1.5 μm or more where the influence of the absorption spectrum by Tb ions appears as an alternative material to the system garnet thick film, and a method of manufacturing the same Is to do.

Based on this, in the present invention, more specifically, the characteristics for the garnet thick film material are set as follows.

(1) High transmittance (low insertion loss) even in a wavelength band exceeding about 1.6 μm. (2) The insertion loss at a thickness where θ _f is 45 degrees is 0.
2 dB or less. (3) θ _{f / T} is lower than the characteristic (about 0.08 deg / ° C.) of the conventional GdBi-based garnet thick film material. (4) a saturation magnetization 4PaiM _S is 500G or less at room temperature. (5) The magnetization reversal temperature T _comp is 0 ° C. or less.

[0011]

SUMMARY OF THE INVENTION The present invention provides a method for growing a garnet substrate on a garnet substrate by liquid phase epitaxial growth.
A bismuth-substituted garnet thick film material composed of a single crystal thick film containing d, Y, Yb, Bi, Fe, and Al as main components, containing at least one of Y and Yb, and having a chemical formula of Gd _{3 -xyz Y x Yb y BizFe 5-} a Al
_a O ₁₂ , provided that x = 0 to 0.2, y = 0 to 0.2, x and y are not simultaneously 0, and z = 0.8
A bismuth-substituted garnet thick-film material having a composition represented by the formula: -1.4, a = 0.2-0.7.

[0012] The bismuth-substituted garnet thick film material according to the present invention comprises:
0 to 3.7 wt% of B ₂ O ₃ is characterized in that which is contained.

According to the present invention, a bismuth-substituted garnet thick film material is grown on an NGG substrate.

According to the present invention, a bismuth-substituted garnet thick film material having good characteristics as a Faraday rotator is obtained by performing a heat treatment for maintaining the single crystal thick film in a temperature range of 950 to 1130 ° C. Is obtained.

Further, according to the present invention, a bismuth-substituted garnet thick film material that solves the above problem is obtained by performing a heat treatment for maintaining the single crystal thick film in an atmosphere having an oxygen concentration of 5% or more. Can be

In the present invention, the concentration of B ₂ O ₃ is set to 0 to
The reason why the content was 3.7% by weight was that the insertion loss was found to be low in this concentration range.

In the present invention, the reason why the bismuth-substituted garnet thick film material is grown on the NGG substrate is as follows.
In contrast to the SGGG substrate often used in the
This is because GG has a large lattice constant and has good compatibility with the bismuth-substituted garnet thick film material. When an NGG substrate is used, even if the garnet thick film grown by the LPE method has a thickness of 500 μm or more, the rate of occurrence of cracks is low.

In the present invention, the reason why the bismuth-substituted garnet thick film material is targeted is that the absorption spectrum of the GdYYbBi (Ga, Al-substituted) garnet thick film does not exist in the wavelength band of 1.6 μm or more. Because.

In the present invention, the heat treatment temperature range of the single crystal thick film is set to 950 to 1130 ° C.
When the temperature is lower than the above, the atoms in the crystal are not sufficiently homogenized, and the insertion loss is not reduced. When the temperature is higher than 1130 ° C., a GdYYbBi-based garnet thick film material, particularly B
This is because insertion loss increases due to decomposition due to evaporation of i ₂ O ₃ .

In the present invention, the heat treatment of the single crystal thick film is performed by
The reason why the atmosphere was set to the atmosphere having the oxygen concentration of 5% or more was that the heat treatment in the atmosphere having the oxygen concentration of 5% or more reduced the insertion loss of the bismuth-substituted garnet thick film material as compared to before the heat treatment (untreated). And an increase in insertion loss at oxygen concentrations below 5%.

The change in the characteristics of the bismuth-substituted garnet thick film is caused by the magnetic moment of each ion constituting the crystal.

[0022]

Embodiments of the present invention will be described below.

The bismuth-substituted garnet thick film is grown by the LPE method as described below. First, PbO, Bi ₂ as a flux component in a platinum crucible
Gd ₂ O ₃ and Y ₂ O as garnet components such as O ₃ and B ₂ O _3
3 , Yb ₂ O ₃ , Fe ₂ O ₃ , Al ₂ O _3, etc.
After dissolving at a temperature of 100 ° C. to prepare a solution, the temperature is lowered to a supercooled state (supersaturated solution state). A garnet substrate is immersed in the solution and rotated for a certain time to grow a bismuth-substituted garnet thick film.

Among the Bi-based garnet thick films, GdBiY
The system garnet thick film is characterized by having a relatively high Faraday rotation capability and a relatively low saturation magnetic field Hs. In general, when a Bi-based garnet thick film is used as a Faraday rotator, the saturation magnetic field Hs or an applied magnetic field exceeding the saturation magnetic field Hs is supplied by a permanent magnet disposed around the saturation magnetic field Hs.
Bi-based saturation magnetization 4PaiM _S garnet thick film is low saturation field Hs is low, it can be a permanent magnet for use in smaller or order to increase the degree of freedom of the characteristics of the permanent magnet, is industrially useful.

[0025]

The present invention will be further described below with reference to examples.

Example 1 High-purity gadolinium oxide (Gd ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), ytterbium oxide (Yb ₂ O ₃ ), ferric oxide (Fe ₂ O ₃ ), oxide Aluminum (Al ₂ O ₃ ), bismuth oxide (Bi
₂ O ₃ ), lead oxide (PbO) and boron oxide (B ₂ O ₃ )
Was used. Using these powders, PbO-B
NGG [chemical formula: Nd ₃ Ga ₅ O ₁₂ , lattice constant: 12.5] was obtained by an LPE method using i ₂ O ₃ -B ₂ O ₃ as a flux.
09] Gd _1.8 Bi _1.2 Fe _4.7 Al
_{0.3 O 12, Gd 1.6 Y 0.} 1 Bi 1.3 Fe 4.5 Al 0.3 O 12, and _{Gd 1.4 Yb 0.2 Bi 1.4 Fe 4.3} Al 0.5 O 1 2 thickness of GdYYbBi garnet single crystal thick film composition represented by about 700μm Nurtured.

For comparison, terbium oxide (Tb
₂ O ₃ ) and the like, and similarly by the LPE method,
SGGG [Chemical formula (GdCa) ₃ (GaMgZr)
₅ O ₁₂ , lattice constant 12.496] Tb _2.0 B
A TbBi-based garnet single crystal thick film having a composition of i _1.0 Fe ₅ O ₁₂ was grown to a thickness of about 700 μm.

Next, the substrate was removed from the garnet single crystal thick film, and both surfaces were mirror-polished to a thickness of about 600 μm.
And FIG. 1 shows these Gd grown by the LPE method.
It is a figure which shows the wavelength dependence of a transmittance | permeability about a YYbBi-system garnet single crystal thick film and a TbBi-system garnet single crystal thick film. As is clear from FIG.
In the wavelength range of 2 μm, the GdYYbBi-based garnet single crystal thick film has a high transmittance.

On the other hand, the wavelength range in which the TbBi-based garnet single crystal thick film shows a high transmittance is only about 1.2 to 1.5 μm. From this result, a GdYYbBi-based garnet single crystal thick film is useful in a wavelength band of 1.5 μm or more. The composition of these garnet thick film materials is EP
Confirmed beforehand by MA analysis.

(Embodiment 2) In the same manner as in Embodiment 1, N
GG on the substrate, _{respectively, Gd 2.0 Bi 1.8 Fe 4. 7} Al
_{0.3 O 12, Gd 1.7 Y 0.1} Bi 1.2 Fe 4.5 Al 0.5 O 12, and represented by the chemical formula of _{Gd 1.5 Yb 0. 2 Bi 1.3 Fe} 4.4 Al 0.6 O 12, the B ₂ O _3, 0,0.05, 1.0, 1.5,
Garnet thick films containing 2.0, 2.5, 3.0, 3.5, and 4.0 wt% were grown to a thickness of about 600 to 800 μm.

The substrate was removed in the same manner as in Example 1, the thickness was adjusted so that the Faraday rotation angle was about 45 degrees at a wavelength of 1.62 μm, and SiO ₂ antireflection films were provided on both surfaces. With respect to these garnet thick film materials, the insertion loss at a wavelength of 1.62 μm under an applied magnetic field of 600 Oe, the Faraday rotation capability, and θ _{f / T} near room temperature were determined. The saturation magnetization was also measured using a vibrating magnetometer (VSM).

The saturation magnetization (4πMs) of these samples is
Approximately 300 to 450 G (Gauss), Faraday rotational ability is approximately 950 to 1250 deg / cm, θ _{f / T} is approximately 0.05 to
0.07 deg / ° C.

FIG. 2 shows GdYYbBi in this embodiment.
Garnet thick film material, insertion loss, B
Is a diagram illustrating the content concentration dependence of ₂ O _3. From FIG. 2, B ₂
It can be seen that there is an effect of reducing the insertion loss when the content of O ₃ is in the range of 0 to 3.7 wt%.

(Embodiment 3) In the same manner as in Embodiment 2, N
Gd containing about 0.5 wt% of B ₂ O ₃ on a GG substrate
_1.7 Bi _1.3 Fe _4.6 Al _0.4 O ₁₂ , Gd _1.4 Y _0.2 Bi _1.4
Fe _4.3 Al _0.7 O _{1 2,} and Gd _1.7 Yb _0.1 Bi _1.2 F
A garnet single crystal thick film represented by the chemical formula of e _4.6 Al _0.4 O ₁₂ was grown to a thickness of about 500 to 800 μm.

Next, in the same manner as in Example 2, the substrate was removed from the garnet single crystal thick film, and 950 ° C., 1000 ° C., 1100 ° C., 11
Heat treatment was performed at 30 ° C. and 1150 ° C. for 20 hours. Thereafter, the thickness was adjusted so that the Faraday rotation angle was about 45 degrees at a wavelength of 1.62 μm, and an SiO ₂ antireflection film was provided on both surfaces, and each characteristic was measured.

The garnet single crystal thick film has a saturation magnetization (4πMs) of about 250 to 450 G, a Faraday rotator of about 1000 to 1300 deg / cm, and a θ _{f / T} of about 0.3.
It was from 0.05 to 0.07 deg / ° C.

FIG. 3 shows GdYYbBi in this embodiment.
FIG. 4 is a diagram showing the relationship between insertion loss and heat treatment temperature for a system garnet thick film material. From FIG.
It can be seen that in the temperature range of ° C., the insertion loss is reduced by the heat treatment as compared with that before the heat treatment (non-treatment), and at a temperature higher than that, the insertion loss sharply increases.

(Embodiment 4) In the same manner as in Embodiment 2, N
Gd containing about 0.5 wt% of B ₂ O ₃ on a GG substrate
_2.2 Bi _0.8 Fe _4.8 Al _0.2 O ₁₂ , Gd _1.5 Y _0.2 Bi _1.3
Fe _4.4 Al _0.6 O _{1 2,} and Gd _1.8 Yb _0.1 Bi _1.1 F
A garnet single crystal thick film represented by the chemical formula of e _4.6 Al _0.5 O ₁₂ was grown to a thickness of about 600 to 900 μm.

Next, in the same manner as in Example 2, the substrate was removed from the garnet single crystal thick film, and the temperature was changed to 1050 ° C.
Then, heat treatment was performed for 10 hours in an atmosphere having an oxygen concentration of 0, 10, 20, 40, 60, 80, and 100%. Then, the thickness was adjusted so that the Faraday rotation angle was about 45 degrees at a wavelength of 1.62 μm, and S
An iO ₂ antireflection film was provided, and each characteristic was measured.

The saturation magnetization (4πMs) of these samples is
Approximately 250-450G, Faraday rotation ability is approximately 700-1
200 deg / cm, θ _{f / T} is about 0.05 to 0.07d
eg / ° C.

FIG. 4 shows GdYYbBi in this embodiment.
FIG. 4 is a graph showing the relationship between insertion loss and oxygen concentration during heat treatment for a system garnet thick film material. FIG. 4 shows that when the oxygen concentration is 5% or more, the insertion loss is reduced by the heat treatment as compared with before the heat treatment (non-treatment). From these results, it can be said that a heat treatment in an atmosphere having an oxygen concentration of 5% or more is useful for a GdYYbBi-based garnet thick film.

Further, all of the GdYYbBi-based garnet thick film materials targeted in Examples 1 to 4 described above had magnetization reversal temperatures T _comp of −40 ° C. or less.

In the first to fourth embodiments, Y and Yb
It does not deal with garnet thick film materials containing both. However, Y and Yb have similar chemical and physical properties to each other, and also substitute for each other and show similar properties in garnet thick film materials. From these facts, Y
And a garnet thick film material containing both Yb and
It is easily presumed that the items described in the first to fourth embodiments are affirmed.

[0044]

As described above, according to the present invention, as a substitute material of a TbBi-based garnet thick film which shows essential absorption in a wavelength band of about 1.6 μm or more,
In a wavelength band of 1.5 μm or more, a garnet thick film material having improved insertion loss and θ _{f / T} can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the wavelength dependence of transmittance of a GdYYbBi-based garnet single crystal thick film in Example 1.

FIG. 2 is a graph showing the dependency of the insertion loss on the concentration of B ₂ O ₃ in a GdYYbBi-based garnet thick film material in Example 2.

FIG. 3 is a diagram showing the relationship between insertion loss and heat treatment temperature for a GdYYbBi-based garnet thick film material in Example 3.

FIG. 4 is a diagram showing the relationship between insertion loss and oxygen concentration during heat treatment for a GdYYbBi-based garnet thick film material in Example 4.

Claims (5)

[Claims] 1. A bismuth-substituted garnet thick film material comprising a single crystal thick film mainly composed of Gd, Bi, Fe, and Al grown on a garnet substrate by a liquid phase epitaxial growth method, wherein the chemical formula is: Gd _3-xyz Y _x Yb _{y
Bi z Fe 5-a Al a} O 12, except x = 0~0.2, y = 0
Bismuth characterized by having a composition expressed by z = 0.8 to 1.4, a = 0.2 to 0.7, and x and y are not 0 at the same time. Substitution type garnet thick film material. Wherein the bismuth-substituted garnet thick film material of claim 1, wherein, bismuth-substituted garnet thick film material, characterized in that B ₂ O ₃ is contained 0 to 3.7 wt%. 3. The method according to claim 1, wherein the single-crystal thick film is heated to 950 to 1130 °
3. The method for producing a bismuth-substituted garnet thick film material according to claim 1, wherein the heat treatment is performed at a temperature in the range described above. 4. The bismuth-substituted garnet thick film according to claim 1, wherein the bismuth-substituted garnet thick film material comprising the single crystal thick film is grown on an NGG substrate. Material manufacturing method. 5. The bismuth-substituted garnet thickness according to claim 1, wherein a heat treatment for maintaining the single-crystal thick film in an atmosphere having an oxygen concentration of 5% or more is performed. Manufacturing method of membrane material.