JPH0359012B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magneto-optic garnet material used in Faraday rotators such as optical isolators and optical switches.

[Conventional technology]

In order to eliminate reflected noise in optical fiber communications, the use of optical isolators has been proposed as disclosed in Technical Research Report OQE78-133 of the Institute of Electronics and Communication Engineers. The Conference on Optical Isolators was held in San Diego, USA in February 1985 to reduce the cost of optical isolators.
Optical Fiber Communication) Purchase number WK1
It has been proposed to use a (GdBi) ₃ (FeAlGa) ₁₅ O ₁₂ garnet thick film grown by a liquid phase epitaxial method as a Faraday rotator, as disclosed in .

[Problem that the invention seeks to solve]

However, the Faraday rotation coefficient of a garnet shows a significant dependence on the ambient temperature, so even if the 45 degree Faraday rotation required for the isolator is guaranteed at room temperature, the rotation angle will change due to changes in the ambient temperature. Increase or decrease. In the case of (GdBi) ₃ (FeAlGa) ₅ O ₁₂ mentioned above, taking the value in the wavelength band of 1.3 μm as an example, the temperature dependence of the Faraday rotation angle is as shown in Figure 2. When the Faraday rotation angle changes as the temperature changes, the isolation value changes as shown in FIG. On the other hand, as the ambient temperature changes, the laser oscillation wavelength also changes, so the Faraday rotation angle also changes. The same applies to the case of a wavelength of 1.5 μm.

An object of the present invention is to provide a magneto-optic garnet that can secure stable isolation values in the 1.3 μm and 1.5 μm wavelength bands without being affected by the temperature dependence of both the Faraday rotation coefficient and the laser oscillation wavelength. It is something to do.

[Means for solving problems]

The present inventors have determined that the sign of the Faraday rotation angle of garnet and its temperature coefficient are
We conducted experiments focusing on the dependence on the chemical species of the ion occupying the 24c position.
Garnet containing ions and La ions,
We have experimentally discovered that it operates stably as an optical isolator in the 1.3 μm and 1.5 μm wavelength bands despite changes in ambient temperature and temperature changes in the laser wavelength, leading to the present invention. That is,
Tb _X La _Y Bi _3-XY Fe ₅ O ₁₂ (X+Y is 0.8≦X
The magneto-optical garnet is characterized by having a composition represented by the chemical formula (expressed in the range +Y≦2.7).

〔Example〕

The present invention will be explained below using examples.

Example 1 A non-magnetic calcium-magnesium-zirconium substituted gadolinium-gallium film with a lattice constant of 12.490 Å was produced from a lead oxide-bismuth oxide-boron oxide flux held in a platinum crucible at 790°C.
A magnetic garnet single crystal film having the chemical formula Tb _2.25 La _0.15 Bi _0.60 Fe ₅ O ₁₂ with no lattice constant mismatch was formed on a garnet substrate {111} to a thickness of 450 μm by liquid phase epitaxial method. When we measured the Faraday rotation coefficient of this garnet film as a function of the ambient temperature at a wavelength of 1.3 μm, we found that the
The results shown in the figure and the column of Example 1 in FIG. 4 were obtained. It exhibited a Faraday rotation of 45 degrees at a thickness of 450 μm. The Faraday rotation coefficients at 0°C and 50°C showed only a 0.5% variation with respect to the value at 25°C. This value is (GdBi) ₃
This is extremely small compared to 4% in (FeAlGa) ₅ O ₁₂ , and an isolation of 45 dB could be secured in the range of 0°C to 50°C. Further, the dependence of the Faraday rotation coefficient on the ambient temperature at a wavelength of 1.5 μm was as shown in the column of Example 1 in FIG. It exhibited a Faraday rotation of 45 degrees at a thickness of 670 μm. The Faraday rotation coefficient at 0°C and 50°C showed a variation of 0.6% with respect to the value at 25°C. Furthermore, when using this material, there is no deterioration in isolation as seen in the prior art, even when the Faraday rotation angle fluctuates due to changes in the oscillation wavelength of the light source laser in optical fiber communication, and reflection noise is reduced. It was effective in removing.

Example 2 A non-magnetic calcium-magnesium-zirconium substituted gadolinium-gallium film with a lattice constant of 12.490 Å was produced from a lead oxide-bismuth oxide-boron oxide flux held in a platinum crucible at 820°C.
Tb _2.2 La _0.5 Bi _3-XY on garnet substrate {111}
A magnetic garnet single crystal film with the chemical formula Fe ₅ O ₁₂ was formed to a thickness of 900 μm by liquid phase epitaxial method. When the Faraday rotation coefficient of this garnet film was measured as a function of the ambient temperature at a wavelength of 1.3 μm, the results shown in the column of Example 2 in FIG. 4 were obtained. It exhibited a Faraday rotation of 45 degrees at a thickness of 900 μm. The Faraday rotation coefficient at 0°C and 50°C is 0.1 relative to the value at 25°C.
It only showed the % variation. This value is
(GdBi) ₃ (FeAlGa) ₅ O It is extremely small compared to 4% in ₁₂ , and in the range of 0℃ to 50℃
We were able to secure 62dB isolation. Further, the dependence of the Faraday rotation coefficient on the ambient temperature at a wavelength of 1.5 μm was as shown in the column of Example 2 in FIG. It exhibited a Faraday rotation of 45 degrees at a thickness of 1300 μm. The Faraday rotation coefficients at 0°C and 50°C showed only a 0.2% variation with respect to the value at 25°C.

Example 3 A non-magnetic calcium-magnesium-zirconium-substituted gadolinium-gallium-garnet substrate {111} with a lattice constant of 12.490A was heated at 770°C from a lead oxide-bismuth oxide-boron oxide flux held in a platinum crucible. , Tb _1.9 La _0.1 Bi _1.0
A magneto-optic garnet single crystal film having the chemical formula Fe ₅ O ₁₂ was formed to a thickness of 300 μm by liquid phase epitaxial method. When the Faraday rotation coefficient of this garnet film was measured as a function of the ambient temperature at a wavelength of 1.3 μm, the results shown in the column of Example 3 in FIG. 4 were obtained. It exhibited a Faraday rotation of 45 degrees at a thickness of 300 μm. The Faraday rotation coefficient at 0°C and 50°C is relative to the value at 25°C.
It showed only a 2.0% variation. This value is
(GdBi) ₃ (FeAlGa) ₅ O It is extremely small compared to 4% in ₁₂ , and in the range of 0℃ to 50℃
We were able to secure 36dB isolation. Further, the dependence of the Faraday rotation coefficient on the ambient temperature at a wavelength of 1.5 μm was as shown in the column of Example 3 in FIG. It exhibited a Faraday rotation of 45 degrees at a thickness of 440 μm. The Faraday rotation coefficients at 0°C and 50°C showed only a 2.2% variation with respect to the value at 25°C.

Example 4 Tb 1.0 _{La 0.4 was} deposited on a nonmagnetic neodymium gallium garnet substrate {111} with a lattice constant of 12.509 A at 760°C from a lead oxide-bismuth oxide-boron oxide flux held in a platinum crucible. Bi _1.5
A magneto-optic garnet single crystal film having the chemical formula Fe ₅ O ₁₂ was formed to a thickness of 250 μm by liquid phase epitaxial method. When the Faraday rotation coefficient of this garnet film was measured as a function of the ambient temperature at a wavelength of 1.3 μm, the results shown in the column of Example 4 in FIG. 4 were obtained. It exhibited a Faraday rotation of 45 degrees at a thickness of 250 μm. The Faraday rotation coefficient at 0°C and 50°C is relative to the value at 25°C.
It showed a variation of only 2.9%. This value is
(GdBi) ₃ (FeAlGa) ₅ O It is extremely small compared to 4% in ₁₂ , and in the range of 0℃ to 50℃
We were able to secure 33dB isolation. Further, the dependence of the Faraday rotation coefficient on the ambient temperature at a wavelength of 1.5 μm was as shown in the column of Example 4 in FIG. It exhibited a Faraday rotation of 45 degrees at a thickness of 375 μm. The Faraday rotation coefficients at 0°C and 50°C showed only a 3.0% variation with respect to the value at 25°C.

Example 5 Nonmagnetic gadolinium, gallium, and gallium with a lattice constant of 12.570 A were produced at 700°C from a lead oxide-bismuth oxide-boron oxide flux held in a platinum crucible.
On scandium garnet substrate {111},
A magneto-optic garnet single crystal film having the chemical formula Tb _1.7 La _0.1 Bi _2.2 Fe ₅ O ₁₂ was formed to a thickness of 150 μm by a liquid phase epitaxial method. When the Faraday rotation coefficient of this garnet film was measured as a function of the ambient temperature at a wavelength of 1.3 μm, the results shown in the column of Example 5 in FIG. 4 were obtained. It exhibited a Faraday rotation of 45 degrees at a thickness of 150 μm. 0℃ and
The Faraday rotation coefficient at 50°C showed only a 3.2% variation with respect to the value at 25°C.
This value is 4% in (GdBi) ₃ (FeAlGa) ₅ O ₁₂
It is small compared to the temperature range of 0℃ to 50℃
We were able to secure 36dB isolation. Further, the dependence of the Faraday rotation coefficient on the ambient temperature at a wavelength of 1.5 μm was as shown in the column of Example 5 in FIG. It exhibited a Faraday rotation of 45 degrees at a thickness of 225 μm. The Faraday rotation coefficients at 0°C and 50°C showed only a 3.3% variation with respect to the value at 25°C.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize an optical isolator that is less susceptible to changes in ambient temperature and that provides stable isolation.

[Brief explanation of drawings]

Figure 1 shows Tb _x La _Y Bi _3-XY Fe ₅ O ₁₂ (X=2.25, Y=
0.15) A diagram showing the temperature dependence of the Faraday rotation coefficient at a wavelength of 1.3 μm for a garnet film. Figure 2 shows the wavelength of a (GdBi) ₃ (FeAlGa) ₅ O ₁₂ garnet film.
Figure 3 shows the temperature dependence of the Faraday rotation coefficient at 1.3 μm. Figure 3 shows the change in isolation value due to the deviation of the Faraday rotation angle from 45 degrees.
FIG. 4 is a diagram showing the temperature dependence of the Faraday rotation coefficient at a wavelength of 1.3 μm for five examples, and FIG. 5 is a diagram showing the temperature dependence at a wavelength of 1.5 μm.

Claims (1)

[Claims] 1 Tb _x La _Y Bi _3-XY Fe ₅ O ₁₂ (X+Y is 0.8
1. A magneto-optical garnet characterized by having a composition represented by the chemical formula (expressed in the range of ≦X+Y≦2.7).