JP2763015B2 - Optical isolator and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator utilizing a magneto-optical effect used in optical communication and optical information processing, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As shown in FIG. 3, the structure of a conventional type of optical isolator comprises a polarizer 14, a 45-degree Faraday rotator 15, an analyzer 16, and a magnet 17. The polarizer 14 and the analyzer 16 are bonded to the 45-degree Faraday rotator 15 with an optical adhesive 18.

The light incident on the optical isolator is a polarizer 1
4 selects a polarization component that matches the polarization plane of the polarizer 14 and enters the 45-degree Faraday rotator 15. The length or thickness of the 45-degree Faraday rotator 15 is determined by the Faraday effect so that the polarization plane of the incident light rotates by 45 degrees while the light passes. Therefore, 4
The polarization plane of the light after passing through the 5-degree Faraday rotator 15 is rotated 45 degrees with respect to the incident light. Therefore, if the polarization plane of the analyzer 16 is rotated by 45 degrees with respect to the polarization plane of the polarizer 14, the light is emitted from the optical isolator without any loss at the analyzer 16.

On the other hand, the return light is directed to the polarizer 14 by 45
The light of the polarization plane rotated by degrees is selected by the analyzer 16. Thereafter, the selected light is incident on the 45-degree Faraday rotator 15, where the non-reciprocity of the Faraday effect (the direction of rotation of the incident polarization plane depends on the material-specific properties of Faraday rotation, the direction in which light travels, and the magnetic field) Are determined to be parallel or anti-parallel.) Therefore, only the polarization component rotated by 90 degrees with respect to the polarization plane of the polarizer 14 enters the polarizer 14. This allows the polarizer 1
There is no component passing through 4, and all return light is blocked by the optical isolator.

As a material of the Faraday rotator, YIG
(Yttrium / Iron / Garnet) and RBiIG (Bismuth-substituted rare earth / Iron / Garnet) are widely used in optical communication.

[0006]

In the above-mentioned conventional optical isolator, when the polarizer, the analyzer and the 45-degree Faraday rotator are fixed, the optical surface is bonded and fixed with an optical adhesive. For this reason, conventional optical isolators
There is a problem that the moisture resistance is poor, and the use under high temperature and high humidity conditions is particularly limited.

Further, when the polarizer, the 45-degree Faraday rotator and the analyzer are adjusted to optimal positions and fixed by bonding,
There is also a problem that it takes time to cure the adhesive and it takes too much time to manufacture the optical isolator.

Accordingly, it is an object of the present invention to provide an optical isolator having excellent moisture resistance.

Another object of the present invention is to provide a method for manufacturing an optical isolator which can be manufactured in a short time.

[0010]

An optical isolator according to the present invention comprises a polarizer, an analyzer, a 45-degree Faraday rotator provided between the analyzer and the polarizer, and a 45-degree Faraday rotator. A magnet that applies a magnetic field to the element, wherein the polarizer, the 45-degree Faraday rotator, the analyzer, and the magnet are fixed with low-melting glass, and the low-melting glass is Is the polarized light
The 45-degree Faraday rotator, the analyzer, and
Has a coefficient of thermal expansion approximately equal to that of the magnet,
Consisting of two annular magnets, one of which is the polarizer and the
45 ° Faraday rotator solidified with the low melting glass
And the other is the 45 degree Faraday rotator and the detection
It is characterized by being fixed with the low melting point glass between the photons .

The method for manufacturing an optical isolator according to the present invention comprises a polarizer, an analyzer, a 45-degree Faraday rotator provided between the analyzer and the polarizer, and a magnetic field applied to the 45-degree Faraday rotator. And a magnet for providing an optical isolator comprising: a first magnet block having a lattice shape formed in advance between the polarizer block and the 45-degree Faraday rotator block; 45 and inserted between the first and second low melting point glass tablets;
A second lattice-shaped magnet block inserted between third Faraday rotator block and analyzer block between third and fourth low-melting glass tablets formed in a lattice in advance; By melting a fourth low-melting glass tablet into first to fourth low-melting glasses, the polarizer block and the 45-degree Faraday rotator block are interposed via the first magnet block. The 45-degree Faraday rotator block and the analyzer block are respectively fixed to each other via a second magnet block; and then cut along a grid line and sufficiently narrower than the grid line width. Alternatively, the polarizer block, the first low-melting glass, the first magnet block, the second
, The 45 ° Faraday rotator block, the third low melting glass, the second magnet block, the fourth low melting glass, and the analyzer block; An optical isolator, which is fixed by the first to fourth low-melting point glasses and includes the polarizer, the 45-degree Faraday rotator, the analyzer, and the magnet, is obtained.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are views showing an optical isolator according to an embodiment of the present invention. FIG. 1A is a front view, and FIG. 1B is a side sectional view.

The illustrated optical isolator includes a rectangular parallelepiped polarizer 1, a rectangular parallelepiped 45-degree Faraday rotator 2, a rectangular parallelepiped analyzer 3, an annular first magnet 4 having a square outer shell, and a square outer shell. And an annular second magnet 5. The 45-degree Faraday rotator 2 is provided between the polarizer 1 and the analyzer 3. A first magnet 4 is inserted between the polarizer 1 and the 45-degree Faraday rotator 2, and a second magnet 5 is inserted between the 45-degree Faraday rotator 2 and the analyzer 3. As shown in FIG. 1, the polarizer 1, the 45-degree Faraday rotator 2, the analyzer 3, the first magnet 4, and the second magnet 5 are fixed to each other by a low-melting glass 6 at the outer periphery. ing. The analyzer 3 is arranged such that its polarization plane is rotated by 45 degrees with respect to the polarization plane of the polarizer 1.

As the 45 degree Faraday rotator 2, bismuth-substituted gadolinium / iron / garnet (GdBi) ₃ Fe ₅ O ₁₂ grown by a liquid phase epitaxial method or the like is used.
Thick film and bismuth-substituted terbium / iron / garnet (Tb
Bi) ₃ Fe ₅ O ₁₂ thick film or bismuth-substituted gadolinium
Iron, aluminum, gallium, garnet (GdBi)
₃ (FeAlGa) ₅ O ₁₂ thick film or the like is used.

In general, bismuth-substituted rare earth / iron / garnet RBiIG has a large Faraday rotation coefficient and a small saturation magnetization, so that a small optical isolator can be realized. In the embodiment shown in FIG. 1, an optical isolator having a side of about 3 mm and a length of about 4 mm is realized. Polarizer 1,
The optical surfaces of the 45-degree Faraday rotator 2 and the analyzer 3 (the light entrance / exit surfaces) are all provided with an antireflection film for air.

Next, a method for manufacturing the optical isolator shown in FIG. 1 will be described with reference to FIGS.

In FIG. 2A, a square polarizer block 8 is shown.
Between the 45-degree Faraday rotator block 11 and
The first magnet block 10-1 having a lattice shape for applying a saturation magnetic field to the Faraday rotator block 11
And second lattice-like low melting point glass tablets 7-1 and 7
-2 between the 45-degree Faraday rotator block 11 and the square-shaped analyzer block 12.
The second magnet block 10-2, which provides a saturation magnetic field to the Faraday rotator block 11, is preliminarily fired into the third magnet block 10-2.
And fourth lattice-like low melting point glass tablets 7-3 and 7
-4 shows a state of being inserted and inserted. The analyzer block 12 is formed in a rectangular shape in advance so that its polarization plane rotates 45 degrees with respect to the polarization plane of the polarizer block 8. Polarization plane of polarizer block 8 and analyzer block 1
The polarizer block 8, the 45-degree Faraday rotator block 11, and the analyzer block 12 are overlapped so that the two polarization planes coincide with each other by the rotation of the polarization plane by the 45-degree Faraday rotator block 11. The optical surfaces of the polarizer block 8, the 45-degree Faraday rotator block 11, and the analyzer block 12 are all provided with an antireflection film for air.

In this way, the polarizer block 8 and the first
Lattice low melting point glass tablet 7-1, first magnet block 10-1, second lattice low melting point glass tablet 7-2, 45 degree Faraday rotator block 11, third lattice low melting point glass tablet 7-3, second magnet block 10-2, fourth lattice-like low melting point glass tablet 7
-4 and the analyzer block 12 in this order, and then 45
The first to fourth lattice-shaped low-melting glass tablets 7-1 to 7-4 are melted at a temperature of about 0 degrees.

Thus, as shown in FIG. 2B, the polarizer block 8, the first magnet block 10-1, the 45-degree Faraday rotator block 11, and the second magnet block 1
0-2 and the analyzer block 12 are fixed. Then, in this state, a magnetic field is applied from the outside to the first and second magnet blocks 1 so as to function as an optical isolator.
The magnetization directions of 0-1 and 10-2 are completely aligned.

Thereafter, the center of the grid line is cut along a cutting line 13 by a blade having a width sufficiently smaller than the grid line width of the grid-shaped first and second magnet blocks 10-1 and 10-2. I do.

As a result, as shown in FIG. 2C, the divided small polarizer 8d, the first magnets 10-1d,
5 degree Faraday rotator 11d, second magnet 10-2d,
Then, an optical isolator in which the analyzer 12d is fixed at its outer peripheral portion with the low-melting glass 9d is completed.
The low-melting-point glass 9d has a thermal expansion coefficient that is a component of the polarizer 8d, the first magnet 10-1d, the 45-degree Faraday rotator 11d, the second magnet 10-2d, and the analyzer 12d. You need to choose something that is almost equal.

[0023]

As is apparent from the above description, the optical isolator according to the present invention comprises a polarizer and a first polarizer.
The magnet, the 45-degree Faraday rotator, the second magnet, and the analyzer are melt-fixed with low-melting-point glass having a thermal expansion coefficient almost equal to those of the constituent elements in the outer peripheral portion, and thus have excellent moisture resistance. In addition, there is an effect that stable characteristics can be obtained even under high temperature and high humidity conditions. Further, there is an effect that an optical isolator having such excellent characteristics can be mass-produced at a time by an easy production method.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical isolator according to an embodiment of the present invention, wherein (a) is a front view and (b) is a side sectional view.

FIG. 2 is a process chart showing a method for manufacturing an optical isolator of the present invention.

3A and 3B are diagrams showing a conventional optical isolator, wherein FIG. 3A is a front view and FIG. 3B is a side sectional view.

[Description of Signs] 1 polarizer 2 45 degree Faraday rotator 3 analyzer 4 magnet 5 magnet 6 low melting point glass 7-1, 7-2, 7-3, 7-4 lattice-like low melting point glass tablet 8 polarizer block 9 Low melting point glass 10-1, 10-2 Magnet block 11 45 degree Faraday rotator block 12 Analyzer 13 Cutting line

Claims (2)

(57) [Claims] 1. A polarizer, an analyzer, a 45-degree Faraday rotator provided between the analyzer and the polarizer, and a magnet for applying a magnetic field to the 45-degree Faraday rotator. In the optical isolator, the polarizer, the 45-degree Faraday rotator, the analyzer, and the magnet are fixed with low-melting glass, and the low-melting glass includes the polarizer and the 45-degree Faraday.
-Heat approximately equal to the rotor, the analyzer, and the magnet
Having a coefficient of expansion, wherein the magnet comprises two annular magnets, one of which is
The low melting point between a polarizer and the 45-degree Faraday rotator.
The other is fixed with a point glass, the other is the 45 degree Faraday time.
Fixed between the trochanter and the analyzer with the low melting glass
An optical isolator characterized in that is. 2. A polarizer, an analyzer, a 45-degree Faraday rotator provided between the analyzer and the polarizer, and a magnet for applying a magnetic field to the 45-degree Faraday rotator. A first and second low-melting glass in which a lattice-shaped first magnet block is previously formed in a lattice between a polarizer block and a 45-degree Faraday rotator block. A tablet is inserted between the 45-degree Faraday rotator block and the analyzer block. A grid-like second magnet block is sandwiched between third and fourth low-melting glass tablets formed in a grid in advance. The first to fourth low-melting glass tablets are melted into first to fourth low-melting glass, so that the polarizer block and the fourth low-melting glass tablet are interposed via the first magnet block. The 5 degree Faraday rotator block and the 45 degree Faraday rotator block and the analyzer block are fixed to each other via the second magnet block. With a cutting margin sufficiently smaller than a line width, the polarizer block, the first low-melting glass, the first magnet block, the second low-melting glass, the 45-degree Faraday rotator block, and the third , The second magnet block, the fourth low-melting glass, and the analyzer block are collectively cut in this order, whereby the outer periphery is fixed with the first to fourth low-melting glasses. Obtaining an optical isolator including the polarizer, the 45-degree Faraday rotator, the analyzer, and the magnet.