JPS61156711A - Faraday rotator - Google Patents

Abstract

PURPOSE:To massproduce by providing a permanent magnet in a ring at least on either Faraday material or a board. CONSTITUTION:After iron garnet Bi:YIG 11 which is exchanged with Y for Bi as Faraday material is liquid-aepitaxially formed by about 0.2 mm on a transparent gadolinium.gallium.garnet (GGG) plate 10 of 4 mm diameter and 0.3 thickness, permanent magnets 121 and 122 made mainly of needle magnetic powder of Sn-Co system are mixed with epoxy resin, and coated 0.2 mm thickness in a ring with leaving a circle of 1.2 mm diameter in a center. While powder is alignment-magnetized in a strong magnetic field, the resin is hardened. According to a need of magnetic field strength, a magnet 122 is omitted and only the magnetic 121 on the gernet film 11 is left, or only the magnet 122 is left. An element of this composition is high in relibility against a mechanical stress, mass production of permanent magnet is easily done, and is produced in a low cost.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a function of rotating the polarization of light by the Faraday effect, and is used for non-reciprocal circuit components such as optical isolators and optical circulators. Regarding the rotor.

[Prior art and its problems]

A Faraday rotator has the function of rotating the plane of polarization of light, and is used as an optical isolator and an optical circulator.

It is a basic element of magneto-optical effect devices such as magnetic sensors that utilize the Faraday effect.

FIG. 2 is a perspective view showing the basic structure of a Faraday rotator, which is composed of a cylindrical Faraday material 1 having a large 7-Arad rotation coefficient F, and a permanent magnet 2 that applies a magnetic field to the Faraday material. When a light beam whose electric field direction is indicated by 4 with respect to the central axis 3 passes through the 7Alade rotator 1, the polarization direction is rotated by θ=FtyVM8. Here, t is the passage length 1M is the magnetization I in the direction of light passage, and M3 is the saturation magnetization.

Conventionally, Faraday materials have a wavelength of 1, for example, 1.3jj
In the m band, YIG (Y3Fe50,2) single crystal is +0.8
．． In the Im band, paramagnetic glass doped with Tb has been used, but since the Faraday rotation coefficient is small, it is difficult to obtain the 45° rotation angle required for optical isolators.

In the former case, it was difficult to make the length less than 2 mtx, and in the latter case, it was difficult to make the length less than several a, and it was not possible to make it compact. However, recently the Faraday rotation coefficient of +Bi' doped is several thousand d.
e Faraday material of g/cm or more, such as Gd2Bi
Fe5012 (0,711 m and above 1.1/jm) is being developed. When this is used, a thickness of several tens to several hundreds of micrometers is sufficient to obtain a rotation of 45 degrees, and the Faraday material can be made smaller.

However, no consideration has been given to the form of a Faraday rotator corresponding to this. That is.

While it is becoming possible to reduce costs and mass-produce Faraday materials using highly productive methods such as liquid phase epitaxial methods, permanent magnets and Faraday materials are still assembled separately.

Productivity cannot necessarily be improved as a Faraday rotator. Furthermore, if the shape of the permanent magnet is the same as in the past, the size is limited by the dimensions of the magnet, making it difficult to downsize. By the way, many permanent magnets are used with a thickness of about 2 mm in inner diameter and 4 to 6 mm in outer diameter. Therefore, there is a need for a Faraday rotator that takes advantage of the smaller size and thicker Faraday material.

[Purpose of the invention]

Accordingly, an object of the present invention is to provide a Faraday rotator that is small and highly productive, taking advantage of the recently developed Faraday material with a large Faraday rotation coefficient.

[Structure of the invention]

The Faraday rotator of the present invention includes two optically transparent substrates (using the reference numerals in FIG.
10), a Faraday material (11) epitaxially grown on a substrate, and a permanent magnet that applies a magnetic field to this Faraday material. This permanent magnet can be deposited on the Faraday material by coating or vapor deposition (12+) or on the opposite substrate (122), or if the magnetic field generated by a single layer magnet is insufficient, the Faraday material and the substrate at the same position (121 and 122)
It is formed.

〔Example〕

Next, the present invention will be explained in detail.

FIG. 1 is a front view (,) and a section (b) taken along line A-A of a Faraday rotator according to an embodiment of the present invention. In FIG. 1, a substrate 10 is an optically transparent gadolinium gallium garnet (hereinafter abbreviated as GGG) plate having a diameter of 4 mm and a thickness of 0.3 mm. The garnet film 11 is a Faraday material.

Iron garnet doped by exchanging Bi with Y) Bi: Y
The IG was grown by liquid phase epitaxial growth on a GGG plate to a thickness of 0.2. The permanent magnets 12° and 122 are mainly made of Sn-Co-based acicular magnetic powder, and this powder is mixed into epoxy resin and placed on the Bi: YIG and GGG substrates with an inner diameter of 1 at the center. ．．
0.2 mtn in a ring shape leaving the circular part of 21111
The powder was coated to a thickness of
It is formed by solidifying xylene resin. 1
3 indicates a light beam.

The Faraday rotator made as described above is.

Overall dimensions: diameter 4+lIK, thickness 0.9 ax
With the cylindrical body, a magnetic field strength of 3500e was obtained, and a Faraday rotation angle of 45° was obtained at wavelengths of 1 and 3 μm.

In the above, when the requirement for magnetic field strength is a little weak, it is possible to omit the permanent magnet 12□ on the GGG substrate 10 and use only the permanent magnet 121 on the Gurnet film 11. If the requirement is even weaker, use permanent magnet 12! It is possible to eliminate the need to form only 122. In addition, to form the permanent magnet 121 +12zk, a mask corresponding to the central effective part of the GGG substrate 10 and the Faraday material 11 is attached.

The magnetic material may be deposited in a strong magnetic field.

〔Effect of the invention〕

As described above in detail, the Faraday rotator of the present invention is plate-shaped, small, and easy to mount, and the constituent elements are integrated, so it is highly reliable against mechanical stresses such as vibrations and shocks. Furthermore, since permanent magnets can be produced in large quantities simultaneously by coating or vapor deposition, productivity is high and costs can be reduced. The Faraday rotator of the present invention is extremely effective when used in magneto-optical devices such as optical isolators and optical circulators.

FIG. 2 is a perspective view showing the configuration of a conventional Faraday rotor.

Explanation of symbols: 10 is GGG substrate, 11 is garnet film (
Faraday material) +121 and 12° are permanent magnets, respectively.

Absolutely 1 picture (α) (b) light 2 diagram

Claims (1)

[Claims] 1. A Faraday rotator comprising an optically transparent substrate, a Faraday material epitaxially grown on the substrate, and a permanent magnet that magnetizes the Faraday material, wherein the permanent magnet is connected to at least one of the Faraday material and the substrate. A Faraday rotator characterized in that it is formed in a ring shape on top of the Faraday rotator.