JPH089702Y2 - Optical isolator - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an optical isolator utilizing the Faraday effect used for optical communication, optical measurement, etc., for realizing a stable extinction ratio characteristic. Regarding the structure.

[Prior Art and its Problems] Recently, an optical communication system using a semiconductor laser as a light source,
Optical application equipment using semiconductor lasers has come into widespread use, and there is an increasing demand for optical isolators that eliminate the return light to semiconductor lasers in order to improve the accuracy and stability of those systems and equipment. It was Up to now, optical isolators with various structures have been proposed, but basically, a pair of polarizing elements such as a polarizer / analyzer, a Faraday rotator, a permanent magnet for generating a magnetic field, and a fixed protection for them are used. It consists of a holder case.

The extinction characteristics of the optical isolator depend on the accuracy of the 45 ° plane of polarization by the Faraday rotator, which is a magneto-optical element, and whether or not the polarization planes of the polarizer and the analyzer are relatively accurately 45 ° different. ing. In the forward direction, the light beam emitted from the semiconductor laser passes through the polarizer to become linearly polarized light, and the Faraday rotator rotates the plane of polarization by 45 °.
The 45 ° plane of polarization is maintained by passing through the analyzer adjusted in different directions of the 45 ° plane of polarization. And in the opposite direction, only the 45 ° plane of polarization passes through the analyzer, and the Faraday rotator rotates the 45 ° plane of polarization further, so that the return light is a plane of polarization rotated 90 ° with respect to the plane of incidence. Then, the light is blocked by the polarizer and a high extinction characteristic is achieved. However, when assembling the optical isolator, a very expensive assembly and adjustment device is required to fix the whole with the polarization planes of the polarizer and the analyzer relatively rotated by 45 °, and the adjustment time become longer. As a result, mass productivity is extremely low, and it is not possible to adequately meet the demand expected in the future, which is a factor that prevents a reduction in the manufacturing cost of the final product.

In consideration of these points, the inventors of the present invention have previously proposed Japanese Patent Application No. 62-23
In No. 6693 and Japanese Utility Model Application No. 62-145786, we proposed a compact and easily adjustable optical isolator structure. However, in this structure, although the optical isolator, which was the initial purpose, was made smaller, easy to adjust, and improved in high extinction characteristics, permanent magnets were directly attracted and adhered to each other.
There was a possibility that the end of the permanent magnet would be damaged and deteriorated. In particular, rare earth magnets have extremely high permanent magnet characteristics, but they are mechanically fragile and have the drawback of being easily damaged when fixed by mutual strong magnetic attraction. No. 63-52630, one of the polarizing elements is fixed by a magnetic material having a through hole in the shape of the polarizing element, and the entire 45 ° between the polarizing elements is magnetically attracted.
We devised a structure that can be assembled without considering damage to the magnet during adjustment.

On the other hand, from the viewpoint of the reliability of the optical isolator, it has been required to permanently fix the component fixing means by using a metal fusion material instead of the organic adhesive. Especially in the optical communication field, high environmental resistance and high aging resistance are required,
Conventional organic adhesives are unstable factors in terms of temperature and humidity characteristics, and are rejected to meet the above-mentioned high requirements. It is considered that the metal fusion fixing of all components is an essential technique.

[Means for Solving the Problems] In order to facilitate the 45 ° rotation adjustment of the polarization planes of the polarizing elements, the present invention divides the entire configuration into two parts.
The optical isolator according to the present invention is characterized by the fixing means essential to the construction of the parts, that is, the polarizing element of either the polarizer or the analyzer, the Faraday rotator holder, the Faraday rotator, the permanent magnet, and the case holder. The two divided bodies are integrally fixed and the other polarizing element, the magnetic yoke, and the case holder are integrally fixed, and the two divided bodies are arranged in a state in which the polarization planes of the polarizing elements arranged respectively are rotated by 45 °. It is a fixed structure. Then, the fixing means is metal fusion, and the metal fusion material is made of two or more kinds of materials having different melting points. The Faraday rotator holder can be made of a non-magnetic material, but in consideration of the magnetic circuit magnetic flux converging property, it is expected that the permanent magnet will be made smaller if it is made of a magnetic material.

In this structure, a permanent magnet on one side of the split body and a magnetic yoke on the other side are arranged, which are magnetically attracted during polarization plane adjustment, and are special for holding the position in the fixing step after adjustment. No assembly equipment is required. Therefore, in the first step, regardless of the orientation of the polarization plane, the two halves are integrally fixed with the high melting point fusion material, and in the second step, the polarization plane is adjusted and the whole is integrated with the low melting point fusion material. Thus, a final optical isolator can be obtained. At this stage, while holding the optical system to be adjusted, focus with the lens and YA
G welding may be carried out, or fusion processing may be carried out as it is taken out from the optical system.

[Embodiment] In the embodiment of the present invention shown in FIG. 1, each of the hollow permanent magnet 1, the Faraday rotator 2, the Faraday rotator holder 3, the polarizer 4, and the case holder 5 is a first divided body. It is configured as A, and Cr, Ni, Au are sequentially formed on the respective contact surfaces in advance by the sputtering method, and then on each m portion.
By inserting the Au-Sn composite financial adhesive and heating and fixing at about 280 ° C., and then similarly heat-fixing the second divided body B consisting of the analyzer 6, the magnetic yoke 7 and the case holder 8, Split body
A and B were formed. In order to integrate these divided bodies, Pb having a melting point lower than that of the Au-Sn alloy is added to the joint n of each case holder 5 and 8.
An optical isolator was completed by fixing with a -Sn composite financial adhesive.

[Effects of the Invention] The present invention enables the metal fusion bonding to be adhered to the whole while maintaining the structure of which mass productivity is extremely high, that is, when the first-stage divided body is manufactured, the angle adjustment of the polarization element and the component There is no need to adjust the position, and it can be mechanically fused and fixed.In the second step, 45 polarization plane adjustments are magnetically attracted to each other, so the optimum position is searched only in the rotation direction, and finally It should be integrated. Therefore, it is clear that the present invention is an extremely effective means for reducing the performance and manufacturing cost of the optical isolator.

[Brief description of drawings]

FIG. 1 is a sectional view showing a split state of an optical isolator according to an embodiment of the present invention. 1: Hollow permanent magnet, 2: Faraday rotator 3: Faraday rotator holder 4: Polarizer, 5,8: Case holder 6: Analyzer, 7; Magnetic yoke

Claims (4)

[Scope of utility model registration request] 1. A polarizing element, a Faraday rotator holder, a Faraday rotator, a permanent magnet and a case holder, which are one of a polarizer and an analyzer, are integrally fixed, and the other polarizing element, a magnetic yoke and a case holder are integrally fixed. An optical isolator having an integrally fixed two-divided body structure, wherein the two divided bodies are fixed in a state in which the polarization planes of the respective polarizing elements rotated by 45 °. 2. The optical isolator according to claim 1, wherein the Faraday rotator holder is made of a magnetic material. 3. The optical isolator according to claim 1, wherein the fixing means is metal fusion. 4. The optical isolator according to claim 3, wherein the metal fusing material is made of two or more kinds of materials having different melting points.