JPH08338965A - Optical isolator - Google Patents

Abstract

PURPOSE: To provide a structure with which the automation of production is easy by mechanically fixing a polarizer, magnetooptical element, magnets and analyzer which are constituting parts to a holder without using adhesives. CONSTITUTION: A garnet crystal thick film and polar core are inserted into the hole of the magnet 6. The magnets 6, the polarizer 3 and the magneto- optical element 5 are fixed by holder pieces 7 and 8 and are spot welded with a YAG laser at the parts of 11, by which a holder piece group l is produced. The analyzer 4 is fixed by holder pieces 9 and 10 and is spot welded with the YAG laser in the part of 12, by which a holder piece group 2 is produced. Further, the polarizer 3 and the analyzer 4 are positioned and are matched with the position of an extinction ratio 0 by bringing the parts of the holder piece 8 and the holder piece 9 of the holder piece groups l and 2 into contact with each other and rotating these pieces and the part of 13 is fixed by spot welding of the YAG laser, by which the optical isolator is produced.

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 the Faraday effect.

[0002]

2. Description of the Related Art When a part of light emitted from a semiconductor laser is reflected by a transmission line or each connection portion of transmission optical components and returned to the semiconductor laser, the oscillation characteristics of the semiconductor laser become unstable and noise increases. Cause to cause. An optical isolator is generally used to prevent the return light from returning.

As shown in FIG. 2, the basic structure of the optical isolator comprises a magneto-optical element 5 having a Faraday effect, a polarizer 3, an analyzer 4 and a magnet 6 for applying a magnetic field to the magneto-optical element 5. The optical axes of the magneto-optical element 5, the polarizer 3 and the analyzer 4 are adjusted. And
The incident light propagating in the direction of the arrow a is transmitted through the polarizer 3 and then becomes linearly polarized light and is incident on the magneto-optical element 5. While propagating in the magneto-optical element 5, the polarization plane of the light is changed by the magnetic field of the magnet 6. Normally, it is incident on the analyzer in a state of being rotated by 45 °, and since the inclination of the analyzer is set in advance to be equal to the inclination of 45 ° of the polarization plane of the incident light, this incident light is transmitted. On the other hand, as indicated by an arrow b, the return light propagating in the opposite direction passes through the analyzer 4 and the magneto-optical element 5 to form a straight line having a polarization plane inclined by 90 ° with respect to the polarization plane of the polarizer 3. This return light in the opposite direction does not pass through the polarizer 3 because it becomes polarized light and enters the polarizer.

When manufacturing such an optical isolator, the structure shown in FIG. 3 is often used. In order to achieve miniaturization, polarizable cores (polarizing glass manufactured by Corning) or rutile single crystals are used for the polarizer 3 and the analyzer 4, and a garnet crystal thick film is used for the magneto-optical element 5. Then, as the magnet 6, a small and high Bs magnet such as an Sm-Co material or an Nd-Fe-B material is used.

Conventionally, in the optical isolator having the structure shown in FIG. 4, when these parts are bonded by a metal bonding method,
Generally, the light transmitting portion of the optical element is masked, and the adhesion portion is vapor-deposited or sputtered to form Ni, Au.
Etc. to form an adhesion pattern (metallized film 18). A holder is bonded onto these patterns via a ring-shaped solder material 17. Melting point of solder is 280 ℃
Therefore, the adhesion is completed by heating to 300 ° C. and then cooling. Since laborious work such as vapor deposition or sputtering work and cleaning work before and after the work are required, this is a cause of cost increase. Furthermore,
Since the manufacturing process is complicated, it is difficult to automate the manufacturing process continuously.

[0006]

SUMMARY OF THE INVENTION The present invention does not use a metal adhesive as well as an organic adhesive used when fixing a polarizer, a magneto-optical element, an analyzer, or a magnet to each holder. By assembling the optical isolator, eliminating the vapor deposition or sputtering work when using the metal bonding method, and cleaning steps before and after that, the cost can be reduced by shortening and simplifying the manufacturing process of the optical isolator. The present invention provides an optical isolator having a structure that can be easily automated.

[0007]

[Means for Solving the Problems] Conventionally, when an organic adhesive or a metal adhesive was used, the dimensional accuracy of the holder was manufactured to about ± 0.1 mm. In order to increase the processing cost, the product cost was increased, and therefore the dimensional accuracy was not increased more than necessary. However, high-reliability optical isolators such as optical isolators for undersea repeaters have been demanded. On the other hand, in recent years, processing technology has improved, it has become relatively easy to perform processing with increased dimensional accuracy, and cost is also high. The invention is made possible because it is not relatively expensive.

The present invention is characterized by fixing without an adhesive, and as shown in FIG. 3, holder pieces 7 and 8 for supporting the polarizer 3, the magneto-optical element 5, and the magnet 6, and a test piece. The holder individual pieces 9 and 10 supporting the photons 4 are manufactured by increasing the dimensional accuracy to manufacture an optical isolator without using an organic adhesive or a metal adhesive. Further, as the material of the holder, by selecting a material having a thermal expansion coefficient of about 3 to 10 × 10 ⁻⁶ and a thermal expansion coefficient relatively close to that of an oxide single crystal material, metal deposition or It is possible to provide an optical isolator that eliminates the sputtering process and the cleaning process before and after the process, can reduce the cost, facilitates the automation of manufacturing, and has high reliability.

[0009]

By increasing the processing accuracy, the polarizer, the magneto-optical element, the magnet, and the analyzer, which are the components of the optical isolator, are mechanically fixed to the holder without using an adhesive.
It becomes possible to assemble an optical isolator, and by selecting a material of the above-mentioned glass material or an oxide single crystal material, which is relatively close to the thermal expansion coefficient of the optical element, as a material of the holder, high reliability can be obtained. The optical isolator can be easily manufactured by automation by simplifying the process.

[0010]

EXAMPLES The present invention will be described in detail with reference to examples.

(Embodiment 1) FIGS. 1 and 2 show the structure of an optical isolator according to the present invention. A garnet thick film crystal was used for the magneto-optical element 5, a polar core was used for the polarizer 3 and the analyzer 4, and an SmCo material was used for the magnet 6. The garnet crystal thick film and the polar core are processed into a 2 mm opening and inserted into the 2 mm opening hole of the magnet 6. Magnet 6, polarizer 3,
The magneto-optical element 5 is fixed by the holder pieces 7 and 8, and the portion 11 is YAG laser spot welded to produce the holder piece group 1. The analyzer 4 is a holder piece 9
And 10 and YAG laser spot welding of the 12 portion to produce a holder piece group 2. Further, regarding the holder piece groups 1 and 2, the portions of the holder piece 8 and the holder piece 9 are brought into contact with each other and rotated to align the polarizer 3 and the analyzer 4 so that the extinction ratio is 0. An optical isolator was produced by fixing 13 parts by YAG laser spot welding. In this embodiment, a Ni31 wt% -Fe alloy is used as the material of the holder, and the dimensional accuracy of the portion in contact with the magneto-optical element, the polarizer, the analyzer, and the magnet is set to about ± 0.05 mm.

(Embodiment 2) The material of the holder pieces 7, 8, 9, and 10 in Embodiment 1 is Ni 45 wt%.
An optical isolator was produced in the same manner as in Example 1 except that the material of -Fe alloy was used.

(Embodiment 3) As a material for the holder pieces 7, 8, 9, and 10 in Embodiment 1, Ni 38 wt% is used.
An optical isolator was produced in the same manner as in Example 1 except that the material of -Fe alloy was used.

(Fourth Embodiment) The polarizer 3 in the first embodiment,
An optical isolator was produced in the same manner as in Example 1 except that rutile single crystal was used as the analyzer 4.

(Embodiment 5) As a material for the holder pieces 7, 8, 9 and 10 in Embodiment 4, Ni 45 wt%
An optical isolator was produced in the same manner as in Example 4 except that the material of -Fe alloy was used.

(Embodiment 6) As a material for the holder pieces 7, 8, 9 and 10 in Embodiment 4, Ni 38 wt% is used.
An optical isolator was produced in the same manner as in Example 4 except that the material of -Fe alloy was used.

With respect to the above-described six embodiments, the number of tests is 10 each with an optical isolator using a metal adhesive, and an impact test (MIL-std-883C method 2003.3 condition B) and a vibration test (MIL) as environmental tests. -S
The results of td-883C Method 2007. 1 Condition A) are shown in Table 1.

[0018]

Each of the embodiments of the present invention is comparable to an optical isolator using a metal adhesive, and in particular, a polarizer, a magneto-optical element, a magnet, an analyzer, etc. are used in this embodiment.
Inconveniences such as parts coming off from various holders do not occur even once, and an optical isolator using an adhesive is obtained. Although environmental tests have not been performed on optical isolators using organic adhesives, optical isolators using organic adhesives have traditionally been inferior in reliability in high temperature and high humidity tests compared to optical isolators using metal adhesives. I did not use it for comparison. In this embodiment, the holder material is Ni31 wt.
% -45 wt% Fe-Ni alloy was used,
It has been found that other materials can exhibit the same effect as long as the optical isolator can be manufactured without using an adhesive.

In this embodiment, the optical isolator having the structure of the one-stage type optical isolator having one magneto-optical element, one polarizer and one analyzer has been described. The results were also obtained as a result of the impact test and the vibration test, which were carried out for the structure constructed without using the agent.

[0021]

In the manufacturing process of the optical isolator according to the present invention, it is possible to eliminate the vapor deposition or sputtering work conventionally performed when the metal adhesive is used, and the cleaning work process before and after these processes, Since only the work of assembling the holder and fixing each component by YAG laser spot welding to the holder, the manufacturing process of the optical isolator is greatly shortened and simplified.
Cost reduction is possible. Further, since the assembling process is simplified, the manufacturing is easy to automate and the manufacturing of the optical isolator at a lower cost is possible. And by manufacturing a holder with good dimensional accuracy at low cost, it is possible to withstand impact tests and vibration tests as well as optical isolators using metal adhesives, and no cracks or distortions occur and high reliability. Optical isolators can be manufactured. Also, because no adhesive is used,
The long-term reliability is also improved without lowering the insertion loss due to the release of gas from the adhesive.

[Brief description of drawings]

FIG. 1 is a view showing a structure of an optical isolator before assembling according to the present invention and explaining an assembling order.

FIG. 2 is an explanatory view showing the function of an optical isolator.

FIG. 3 is a sectional view showing the structure of an optical isolator after assembly according to the present invention.

FIG. 4 is a sectional view showing the structure of a conventional optical isolator.

[Explanation of symbols]

 1 Holder piece group 2 (showing the order of assembly) Holder piece group 3 (showing the order of assembly) 3 Polarizer 4 Analyzer 5 Magneto-optical element 6 Magnet 7 Holder piece before assembly 8 Holder piece before assembly 9 Holder piece before assembly 10 Holder piece before assembly 11 YAG laser spot welding spot (welding sequence 1) 12 YAG laser spot welding spot (welding sequence 2) 13 YAG laser spot welding spot (welding sequence 3) 14 External holder 15 Polarizer side end holder 16 Analyzer side end holder 17 Solder material 18 Metallized film a Direction of incident light b Direction of return light

Claims (2)

[Claims] 1. A polarizer, a magneto-optical element, a magnet, and an analyzer, which are components of an optical isolator, are mechanically fixed and assembled to a holder holding these components without using an adhesive. An optical isolator characterized by that. 2. The optical isolator according to claim 1, wherein the material of the holder is a Fe—Ni alloy having a Ni content of 31 wt% to 45 wt%.