JPH06167675A - Optical isolator - Google Patents

Abstract

PURPOSE:To suppress distortion generated in a porous core at the time of metal adhesion and to prevent crack by producing a holder for holding a polarizer and analyzer for the optical isolator of a specific Fe-Ni alloy. CONSTITUTION:The alloy consisting essentially of Fe-Ni composed of 32+ or -1wt.% or 42+ or -1wt.% Ni content is used for the end part holder 8 for supporting the polarizer 3 and the analyzer 4. Namely, the coefft. of thermal expansion of the polar core is 6.5X10<-6>/ deg.C and the case the coefft. of thermal expansion of the Ni-Fe alloy attains 6.5X10<-6>/ deg.C is only the cases of 32wt.% and 43wt.% of the Ni content. The crack decreases if the difference in the coefft. of thermal expansion is <=10% (preferably <=5%) in such a case and, therefore, the adequate range of the Ni content is 32+ or -1wt.% or 42+ or -1wt.%. Then, the optical isolator having the high reliability is obtd. by using an adhesion method which does not generate the crack in the polar core at the time of adhesion.

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 visible light semiconductor laser is used as a light source for an optical signal transmission system for optical measurement or the like, a part of light emitted from the semiconductor laser is reflected by a transmission line or each connection portion of transmission optical parts. Returning to the semiconductor laser causes instability of the oscillation characteristics of the semiconductor laser and an increase in noise.
An optical isolator is generally used to prevent the return light from returning.

As shown in FIG. 3, 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 becomes linearly polarized light after passing through the polarizer 3 and enters the magneto-optical element 5, and 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, the light 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, the incident light is transmitted. On the other hand, the return light propagating in the opposite direction as shown by the arrow b is transmitted through the analyzer 4 and the magneto-optical element 5 to become linearly polarized light having a polarization plane inclined by 90 ° with respect to the polarization plane of the polarizer 3. Since it is incident on the polarizer, the return light in the opposite direction is reflected by the polarizer 3
Does not penetrate.

When manufacturing such an optical isolator, the structure shown in FIG. 2 is often used. In order to achieve miniaturization, a polar core (polarizing glass manufactured by Corning Co., Ltd.) which can be thinned is used for the polarizer 3, and a high B is used for the magnet 6.
The Sm-Co material or the Nd-Fe-B material which is s is used. Further, when assembling these, if the organic bonding method is used to bond the parts, the durability is remarkably deteriorated, so that the metal bonding method using the metal solder is used. The metal bonding method is a method of bonding each component through metal solder. Au / Sn (= 80/20) alloy is mainly used as the metal solder. Here, the end holder 8, the outer holder 9, the inner holder 7, and the magnet 6 can be surface-treated by Ni plating or the like to be surface-treated so that solder is easily attached.
Since the magneto-optical element and the polarizer and analyzer using the polar core are non-metal, plating is impossible. Therefore, the metallized sputtering method by masking is generally used. In this method, the light transmitting portion of the optical element is masked and the adhesive portion is sputtered with N
The adhesive pattern is formed of i, Au or the like.

A holder is bonded onto these patterns via ring type solder. Melting point of solder is 280 °
Therefore, the adhesion is completed by heating to 300 ° and then cooling.

[0006]

However, since the polar cores used for the polarizer and the analyzer and the end holder have different coefficients of thermal expansion, crystal cracks are generated during cooling and the isolator characteristics are deteriorated. there were. An object of the present invention is to prevent cracks by suppressing the strain generated in the polar core during metal bonding as much as possible.

[0007]

In order to solve the above-mentioned problems, an object of the present invention is to provide a Ni content 32 ± 1 wt% or 42 ± 1 in an end holder 8 supporting a polarizer 3 and an analyzer 4.
It is an object of the present invention to provide a highly reliable optical isolator by using a bonding method in which a polar core is not cracked at the time of bonding by using an alloy containing wt% of Fe-Ni as a main component.

[0008]

In general, when two kinds of substances having different thermal expansion coefficients are joined via solder, the temperature is raised to the melting point of the solder or higher, and then, when the material is cooled, distortion occurs due to the difference in thermal expansion. In the case of ductile metals, this strain can be absorbed as internal stress, but in the case of glass such as polar core, the strain due to compressive or tensile stress cannot be absorbed and cracks occur. If the materials have the same coefficient of thermal expansion, this will not occur and neither distortion nor cracking will occur.

FIG. 1 shows the relationship between the Ni content of the Fe-Ni alloy and the coefficient of thermal expansion. The thermal expansion coefficient of polar core is 6.
It is 5 × 10 ⁻⁶ / ° C., and the Ni—Fe alloy has a thermal expansion coefficient of 6.5 × 10 ⁻⁶ / ° C. according to FIG.
Only in the case of 2 wt% and 42 wt%. If the difference in the coefficient of thermal expansion is 10% or less, cracking will decrease (preferably 5% or less), so the optimum Ni content range is 32 ± 1 wt.
% Or 42 ± 1 wt%.

[0010]

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

[0011]

Embodiment 1 FIG. 2 shows a structural diagram of an isolator according to the present invention. Garnet was used for the magneto-optical element 5, and a polar core was used for the polarizer 3 and the analyzer 4. The garnet and polar core are processed to φ2 mm, and the metallized portion has a ring shape with a width of 0.2 mm (inner diameter 1.5 mm). The end holder 8 is made of Ni32wt% -Fe alloy, the outer holder 9 is made of SUS304, and the inner holder 7 is made of SUS4.
30, SmCo material is used for the magnet. Solder is Au
An optical isolator was produced using the / Sn20% preform (trade name).

[0012]

Example 2 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was Ni42 wt% -Fe alloy.

[0013]

Example 3 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was Ni77 wt% -Fe alloy.

[0014]

Example 4 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was 29 wt% Ni-17 wt% Co-Fe alloy.

[0015]

Example 5 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was 18 wt% Cr-8 wt% Ni-Fe alloy.

[0016]

Example 6 An optical isolator was manufactured in the same manner as in Example 1 except that the material of the end holder 8 was Ni40 wt% -Fe alloy.

[0017]

Example 7 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was Ni44 wt% -Fe alloy.

[0018]

Example 8 An optical isolator was produced in the same manner as in Example 1 except that the material of the end holder 8 was Ni41 wt% -Fe alloy.

[0019]

[Embodiment 9] An optical isolator was manufactured in the same manner as in Embodiment 1, except that the material of the end holder 8 was Ni43 wt% -Fe alloy.

Table 1 shows the thermal expansion coefficient of the end holder material, the presence or absence of cracks in the polar core, and the result of the heat cycle test for the above examples.

[0021]

[Table 1]

The heat cycle test was conducted with a profile as shown in FIG.

As is clear from Table 1, the Ni content is 32.
By using a wt% or 42 wt% FeNi alloy for the end holder, it is possible to manufacture a highly reliable metal junction isolator with no crack in the polar core.

[0024]

According to the method of the present invention, a highly reliable optical isolator having no cracks in the polarizer and the analyzer can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a Ni content of a Fe—Ni alloy and a thermal expansion coefficient.

FIG. 2 is a sectional view showing the structure of an optical isolator.

FIG. 3 is an explanatory diagram showing a basic configuration of an optical isolator.

FIG. 4 is a diagram showing a profile of a heat cycle test.

[Explanation of symbols] 3 Polarizer 4 Analyzer 5 Magneto-optical element 6 Magnet 7 Inner holder 8 End holder 9 Outer holder 10 Solder adhesive part a Direction of incident light b Direction of returning light

Claims (1)

[Claims] 1. A holder for holding a polarizer for an optical isolator and an analyzer has a Ni content of 32 ± 1 wt% or 42 ±.
An optical isolator made of a Fe-Ni alloy composed of 1 wt%.