JPH0527198A - Optical isolator - Google Patents

Abstract

PURPOSE:To provide the optical isolator which has superior performance without generating reflected light nor scattered light and is easily manufactured. CONSTITUTION:The optical isolator 10 consists of a polarizer 1, a Farady rotator 3, an analyzer 2, and a cylindrical magnet 4 which applies a magnetic field to a Farady rotator 3, and the Farady rotator 3 is sandwiched fixedly between two solderable metallic members 13 and 14 inside the cylindrical magnet 4, which is soldered to the metallic members 13 and 14. The polarizer 1 (analyzer 2) is fixed among solderable metallic members 5, 11, and 12 (metallic members 6, 15, and 16), which are soldered to one another. The metallic members 11-16 have thin black films 30 formed on their surfaces exposed to an optical path side. The metal of the metallic members 11-16 are selected preferably among silver, gold, cadmium, tin, copper, and alloy consisting principally of them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is an optical component used in, for example, an optical communication system or an optical measuring instrument, and is for preventing light emitted from a light source from being reflected by an end face of the optical system and returning to the light source. The present invention relates to an optical isolator.

[0002]

2. Description of the Related Art When light from a light source is transmitted through an optical system, the light reflected by the end surface of the optical system returns to the light source. For example, in signal transmission using an optical fiber, the light emitted from a laser light source is projected onto the end face of the fiber through a lens, and most of it enters the fiber as transmitted light, but is reflected by the lens and the end face of the fiber. After returning to the laser light source, the end face of the laser light is reflected again and becomes noise. Optical isolators are used to eliminate such noise. In optical isolators, the ability to eliminate noise is high and the loss of light transmittance is small,
That is, low insertion loss is required.

FIG. 3 shows a sectional view of the optical isolator 10. In the figure, a polarizer 1, an Faraday rotator 3, and an analyzer 2, which are optical elements, are arranged in this order, and are assembled together with a metal member 5, 6 that is a holding jig and a cylindrical magnet 4 that applies a magnetic field to the Faraday rotator 3. Stored in the outer cylinder 7. The optical isolator 10 is fixed by joining the boundary portion of each component with solder or an adhesive. When each component of the optical isolator is joined by soldering, for example, JP-A-1-2002
As disclosed in Japanese Patent No. 23, a solderable metal film must be formed at the boundary between components.

When the light from the light source is incident on the polarizer 1 using the optical isolator 10, since the light is reflected by the metal, a part of the light hits the metal members 5 and 6 and the cylindrical magnet 4 and is reflected light. And scattered light is generated. The generated reflected light and scattered light are placed on the optical path and become noise. Further, when the parts of the optical isolator are joined by solder, the light is reflected even by the solder.

[0005]

When the parts of the optical isolator are joined with solder, for example, the optical element and the metal member have different coefficients of thermal expansion. Therefore, when the parts are joined directly with the solder, contraction occurs when the solder is solidified and mechanical distortion occurs. Occurs and the performance deteriorates. Therefore, it is preferable that the optical element is not directly soldered to other components but sandwiched and fixed by a metal member.

The present invention has been made in order to solve the problem that light is reflected by the metal in an optical isolator in which an optical element is fixed by a metal member. The reflected light and the scattered light are not generated and the performance is improved. It is an object of the present invention to provide an optical isolator which is an excellent optical isolator and can be easily manufactured.

[0007]

An optical isolator of the present invention made to achieve the above object will be described with reference to FIG. 1 corresponding to an embodiment.

In the figure, in an optical isolator 10 comprising a polarizer 1, a Faraday rotator 3, an analyzer 2, and a cylindrical magnet 4 for applying a magnetic field to the Faraday rotator 3, the Faraday rotator 3 is a solderable cylindrical magnet. It is arranged inside 4 and is fixed by being sandwiched between two solderable metal members 13 and 14, and the metal members 13 and 14 and the cylindrical magnet 4 are joined by solder. The polarizer 1 is sandwiched and fixed between the solderable metal members 5, 11, and 12.
2 and the metal member 5 are joined by solder. The analyzer 2 is sandwiched and fixed by solderable metal members 6, 15 and 16, and the metal members 15 and 16 and the metal member 6 are joined by solder. The metal members 11, 12, 13, 14, 15,
16 is exposed on the optical path side, and a black thin film 30 is formed on the inner surface parallel to the optical axis and the side surface perpendicular to the optical axis.
Holes 20 into which solder is inserted are formed in the metal members 5 and 6 and the cylindrical magnet 4.

The metal of the solderable metal member is
It is preferably selected from silver, gold, cadmium, tin, copper, and alloys mainly containing these metals.

When silver is used for the metal member, when forming a black thin film, it is preferable to sulfide the surface of silver to form a black silver sulfide thin film.

[0011]

When the surface of the metal member is made black, all the light that hits the metal member is absorbed and becomes non-reflective, so that reflected light or scattered light does not occur. The solder is inserted into the hole 20 and melted,
Since it solidifies, it does not protrude to the outside of the joint portion, and reflected light due to solder does not occur.

Further, since the optical element is sandwiched and fixed by the solderable metal member, the optical element and the metal member having different thermal expansion coefficients do not have to be directly joined by the solder, so that when the solder solidifies. Does not cause mechanical strain due to shrinkage.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view of an optical isolator according to an embodiment of the present invention.

The optical isolator 10 shown in the figure has a polarizer 1, a Faraday rotator 3, an analyzer 2, a cylindrical magnet 4 for applying a magnetic field to the Faraday rotator 3, and metal members 5, 6, 11 ,.
12, 13, 14, 15, and 16 are arranged in the assembled outer cylinder 7 and joined by solder to be integrally formed. Hole 20 provided in metal member 5, metal member 6, and cylindrical magnet 4
Is a hole for inserting solder.

The polarizer 1 is a glass polarizing plate formed on the inner peripheral surface of the metal member 5, and the analyzer 2 is a glass polarizing plate formed on the inner peripheral surface of the metal member 6 in a cylindrical shape having an outer diameter. Faraday rotator 3
Is made of bismuth-substituted rare earth iron garnet, and is formed into a cylindrical shape having an outer diameter that can be accommodated in the solderable cylindrical magnet 4.

Metal members 5, 6, 11, 12, 13, 1
4, 15, 16 are all made of silver. The metal member 5 (or the metal member 6) has the same outer diameter as the cylindrical magnet 4, and the width is the sum of the widths of the polarizer 1 (or the analyzer 2) and the metal members 11 and 12 (or the metal members 15 and 16). Form equally.
Each of the metal members 11, 12, 13, 14, 15, 16 forms a black metal thin film 30 whose main component is silver sulfide on the inner surface and side surface thereof. The method of forming the metal thin film 30 is as follows. After coating the soldering part with wax or heat resistant resin, add 3 to 3 in a gas containing hydrogen sulfide.
Leave for 10 minutes. Then, the wax or the heat-resistant resin is removed with a solvent to obtain a metal part with a black film.

The width of the cylindrical magnet 4 is the Faraday rotator 3,
And the sum of the widths of the metal members 13,14. The width of the outer cylinder 7 is formed to be equal to the sum of the widths of the metal member 5, the cylindrical magnet 4, and the metal member 6.

Metal member 5, metal member 6, and cylindrical magnet 4
Respectively, four holes 20 are provided at positions symmetrical to the left and right ends in the radial direction and in a direction perpendicular to the optical axis. Solder made of tin, lead and silver is inserted into each hole 20.

The polarizer 1 (or the analyzer 2) is a metal member 5
(Or it is arrange | positioned inside the metal member 6), it pinches | interposes from both sides and is fixed by the metal members 11 and 12 (or the metal members 15 and 16). The Faraday rotator 3 is arranged inside the cylindrical magnet 4, and is sandwiched and fixed by the metal members 13 and 14 from both sides. Next, melt the solder inserted in each hole 20,
The metal member 5 and the metal members 11 and 12, and the metal member 6 and the metal members 15 and 16 are joined by soldering. Also, the cylindrical magnet 4
And the metal members 13 and 14 are joined with solder.

The entire parts described above are arranged inside the outer cylinder 7 in the order shown in FIG. 1, and the outer cylinder 7 and the metal member 11 and the outer cylinder 7 and the metal member 16 are joined and fixed by soldering, and the optical isolator 10 is connected.
Is completed. The beam diameter on which the light of the optical isolator 10 can enter is Φ1 mm.

Using the optical isolator 10, polarized light of Φ 0.5 mm was made incident on the center of the beam diameter from the side of the polarizer 1.
The insertion loss at this time was 0.4 dB. Next, when light is incident from the side of the analyzer 2 which is the opposite direction, the insertion loss is 38d.
It was B.

Further, the incident optical axis is set to 0. from the center of the beam diameter.
Moved to the outer peripheral direction by 3 mm, and from the side of the polarizer 1 Φ 0.5 mm
Of polarized light. At this time, the reflected light generated by hitting the metal member is 0.05% or less of the incident light amount, and when light is incident from the analyzer 2 side in the opposite direction, the insertion loss is 38 dB, which is not lower than the above. It was

As another embodiment, a black NiP metal thin film is formed at the same location as the metal member by electroless plating,
An optical isolator with a beam diameter of 1.2 mm was made. When a polarized light of Φ0.5 mm was made incident on the center of the beam diameter from the side of the polarizer 1, the insertion loss was 0.3 dB. Reverse analyzer 2
When the polarized light is incident on the center of the beam diameter from the side, the insertion loss is 4
It was 2 dB. In addition, the incident optical axis is moved from the center of the beam diameter of the polarizer 1 to the outer peripheral direction by 0.5 mm, and Φ is 0.5 mm.
Of polarized light. At this time, the reflected light generated by hitting the metal member is 0.05% or less of the incident light amount, and when the light is incident from the side of the analyzer 2 in the reverse direction, the insertion loss is 42 dB. Did not fall.

For comparison, the optical isolator disclosed in JP-A-1-200223 was used, and light was incident from the light source of the laser diode, and the same measurement as above was performed. In this optical isolator, a polarizer and an analyzer are placed inside a cylindrical metal member, a solderable metal film is formed at the joints of all components, and the components are joined with tin-lead solder. An optical isolator having a beam diameter of Φ1 mm was manufactured. Φ
Insertion loss was 0.5 dB when light was made incident on the center of the beam diameter of the polarizer using polarized light of 0.5 mm, and insertion loss was 35 dB when light was made incident from the analyzer 2 side in the opposite direction.
In addition, the incident optical axis is 0.3 m from the center of the beam diameter of the polarizer.
When it moved in the outer peripheral direction, it collided with a metal member and about 1% of the incident light amount returned to the light source as reflected light. When light was incident from the analyzer 2 side in the opposite direction, the insertion loss was 28 dB, which was from the forward direction. It decreased compared to the incidence.

As the metal member, not only silver but also gold, cadmium, tin, copper and alloys mainly containing them, which are easy to solder, may be used. If the metal member is as described above,
When forming a metal thin film that absorbs light, there is no need to mask the joint with other parts.After forming a metal thin film that absorbs light on the entire surface of the metal member, the metal thin film at the joint is removed to remove the metal surface. You can put out. The metal thin film may have a composition that absorbs light having the same wavelength as the light used in the optical isolator, and examples of the metal thin film other than the black thin film include gold sulfide (gold black) and black zinc.

The metal member for fixing the polarizer 1 and the analyzer 2 may be formed, for example, as shown in FIG. Polarizer 1
However, the same applies to the case of the analyzer 2. The metal member 5 is formed with one side open, the polarizer 1 is arranged inside the metal member 5 and fixed by the metal member 11, and the metal member 5 and the metal member 11 are joined by soldering. The metal member 5 has a black thin film 30 formed on the side surface perpendicular to the optical axis and on the inner surface exposed to the optical path side and parallel to the optical axis. Metal member 1
1, the black thin film 30 is formed on the inner surface and the side surface.

[0028]

As described above in detail, the optical isolator of the present invention can prevent reflected light and scattered light by providing a black thin film that absorbs light on the surface of the metal member,
An optical isolator with excellent characteristics can be provided. Further, since it is not necessary to form a metal film on the component for soldering, the manufacturing is simple.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical isolator of an embodiment to which the present invention is applied.

FIG. 2 is a cross-sectional view showing that an optical element is fixed by a metal member whose one side is open.

FIG. 3 is a sectional view of a conventional optical isolator.

[Explanation of symbols]

1 is a polarizer, 2 is an analyzer, 3 is a Faraday rotator, 4 is a cylindrical magnet, 5 and 6 are metal members, 7 is an outer cylinder, 10 is an optical isolator, 11, 12, 13, 14, 15, 16 are A metal member, 20 is a hole, and 30 is a thin film.

Claims (3)

[Claims] 1. An optical isolator comprising a polarizer, a Faraday rotator, an analyzer, and a magnet for applying a magnetic field to the Faraday rotator, wherein the Faraday rotator is arranged inside the magnet and two solderable metals are used. The metal member and the magnet are soldered together, the polarizer and the analyzer are each secured by at least two solderable metal members, and at least two metal members are soldered together. An optical isolator characterized in that 2. The metal of the solderable metal member is selected from silver, gold, cadmium, tin, copper, and alloys mainly containing these metals. Optical isolator. 3. The optical isolator according to claim 1, wherein the metal member is silver, and the black color is formed by sulfurizing the silver.