JPH08327950A - Optical isolator - Google Patents

Abstract

PURPOSE: To obtain a metal fusion type visual light isolator having high impact resistance and high reliability by forming metallized films on the flanks of a Faraday rotor to be joined and soldering a magnet subjected to a plating treatment thereto. CONSTITUTION: The metallized films 11 are formed on at least one surface, for example, all surfaces, of the four flanks of a CdMnHgTe single crystal 2 which is the Faraday rotor on which antireflection films are formed on light incident and exit surfaces. This CdMnHgTe single crystal 2 having the metallized films is thereafter inserted into the cylindrical magnet plated with Ni. This optical crystal and the magnet 5 are soldered with a solder material (Au-Sn) 7. Further, the magnet 5, a polarizer and a polarizer side end holder are soldered and an analyzer is soldered to an analyzer side end holder, then, the polarizer side holder and the analyzer side holder are welded by a YAG laser to an external holder. The visible light isolator is thus formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator used for optical communication, optical measurement, etc., and more particularly to an optical isolator used in the visible wavelength range.

[0002]

2. Description of the Related Art In recent years, an optical communication system using a semiconductor laser as a light source and an optical application device using a semiconductor laser have been widely used, and further, their applications and scales have been expanded. An optical isolator is used for the purpose of removing the returning light to the semiconductor laser in order to improve the accuracy and stability of these optical communication systems and optical application equipment. In particular, fiber amplifiers are indispensable in order to take advantage of features such as low noise, wide band, and high output.

At present, a bismuth-substituted garnet thick film is put into practical use as a Faraday rotator material for optical communication optical isolators in the 1.3 μm band and the 1.5 μm band. However, 0.98 μm used in fiber amplifiers
At a short wavelength such as the band, 1.047 μm band, there was a problem that the crystal transmission loss increased due to the existence of a strong absorption edge based on Fe ions, so that it was not put to practical use.

To solve this problem, CdMnTe or Cd
A study is being made to put a so-called visible light isolator into practical use for a short wavelength of 1 μm band or less by using a MnHgTe single crystal as a Faraday rotator.

The structure of this optical isolator comprises an optical element consisting of a polarizer, an analyzer and a Faraday rotator, a permanent magnet for generating a magnetic field, and a holder for fixing and protecting them.

Conventionally, an organic adhesive has been used as a method for fixing and adhering each optical element to a holder, but the stability of the adhesive force for a long period of time is poor, and this gas accompanies the release of gas from the adhesive. Since an organic film is formed on the crystal surface by laser light to increase insertion loss, long-term reliability cannot be ensured.

Therefore, when it is used for a repeater for optical communication or the like, an optical isolator which requires a high degree of reliability for a long period of time is formed by a metal fusion method instead of the conventional fixing method using an organic adhesive. Optical isolators are used. Furthermore, in the optical isolator for fiber amplifier, compared with the optical isolator of the optical communication repeater,
Since light with a power of 00 times or more passes therethrough, it is desired to put a visible light isolator formed by a metal fusion method into practical use.

Here, the 1.3 μm band and 1.5 μm are shown in FIG.
FIG. 2 is a cross-sectional view of a metal fusion splicing type optical isolator used for band optical communication. The optical element including the polarizer 1 and the Faraday rotator 2 and the polarizer side end holder 4 are simultaneously fixed by the solder material 7, and the analyzer 3 and the magnet 5 are
It is soldered to the analyzer side end holder 6. The polarizer-side end holder 4 and the analyzer-side end holder 6 are joined by laser welding via the external holder 12 to form a one-stage optical isolator. At this time, the solder fixing metallized film 11 of each optical element is formed in a portion where light does not pass, as shown in FIG.

[0009]

However, CdMn used in the Faraday rotator of the visible light isolator.
For Te and CdMnHgTe single crystals, a metallized film was formed in the same manner as the conventional one, and a metal fusion-type optical isolator was formed. Then, a drop test was conducted. Both single crystals were peeled from the holder even when dropped from 30 cm. It wasn't practical.

A technical object of the present invention is to provide a visible light metal fusion type optical isolator having a significantly improved impact resistance.

[0011]

According to the present invention, in a visible light metal fusion type optical isolator, a metallized film is formed on at least one of the side surfaces of a Faraday rotator to be joined, and a magnet is plated. By directly soldering, a visible light isolator having high impact resistance and high reliability can be provided.

[0012]

As a result of extensive studies on the above-mentioned problems, CdMnTe and Cd used as visible light isolators
Regarding the MnHgTe single crystal, the soldering did not have sufficient adhesive strength because the metallized film had no problem and the single crystal itself was fragile, so that the single crystal joint could not withstand the impact. , I found that it was because of the destruction.

Furthermore, CdMnTe or CdMnHgTe
The Verdet constant of a single crystal is as small as 1/5 to 1/10 of that of bismuth-substituted garnet. Therefore, the crystal must be elongated in the optical axis direction for use as an optical isolator.

Therefore, the conventional method of forming the metallized film on the optical surface has a so-called cantilever structure in which a rectangular parallelepiped crystal is supported only on one bottom surface, and the impact is concentrated on the bonding surface. It has caused the destruction of the crystals.

Further, since the metallized film is formed on the optical surface, the metallized film must be formed only in a place where light does not pass, so that the usable area is limited, and the impact per unit area of the metallized film is limited. It was increasing in power.

From the above, by forming a metallized film on at least one of the side surfaces of the crystal and solder-bonding it to the plated magnet, the area of the bonding portion is increased, and the area per crystal unit area is increased. Impact can be reduced and impact resistance can be improved.

[0017]

EXAMPLES Hereinafter, examples will be described in detail.

Example 1 As shown in FIG. 1 (a), a CdMnHgTe single crystal 2 (1.3 mm × 1.3) which is a Faraday rotator having an antireflection film formed on the light entrance / exit surface.
mm x 2.5 mm) on four sides (1.3 mm x 2.5 m)
m) The metallized film 11 was formed on all (only two surfaces are visible in the figure). At this time, the metallized film was composed of Cr as a base film of 0.35 μm and an intermediate film of Ni.
Of 0.35 μm and Au as a bonding film of 0.15 μm
It was formed as a layer film. Then, FIG. 1 (b) and FIG.
As shown in (c), a CdMnHgTe crystal on which a metallized film was formed was inserted into a Ni-plated cylindrical magnet (outer diameter φ4 mm, inner diameter φ1.6 mm, length 2.7 mm). Au—Sn: melting point 280 ° C.) 7 was used to solder-bond the optical crystal and magnet. Further, as shown in FIG. 2, the magnet 5, the polarizer 1, and the polarizer-side end holder 4 are solder-bonded, the analyzer 3 is solder-bonded to the analyzer-side end holder 6, and then the polarizer-side Attach the holder 4 and the analyzer side holder 6 to the external holder 12
Welded with an AG laser to form a visible light isolator. The metallized film is not shown in FIG.

(Embodiment 2) Cd which is a Faraday rotator
Of the side surfaces of the MnHgTe single crystal 2, as shown in FIG. 3A, the metallized film 11 is formed only on one side, and
As shown in (b) and FIG. 3 (c), the visible light isolator was formed by soldering with the plated magnet 5.

The visible light isolator manufactured as described above was subjected to a drop test. Table 1 shows the results. In addition, in this case, the determination (OK) was made based on the fact that there was no peeling or cracking of the crystal after falling.

(Table 1)

As is apparent from Table 1, according to the present invention,
The impact resistance could be increased significantly.

[0023]

As described above, according to the present invention,
In the visible light metal fusion type optical isolator, a metallized film is formed on at least one of the side surfaces of the Faraday rotator to be joined, and by soldering with a plated magnet, high impact resistance and high A reliable visible light isolator can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, FIG. 1 (a) is a perspective view, FIG. 1 (b) is a horizontal sectional view, and FIG. 1 (c) is a vertical sectional view.

FIG. 2 is a sectional view of an isolator according to an embodiment of the present invention.

FIG. 3 is an explanatory view showing another embodiment of the present invention, FIG.
Is a perspective view, FIG. 3 (b) is a horizontal sectional view, and FIG. 3 (c) is a vertical sectional view.

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

FIG. 5 is a perspective view showing a metallized film formed on a conventional optical element.

[Explanation of symbols]

 1 Polarizer 2 Faraday rotator 3 Analyzer 4 Polarizer side end holder 5 Magnet 6 Analyzer side end holder 7 Solder material 11 Metallized film 12 External holder

Claims (1)

[Claims] 1. A metal fusion-type optical isolator comprising an optical element including a polarizer, an analyzer, and a Faraday rotator, a permanent magnet for generating a magnetic field, and a holder, wherein a side surface of the Faraday rotator is included. An optical isolator characterized in that a metallized film is formed on at least one surface and soldered to a plated magnet.