JP2922627B2 - Optical isolator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical isolator applied to a high-speed, large-capacity optical communication system or the like, and to a high reliability optical isolator.

In recent years, with the increase in speed and capacity of optical communication, high-performance semiconductor lasers have been used as light sources. This semiconductor laser is sensitively affected by reflected return light from an optical fiber or the like, and has a phenomenon in which the oscillation characteristics of the laser become unstable. In order to prevent the reflected return light from reaching the semiconductor laser, an optical isolator having a high reverse loss is essential.

A laser module with an optical isolator having an optical fiber attached to this semiconductor laser is used. Since high reliability is required for these optical components such as optical isolators, the conventional resin fixing with an adhesive or the like is inferior in reliability due to generation of gas and the like. Therefore, a fixing method other than resin is required for fixing the optical component. As this fixing method, a fixing method using solder is used.

[Prior Art] FIG. 4 is a view for explaining the structure of an optical isolator, wherein 1 is a Faraday rotator, 2a and 2b are polarizers, 3 is a hollow permanent magnet, and 4a ′ and 4b ′ are A rotary holder 6 for fixing the polarizers 2a and 2b is an outer case for reinforcing the strength of the entire optical isolator.

When assembling an optical isolator according to the conventional technique as shown in FIG. 5, a Faraday rotator 1 and two polarizers 2a and 2b are used.
Is inserted through the holes 10a, 10b in the axial direction of the rotary holders 4a ', 4b', and the adhesive is inserted and fixed through the holes 5a, 5b, 5c for pouring the adhesive.

Reference numeral 9 shown in FIGS. 4 and 5 is a ring-shaped spacer for preventing the Faraday rotator 1 and the polarizer 2b from coming into direct contact.

In the above prior art, a fixing method using a resin such as an adhesive has been performed for assembling the optical isolator. It has been a problem for resin adhesives and the like to generate gas after curing. For this reason, optical components using resin bonding are inferior in high reliability. Therefore, there is a problem that a high-performance and highly reliable optical isolator cannot be realized.

Therefore, an invention of joining and integrating by soldering was made (see Japanese Patent Application Laid-Open No. 1-2200223).

[Problems to be Solved by the Invention] In the above-mentioned joining by soldering, solder is inserted from the holes 5a, 5b, and 5c and irradiated with a laser beam to perform soldering, similarly to joining with a conventional adhesive. In this case, there is a problem that the melting of the solder is uneven and the reliability is lacking.

To solve the above problems, a Faraday rotator,
It is conceivable to employ bonding by a plate-like solder in an optical isolator including a hollow permanent magnet included therein and polarizers on both sides of the Faraday rotator.

However, if the melting amount of the solder is excessive, the solder melts out to the outer peripheral portion of the optical isolator, and the outer diameter dimension changes, so that the optical isolator cannot be incorporated into a highly accurate optical device such as a semiconductor laser module. There was a problem.

Therefore, an object of the present invention is to provide a highly reliable bonding method and a highly reliable optical isolator that has become possible for the first time.

[Means for Solving the Problems] An optical isolator of the present invention comprises a Faraday rotator, a hollow permanent magnet containing the Faraday rotator, polarizers on both sides of the Faraday rotator, and a holder for fixing the polarizer. In the optical isolator having the end faces of the Faraday rotator and the polarizers and the holders on both sides joined by soldering, the soldering end faces of the holder and the permanent magnet are subjected to a metallizing process,
An optical isolator provided with a portion to which solder is not attached without performing metallization at an edge end where an inner diameter portion and an outer diameter portion of the holder and an end surface of the permanent magnet overlap an outer peripheral portion.

For example, the Faraday rotator 1 and the polarizer 2b are
Then, the respective end faces are soldered through, and these are inserted into the permanent magnet 3, and one end of the polarizer 2b is soldered to the end face of the holder 4b. On the other hand, the end face of the permanent magnet 3 is also soldered to the end face of the holder 4b. At this time, at least the end surfaces to be soldered of the rotary holders 4a and 4b, the permanent magnets 3 and the spacers 9 are subjected to solder metallization (NI-Au alloy) treatment. The inner diameter portion 12 and the outer diameter portion 13 are not metallized, and the edge end 15 where the end surface of the permanent magnet 3 intersects with the outer peripheral surface is not metallized. As described above, since the portion to which the solder does not adhere is provided by not performing the metallization, it is possible to prevent the solder from protruding outside.

[Example] Hereinafter, an example of the present invention will be described in detail.

FIG. 1 is a configuration diagram for explaining an embodiment of the present invention. In this figure, the polarizer 2b, the spacer 9, and the Faraday rotator 1 are sequentially stacked on the rotary holder 4b, and a plate-like solder foil 7b is sandwiched between the components, and fixed by melting the solder. At this time, a plate-like solder foil 7c may be aligned between the rotary holder 4b and the permanent magnet 3, and each may be inserted and fixed from above the magnet. Here, the permanent magnet 3 is not magnetized so that the Faraday rotator 1 is easily mounted.

The rotating holders 4a and 4b, the permanent magnet 3 and the spacer 9
Metallization (Ni-Au alloy) treatment for solder bonding is performed on the end face. Metallization is applied to the rotating holder except for the inner diameter part 12 and the outer diameter part 13, and further, the end face and the outer circumference for the permanent magnet 3 are processed. Metallization is performed except for the edge end 15 where the surfaces intersect. Since the solder does not spread to a portion that has not been subjected to the metallization process, the presence of the portion that is not subjected to the metallization can prevent unnecessary protrusion of the solder. After each part is fixed,
The magnetic field applied to the Faraday rotator 1 can be obtained by magnetizing the permanent magnet 3.

With such a structure, it will be understood that the assembling method is much simpler than that of the prior art mounting method shown in FIG. 5, and unnecessary solder protrusion can be prevented.

FIG. 2 is another configuration diagram for explaining the embodiment of the present invention. In this case, the polarizer 2a is
Is fixed by a plate-shaped solder foil 7b. The holder is metallized with solder metallization (Ni-Au alloy) except for the inner diameter part 12 and the outer diameter part 13 of the rotary holder.

FIG. 3 is a perspective view of an optical isolator for explaining an embodiment of the present invention. Here, the rotating holder 4a is also fixed by the ring-shaped solder foil 7a. In order to join the rotary holder 4a, the solder foil 7a having a lower melting point than 7b and 7c is used. Even if the solder foil 7a is melted at the time of assembling, unnecessary protrusion of the solder can be prevented by the portion without metallization, and the dimension of the outer peripheral portion of the optical isolator does not change.

[Effects of the Invention] As is clear from the above description, when the structure of the present invention is used, the solder cannot protrude to the inner peripheral portion or the outer peripheral portion of the optical isolator, so that the outer diameter dimension does not change. It can be incorporated into a high-precision optical system device such as a semiconductor laser module without any problem. Therefore, a highly reliable optical isolator can be realized while further improving the assembly efficiency.

[Brief description of the drawings]

1 to 3 are structural views for explaining an embodiment of the present invention, and FIGS. 4 and 5 are structural views for explaining a conventional technique. 1; Faraday rotator, 2a, 2b; polarizer, 3; permanent magnet, 4a, 4b, 4a ', 4b'; rotating holder 5a, 5b, 5c; through hole, 6; outer case 7a, 7b, 7c; plate Solder foil 9; spacer, 10a, 10b; insertion opening, 12; inner diameter, 13; outer diameter, 15; magnet end

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 27/28

Claims (1)

(57) [Claims] 1. A Faraday rotator, a hollow permanent magnet containing the Faraday rotator, and polarizers on both sides of the Faraday rotator.
And an optical isolator having a holder for fixing the polarizer and joining the Faraday rotator and the respective end faces of the polarizer and the holder on both sides by soldering, wherein a soldered end face of the holder and the permanent magnet is provided. The metallization process is performed on the other hand, and on the other hand, the inner end portion and the outer diameter portion of the holder and the edge end where the end surface of the permanent magnet overlaps the outer peripheral portion are provided with a portion to which the solder is not attached without performing the metallization process. Characteristic optical isolator.