JPH01200223A - Optical isolator and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical isolator used in optical communication systems, optical measuring instruments, etc., and more specifically, the present invention relates to an optical isolator used in optical communication systems, optical measuring instruments, etc. The present invention relates to an optical isolator in which all the joints are formed and integrated by soldering, and a method for manufacturing the same.

[Prior Art] An optical isolator is an irreversible optical device that allows light to pass in one direction but blocks light to pass in the opposite direction, and is used, for example, in optical communication systems that use a semiconductor laser as a light source. It is used to prevent laser light from returning to the light source side due to reflection.

The optical isolator is constructed by arranging a 45 degree Faraday rotator 12 between a polarizer lO and an analyzer 11, as shown in FIG. Here, the polarizer 10 and the analyzer 11 have a structure in which prisms 16 and 17 are mounted in prism holders 14 and 15, and the Faraday rotator 12 has a permanent magnet 18.
It has a structure in which a magneto-optical crystal 20 is mounted inside.

Such an optical isolator was assembled by applying adhesive to the joint surfaces of each component and fixing all components with the adhesive. The bonded locations are indicated by broken lines in FIG.

[Problem to be solved by the invention] However, the reliability of adhesives in devices such as optical isolators that require high-precision assembly has not yet been fully established.
There are problems such as thermal expansion, which is a major factor in reducing the reliability of assembled optical isolators.

The purpose of the present invention is to solve the problems of the prior art as described above, to reduce the change in optical properties due to ambient temperature fluctuations, to stabilize the optical properties over a long period of time, to extend the service life, and to improve reliability. An object of the present invention is to provide an optical isolator and a method for manufacturing the same, which can have high productivity and greatly improve productivity.

[Means for Solving the Problems] The present invention, which can achieve the above object, includes a magneto-optic crystal in a permanent magnet between a polarizer and an analyzer, both of which have a structure in which a prism is mounted in a prism holder. In an optical isolator in which a Faraday rotator equipped with a Faraday rotator is arranged and integrated, a metal film that can be soldered is formed on the parts where each component is connected to each other. be.

Here, the coupling between the prism holder and the prism and the coupling between the permanent magnet and the magneto-optical crystal can be achieved by, for example, forming a through hole in the prism holder and the permanent magnet that reaches from the outside to the inside, inserting solder, and passing the laser beam through the through hole. There is a method of irradiating and soldering.

It is desirable to connect the permanent magnet and the prism holder by forming a taper, groove, etc. on the outer periphery of one of them, and using this to solder from the outside.

Gold plating, for example, is suitable for forming a metal film that can be soldered onto the joints between the parts.

[Function] In the present invention, the connection between the prism holder and the prism and the connection between the permanent magnet and the magneto-optic crystal are all performed by soldering,
The polarizer, Faraday rotator, and analyzer made by these devices are also connected to each other and integrated by soldering.

Therefore, since the present invention does not use adhesives that have problems with reliability, various problems with adhesives such as outgassing from the adhesive and thermal expansion of the adhesive due to ambient temperature fluctuations can be avoided. No problems occur, the optical characteristics are stabilized, and the lifespan is extended.

[Embodiment] FIG. 1 is an exploded perspective view showing an embodiment of an optical isolator according to the present invention. This optical isolator, like the conventional one,
It has a structure in which a 45-degree Faraday rotator 34 is arranged between a polarizer 30 and an analyzer 32, and the polarizer 30 and analyzer 32 are coupled and integrated.

The Faraday rotator 34 is composed of a cylindrical permanent magnet 36 magnetized in the axial direction and a cylindrical magneto-optic crystal 38 mounted inside the permanent magnet 36 .

In the present invention, the permanent magnet 36 is formed with a through hole 40 extending from its outer peripheral surface to its inner peripheral surface, and the entire surface of the permanent magnet 36 and the outer peripheral surface of the magneto-optic crystal 38 (that is, excluding the optical surfaces at both ends) are It is gold plated. The permanent magnet 36 is made of, for example, a samarium-cobalt magnet, and the magneto-optic crystal is made of YIG (yttrium-iron-garnet) single crystal in the long wavelength region of 1.2 μm or more.

As shown in FIG. 2, the magneto-optic crystal 38 is inserted inside the permanent magnet 36 and connected by soldering. This soldering is performed by inserting solder 42 into the through hole 40 and irradiating a laser beam through the through hole 40. In this way, the Faraday rotator 34 is assembled.

Both the polarizer 30 and the analyzer 32 are mounted in a prism holder 44.
It has a structure in which prisms 46 and 47 are mounted inside 45. The prism holders 44 and 45 are both cylindrical, and have the same outer peripheral surface as the permanent magnet 36 on the outside, and the prism 46 on the inside.
．． 47 is inserted, and a tapered surface 50.51 is provided on the outer peripheral side of the surface facing the permanent magnet 36.
is formed, and a through hole 5 extending from the outer circumferential surface to the inner surface
2.53. Here, prism holder 4
4.45 is made of, for example, aluminum, and its entire surface is plated with gold. Also prism 46.47
is made of, for example, BK-7, and has gold plating on all four sides except for the optical surfaces on both sides.

Since the polarizer 30 and the analyzer 32 have the same structure as described above, only the polarizer 30 will be described below. Polarizer 3
0, the prism 46 is inserted into the rectangular through hole 48 of the prism holder 44 and coupled as shown in FIG. This bonding is achieved by inserting solder 56 into a through hole 52, irradiating a laser beam through the through hole 52, and melting the solder 56 by the heat, thereby bonding.

The polarizer 30, Faraday rotator 34, and analyzer 32 thus assembled are arranged in that order as shown in FIG. 4, and soldered using the tapered surfaces 50.degree. 51. This soldering is performed by placing solder 58 on the tapered surfaces 50 and 51 and irradiating the tapered surfaces with a laser beam.

As described above, according to the present invention, the optical isolator is assembled by connecting each component by soldering.

Note that the present invention is not limited to the above configuration. In the above embodiment, a tapered surface is formed around the entire circumference of the prism holder, but with such a structure, there is a risk that the solder will spread too much during soldering, so grooves are formed in multiple places and the Soldering may also be performed. The metal film formed on the bonding surface between each component is not limited to a gold plating film, and any metal film that is suitable for soldering may be used. The metal film is formed at the joint portion, and it is not necessary to form such a metal film on the outer circumferential surfaces of the prism holders 44 and 45, the outer circumferential surfaces of the permanent magnets 36, and the like. However, since masking and other processes become trivial, it is easier to manufacture these components by gold-plating them all except for the optical surfaces on both sides of the prism holder 46 and 47 and the optical surfaces on both sides of the magneto-optic crystal 38. It's easy.

[Effects of the Invention] As described above, the present invention has a structure in which a solderable metal film is formed at the joining portions of each component, and all component parts are integrated by soldering. Since there is no need to use adhesives that are problematic in terms of problems, the following excellent effects can be achieved.

First, outgassing from the adhesive due to increased ambient temperature is eliminated, extending the life of the component parts. Further, in the conventional technology, optical axis misalignment occurred due to thermal expansion of the adhesive due to fluctuations in ambient temperature, but in the present invention, such optical axis misalignment is suppressed as much as possible and optical characteristics are stabilized. Furthermore, since the life of solder is longer than that of adhesive, the characteristics of the optical isolator are stabilized over a long period of time. Furthermore, there is no need to wait for the adhesive to harden during production, greatly improving productivity.

In particular, when coupling a prism holder and a prism or a permanent magnet and a magneto-optical crystal, a through hole is formed in the prism holder and the permanent magnet from the outside to the inside, solder is inserted, and a laser beam is irradiated through the through hole. By employing a manufacturing method that involves soldering, these components can be assembled quickly and easily.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of the optical isolator according to the present invention, FIG. 2 is a sectional view of its Faraday rotator,
FIG. 3 is a sectional view of the polarizer, and FIG. 4 is an overall configuration diagram of the assembled optical isolator. Further, FIG. 5 is an explanatory diagram showing an example of the prior art. 30... Polarizer, 32... Analyzer, 34... Faraday rotator, 36... Permanent magnet, 38... Magneto-optic crystal, 40,52.53... Through hole, 44. 45・
... Prism holder, 46.47... Prism, 50
．． 51...Tapered surface. Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A Faraday rotator, in which a magneto-optic crystal is mounted in a permanent magnet, is disposed between a polarizer and an analyzer, both of which have a structure in which a prism is mounted in a prism holder, and are coupled and integrated. 1. An optical isolator characterized in that a solderable metal film is formed on the parts of the component parts where they are joined to each other, and all the parts are joined together by soldering. 2. The coupling between the prism holder and the prism and between the permanent magnet and the magneto-optical crystal is achieved by forming a through hole in the prism holder and the permanent magnet that reaches from the outside to the inside, inserting solder, and passing the laser beam through the through hole. 2. The method of manufacturing an optical isolator according to claim 1, further comprising irradiating and soldering.