JPH01238611A - Optical isolator device - Google Patents

Abstract

PURPOSE:To obtain the optical isolator device which has high accuracy and high reliability and can be miniaturized by disposing and integrating the respective calcite prism sides of two polarizing prisms formed by combining glass prisms and the calcite prisms to a Faraday rotor. CONSTITUTION:An optical system consisting of the polarizing prism 5, the Faraday rotor 6 and the polarizing prism 7 is supported in a cantilever state in a device body 4 by a supporting member 9. The polarizing prisms 5 and 7 respectively have the glass prisms 12, 15 and the calcite prisms 13, 14 disposed to the Faraday rotor 6 side. Laser light is assumed to progress from the left side to the right side with respect to the prism 5 and the linearly polarized light is first maintained for the return light by the polarizing prism 7 even if the glass prism has double refractiveness after a high-temp. test; further, the return light arriving at the polarizing prism 5 through the Faraday rotor 6 is extinguished by the polarizing prism 5 and, therefore, the high isolation is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical isolator device used for the purpose of removing returning light to a semiconductor laser device, which is a type of laser light source, for example.

(Prior art) In recent years, optical communication systems and optical application equipment that use semiconductor laser devices as light sources have been used in various technical fields, and such systems and equipment include methods to remove light returning to the semiconductor laser device. Generally, various optical isolator devices are added for this purpose.

A conventional example of such an optical isolator device (Japanese Patent Laid-open No. 1983-
No. 148918, JP-A-62-148919)
As shown in the figure.

In the optical isolator device 30 shown in the figure, 31 is a protective case, 32 and 33 are a polarizer fixing device and an analyzer fixing device into which a polarizer 34 and an analyzer 35 are inserted and fixed,
A polarizer 34 and an analyzer 35 are installed on the inner surface of the optical axis.
V groove for 45 degree rotation 36.37 that allows 5 degree rotation
is provided parallel to the optical axis A. 38 and 39 are ring-shaped apertures provided inside the polarizer fixing device and analyzer fixing device 33 to block the transmitted light from the V-grooves 36 and 37. 40 has a Faraday rotation angle of 4
The 5 degree Faraday rotator is made of a YIG crystal, which is installed at an angle of 8 degrees with respect to the optical axis A, and its peripheral portion is fixed by a Faraday rotator fixing device 41. A permanent magnet 42 is disposed around the Faraday rotor fixing device 41 and is made of a samarium cobalt magnet.

Furthermore, regarding the device, the polarizer 35 is attached to the protective case 3.
A technique has also been disclosed in which the V-groove 36 is filled with a rubber-based adhesive having elasticity when inserted into the V-groove 1, and distortion of the polarizer 34 and the analyzer 35 can also be prevented by using this rubber-based adhesive.

However, in the optical isolator device 30 having the above configuration, the polarizer 34. Faraday rotator 40, analyzer 35
Because the parts are not in close contact with each other and are spaced apart, there is a possibility that dust may enter between the parts, causing optical loss of the laser beam, or that the entrance or exit surfaces of each part may become cloudy due to environmental conditions. There are problems in that it is expensive, lacks reliability, and increases the overall shape of the device, especially its length. Furthermore, in the case of the conventional device described above, the polarizer 34°, the Faraday rotator 40, and the analyzer 35 are each supported separately by the protective case 31 or the aperture 38°39, so the number of parts for the entire device is reduced. There is also the problem that there are too many.

Further, a lotion prism made of calcite is generally used for an optical isolator polarizer and analyzer. However, since the Rochon prism has good linear polarization degree and extinction ratio in only one direction, it is difficult to make a high-performance optical isolator.

(Problems to be Solved by the Invention) As is clear from the above-mentioned prior art, an optical isolator device that integrates a Faraday rotator and two polarizing prisms and has a sufficient structure in terms of reliability has not yet appeared. The current situation is that there is no such thing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical isolator device that can ensure sufficient reliability, has a small number of parts, and can be downsized.

[Structure of the Invention] (Means for Solving the Problem) The invention according to claim 1 provides an optical isolator device having a Faraday rotator and two polarizing prisms.
The two polarizing prisms are constructed by combining a glass prism and a calcite prism.

Further, the invention according to claim 2 is the configuration according to claim 1, in which calcite prisms are respectively arranged on the Faraday rotator sides of the two polarizing prisms.

Furthermore, the invention according to claim 3 provides a Faraday rotator and two
In an optical isolator device having two polarizing prisms, the Faraday rotator and the two polarizing prisms are integrated with an optical adhesive and are mounted in a cantilevered state within the device body.

(for production) The operation of each device having the above configuration will be explained below.

According to the invention as claimed in claim 1, since the two polarizing prisms constituting the optical isolator device are each constructed by a combination of a glass prism and a calcite prism, it is possible to determine which of the two directions of the prism the light is incident on. Since the extinction ratio and degree of linear polarization are good even when using calcite, it is possible to create an optical isolator with low cost and high performance compared to the conventional lotion prism that uses only calcite.

According to the invention described in claim 2, there are two on the Faraday rotator side.
Since the calcite prism is arranged in two polarizing prisms, even if the glass prism has birefringence, the polarization degree and extinction ratio for the returned light are good, and the reliability of this device can be improved.

Furthermore, according to the third aspect of the invention, the two polarizing prisms and the Faraday rotator are integrated with an optical adhesive, and there is no gap between them, so that the size can be reduced. In addition, since these are attached to the main body of the device in a cantilevered manner, there are fewer parts to attach, and the effect of distortion on the polarizing prisms can be reduced compared to a structure in which both polarizing prisms are fixed. .

(Example) Examples of the present invention will be described in detail below. First, the present invention will be explained in detail with reference to FIGS. 6 and 7.

FIG. 6 shows a polarizing prism 5 applied to the present invention, and FIG. 7 shows a conventional Rochon prism 50.

The polarizing prism 5 is constructed by combining a glass prism 12 and a calcite prism 13. That is,
This polarizing prism 5 is made of a glass prism 12 and a calcite prism 13 with a right triangular cross section whose optical axis is orthogonal to the direction in which light passes, as shown in FIG.
It is adhered by.

The lotion prism 50 has a calcite prism 51 with a right triangular cross section whose optical axis is oriented parallel to the direction of light passage, and a calcite prism 51 with a right triangular cross section whose optical axis is orthogonal to the direction of light passage as shown in FIG. A triangular calcite prism 51 is bonded with an optical adhesive H.

The characteristics of both the prisms 5 and 50 are shown in Table 1-1 below.
Shown in 2.

The method for measuring the degree of linear polarization and extinction ratio is the same as that shown in FIGS. 4 and 5, which will be described later.

As is clear from Table 1-1 and -2, in the lotion prism 50, the linear luminous intensity is the same as that of the calcite prism 51.
It is good when light enters from the side, but bad when the opposite is the case. On the other hand, the modified prism 5 has good linear polarization degree and extinction ratio regardless of whether the light enters from either the glass prism 12 side or the calcite prism 13 side.

From the above results, when using the conventional Rochon prism 50 as a polarizing prism of an optical isolator, it is necessary to limit the arrangement of the prism so as to improve isolation. Therefore, by using a prism by combining the glass prism 12 and the calcite prism 13 as in the present invention, a high-performance optical isolator can be manufactured without limiting the arrangement of the prisms. Also, since one side is made of glass, it has the advantage of being inexpensive to manufacture.

Next, an example device will be described based on the above principle.

The optical isolator device 1 shown in FIG.
A cylindrical device main body 4 provided with a polarizing prism 5. An optical system 8 consisting of a Faraday rotator 6 and a polarizing prism 7, a support member 9 that supports the optical system 8 in a cantilevered state, and a magnet disposed inside the device main body 4 and outside the optical system 8. 10.

In this embodiment, it is assumed that the laser beam travels from the left side to the right side of the prism 5 as shown in FIG. 1, and the left end surface of the polarizing prism 5 in the figure is referred to as the "incident end" , the right end surface is defined as the "outgoing end" in the following explanation. The same applies to the Faraday rotator 6 and the other polarizing prism 7.

The device main body 4 has a cylindrical shape with a bottom and is joined to an aluminum case 4a having a hole 2 formed in the center of the bottom plate thereof, and an opening portion of the case 4a on the opposite side to the hole 2,
and an aluminum case 4b having a hole 3 formed in its center.

As shown in FIG. 2, the polarizing prism 5 of the optical system 8 is bonded to a square incident-side glass plate 11 on which an anti-reflection film C1 is formed on the incident end side. It includes a glass prism 12 with a right triangular cross section and a calcite prism 13 with a right triangular cross section connected to the glass prism 12.

And a glass prism 12 and a calcite prism 13
The polarizing prism 5 has a symmetrical shape, and its hypotenuse portions are joined together, so that the polarizing prism 5 has a substantially cubic shape.

As shown in an enlarged view in FIG. 2(b), an antireflection film C is provided on the incident end side and the output end side of the Faraday rotator 6, respectively.
3 and C4 are formed, and the input end side of this Faraday rotator 6 is adhered to the output end of the polarizing prism 5 with an optical adhesive S1.

Further, the output end side of the Faraday rotator 6 is adhered to the entrance of the polarizing prism 7 to be used with an optical adhesive S2.

The polarizing prism 7 includes a calcite prism 14 with a right triangular cross section arranged on the Faraday rotator 6 side, and a glass prism 15 with a right triangular cross section arranged with its hypotenuses joined to the calcite prism 14. , an output-side glass plate 16 having an anti-reflection film C2 on the output end joined to the output end side of the glass prism 15 is provided.

And Prism 14 made by Calca Ui. glass prism 1
Reference numeral 6 indicates a symmetrical shape, so that the polarizing prism 7 has a substantially cubic shape.

Further, as shown in FIG. 2(a), the polarizing prism 7 is rotated, for example, by 45 degrees with respect to the polarizing prism 5, so that the isolation is maximized, and the Faraday rotator 6 is rotated.
is glued to.

The supporting member 9 is made of aluminum and has a semicircular shape as shown in FIG. The polarizing prism 5 is placed in the rectangular recess provided in the
The entrance side glass plate 11 and a part of the glass prism 12 are fitted.

That is, the integrated optical system 8 is supported by the support member 9 in a cantilevered manner with its optical axis aligned with the optical axis A.

Next, consideration of the high temperature reliability of the polarizing prism 5 (or 7) described above bonded to the support member 9 made of aluminum will be discussed.

A mode in which the glass prism 12 and the calcite prism 13 are supported by the aluminum support member 9 is as follows.
There are three embodiments shown in FIGS. 3(a), (b), and (c).

That is, as shown in FIG. 3(a), both the glass prism 12 and the calcite prism 13 are supported by the support member 9, and as shown in FIG. 3(b), a part of the glass prism 12 is supported. Figure 3 (C
), it is prohibited to support only a part of the calcite prism 13.

Tables 2 and 3 show the measurement results of the degree of linear polarization and extinction ratio after the high temperature test in these three embodiments.

As shown in FIG. 4, the device for measuring the degree of linear polarization is such that a laser beam from a laser light source 21 is incident on a polarizing prism 5 through a first optical fiber 22, and the light emitted from the polarizing prism 5 is converted into a Glan-Thompson polarizer. The light is guided to a light receiving element 25 via a prism 23 and a second optical fiber 24.

The extinction ratio measuring device, as shown in FIG. 5, has the same components as the device shown in FIG. This is what I did.

(Leaving space below) = 14- Table 2 Linear polarization degree Table 3 Extinction ratio In Tables 2 and 3, among the measurement results corresponding to each sample number, the upper row shows the results when the laser beam is applied from the glass prism side. The lower row shows the results measured by entering the laser beam from the calcite prism side.

As is clear from Table 2, the degree of linear polarization is good when the laser beam is incident from the glass prism side, and is significantly degraded when the opposite is the case.

Further, the extinction ratio is good when the laser beam is incident from the calcite prism side, and becomes significantly worse when the opposite is the case.

Next, the operation of the optical isolator device 1 having the above-mentioned configuration will be explained, taking also into account the measurement results shown in Tables 2 and 3, and mainly focusing on its structure.

According to this optical isolator device 1, Table 2.

As is clear from the measurement results in Table 3, it is considered that the glass prism has birefringence due to strain caused by adhesion between the polarizing prism and the support member during the high temperature test.

Therefore, according to the optical isolator device 1, even if the glass prism 12 has birefringence after a high-temperature test, the returning light shown in FIG. Since the returning light that reaches the polarizing prism 5 via the polarizing prism 5 is extinguished by the polarizing prism 5, a high absorption rate can be obtained.

In addition, since the optical system 8 is integrated using optical adhesives 31 and 32, there is no possibility of dust or the like getting in between them and clouding phenomenon, which also increases reliability. At the same time, the dimension in the direction of the optical axis A is also reduced, making it possible to downsize the device.

Furthermore, since the optical system 8 is cantilever-supported by the support member 9, parts for supporting the Faraday rotator 6 and the polarizing prism 7 are not required, and the number of parts can be reduced.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made within the scope of the invention.

[Effect of the invention] According to the present invention described in detail above, the following effects are achieved.

According to the first aspect of the invention, it is possible to provide an inexpensive and high-performance optical isolator device.

According to the invention described in claim 2, the glass prism 1B
- Even if the beam has birefringence due to distortion, it is possible to provide an optical isolator device that can improve isolation against returned light and contributes to improved reliability.

According to the invention as set forth in claim 3, it is possible to provide an optical isolator device that has high reliability, can be downsized, and can reduce the number of parts by integrating the optical system and supporting it in a cantilever manner. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention, and FIG.
) is an enlarged perspective view showing the optical system and support member of the same device, FIG. 2(b) is an enlarged side view of the optical system of the same device, and FIG. 3(a)
＞, (b), and (c) are perspective views showing three aspects of adhesion of the glass prism and calcite prism to the support member, respectively. Fig. 5 is a schematic configuration diagram showing an extinction ratio experimental device, Fig. 6 is a side view of a polarizing prism applied to the present invention, Fig. 7 is a side view of a conventional Rochon prism, and Fig. 8 is a cross-sectional view of the conventional device. It is. 1... Optical isolation, 4... Device body, 5.
...Polarizing prism, 6...Faraday rotator, 7...
- Polarizing prism, 9... Support member, 31, S2...
・Optical adhesive. Agent Patent Attorney Masayoshi Misawa Figure 2 (b) (C) Yu rJ Rii2'P (J ¥4 Figure 6 Figure 7 Procedural Amendments June 9, 1986)

Claims (3)

[Claims] (1) An optical isolator device having a Faraday rotator and two polarizing prisms, wherein the two polarizing prisms are configured by combining a glass prism and a calcite prism. (2) The optical isolator device according to claim 1, wherein calcite prisms are arranged on the Faraday rotator sides of the two polarizing prisms. (3) In an optical isolator device having a Faraday rotator and two polarizing prisms, the Faraday rotator and two polarizing prisms are integrated with an optical adhesive and are mounted in a cantilevered state within the device body. An optical isolator device characterized by: