JPH0369901A - fiber optic polarizer - 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 fiber polarizer, which is composed of an optical fiber and allows only light having a specific polarization component to pass therethrough.

[Prior art] When guiding laser light through an optical fiber, such as an optical modulator or optical isolator that operates effectively only on light with a specific polarization direction, the light emitted from the optical fiber or the light transmitted through the optical fiber is It needs to be linearly polarized light with a specific polarization direction.

Conventionally, in order to linearly polarize light transmitted through an optical fiber, a method has been used in which an optical fiber 81 is cut and a polarizer 82 is inserted between the two, as shown in FIG.

[Problems to be Solved by the Invention] However, in the method of cutting an optical fiber and inserting a polarizer therebetween, diffraction and reflection of light occur at the cut portion of the optical fiber, resulting in increased loss.

Furthermore, the mechanical strength of the cut portion is reduced and the axis of the optical fiber is misaligned, resulting in a reduction in reliability.

The present invention has been made to solve the above-mentioned problems, and it propagates through a polarization-maintaining fiber by removing a part of the cladding of the polarization-maintaining fiber and loading a metal film thereon. The object of the present invention is to provide an optical fiber type polarizer which is characterized by attenuating one of two eigenmodes and converting it into linearly polarized light, and which has no loss and is highly reliable.

[Means for Solving the Problem] In order to achieve this object, the optical fiber polarizer of the present invention has a polarization plane that is parallel to the vibration direction of the electric field of one of the two orthogonal eigenmodes propagating through the polarization-maintaining fiber. In this direction, a part of the cladding of the polarization-preserving fiber is removed, and a metal film is provided on the removed part.

[Operation] The eigenmode in which the electric field vibrates in a direction parallel to the film surface of the metal film of the optical fiber polarizer of the present invention having the above configuration is not attenuated by the metal film. On the other hand, the eigenmode in which the magnetic field vibrates parallel to the surface of the metal film is attenuated by the metal film. Therefore, of the two eigenmodes propagating through the polarization-maintaining fiber, only the mode in which the direction of vibration of the electric field is parallel to the film surface of the metal film passes through, so that linearly polarized light is obtained.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the main parts of an embodiment of the optical fiber polarizer of the present invention, and the optical fiber polarizer 10 is composed of a polarization maintaining fiber 11 and a metal film 12. The polarization maintaining fiber 11 has a core 13°, a cladding 14, and a core 1
The core 13 is composed of an elliptical jacket 15 and a support 16, which apply anisotropic strain to the core 13 and change the curvature ratio in the perpendicular direction of the core 13 by a photoelastic effect. In this optical fiber, the long axis or short axis of the elliptical jacket 15 becomes the unique polarization axis, and the linearly polarized light component incident in this direction is preserved. In the configuration example shown in FIG. 1, a part of the cladding 14 is removed in a direction parallel to the long sleeve of the elliptical jacket 15, and a metal film 12 is provided thereon.

Of the two eigenmodes propagating through the optical fiber 10, the mode in which the electric field oscillates in a direction parallel to the long axis of the elliptical jacket 15 is not attenuated by the metal film 12. However, the electric field oscillates parallel to the short axis of the elliptical jacket 15,
The eigenmode in which the magnetic field vibrates parallel to the film surface of the metal film 12 is attenuated by the metal film 12 and cannot be propagated through the polarizer 10 . As a result, linearly polarized light in which the electric field oscillates parallel to the long sleeve of the elliptical jacket 15 is obtained.

Next, a method for manufacturing an optical fiber polarizer will be described with reference to FIG. As shown in FIG. 2(a), the polarization maintaining fiber 11
A photoresist 21 is applied in advance to the end surface 20 of. Next, parts of the cladding 14, the elliptical jacket 15, and the support 16 are removed using a diamond blade or the like in a direction parallel to the long axis a of the elliptical jacket 15, as shown in 2e (b). Here, A4. A metal film 25 such as Au is formed. Thereafter, an optical fiber polarizer can be formed by removing the photoresist as shown in FIG. 2(c). However, even if a metal film is attached around the support 16, the light is confined in the core 13 and the cladding 14, so there is no effect.

Further, as shown in FIG. 3(a), the oval jacket 15 is removed in a direction parallel to the long sleeves at a position pre-separated from the core 13. Thereafter, the vicinity of the end face may be etched using hydrofluoric acid or the like to remove the cladding 14 to a required thickness as shown in FIG. 3(b). Thereby, the removal amount of the cladding 14 can be controlled with high precision.

The present invention is not limited to the embodiments detailed above, and various changes can be made without departing from the spirit thereof.

For example, in this embodiment, a part of the cladding 14 was removed in a direction parallel to the long sleeve of the elliptical jacket, but as shown in FIG. A membrane 25 may also be provided. Furthermore, not only one side of the cladding but also both sides of the cladding 13 may be removed and the metal film 25 provided thereon as shown in FIG. It is not necessary to remove all of one side of the elliptical jacket 15 and the support 16, but as shown in FIG. 6, a part of them is removed by means such as ion beam etching, and the cladding 14 is removed parallel to the long sleeve of the elliptical jacket 15. You may. Of course, as shown in FIG. 2, one side of the elliptical jacket 15 and support 16 may be completely removed by ion beam etching, sputter etching, plasma etching, or the like. Furthermore, mechanical processing using the above-mentioned diamond blade, chemical etching using hydrofluoric acid, ion etching, etc.
A portion of the cladding may be removed using a combination of dry etching such as beam etching.

In FIG. 1, the end face of the fiber is processed, but the middle of the optical fiber may be processed in the same way as shown in FIG. Furthermore, the groove portion may be filled with ultraviolet curing resin or the like.

The thickness of the metal film is not particularly limited, as long as it is thick enough to prevent the electric field of light from leaking to the outside of the metal film.

Further, a protective layer or the like may be further provided on the metal film.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, a part of the cladding of a polarization-maintaining fiber is connected to one of the two orthogonal eigenmodes propagating through the polarization-maintaining fiber. Since the electric field is removed in a direction parallel to the vibration direction of the electric field and a metal film is loaded on top of it, the mode in which the electric field vibrates in a direction perpendicular to the metal film is attenuated by the metal film. Therefore, linearly polarized light in which the electric field oscillates parallel to the metal film surface is obtained. As a result, linearly polarized light cannot be obtained without inserting a polarizer between optical fibers, so it is possible to realize a highly reliable optical fiber polarizer without loss. Furthermore, when connecting an optical fiber to an optical modulator or the like, there is no need to insert a polarizer into the connection part, so connection loss can be reduced.

[Brief explanation of drawings]

1 to 8 show embodiments embodying the present invention. FIG. 1 is a block diagram of an optical fiber polarizer to which this embodiment is applied, and FIG. FIG. 3 is an explanatory diagram showing a method for manufacturing a polarizer, FIG. 3 is an explanatory diagram showing another method for manufacturing the optical fiber polarizer, and FIGS. 4 to 6 show other embodiments of the optical fiber polarizer. 7 is a perspective view showing another embodiment of the optical fiber, and FIG. 8 is a sectional view showing another embodiment of the optical fiber.
FIG. 2 is an explanatory diagram showing a means for obtaining linearly polarized light by combining a conventional optical fiber and a polarizer. In the figure, 10 is an optical fiber polarizer, 11 is a polarization maintaining fiber, 12 is a metal film, 13 is a core, 14 is a cladding, 1
5 is an oval jacket and 16 is a support.

Claims (1)

[Claims] 1. In a polarization-maintaining fiber in which two orthogonal polarization eigenmodes propagate, a part of the cladding is removed in a direction substantially parallel to the vibration direction of the electric field of one eigenmode, and a metal film is formed in the removed part. An optical fiber polarizer characterized by being provided with.