JPS59121314A - Faraday rotor - Google Patents

Abstract

PURPOSE:To obviate the generation of an abnormal fluctuation in light level in the stage of changing over a Faraday's rotation angle by providing a closed electric path having about 45 deg. angle relative with the transmission direction of light so as to enclose a Faraday rotor. CONSTITUTION:A magnetic field in the direction opposite from the magnetic field that has been impressed till then by a means for changing the rotation angle in order to induce the effect of the Farady rotation in the opposite direction in a Faraday rotor 1 is impressed on said Faraday rotor which consists of a thin YIG plate, a means for impressing the magnetic field for changing the Farady's rotation angle and a closed electric circuit 3 and acts the effect of Faraday rotation in a certain direction. Induced current flows in the circuit 3 on account of a change in the magnetic flux generated in the stage of said changing over by which a magnetic field in the horizontal direction for the purpose of maintaining the magnetization in a satd. state is generated. The irregular fluctuation in the magnetic domain generated until the magnetic field attains the satd. state in the opposite direction through an unsatd. state is eliminated in the stage of changing over the rotation angle and the abnormal fluctuation in the light level in said stage is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a Faraday rotator used for winding, wintering, etc., and particularly to a means for preventing irregular fluctuations of magnetic domains within an element when switching the direction of Faraday rotation. Regarding a Faraday rotator with.

(2) Background of the technology In order to reverse the rotation angle of the Faraday rotator, the direction of the magnetic field applied to the direction of light transmission is reversed.

However, there is a problem with conventional magnetic field changing means of this type, and when changing it, the Faraday rotation angle becomes unstable, resulting in an undesirable phenomenon in which the optical level of the switch output fluctuates abnormally. There is a need for the development of technological means that can do this.

(3) Conventional technology and problems Conventionally, a Faraday rotator (YIG) has been used in optical switches, etc., but in order to reverse the Faraday rotation angle, it is necessary to reverse the direction of the magnetic field applied to the Faraday rotator. ing. During the reversal, the magnetization goes from a saturated state to zero, and then goes to a saturated state in the opposite direction. During such changes in the unsaturated state of magnetization, the magnetic domains within the two Faraday rotators fluctuate irregularly.

There is a problem in that the light is scattered, causing abnormal fluctuations in the light level.

(4) Purpose of the Invention The present invention was devised in view of the drawbacks of conventional Faraday rotators as described above, and its purpose is to provide a Faraday rotator that does not cause abnormal fluctuations in light level when switching the Faraday rotation angle. Our goal is to provide the following.

(5) Structure of the invention And, this object is a Faraday rotator that reverses the direction of the magnetic field applied in the light transmission direction when reversing the Faraday rotation direction, and the Faraday rotator is aligned in the light transmission direction.
This is achieved by surrounding the Faraday rotator with a closed circuit having an angle of at least 100 degrees or close to it.

(6) Examples of the invention The present invention will now be described in detail with reference to the accompanying drawings.

The accompanying drawings illustrate one embodiment of the invention. In this diagram,
1 is a Faraday rotator of the present invention, which consists of a YIGii plate 2 and a Faraday rotation angle changing magnetic field applying means for reversibly applying a magnetic field in a horizontal light transmission direction with respect to one drawing of this thin plate 2 (see the drawing). (not shown) and a closed circuit 3 surrounding the YIG thin plate 2 at an angle of 45 degrees or in the vicinity of the direction of transmission of the light. The magnetic field applying means for changing the Faraday rotation angle is, for example, an electromagnet having a semi-hard magnetic material in its core.

Next, the operation of the two Faraday rotators of the present invention will be explained.

In order to produce a Faraday rotation effect in the direction of the Faraday rotator 1, a magnetic field in the direction of the light transmission direction is applied to the Faraday rotation angle changing magnetic field applying means to the Faraday rotator 1. For example, when the magnetic field applying means is an electromagnet having a semi-hard magnetic material in its core.

Pulse power for switching is supplied to the electromagnet only when the magnetic field is reversed, and after the switching, a magnetic field is applied to the rotor 1 due to the self-holding function of the electromagnet.

In order to produce a Faraday rotation effect in the opposite direction, the Faraday rotation angle changing magnetic field applying means applies a magnetic field to the Faraday rotator 1, which is thus subjected to a Faraday rotation effect in the opposite direction. A magnetic field in the opposite direction to the magnetic field is generated within the Faraday rotator.

An induced current flows in the closed circuit 3 due to the change in magnetic flux that occurs during this switching, thereby generating a magnetic field in a direction transverse to the above-mentioned magnetic field. This magnetic field is intended to keep the magnetization being switched close to saturation.

Therefore, when the Faraday rotation angle is switched, irregular fluctuations in the magnetic domain that occur when the magnetic field passes through an unsaturated state and reaches a saturated state in the opposite direction are eliminated. In addition, abnormal fluctuations in the optical level at that time can be removed.

Such a relationship is maintained even when switching from the above-mentioned opposite Faraday rotation action to the above-mentioned directional Faraday rotation action.

(7) Effects of the invention As described above, according to the second invention, when the magnetic field for changing the Faraday rotation angle is switched, an induced magnetic field is generated in a direction transverse to the magnetic field, thereby suppressing irregular fluctuations of the magnetic domains within the element. Since it can be prevented, abnormal fluctuations in optical level can be eliminated.

[Brief explanation of the drawing]

The accompanying drawings illustrate one embodiment of the invention. In the figure, 1 is a Faraday rotator and 2 is a y+c thin plate. 3. It is a closed circuit.

Claims (1)

[Scope of Claims] +11 Faraday A Faraday rotator that reverses the direction of a magnetic field applied to the light transmission direction when reversing the direction of rotation, the Faraday rotator at 45 degrees or less with respect to the light transmission direction. A Faraday rotator characterized in that a closed current path forming an angle in the vicinity is provided surrounding the Faraday rotator. (2) The Faraday rotator according to claim 1, wherein the means for applying a magnetic field in the direction of transmission of the light is constituted by an electromagnet having a core of a semi-hard magnetic material.