JPH0429112A - Magneto-optical devices and optical isolators - Google Patents

Abstract

PURPOSE:To prevent the magnetooptic device from being deteriorated in characteristics owing to variation of an external magnetic field applied to a magnetooptic medium by obtaining the accurate value of a magnetic field applied perpendicularly to the closed circuit of a closed circuit part consisting of quantum thin lines from the value of magnetic resistance and varying the value of the magnetic field to a desired value. CONSTITUTION:When the external magnetic field which is applied to the magnetooptic medium varies, the resistance value of the closed circuit part 4 consisting of quantum thin lines vibrates, so large variation in the resistance value of the closed circuit part 4 due to the fine variation of the external magnetic field is obtained and the value of the external magnetic field applied to the magnetooptic medium is found from the value of the resistance of the closed circuit part 4; and a means 11 which controls the current of the electromagnet 5 for applying the external magnetic field easily controls the external magnetic field to a constant value. Consequently, the magnetoopticl device which has no deterioration in characteristics due to the variation of the external magnetic field applied to the magnetooptic medium is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magneto-optical device and an optical isolator used in optical recording, optical communication, optical measurement, etc.

Conventional technology As a conventional technology, an optical isolator for visible light using Zn5e as a magneto-optic medium was developed by Abride Optics (
APPLIE [l 0PTIC5) V O1,16
, No.6.1) p., 1584-1587 (1977
) has been reported. An optical isolator is a 4-wire optical isolator between a polarizer and an analyzer whose transmission polarization directions of light are arranged at 46 degrees from each other.
A magneto-optical medium with a Faraday rotation angle of 5 deg was placed (configured), and the light in the forward direction that passed through the polarizer received a Farabou rotation of 45 deg when passing through the magneto-optic medium. The light that has passed through the analyzer is rotated by 145 degrees when passing through the magneto-optic medium due to the non-reciprocity of the Faraday effect of the magneto-optic medium, and the light is perpendicular to the transmitted polarization direction of the polarizer and cannot be transmitted. It is something that you have.

The Faraday rotation angle θ of Zn5e is expressed as θ=VBd1 is the Verdet constant, B is the external magnetic field in the propagation direction of light, and d is the optical path length in the magneto-optic medium. In this example, the Verdet constant V=8 at the wavelength λ=8328A of the light source used. 7*
10-”deg/ (cm*G), d=0.432c
An external magnetic field B is applied to obtain a Faraday rotation of 42.35 deg in m, and the transmission polarization directions of the polarizer and analyzer are set to be 42.35 deg.

Problem to be Solved by the Invention As shown in the prior art, the Faraday rotation angle θ is θ=V
Since it is given by Bd, when the value of the external magnetic field B to be applied changes, θ changes, leading to deterioration of the isolation ratio.

For example, V=6. 7* 100-3d
e/(cm*G), Zn5 with d=0°432cm
When applying an external magnetic field of 15547G to obtain a Faraday rotation angle of 45 degrees at e, the Faraday rotation angle is 46 degrees with only a 2% change in the external magnetic field.
It becomes eg.

The transmission polarization directions of the polarizer and analyzer are fixed at 45deg from each other, and the initial isolation ratio is -35dB.
When obtained, the Faraday rotation angle of the magneto-optic medium is 45
The isolation ratio deteriorated to -32 dB when the signal was shifted by 1 degree from 1 degree. The present invention prevents characteristic deterioration of a magneto-optical device due to fluctuations in an external magnetic field applied to a magneto-optic medium. Further, in the optical isolator, deterioration of the isolation ratio due to fluctuations in the external magnetic field applied to the magneto-optic medium is prevented.

Means for Solving the Problems The present invention provides a magneto-optic medium that constitutes a closed circuit section consisting of a light irradiation section and a quantum wire, in order to prevent characteristic deterioration of a magneto-optical device due to fluctuations in an external magnetic field applied to the magneto-optic medium. , means for applying a magnetic field perpendicularly to a closed circuit of the closed circuit section made of the quantum wire for magnetizing the magneto-optic medium, and means for measuring the magnetic resistance of the closed circuit made of the quantum wire, It is possible to change the value of the magnetic field to a desired value by obtaining an accurate value of the magnetic field applied perpendicularly to the closed circuit of the closed circuit section made of the quantum wire from the value of magnetic resistance. This paper proposes a magneto-optical device characterized by: In addition, in the optical isolator, in order to prevent deterioration of the isolation ratio due to fluctuations in the external magnetic field applied to the magneto-optic medium, the present invention includes a polarizer, an analyzer having a polarization transmission angle of 45 degrees with respect to the polarizer, and a light irradiation device. a magneto-optical medium constituting a closed circuit section made of a quantum wire and a quantum wire, a means for applying a magnetic field perpendicularly to the closed circuit of the closed circuit section made of the quantum wire for magnetizing the magneto-optic body;
and a means for measuring the magnetic resistance of the closed circuit made of the quantum wire, and obtaining an accurate value of the magnetic field applied perpendicularly to the closed circuit of the closed circuit portion made of the quantum wire from the value of the magnetic resistance. The value of the magnetic field is always accurately 45 deg.
This paper proposes an optical isolator that is characterized by providing a Faraday rotation of .

Function: The magneto-optical device of the present invention changes the value of an external magnetic field applied perpendicularly to the closed circuit section made of quantum wires made of a magneto-optic medium using the Ahranov-Bohm effect. It can be known as the oscillating magnetic resistance value. In other words, a small change in the external magnetic field can be observed as a large change in magnetoresistance than a normal change in magnetoresistance value. By reading changes in the external magnetic field from this magnetoresistance change and feeding it back to the control of the external magnetic field application mechanism, the external magnetic field applied to the light irradiation part of the magneto-optical device of the present invention is kept constant and the characteristics of the magneto-optical device are prevented from deteriorating. It's a spider. Further, the optical isolator of the present invention has the same effect as the magneto-optical device of the present invention to keep the external magnetic field applied to the light irradiation part constant and prevent deterioration of the Eitz-Rayon ratio.

Embodiment A schematic diagram of an embodiment of the magneto-optical device of the present invention is shown in FIG. Zn is deposited as a magneto-optical medium on a fluorinated aluminum substrate 1.
5e2 is grown by the MOVPE method, and the closed circuit part 4 made of the light irradiation part 3 and the quantum wire is formed by ion beam processing. Electromagnets 5 are placed on both sides of the magneto-optic medium as an example of means for applying an external magnetic field to the magneto-optic medium. By passing a constant current through the current input and output ends 6.7 of the closed circuit section 4 made of quantum wire and measuring the voltage between the voltage measurement ends 8.9,
Means 10 for measuring the resistance of the closed circuit section 4 made of quantum wires
It has means 11 for determining the value of an external magnetic field to be applied to the magneto-optic medium from the resistance value of the closed circuit section 4 made of the quantum wire obtained and controlling the current of the electromagnet 5 that applies the external magnetic field.

When the external magnetic field applied to the magneto-optic medium changes, the resistance value of the closed circuit section 4 made of quantum wires oscillates. Therefore, the resistance value of the closed circuit section 4 made of quantum wires changes in response to a small change in the external magnetic field. is obtained, the value of the external magnetic field to be applied to the magneto-optic medium is determined from the resistance value of the closed circuit section 4 made of quantum wires, and the external magnetic field is easily kept constant by the means 11 for controlling the current of the electromagnet 5 that applies the external magnetic field. It was possible to control the value to a value of , and prevent deterioration of the characteristics of the magneto-optical device.

Note that optical switches, optical circulators, optical isolators, etc. may be constructed by combining optical components such as polarizers and lenses with the schematic diagram of the magneto-optical device shown in FIG. The means for providing may be other than this example.

FIG. 2 shows a schematic diagram of the optical isolator of the present invention. Between the polarizer 20 and the analyzer 21 with the transmission polarization direction of light set at 45 degrees, Zn5e2 is grown as a magneto-optical medium on the fluorinated substrate 1 by the MOVPE method, and Faraday rotation of 45 degrees is performed using a desired external magnetic field. A light irradiation section 3 processed into an optical waveguide 22 having a waveguide length corresponding to an angle, and a closed circuit section 4 made of a Zn5e2 quantum wire formed by ion beam processing are provided. Electromagnets 5 are placed on both sides of the magneto-optic medium as an example of means for applying an external magnetic field to the magneto-optic medium. The resistance of the closed circuit section 4 made of quantum wires is measured by passing a constant current through the current input/output ends 6.7 of the closed circuit section 4 made of quantum wires and measuring the voltage between the voltage measurement terminals 8.9. It has means 11 for determining the value of an external magnetic field to be applied to the magneto-optic medium from the resistance value of the means 10 and the closed circuit section 4 made of the obtained quantum wire, and controlling the current of the electromagnet 5 that applies the external magnetic field. When the external magnetic field applied to the magneto-optic medium changes, the Faraday rotation angle of the light guided through the optical waveguide 22 deviates from 45 degrees, and at the same time, the resistance value of the closed circuit section 4 made of quantum wire changes. Since the resistance value of the closed circuit section 4 made of quantum wires oscillates in response to changes in the external magnetic field, a large change in the resistance value of the closed circuit section 4 made of quantum wires can be obtained in response to a slight change in the external magnetic field. The value of the external magnetic field applied to the magneto-optical medium is determined from the resistance value of the closed circuit section 4 made of quantum wires, and the external magnetic field is easily controlled to a constant value by means 11 for controlling the current of the electromagnet 5 that applies the external magnetic field. This made it possible to prevent deterioration of the isolation ratio of the optical isolator.

Effects of the Invention By the magneto-optical device of the present invention, a magneto-optical device was obtained that does not suffer from characteristic deterioration due to fluctuations in the external magnetic field applied to the magneto-optic medium. By using the optical isolator of the present invention, an optical isolator which does not suffer from deterioration of the Eysle/yaw/ratio due to fluctuations in the external magnetic field applied to the magneto-optic medium was obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a magneto-optical device according to an embodiment of the present invention, and FIG.
The figure is a schematic diagram of an optical isolator according to an embodiment of the present invention. 2... Zn5e, 3... Light irradiation part, 4... Closed circuit part, 6... Current input end, 7... Current output end, 8, 9
...Voltage measurement end.

Claims (2)

[Claims] (1) a magneto-optical medium constituting a closed circuit section made of a light irradiation section and a quantum wire, a means for applying a magnetic field perpendicularly to the closed circuit of the closed circuit section made of the quantum wire for magnetizing the magneto-optic medium; and means for measuring the magnetic resistance of the closed circuit made of the quantum wire, and obtaining an accurate value of the magnetic field applied perpendicularly to the closed circuit of the closed circuit portion made of the quantum wire from the value of the magnetic resistance. A magneto-optical device characterized in that the value of the magnetic field can be changed to a desired value. (2) a polarizer, an analyzer having a polarization transmission angle of 45 degrees with respect to the polarizer, a magneto-optic medium constituting a closed circuit section consisting of a light irradiation section and a quantum wire, and the quantum for magnetizing the magneto-optical body. means for applying a magnetic field perpendicularly to a closed circuit of a closed circuit portion made of a thin wire, and means for measuring magnetic resistance of the closed circuit made of the quantum wire, and the closed circuit made of the quantum wire is determined based on the value of the magnetic resistance. An optical isolator characterized in that the value of the magnetic field is always accurately given a Faraday rotation of 45 degrees by obtaining an accurate value of the magnetic field applied perpendicularly to the closed circuit of the optical isolator.