JPS6271927A - Variable polarizing element - Google Patents

Abstract

PURPOSE:To obtain a large polarizing angle by reflecting light between a magnetized magnetic body and a film having a high reflection factor plural times. CONSTITUTION:Current I is made to flow into a coil 5 and a magnetic field is generated in the magnetic body 2 in the arrow direction e.g. Linearly polarized light 4a is irradiated from a part on which a metallic film 3 is not arranged to a glass body 1 at an angle approximately vertical to the surface of the magnetic body 2. The light made incident into the glass body 1 is repeatedly reflected and projected from the part of the glass body 1 on which the metallic film 3 is not arranged to the outside. The polarizing angle of the outgoing light 4b is a value obtained by multiplying a polarizing angle generated each reflection by the number of times of reflection, so that a large polarizing angle can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to a variable polarization element using the Kerr (err) effect.

[Conventional technology]

The magneto-optic effect is a phenomenon in which the polarization plane of light is rotated by a magnetic field, and includes the Faraday effect for transmitted light and the Kerr effect for reflected light.

Furthermore, the Kerr effect includes an electro-optic Kerr effect and a magneto-optic Kerr effect. The magneto-optical Kerr effect is a phenomenon in which when linearly polarized light is irradiated onto a magnetic material magnetized in the same direction, the reflected light becomes elliptically polarized.

There are optical isolators, circulators, magneto-optical recording, etc. that utilize this effect.

[Problem that the invention seeks to solve]

However, since the polarization angle obtained with the conventional variable light leakage element using the above effects is very small, there is a certain limit to the performance of devices such as circulators using this element.

The purpose of the present invention is to use the Kerr effect to achieve a large polarization angle of 1.
An object of the present invention is to provide a variable polarization element having a configuration in which the polarization can be adjusted.

``Structure of the Invention'' (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention uses a glass-like object made of a material with low light attenuation and having two parallel surfaces inside. a member having a magnetic material provided on one surface and a metal film provided on the other surface, and a means for applying a magnetic field to the magnetic material, and the light linearly polarized from a part of the glass-like object is provided. is incident, this light is reflected multiple times between the magnetic material and the metal film, and is extracted from another part of the glass-like object.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram showing an example of the external configuration of a variable polarizing element according to the present invention, and FIG. 2 is a sectional view of FIG. 1. In FIGS. 1 and 2, reference numeral 1 indicates an object made of a material that attenuates light less, such as optical glass. This is referred to as a glass body in this specification. This glass body 1 has a structure having two parallel surfaces. 2 is a magnetic material, and is provided on one surface of the glass body 1. A metal film 3 is provided on the other surface of the glass body 1. This metal film 3 has a high light reflectance and is made of a non-magnetic material. 5 is a coil. In FIG. 1, the glass body 1 etc. are drawn separated from the coil 5, but this is done to make it easier to understand the structure of each part, and in reality, the glass body etc. are arranged inside the coil 5.

The variable polarization element of FIGS. 1 and 2 configured as described above operates as follows.

A current ■ is passed through the coil 5 to generate a magnetic field, and a magnetic field is generated in the magnetic body 2 in FIG. 2, for example, in the direction of the arrow.

Linearly polarized light 4a is irradiated onto the glass body 1 from a portion where the metal film 3 is not placed at an angle close to perpendicular to the surface of the magnetic body 2. The light incident on the glass body 1 is reflected many times between the surface on which the magnetic material 2 is disposed and the surface on which the metal film 3 is disposed, as shown in FIG. Then, it exits from the portion of the glass body 10 where the metal film 3 is not disposed. The polarization angle of the emitted light 4b is the number of reflections times the polarization angle produced by one reflection. That is, a large polarization angle can be achieved.

Here, since the polarization angle depends on the strength of magnetization of the component in the same direction as the traveling direction of the light, it is preferable to use a perpendicular magnetization film as the magnetic body 2 in FIG.

In this way, in the device shown in Figure 1, the strength of magnetization of the magnetic body 2 can be controlled by controlling the magnitude of the current 1 flowing through the coil 5, and as a result, the polarization angle can be varied. can.

FIG. 3 is a diagram showing another external configuration example of the variable polarizing element according to the present invention, and FIG. 4 is a sectional view of FIG. 3. In FIGS. 3 and 4, each component is the same as in FIG. 1, but the thickness of the glass body 1 and the magnetization characteristics of the magnetic body 2 are different. In FIGS. 3 and 4, the thickness of the glass body 1 is thinner than that in FIG. 1, and the magnetic body 2 uses an in-plane magnetization film as opposed to the perpendicular magnetization film in FIG.

In FIGS. 3 and 4, since an in-plane magnetized film is used as the magnetic body 2, the light 4a is incident on the glass body 1 at an angle relatively parallel to the magnetic body 2. Then, the axial direction of this in-plane magnetized film, which is easy to magnetize, is made substantially perpendicular to the direction in which light travels. By passing a current through the coil 5, the magnetization perpendicular to the traveling direction of the light is rotated within the plane, and the magnitude of the polarization angle is made variable.

In the present invention, if permalloy with good frequency characteristics is used for the ferromagnetic film, high-speed light leakage angle control can be performed.

C. Effects of the Present Invention As described above, according to the present invention, the following effects can be obtained.

In the present invention, light is reflected multiple times between a magnetized magnetic body and a film with high reflectance. Therefore, it is possible to polarize the light to be twice as many times as the number of reflections than the polarization angle obtained by - times of reflection, so a large polarization angle can be obtained.
Moreover, by changing the strength of the magnetic field, the polarization angle can be varied. Furthermore, since polarization is caused by a ferromagnetic film, the energy required to maintain the polarization angle is, in principle, zero.

The variable polarization element shown in Figure 1 uses a perpendicular magnetization film, so it is not suitable for changing the polarization angle in an analog manner.
Since a large polarization angle can be obtained, it can be used for switching purposes. The embodiment shown in FIG. 3 is the opposite; although the polarization angle is not as large as that shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the external configuration of the variable polarizing element according to the present invention, FIG. 2 is a sectional view of FIG. 1, and FIG. 3 is a diagram showing another example of the external configuration of the variable polarizing element according to the present invention. The fourth factor is the sectional view of FIG. 1... Glass body, 2... Magnetic material, 3... Metal film,
5...Coil. Figure 1 Figure 2

Claims (1)

[Claims] A glass-like object made of a substance with low light attenuation and having two parallel surfaces is sandwiched therein, a magnetic material is provided on one surface, and a metal film is provided on the other surface. a member, and means for applying a magnetic field to the magnetic body, and linearly polarized light is incident from a part of the glass-like object,
A variable polarizing element configured such that this light is reflected multiple times between the magnetic material and the metal film and is extracted from another part of the glass-like object.