JPH04128715A - Optical modulator - Google Patents

Abstract

PURPOSE:To enable high-speed, wide-band optical modulation and optical deflection by composing the optical modulator of a magnetooptic control means and a polarizing prism made of a birefringent member which separates incident luminous flux into at least two linear polarized light components having mutually orthogonal planes of polarization and projects them. CONSTITUTION:The optical modulator consists of the polarizing prism 5 made of the birefringent member and a magnetic field producing means 6 which produces a magnetic field for controlling the polarizing prism 5 magnetically. A general Wollaston prism formed by cementing, for example, crystal body prisms P1 and P2 having mutually orthogonal optical axes (Z axis) is used as the polarizing prism 5. Both the prisms have birefringent effect and separates the transmitted incident light 1 into two pieces 2 and 3 of projection luminous flux which have a constant mutual separation angle theta from a projection surface 5a and also have mutually orthogonal planes of polarization. Therefore, plural projection light beams can be polarized and deflected under single control, which is suitable for an optical modulator for high-speed processing and the planes of polarization of the respective beams cross each other at right angles to cover a wide range. Consequently, the high-speed, wide-band optical modulation and optical deflection become possible.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an optical modulator that changes the intensity, phase, etc. of a light wave in response to a control signal applied from the outside, and is particularly applicable to the field of optical information processing. This invention relates to a prism-type optical modulator suitable for.

B1 Summary of the Invention The present invention is an improved magneto-optic light modulator,
By providing a magneto-optical control means that utilizes the Faraday effect and a polarizing prism made of a birefringent member that separates an incident light beam into at least two light beams whose polarization planes are perpendicular to each other and outputs the two, the so-called 1 beam This realizes an input multi-beam output optical modulator.

BACKGROUND OF THE INVENTION In the field of optoelectronics, including optical communications, measurement, data processing, etc., technology for modulating light plays an extremely important role. As is well known, among this type of optical modulation technology, there are electro-optic optical modulators, acousto-optic optical modulators, magneto-optical optical modulators, etc. as deflection control means, and these all use the action of external energy to control the incident light flux. The amount of deflection of the emitted light beam is controlled. For example, in the conventional magneto-optic light modulator shown in FIG.
The plane of polarization is rotated by utilizing the Faraday effect that occurs when the light passes through the magneto-optical medium 32 magnetized by the magnetic field forming means 35 consisting of the magneto-optical medium 32 and the magneto-optical medium 32.

That is, when light having a plane of polarization in the direction indicated by the arrow on the polarizer 33 travels through the magneto-optic medium 32, the linearly polarized light 31 is influenced by the magnetic field so that the plane of polarization is in the direction indicated by the arrow on the analyzer 34. It's rotating. The amount of rotation is approximately proportional to the strength of the magnetic field and the length of the magneto-optic medium 32, so for example, the strength of the magnetic field can be adjusted by controlling the amount of current flowing through the coil 35a, thereby controlling the amount of rotation of the plane of polarization. are doing.

Note that 36 is a compensating plate for aligning polarized light.

B0 Problems to be Solved by the Invention However, conventional optical modulators of this type, typified by the magneto-optic modulator shown in FIG.
It is a one-beam input one-beam output type optical modulation means, and in the future,
With the development of optical information processing technology, there has been a problem that it is extremely inadequate for use as a modulator for optical equipment that requires high-speed, broadband optical modulation and optical deflection.

The present invention was created in view of such problems,
The aim is to create a small and compact device that can be used with optical equipment that requires high-speed, broadband optical modulation and optical deflection.
An object of the present invention is to provide a beam input multi-beam output type optical modulator.

E9 Means for Solving the Problems In the present invention, in order to solve the above problems, in an optical modulator having a magneto-optical control device for controlling the polarization and deflection of an output light beam with respect to an input light beam, the magneto-optic control device comprises: Magneto-optical control means using the Faraday effect,
A polarizing prism made of a birefringent member separates the incident light beam into at least two linearly polarized light components whose polarization planes are orthogonal to each other and outputs the separated light beams.

F9 action - When a magnetic field is applied to the incident light flux of two linearly polarized lights and magnetic control is performed, the plane of polarization is rotated by the Faraday effect.

Furthermore, when the light passes through a polarizing prism made of a birefringent material, it is separated into at least two linearly polarized components whose polarization planes are orthogonal to each other. This makes it possible to perform deflection control in a so-called one beam input multiple beam output type.

G. Embodiments Hereinafter, embodiments of the optical modulator according to the present invention will be described with reference to the drawings.

First, to outline the optical modulator to which this embodiment is applied, this type of optical modulator has a magneto-optical control device that controls the polarization and deflection of an output beam with respect to an input beam. In FIG. 3 showing the conventional example described above, for example, the magneto-optic control device 30 is composed of a magneto-optic medium 32 and a magnetic field forming means 35 for forming a magnetic field for magnetically controlling the magneto-optic medium 32. ing.

Next, a prism type optical modulator according to a first embodiment of the present invention will be explained with reference to FIG.

Here, FIG. 1 is a configuration diagram of a prism type optical modulator, and 4
indicates a magneto-optical control device.

Specifically, the magneto-optical control device 4 includes a polarizing prism 5 made of a birefringent material, and a magnetic field forming means 6 for forming a magnetic field for magnetically controlling the polarizing prism 5. Note that 5a and 5b indicate an incident surface and an exit surface of the polarizing prism 5.

To explain in more detail, the polarizing prism 5 is a general-purpose Wallaston prism in which, for example, crystal prisms P1 and P2 whose optical axes (Z-axes) are orthogonal to each other are joined. All of these prisms have a birefringence effect, and the incident light 1 that passes therethrough is converted into two beams of light that are output from the output surface 5a with a constant separation angle θ and polarization planes that are perpendicular to each other. be.

Further, the magnetic field forming means 6 includes, for example, a coil 6a wound around the outer periphery of the crystal prism P1, and a power source 6b that supplies electric power to the coil 6a and controls the amount of current. It is also possible to arrange a magnetic material around the side of the crystal prism P1, and to control the intensity of the magnetic lines of force emitted by the magnetic material using an electric current or the like.

When the magneto-optical control device 4 having the above configuration is configured as described above,
The prism type optical modulator according to this embodiment includes a polarizing prism 5
Taking into account both the characteristics of 1 and the Faraday effect caused by the magnetic field forming means 6, it is possible to perform so-called one-beam input and multiple beam output type optical modulation. That is, when the incident light beam 1 of linearly polarized light passes through the polarizing prism 5, first, when passing through the crystal prism P1 that constitutes the polarizing prism 5, the plane of polarization of the incident light beam 1 is rotated under the influence of the magnetic field. The amount of rotation is controlled. Next, due to the birefringence effect of the polarizing prism 5, at least three beams of light 2 having mutually orthogonal polarization planes are emitted.
, 3. Arrows 2a and 3a indicate respective mutually orthogonal polarization planes of the emitted light 2.3.

As described above, in this embodiment, the magneto-optical control device 4 is composed of a polarizing prism 5 made of a birefringent material and a magnetic field forming means 6 for forming a magnetic field for magnetically controlling the polarizing prism 5. Therefore, it has both the functions of a conventional magneto-optic light modulator and a polarizing prism, and can obtain the polarization and deflection characteristics of one beam input and multiple beam output, and can also change the polarization of each output beam using external energy (magnetic field). surface can be controlled.

Next, a prism type optical modulator according to a second embodiment of the present invention will be explained with reference to FIG.

In this figure, 20 is the magneto-optical control device in this embodiment, and 25 is the conventional device 3 in FIG.
2, 25a is its entrance surface, 25b is its exit surface, and on the outer periphery of the magneto-optic medium 25, there is a magnetic field forming means 26 consisting of a coil 26a and a power source 26b, similar to the one 35 shown in FIG. is installed.

24 is Patent Application No. 1-31829 filed by the applicant.
The polarizing prism described in No. 0 has birefringence and is made of anisotropic crystal, and its entrance surface 24a is formed parallel to the optical axis (Z-axis) of the crystal shown by the arrow, and the An output surface 24b is formed with an angle α in a range of more than 0 degrees and less than 90 degrees with respect to the surface 24a.

The polarizing prism 24 is placed on the rear side of the magneto-optic medium 25, which is provided perpendicularly to the traveling direction of the light beam 21, that is, on the exit surface 2.
5b, with its entrance surface 24a being in close contact with it.

In the prism type optical modulator with the above configuration, the linearly polarized light beam 2
1 enters the magneto-optical control device 20, the plane of polarization is rotated due to the Faraday effect when it passes through the magneto-optic medium 25 magnetized by the magnetic field forming means 26. The amount of rotation of the plane of polarization depends on the strength of the magnetic field and the magneto-optic medium 25.
Since it is approximately proportional to the length of the light beam in the passing direction, it can be controlled by adjusting these.

Next, the light beam whose polarization plane has been rotated passes through the polarizing prism 24.
are incident perpendicularly to the incident surface 24a, that is, perpendicularly to the optical axis (Z axis), have a separation angle of θ due to the birefringence of the polarizing prism 24, and have polarization characteristics that differ by 90 degrees. The output light beams 22 and 23 are polarized. arrow 2
2a and 23a indicate mutually orthogonal polarization planes of the emitted lights 22 and 23, respectively.

Note that by changing the inclination angle α formed by the entrance surface 24a and the exit surface 24b, the separation angle θ of the output lights 22 and 23 can be variously changed.

In this way, in this embodiment, the magneto-optical control device 20 is
A magneto-optic medium 25 that allows the incident light beam 21 to pass from the front side to the rear side, and a light beam that is disposed on the rear side of the magneto-optic medium 25 and is made of an anisotropic crystal and is formed parallel to the optical axis. A birefringent polarizing prism 24 having an incident surface 24a and a light beam output surface 24b having an angle α in a range of more than 0 degrees but not more than 90 degrees with respect to the incident surface 24a.
and a magnetic field forming means 26 for forming a magnetic field for magnetically controlling the magneto-optic medium 25, so it has both the functions of a conventional magneto-optic modulator and a polarizing prism,
Polarization and deflection characteristics of beam input and output of multiple beams can be obtained, and the polarization plane of each output beam can be controlled by external energy (magnetic field).

In this embodiment, the magneto-optical medium 25 and the polarizing prism 24 are disposed in close contact with each other, but they may be disposed with an appropriate gap between them.

H1 Effects of the invention As explained above, the present invention is suitable for optical modulators for high-speed processing because it is possible to polarize a plurality of emitted light beams by controlling -, and moreover, the polarization planes of each beam are orthogonal to each other. Since it covers a wide band, it is extremely effective in constructing optical equipment for the optical information processing field, which requires high-speed, wide-band optical modulation and optical deflection.

Further, there is an effect that it becomes easier to reduce the size and weight of these optical devices.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a prism-type optical modulator according to a first embodiment of the present invention, FIG. 2 is a block diagram of a prism-type optical modulator according to a second embodiment of the present invention, and FIG. 3 is a conventional general FIG. 2 is a configuration diagram of a typical magneto-optic light modulator. 4゜20゜O...magneto-optical control device, 5゜24...polarizing prism, 25゜2...magneto-optical medium 6゜26゜34...magnetic field forming means (electromagnet) and one other person. Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) In an optical modulator having a magneto-optical control device that controls the polarization of an output light beam with respect to an incident light beam, the magneto-optic control device controls the input light beam into at least two components whose polarization planes are orthogonal to each other. An optical modulator comprising: a polarizing prism made of a birefringent member that separates and emits linearly polarized light; and a magnetic field forming means for forming a magnetic field for magnetically controlling the polarizing prism. (2) In an optical modulator having a magneto-optical control device that controls polarization and deflection of an output light beam with respect to an incident light beam, the magneto-optic control device includes a magneto-optic medium that allows the input light beam to pass from the front side to the rear side. and a light flux incident surface that is arranged on the rear side of this magneto-optic medium and is made of an anisotropic crystal and is formed parallel to the optical axis, and a light flux incident surface that extends over 0 degrees and 90 degrees with respect to this incident surface. A light comprising: a birefringent polarizing prism having a light beam exit surface with an angle not exceeding the range; and a magnetic field forming means for forming a magnetic field for magnetically controlling the magneto-optic medium. modulator.