JPH09146058A - Light switch - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a compact and highly reliable optical switch by controlling light (electromagnetic wave) having a wide range of wavelengths from ultraviolet rays to microwaves and having a large light quantity by a magnetic field or signal light. To do. A He-Ne laser 9 is used as a light source, and an input light I
_The laser light which is _O is made incident on the polarizer 2, the light emitted from the polarizer 2 is passed through the Faraday rotator 1 having the length L, the passed light is made incident on the analyzer 3 and emitted from the analyzer 3. The light is detected by the photomultiplier tube 10. A coil 4 for generating a magnetic field is wound around the Faraday rotator 1, and the intensity of the magnetic field is controlled by the current i flowing through the coil 4. Further, the polarization planes of the polarizer 2 and the analyzer 3 are made to coincide with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical or electromagnetic drive type optical switch capable of controlling the ratio of transmitted light to incident light by turning on / off a control light or an electromagnetic signal.

[0002]

2. Description of the Related Art A conventional optical switch is generally called a sector which irradiates a rotating plate having a hole with light and mechanically chops the light. FIG. 6 is an outline of the sector. FIG. 6A shows a conceptual diagram, and FIG. 6B shows a relationship diagram between light intensity and time. In FIG. 3A, the light source 13
A chopping light is provided by interposing a rotating body having a pinhole 12 (micropore) called a sector 11 for passing light between the lines connecting the and the detector 14. In the same figure (b), two pinholes 12 are provided diagonally on the rotary body of the same figure (a), and when the rotary body is rotated at a rotation speed of A (rpm), 30 / The output light I having a cycle of A (sec) arrives. This output light intensity is the same as the input light intensity (for non-divergent light). Naturally, this cycle can be changed by changing the number of rotations of the rotating body which is the sector 11, and the number of times the light is turned on / off per unit time, that is, the so-called switching frequency can be changed. Also, simply turning on the light
There is also a method of electrically turning on / off the light source itself as represented by a laser beam when it is limited to the off operation.

[0003]

However, although the method using the sector is simple in principle, a movable part such as a rotating body and a driving device for driving the moving part are required, and the device becomes large. Furthermore, it is difficult to rotate the rotating body at a high speed of MHz or the like, or to rotate the rotating body with high accuracy at a constant speed, and it is difficult to increase the reliability of the device due to wear of the rotating portion. On the other hand, the laser element has a very limited wavelength of light, and it is impossible to obtain an electromagnetic wave in a wide wavelength range from ultraviolet rays to microwaves. There is also a restriction on the amount of light.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a compact and highly reliable optical switch by controlling light (electromagnetic waves) having a wide range of wavelengths from ultraviolet rays to microwaves and having a large amount of light with a magnetic field or signal light.

[0005]

In order to achieve the above object, a polarizer that allows a predetermined electric vector component of light emitted from a light source to pass through, and a Faraday that rotates an electromagnetic vector of the light passing through the polarizer. It is configured to include a rotor and an analyzer that allows a predetermined electric vector component of light that has passed through the Faraday rotator to pass therethrough, and a structure for adding a magnetic field to the Faraday rotator is added. The structure that applies this magnetic field is preferably a coil that surrounds the Faraday rotator. YIG, Gd as crystals that are the base of the Faraday rotator
_{1.8 Bi 1. 2 Fe 5 O 12} , NiFe 2 O 4, Fe, C
o, Ni, YFeO ₃ , FeBO ₃ , FeF ₃ , Eu
It is effective to use any one of O, CdCr ₂ Se ₄ and Cd _0.55 Mn _0.45 Te.

Further, a polarizer that allows a predetermined electric vector component of the light emitted from the light source to pass therethrough, a Faraday rotator that rotates the electromagnetic vector of the light that has passed through the polarizer, and a predetermined Faraday rotator that has passed through the Faraday rotator. The Faraday rotator may be provided with a signal light source for adding signal light to the Faraday rotator.
This Faraday rotator consists of a crystal in which a small amount of magnetic atoms or ions are dissolved in the base crystal, and the d orbitals of magnetic atoms or ions are within the band gap of the crystal, and depending on the crystal field. Make it split into two energies. This base crystal is CdT
In the II-VI group compound semiconductor represented by e, the atom or ion having magnetism is preferably an iron group transition metal element represented by Mn. Further, it is effective to add Hg element as a magnetic impurity to the iron group transition metal element. It is preferable that the signal light has energy corresponding to the energy width of the two d orbits into which the signal light is split. In order to control the internal magnetic field of the Faraday rotator formed of the magnetic atoms or ions, a permanent magnet or a magnetic field generating coil may be provided as an external magnetic field.
The light emitted from the light source may be electromagnetic waves such as ultraviolet rays, visible light, infrared rays and microwaves.

Next, the operating principle of the present invention will be described. The Faraday effect, which is the basis of the present invention, means that when light passes through a medium placed in a magnetic field, the plane of polarization of incident light rotates. In the case of a paramagnetic material, the rotation angle θ is given by the following equation.

[0008]

## EQU1 ## θ = VHL (1) (V: Verdet constant, H: Applied magnetic field strength, L: Faraday rotator length) V is the Faraday rotator base material (in the case of the base material of claim 3)
In the base material described in claim 6, the value of V can be changed by applying light having a predetermined energy to the Faraday rotator. Therefore, in claim 1, the rotation angle θ is changed by H (applied magnetic field strength), and in claim 4, V is changed by the signal light (laser light),
By changing the rotation angle θ, output light can be turned on / off, or output light attenuated with respect to the input light can be emitted. When H is changed by the coil current, the relationship between H and the coil current follows the formula of H = kNi (k: constant, N: number of windings of coil, i: current flowing in coil). When the polarization planes of the polarizer and the analyzer are the same, by intermittently energizing the coil, a current is generated to generate a magnetic field that causes the rotation angle of the polarization plane of the light passing through the Faraday rotator to rotate by 90 °. Output light can be turned on and off. Moreover, the applied magnetic field strength H is changed by changing the magnitude of the coil current, and the rotation angle θ is changed.
The size of the output light (the size of the input light × cos θ) can be changed. In the case of changing V by signal light, an iron group transition metal element such as Mn (magnetic atom or ion) is added to a II-VI group compound semiconductor such as CdTe, which is a matrix as a Faraday rotator, It is a dilute magnetic alloy. This transition metal atom is generally affected by the crystal field (ligand field), and the d orbital is split into two (the splitting energy difference is Δ). Letting Eg be the forbidden band width of the host crystal, Δ << Eg and d of the transition metal element is within the forbidden band width.
When the orbital is split into two, for example, the Mn ion placed in a strong ligand field usually has a small number of unpaired electrons, and when irradiated with a signal light of Δ energy, it becomes two. Electronic transition occurs between the split d orbitals, the number of unpaired electrons increases, and the value of V increases. Therefore, the plane of polarization of the light passing through the Faraday rotator is rotated by 90 ° by the irradiation of the signal light, and the input light can be turned on / off. Further, the intensity of the output light can be changed by changing the intensity of the signal light.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the essential parts of a first embodiment of the present invention. The light source is a He-Ne laser 9 (helium / neon laser: 10 mW, λ = 1.15 μm),
The laser light which is the input light _IO is incident on the polarizer 2, the light emitted from the polarizer 2 is passed through the Faraday rotator 1 having the length L, and the passed light is incident on the analyzer 3 and the analyzer 3 The light emitted from the photomultiplier tube 10 is detected. Faraday rotator 1
A coil 4 for generating a magnetic field is wound around, and the strength of the magnetic field is controlled by a current i flowing through the coil 4. Further, the polarization planes of the polarizer 2 and the analyzer 3 are made to coincide with each other. As the Faraday rotator 1, a cylindrical YIG (Yttrium-Ion-Garnet, 3Y ₂ O ₃ 5Fe ₂ O ₃ ) having a radius of 4 mm and a length of 20 mm is used. The coil is formed by winding 20 turns of a copper wire having a diameter of 0.5 mm. Instead of YIG, Gd _1.8 Bi _1.2
Fe ₅ O ₁₂ , NiFe ₂ O ₄ , Fe, Co, Ni, YF
eO ₃ , FeBO ₃ , FeF ₃ , EuO, CdCr ₂ S
The same effect can be obtained by using e ₄ and Cd _0.55 Mn _0.45 Te.

FIG. 2 shows the relationship between the input light and the output light when a rectangular wave current is passed through the coil of the first embodiment. The upper side shows the coil current i, and the lower side shows the output light I. The input light I ₀ proportional to the coil current i is applied to the Faraday rotator 1 through the polarizer 2, and a current i of about 1.13 A is turned on / off at 1 sec intervals to the coil 4 which gives a magnetic field to the Faraday rotator 1. Then, the light emitted from the Faraday rotator 1 is applied to the photomultiplier tube 10 through the analyzer 3 and the intensity of the output light I is detected. When the external magnetic field is applied to the Faraday rotator 1 by the coil 4, the polarization plane of the light rotates and rotates 90 ° with respect to the polarization plane of the input light I ₀ , the light cannot pass through the analyzer 3, and the light is blocked. . When the current i is set to zero and the external magnetic field is eliminated, the input light I ₀ passes through the polarizer 2, the Faraday rotator 1 and the analyzer 3. An optical switch capable of turning on / off output light by turning on / off an external magnetic field is obtained.

FIG. 3 shows the relationship between the coil current and the output light when a sinusoidal current is passed through the coil of the first embodiment. The output light I ₀ becomes maximum when the current i is zero, and the output light I ₀ becomes zero when the current i is maximum. Also in this case, the optical switch is used as in FIG. FIG. 4 shows a block diagram of the essential parts of the second embodiment. The light source is a He-Ne laser 9 (helium / neon laser: 10 mW, λ = 1.15 μm), and the input light I
The laser light as ₀ is incident on the polarizer 2, the light emitted from the polarizer 2 is passed through the Faraday rotator 5, the passed light is incident on the analyzer 3, and the light emitted from the analyzer 3 is photoelectron-enhanced. Detect with double tube 10. The Faraday rotator 1 is a zinc-blende-type Mn-doped CdTe crystal body 5 (Cd _0.55 Mn _0.45 Te) obtained by doping a CdTe compound semiconductor with Mn, and has a cross-sectional area of about 10 mm × 10 mm and a length of 10 mm. . The permanent magnet 6 that gives the Faraday rotator 1 an external magnetic field of applied magnetic field strength H is an OP magnet (Co _0.75 Fe _2.25 O ₄ ) and has a holding force H _C of 15
It is 00 Oersted (0e). Of course, instead of the permanent magnet 6, a coil may generate a magnetic field. Polarizer 2
And the plane of polarization of the analyzer 3 are matched. Polarizer 2,
The Faraday rotator 1, the analyzer 3, and the permanent magnet 6 are housed in the same package 8, and an input light port, an output light port, and a signal light port (diameter of about 5 mm) are provided in the package 8, and a semiconductor laser is used as the signal light I _S. 7 (GaAlAs: 5W Pulse, λ = 1.15
The photomultiplier tube 10 is used as a detector of the output light I by using the emitted light from (.

FIG. 5 shows the relationship between input light and output light when the signal light of the second embodiment is pulsed light. With the magnetic field H applied by the permanent magnet 6, the signal light I _S (laser light) is turned on and off at intervals of 1 μs. Signal light I on the Faraday rotator 1
_When the laser light of _S is irradiated, the polarization plane of the input light I ₀ is rotated by 90 °, the output light I is not emitted from the analyzer 3, and the input light I _S is blocked. When there is no signal light I _S , the input light I ₀ passes through the polarizer 2, the Faraday rotator 1 and the analyzer 3.

In the first and second embodiments, the size of the apparatus excluding the light source and the photomultiplier tube can be reduced to several tens of μm, and the optical switch excluding the light source and the photomultiplier tube is used. The section can be inserted in the middle of a glass fiber for optical communication to turn on / off the light passing through the fiber. The rotation angle θ is changed by changing the magnitude of the coil current i and the intensity of the signal light I _S , and the intensity of the output light I = (intensity of the input light I _S ) × cos θ.
Accordingly, the intensity of the output light I can be changed. Therefore, it is possible to provide an optical switch in which the light intensity can be changed while turning the light on and off.

[0014]

According to the present invention, in a system composed of a polarizer-Faraday rotator-analyzer, the light incident on the polarizer (input light) is polarized by the Faraday rotator. The light emitted from the analyzer (output light) can be blocked by rotating 90 °. The polarization plane is rotated by applying a magnetic field to the Faraday rotator or irradiating it with signal light. Further, by rotating the polarization plane at a rotation angle other than 90 °, it is possible to obtain output light that is attenuated to an arbitrary intensity with respect to the input light. Since the input light can be turned on and off magnetically or optically without turning the light on and off by a mechanical mechanism, the structure can be made extremely small and the accuracy is high, and a wide range of electromagnetic waves from ultraviolet rays to microwaves can be used as the input light. Can be turned on and off. Further, since there is no mechanical mechanism, it is possible to reduce the size and increase the reliability of the device.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a first embodiment of the present invention.

FIG. 2 is a relationship diagram of input light and output light when a rectangular wave current is applied to the coil of the first embodiment.

FIG. 3 is a relational diagram of input light and output light when a sinusoidal current is applied to the coil of the first embodiment.

FIG. 4 is a configuration diagram of a main part of a second embodiment of the present invention.

FIG. 5 is a relationship diagram of input light and output light when the signal light of the second embodiment is pulsed light.

FIG. 6 is an outline of a sector, where (a) is a conceptual diagram and (b) is a relationship diagram between light intensity and time.

[Explanation of symbols]

 1 Faraday rotator 2 Polarizer 3 Analyzer 4 Coil 5 Mn-doped CdTe crystal 6 Permanent magnet 7 GaAlAs semiconductor laser 8 Package 9 He-Ne laser 10 Photomultiplier tube 11 Sector 12 Pinhole 13 Light source 14 Detector

Claims (10)

[Claims] 1. A polarizer for passing a predetermined electric vector component of light emitted from a light source, a Faraday rotator for rotating an electromagnetic vector of light passing through the polarizer, and a predetermined for light passing through the Faraday rotator. And an analyzer for passing the electric vector component of the above, and a structure for applying a magnetic field to the Faraday rotator is added. 2. The optical switch according to claim 1, wherein the structure for applying a magnetic field is a coil surrounding a Faraday rotator. 3. The material of the Faraday rotator is YIG,
Gd _1.8 Bi _1.2 Fe ₅ O ₁₂ , NiFe ₂ O ₄ , Fe,
Co, Ni, YFeO ₃ , FeBO ₃ , FeF ₃ , Eu
The optical switch according to claim 1, wherein the optical switch is any one of O, CdCr ₂ Se ₄ , and Cd _0.55 Mn _0.45 Te. 4. A polarizer for passing a predetermined electric vector component of light emitted from a light source, a Faraday rotator for rotating an electromagnetic vector of light passing through the polarizer, and a predetermined for light passing through the Faraday rotator. And an analyzer for passing the electric vector component of 1., and a signal light source for giving signal light to the Faraday rotator is added. 5. A Faraday rotator is a crystal in which a small amount of magnetic atoms or ions are dissolved in a host crystal, and the d orbitals of the magnetic atoms or ions are within the band gap of the crystal. The optical switch according to claim 4, wherein the optical switch is split into two energies by a crystal field. 6. The host crystal is represented by CdTe II.
6. The optical switch according to claim 5, wherein in the compound semiconductor of group VI, the atom or ion having magnetism is an iron group transition metal element represented by Mn. 7. The optical switch according to claim 6, wherein an Hg element is also added as a magnetic impurity. 8. The optical switch according to claim 4, wherein the signal light has energy corresponding to the energy width of two d orbits in which the signal light is split. 9. A permanent magnet or a magnetic field generating coil is provided as an external magnetic field in order to control the internal magnetic field of the Faraday rotator formed of magnetic atoms or ions. Light switch. 10. The optical switch according to claim 1, wherein the light is an electromagnetic wave containing any one of ultraviolet light, visible light, infrared light and microwave.