JPH0534714A - Optical switch - Google Patents

Abstract

PURPOSE:To provide 1X2 and 2X2 optical switches with the liquid crystals alone without using quartz polarizers or Faraday rotors. CONSTITUTION:This optical switch 51 consists of three sheets of double refractive crystal plates 22 to 24, the liquid crystals 52 of the 1st group to be inserted between the 1st and 2nd double refractive crystal plates, the liquid crystals 53 of the 2nd group to be inserted between the 2nd and 3rd double refractive crystal plates, >=1 ray incident ports 28, and plural ray exit ports 29, 30. The sepn. directions of the ordinary rays and extraordinary rays of the double refractive crystal plates are so set that the above-mentioned directions of the 1st and 3rd double refractive crystal plates 22, 24 coincide and the directions of the 2nd double refractive crystal plate 23 varies from the directions of the 1st and 3rd double refractive crystal plates 22, 24. The polarization direction of the liquid crystals of the 1st group is so set that the polarization direction of the rays coincide with the 2nd double refractive crystal plate 23 and the polarization direction of the liquid crystals of the 2nd group is so set that the polarization direction coinciding with the 2nd double refractive crystal plate 23 intersects orthogonally with the 3rd double refractive crystal plate 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical path switching optical switch which is preferably used in optical communication or optical experimental systems.

[0002]

2. Description of the Related Art Conventionally, various types of optical switches for switching an optical path have been developed and provided in an optical communication system or an optical experiment system. By controlling an external magnetic field to control a polarization direction of a light beam. An optical switch that can switch the optical path is one of them.

As an example of the above optical switch, an optical switch 1 as shown in FIG. 11 (Japanese Patent Publication No. 59-44606) has already been used.
Issue). This optical switch 1 includes a pair of polarizing prisms 2 and 3, a Faraday rotator (non-reciprocal rotator) 4, an optical compensator 5, total reflection mirrors 6 and 7, light incident ports 8 and 9, and light emitting ports. -It is configured roughly from 10 and 11.

Here, the polarizing prisms 2 and 3 separate the incident light beam into two orthogonal components (s-wave component and p-wave component) or combine the two orthogonal components that have entered.

The Faraday rotator 4 and the optical compensator 5 are set as follows for incident light. That is,
When the light travels from the left side to the right side in FIG. 11, the polarization direction of the light does not change due to the canceling effect of the rotation directions of the Faraday rotator 4 and the optical compensation plate 5, and the right side to the left side in FIG. When traveling toward one side, the directions of the external magnetic field H acting on the Faraday rotator 4 and the direction of the crystal axis of the optical compensator 5 are adjusted so that the polarization directions of the lights are rotated by 90 ° due to the mutual rotation of the lights. It is set.

Therefore, in the optical switch 1, the light L _i incident from the light incident port 8 is separated into two orthogonal components (s-wave component and p-wave component) by the polarization prism 2. Finally, the polarization prism 3 combines these orthogonal components again, and the combined light L _j
Is emitted from the light emitting port 10.

Similarly, the light L _k incident from the light incident port 9 is separated and combined by the polarization prisms 2 and 3.
The combined light L _m is emitted from the light beam emission port 11.

Further, the optical switch 1 set as described above
11, if the direction of the external magnetic field H acting on the Faraday rotator 4 is reversed by some method, when the light travels from the right side to the left side in FIG. The polarization direction of light does not change due to the offsetting effect of the rotation direction. When traveling from left to right in FIG.
Just rotate.

Therefore, in the optical switch 1, the light L _i incident from the light incident port 8 is not emitted from the light emitting port 10 but is emitted from the light emitting port 11 and is similarly incident. The light L _k incident from the port 9 can be operated as an optical switch in which the light L _k is emitted from the light emitting port 10 without being emitted from the light emitting port 11.

However, since the above optical switch 1 uses the polarizing prisms 2 and 3, the light emitting port 1 is used.
There is a drawback that the isolation between 0 and 11 cannot be increased.

The reason is that it is technically difficult to suppress the amount of leakage of the p-wave component to be transmitted into the s-wave component to be reflected by the polarizing prism 2 (3) to -30 dB or less. Therefore, the light is emitted to the light ray emission port which is not desired to appear.

Further, when the two lights separated into the orthogonal components are combined, the traveling direction of the lights is changed by the reflection of the total reflection mirrors 6 and 7, so that it is necessary to align the rays with high accuracy. Therefore, there is also a drawback that a high level of technology is required to manufacture the optical switch 1.

In the example of FIG. 11, the traveling direction of light is changed by the polarization prisms 2 and 3 and the total reflection mirrors 6 and 7. Here, assuming that the optical path length from the reflected position to the combined position is L, if there is an error of Δθ in the reflected angle, a position shift of LΔθ occurs at the combining point. The positional deviation at the combining point is
(10) (11) increases the coupling loss with the optical waveguide connected to the optical waveguide and causes polarization dependence, and practically configures each component while maintaining Δθ within 5 seconds. Must be implemented.

Therefore, as an optical switch that solves various drawbacks of the optical switch 1 described above, an optical switch using a reciprocal and non-reciprocal rotor and a liquid crystal plate as shown in FIG. 12 is considered.

The optical switch 21 includes first to third birefringent crystal plates 22 to 24 arranged at a predetermined interval along the traveling direction of light rays, a first birefringent crystal plate 22 and a second birefringent crystal plate 22. Of the first group of rotors 25 inserted between the second birefringent crystal plate 23 and the second birefringent crystal plate 23 of the second group. Rotor 26 and the first
The liquid crystal plate 27 inserted between the rotor 25 of the group and the second birefringent crystal plate 23, the light incident port 28 provided on the first birefringent crystal plate 22, and the third birefringent crystal. The light beam emission port 2 provided on the plate 24 so as to be aligned in the Y axis direction.
9 and 30, and is configured to control the polarization direction of light by changing the voltage application state of the liquid crystal plate 27,
It operates as an optical switch.

Here, in FIG. 12, solid lines with arrows in the first to third birefringent crystal plates 22 to 24 represent ordinary rays, and broken lines with arrows represent extraordinary rays.

Further, in this figure, the direction from the light incident port 28 side to the light emission ports 29, 30 side, that is, the direction from the left side to the right side in FIG. The configuration and action will be described by using the Cartesian coordinate system in which the positive direction of the Y axis is the positive direction of the Y axis and the positive direction of the X axis is the positive direction of the X axis.

The clockwise direction is the direction in which the right-handed screw turns when the right-handed screw travels in the same direction as the light ray when the light-ray proceeds in the positive direction of the Z-axis. In the case of the rays,
This is the direction in which the electric field vector rotates in the direction in which the right hand screw rotates. For an observer facing the positive direction of the Z axis, the clockwise rotation direction is defined as positive rotation.

A lens 31 and an optical fiber 32 are coaxially provided between the first birefringent crystal plate 22 and the light incident port 28, and the third birefringent crystal plate 24 and the light exit port 2 are provided.
9, a lens 33 and an optical fiber 34 are coaxially provided, and a lens 35 and an optical fiber 36 are coaxially provided between the third birefringent crystal plate 24 and the light exit port 30. It is provided in.

The first group of rotators 25 is composed of reciprocal and non-reciprocal rotators that rotate the polarization directions of light rays by the same angle. The first reciprocal counterclockwise rotation is arranged in the same plane. A 45 ° rotor (hereinafter simply referred to as a first reciprocal left rotor) 41, a first reciprocal clockwise 45 ° rotor (first reciprocal right rotor) 42, and reciprocal rotations of these. It is composed of a first non-reciprocal Faraday-45 ° rotator (first Faraday rotator) 43 arranged in parallel with the child.

The rotor 26 of the second group has the same structure as the rotor 25 of the first group, and has a second reciprocal counterclockwise 45 ° rotor (second rotor) arranged in the same plane. Reciprocal left rotor) 44, second reciprocal clockwise 45 ° rotor (second
A reciprocal right rotator) 45, and a second non-reciprocal Faraday-45 ° rotator (second Farade-rotor) 46 arranged in parallel with these reciprocal rotators.

As the birefringent crystal plates 22, ..., Calcite or rutile crystals are used, and the reciprocal rotor 41 ,.
A quartz optical rotator or a half-wave plate, and a Faraday rotator 43, 46 is a bismuth (Bi) -substituted YI.
G crystals and GBIG thin film crystals are preferably used. Also,
As the liquid crystal plate 27, one that does not rotate the polarization direction of a light beam when a voltage is applied and rotates 90 ° when no voltage is applied is used.

The birefringent crystal plate 22 of the optical switch 21,
The direction in which the ordinary ray and the extraordinary ray are separated is different from the direction in which the second birefringent crystal plate 23 is separated from the direction in which the first birefringent crystal plate 22 and the third birefringent crystal plate 24 are separated, The separation directions of the first birefringent crystal plate 22 and the third birefringent crystal plate 24 are set to coincide with each other.

Further, the first reciprocity is set so that the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate 22 coincide with each other at the incident end face 23a of the second birefringent crystal plate 23. Left rotor 41, first reciprocal right rotor 42, first
Direction of rotation of each Faraday-rotor 43 of the
The strength and direction of the external magnetic field H acting on the Faraday rotator 43 are set, and the polarization direction of the liquid crystal plate 27 is also set.

Further, the polarization directions of the two light rays which are coincident with each other on the emission end face 23b of the second birefringent crystal plate 23 are the third,
Of the second reciprocal left rotator 44, the second reciprocal right rotator 45, and the second Faraday rotator 46 so as to be orthogonal to each other at the incident end surface 24a of the birefringent crystal plate 24, and External magnetic field H acting on the second Faraday rotator 46
Strength and direction are set.

Next, the operation and the like of the optical switch 21 will be described with reference to FIGS.

FIG. 13 is an observation of the polarization state and spatial position of the light ray in the optical path A ₁ from the incident port 28 to the light ray emission port 29 in the optical switch 21 from the incident light side (light ray incident port 28 side). . Hereinafter, these polarization states will be indicated by reference numerals Z1 to Z9.

Now, the direction of the external magnetic field H and the rotation direction of each of the first reciprocal left rotor 41, the first reciprocal right rotor 42, the second reciprocal left rotor 44, and the second reciprocal right rotor 45. ,
By properly selecting the applied state of the electric field of the liquid crystal 27, when the incident light ray L _p travels from left to right in FIG. 12, the polarization direction at the incident end face 23 a of the second birefringent crystal plate 23 becomes an ordinary ray. Can be configured.

Ray L _p incident from the ray incident port 27
Is in the Z1 state, but is split into a ray L ₁₁ and a ray L ₁₂ on the XZ plane by the first birefringent crystal plate 22. The ray L ₁₁ is an ordinary ray (O− to the first birefringent crystal plate 22).
ray), and the ray L ₁₂ is an extraordinary ray (E-ray). The respective polarization directions are orthogonal to each other in the Y-axis direction and the X-axis direction like Z2.

The light beams L ₁₁ and L ₁₂ which are orthogonal to each other are polarized in the first reciprocal left rotator 41 whose rotation directions are different from each other.
Alternatively, they pass through the first reciprocal right rotator 42 and are in the same direction. Here, the first reciprocal left rotator 41 is rotated counterclockwise when viewed from the incident direction of the light ray L ₁₁ , and the first reciprocal right rotator 42 is rotated clockwise when viewed from the incident direction of the light ray L ₁₂ . At this time, the polarization state is Z3.

Next, the first Faraday rotator 43 further rotates the light rays L ₁₁ and L ₁₂ counterclockwise by 45 ° so that the polarization directions of these light rays L ₁₁ and L ₁₂ are parallel to the X axis. (Z4 state).

These light rays L ₁₁ and L _{12 which} are parallel to the X-axis direction then pass through the liquid crystal plate 27.
When a voltage is applied to the liquid crystal plate 27, the polarization directions of the light rays that pass therethrough do not change, so these light rays L ₁₁ ,
L ₁₂ passes through the liquid crystal plate 27 while maintaining the state of Z4 (Z
5 state), the incident end face 23a of the second birefringent crystal plate 23
Incident on.

The crystal axis of the second birefringent crystal plate 23 is arranged so that the two light rays L ₁₁ and L ₁₂ polarized in the X-axis direction become ordinary rays. Therefore, the light rays L ₁₁ and L ₁₂ that have entered the second birefringent crystal plate 23 propagate as ordinary rays in the second birefringent crystal plate 23 without changing the polarization direction.

The two light rays L ₁₁ and L ₁₂ (Z6 state) that have passed through the second birefringent crystal plate 23 are reflected by the rotor 26 of the second group.
Will pass through. Here, the rotor 25 of the first group
Of without rotating the polarization direction of the light beam L ₁₁ opposite the action, the polarization direction of the light beam L ₁₂ to rotate 90 °, a second reciprocal left rotator 44, a second reciprocal right rotator 45, the second The Faraday rotators 46 are arranged respectively. The rotation direction of the second Faraday rotator 46 may be the same as that of the first Faraday rotator 43.

In this case, the light ray L ₁₁ passes through the second reciprocal right rotator 45 and the second Faraday rotator 46 to cancel the rotation of the polarization direction, and as a result, the polarization direction does not rotate. , Ray L ₁₂ is the second reciprocal left rotator 4
4 and the second Faraday rotator 46 rotate the polarization direction counterclockwise by 45 °, respectively, and as a result, rotate the polarization direction by 90 ° (Z8 state).

Therefore, at the incident end face 24a of the third birefringent crystal plate 24, the polarization directions of the two light rays L ₁₁ and L ₁₂ are orthogonal to each other. At this time, the light ray L ₁₁ becomes an extraordinary ray (E-ray) and the light ray L ₁₂ becomes an ordinary ray (O-ray) with respect to the third birefringent crystal plate 24.
The two light rays L ₁₁ and L ₁₂ are spatially coincident and combined at the exit end face 24b of the light beam (state of Z9), and the light ray exit port 29
Is emitted (light ray L _q ).

[0037] FIG 14 is switched from the optical path A ₁ in the optical path A ₂ in the optical switch 21, when the light beam incident from the input port 28 was set to be emitted from the light output port 30, the light in the optical path A ₂ The polarization state and the spatial position are observed from the incident light side (ray incident port 28 side).

In this case, the above optical path A is reached until the state of Z4.
_Since it is exactly the same as the case of _1, the description is omitted.

The light rays L ₁₁ and L ₁₂ (state Z4) emitted from the first Faraday rotator 43 enter the liquid crystal plate 27. In this case, since no voltage is applied to the liquid crystal plate 27, the light beam L ₁₁ rotates 90 ° counterclockwise and the light beam L ₁₂ rotates 90 ° clockwise (Z5 state).

The light rays L ₁₁ and L ₁₂ that have passed through the liquid crystal plate 27 are
It is incident on the incident end face 23a of the second birefringent crystal plate 23.
In this case, the light rays L ₁₁ and L ₁₂ propagate as an extraordinary ray in the second birefringent crystal plate 23 while moving in the negative direction of the Y axis.

Output end face 23b of the second birefringent crystal plate 23
The light beams L ₁₁ and L ₁₂ emitted from the laser beam pass through the rotor 26 of the second group.

In this case, the light ray L ₁₁ passes through the second reciprocal right rotator 45 and the second Faraday rotator 46, so that the polarization direction is rotated by 90 °, but the light ray L ₁₂ is second. Reciprocal left rotator 44 and second Faraday rotator 46
By passing through, the polarization directions are canceled out and they do not rotate (Z8 state).

Therefore, at the incident end face 24a of the third birefringent crystal plate 24, the polarization directions of the two light rays L ₁₁ and L ₁₂ are orthogonal to each other. At this time, the light ray L ₁₁ becomes an extraordinary ray (E-ray) and the light ray L ₁₂ becomes an ordinary ray (O-ray) with respect to the third birefringent crystal plate 24.
The two light rays L ₁₁ and L ₁₂ are spatially coincident and combined at the exit end face 24b of the light (state of Z9), and the light ray exit port 30
(Light ray L _r ).

In this optical switch 21, the light ray L _p incident from the light ray incident port 28 is emitted from the light ray emission port 29 when a voltage is applied to the liquid crystal plate 27, and is emitted when a voltage is not applied to the liquid crystal plate 27. It has a function of switching the optical path, that is, the light is emitted from the light ray emission port 30 without being emitted from the port 29, and the operation as an optical switch can be realized. Therefore, it can be used as a 1 × 2 optical switch.

[0045]

However, in the above optical switch 21, a crystal rotator or a half-wave plate is used as the reciprocal rotators 41, ..., And bismuth is used as the Faraday rotators 43 and 46. (Bi) Substitution YIG
Since crystals and GBIG thin film crystals are used, there is a drawback that the entire optical path length must be large and miniaturization cannot be supported. For example, using a quartz optical rotator to rotate the plane of polarization by 45 ° requires a length of at least 16 mm.

Further, since the Faraday rotators 43 and 46 which perform non-reciprocal operation are used, there is a drawback that bidirectionality is lost. Further, although the optical switch 21 functions as a 1 × 2 optical switch, it is extremely difficult to perform the function as a 2 × 2 optical switch.

The present invention has been made in view of the above circumstances, and is a reciprocal rotator such as a quartz optical rotator or a half-wave plate, or a Faraday rotator such as a Bi-substituted YIG crystal or a GBIG thin film crystal. The entire optical path length can be shortened without using the optical switch, the manufacturing including the optical coupling becomes easier than the conventional optical switch, and further, an optical switch that can function as a 2 × 2 optical switch is provided. To provide.

[0048]

In order to solve the above problems, the present invention employs the following optical switch. That is, in the optical switch according to claim 1, three birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and the light polarization is performed between the first and second birefringent crystal plates. A first group of liquid crystals whose direction can be changed is inserted, and a second group of liquid crystals having the same function as the first group of liquid crystals is also inserted between the second and third birefringent crystal plates. The first birefringent crystal plate is provided with at least one light incident port and the third birefringent crystal plate is provided with a plurality of light exit ports to separate an ordinary ray and an extraordinary ray of the birefringent crystal plate. As for the direction, the separating directions of the first and third birefringent crystal plates coincide with each other, and the separating direction of the second birefringent crystal plate separates the first and third birefringent crystal plates. Set different from each other and separated by the first birefringent crystal plate As the polarization direction of the ordinary and extraordinary rays which coincide with each other at the entrance end face of the second birefringent crystal plate, set each of the polarization directions of the liquid crystal of the first group,
The light emitting end faces of the second birefringent crystal plate are coincident with each other.
The polarization directions of the liquid crystals of the second group are set such that the polarization directions of the light rays of the book are orthogonal to each other at the incident end surface of the third birefringent crystal plate.

Further, in the optical switch according to the second aspect, four birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and between the first and second birefringent crystal plates. A first group of liquid crystals capable of changing the polarization direction of light rays is inserted, and a second group of liquid crystals having the same function as that of the first group of liquid crystals is provided between the second and third birefringent crystal plates. A third group of liquid crystals having the same function as the first group of liquid crystals is inserted between the third and fourth birefringent crystal plates, and a plurality of light rays are incident on the first birefringent crystal plate. A port is provided, and a plurality of ray exit ports are provided on the third birefringent crystal plate, and the directions in which the ordinary ray and the extraordinary ray of the birefringent crystal plate are separated are set to the first and fourth birefringent crystal plates, respectively. The separating directions of the two birefringent crystal plates are separated from each other. Direction also coincide, and the first and fourth of the direction in which separation of the birefringent crystal plate second and third
Are set so as to be different from the separating direction of the birefringent crystal plate, and the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate are on the incident end face of the second birefringent crystal plate. The polarization directions of the liquid crystals of the first group are set so that they coincide with each other, and the polarization directions of the two light rays that coincide at the exit end face of the second birefringent crystal plate are
The respective polarization directions of the liquid crystals of the second group are set so that the incident end faces of the third birefringent crystal plate are also coincident with each other, and the emission end faces of the third birefringent crystal plate are coincident with each other. The polarization directions of the liquid crystals of the third group are set so that the polarization directions of the two light rays are orthogonal to each other at the incident end surface of the fourth birefringent crystal plate.

[0050]

In the optical switch according to claim 1 of the present invention, the first
Among the one or more (N) light incident ports provided on the birefringent crystal plate, the light rays incident from the light incident port i (1 ≦ i ≦ N) are provided on the third birefringent crystal plate. Of the plurality (M) of light exit ports, the light exit port k (1
≦ k ≦ M), the applied voltage of each liquid crystal of the first group of liquid crystals and the second group of liquid crystals is set to either an on state or an off state.

Here, when the applied voltage of each liquid crystal of the first group of liquid crystals and the second group of liquid crystals is on,
By switching the f state and the off state to the on state, respectively, a 1 × 2 optical switch in which the light beam incident from the light incident port i is not emitted from the light emission port k but is emitted from the light emission port k + 1 The operation of.

Further, in the optical switch according to the second aspect, the light is incident from the light incident port i (1≤i≤N) among a plurality (N) of light incident ports provided on the first birefringent crystal plate. A plurality of (M) rays are provided on the third birefringent crystal plate.
Ray exit ports k (1 ≦ k)
≦ M), and also the light incident port i + 1
A light beam incident from the liquid crystal of the first group, the second group of liquid crystals, and the third group of liquid crystals is turned on or off so that the light beam incident from
Set to one of the states.

Here, among the liquid crystals of the first group, the second group of liquid crystals, and the third group of liquid crystals, some of the liquid crystals have an applied voltage in the on state and are in the off state and the off state. When each of them is switched to the on state, the light ray incident from the light ray incident port i is not emitted from the light ray emission port k, is emitted from the light ray emission port k + 1, and the light ray incident from the light ray incident port i + 1 is a light ray. An operation as a 2 × 2 optical switch is performed in which light is emitted from the light ray emission port k without being emitted from the emission port k + 1.

[0054]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view of an optical switch 51 which is an embodiment of the optical switch according to the first aspect. In the optical switch 51, the same components as those of the optical switch 21 described above are designated by the same reference numerals, and the description thereof will be omitted.

The optical switch 51 includes first to third birefringent crystal plates 22 to 24 arranged at a predetermined interval along the traveling direction of the light beam, the first birefringent crystal plate 22 and the second birefringent crystal plate 22. First group of liquid crystal type polarization rotators (hereinafter simply referred to as liquid crystal rotators) 52 inserted between the birefringent crystal plate 23 and
And a second birefringent crystal plate 23 and a third birefringent crystal plate 24.
A second group of liquid crystal rotators 53 inserted between the first and second birefringent crystal plates 22, and a light incident port 28 provided on the first birefringent crystal plate 22.
The third birefringent crystal plate 24 is roughly configured by light beam emission ports 29 and 30 provided in parallel with each other in the Y-axis direction.

The liquid crystal rotator 52 of the first group is a liquid crystal type polarization rotator capable of rotating each polarization plane by controlling each applied voltage independently.
It is composed of a pair of liquid crystal plates 55 and 56 arranged in the same plane. The liquid crystal rotator 53 of the second group is also composed of a pair of liquid crystal plates 57 and 58 arranged in the same plane as the liquid crystal rotator 52 of the first group.

The liquid crystal plates 55, ... Are rectangular flat plate-shaped transparent cells filled with Twisted Nematic liquid crystal (TN liquid crystal), and the light input and output end faces of this transparent cell are usually ITO thin films. And the like glassy transparent electrode is formed.

The TN liquid crystal has its molecular axis aligned in parallel with the incident (out) end face of light, and is twisted by 90 ° in the axial direction from one end face to the other end face. This TN
In the liquid crystal, when no voltage is applied, the electric field oscillation direction of the light is rotated by 90 ° when the light passes through the TN liquid crystal due to the twist of the liquid crystal in the axial direction. In the state where a voltage is applied, the axial direction of the liquid crystal comes along the voltage application direction, and the electric field oscillation direction of light passes through this liquid crystal without changing.

The first to third birefringent crystal plates 22 to 24 of the optical switch 51 are arranged under the following conditions. First birefringent crystal plate 22 and third birefringent crystal plate 24
Is an extraordinary ray of X as the ray propagates in the positive direction of the Z axis.
It is arranged so as to move in the negative direction of the X axis on the -Z plane. The second birefringent crystal plate 23 is arranged so that the extraordinary ray moves in the Y-axis negative direction on the YZ plane as the ray propagates in the Z-axis positive direction.

Next, the operation of the optical switch 51 will be described with reference to FIGS. 2 shows the optical switch 5
1, the light incident port 28 to the light exit port 29
The polarization state and the spatial position of the light ray on the optical path B ₁ toward the light source are observed from the incident light side (the light ray incident port 28 side). Hereinafter, these polarization states will be indicated by reference numerals Z1 to Z6.

Here, the liquid crystal plates 55 and 58 are in a state where no voltage is applied (off state), and the liquid crystal plates 56 and 58 are
57 is in a state where a predetermined voltage is applied (on state).

Ray L _p incident from the ray entrance port 28
Is in the Z1 state, but is split into a ray L ₁₁ and a ray L ₁₂ on the XZ plane by the first birefringent crystal plate 22. The ray L ₁₁ is an ordinary ray (O− to the first birefringent crystal plate 22).
ray), and the ray L ₁₂ is an extraordinary ray (E-ray). Each electric field component is in an orthogonal state facing the Y-axis direction and the X-axis direction like Z2.

The separated light rays L ₁₁ and L ₁₂ are then incident on the liquid crystal rotator 52 of the first group. The electric field component of the light beam L ₁₁ and the light L ₁₂ that are orthogonal to each other, the liquid crystal plate 55 the light beam L ₁₁ is not a voltage is applied, light L ₁₂ passes through each of the liquid crystal panel 56 to which a predetermined voltage is applied This makes it parallel to the X axis. Here, the liquid crystal plate 55 causes the light beam L ₁₁
However, the liquid crystal plate 56 does not rotate the light beam L ₁₂ . The polarization state at this time is Z
It is 3.

The light rays L ₁₁ and L in this polarization state
₁₂ propagates through the second birefringent crystal plate 23 as an ordinary ray. The polarization state at this time is Z4.

These rays L ₁₁ and L ₁₂ parallel to the X-axis direction
Will then pass through the second group of liquid crystal rotators 53. The electric field components of the light ray L ₁₁ and the light ray L ₁₂ which are parallel to each other are the liquid crystal plate 57 to which the light ray L ₁₁ is applied with a predetermined voltage.
When the light rays L ₁₂ pass through the liquid crystal plate 58 to which no voltage is applied, the light rays L ₁₂ are orthogonal to each other and become the state of Z5.

The light ray L _{11 is} directed to the third birefringent crystal plate 24.
Becomes an extraordinary ray (E-ray) and the ray L ₁₂ becomes an ordinary ray (O-ray), so that the two rays L ₁₁ and L ₁₂ are spatially separated from each other on the exit end face 24b of the third birefringent crystal plate 24. They are coincident and combined (Z6 state), and are emitted from the light ray emission port 29 (light ray L _q ).

[0068] Figure 3, when the manner emits light incident from the light incident port 28 by switching the optical path B ₁ in the optical path B ₂ in the optical switch 51 from the light emission port 30, light in the optical path B ₂ The polarization state and the spatial position of No. 2 are observed from the incident light side (ray incident port 28 side).

Here, the liquid crystal plates 55 and 58 are in a state where a predetermined voltage is applied (on state), and the liquid crystal plates 56 and 57 are in a state where no voltage is applied (off state).

Ray L _p incident from the ray incident port 28
However, the operation until the light beam L ₁₁ and the light beam L ₁₂ are separated on the XZ plane by the first birefringent crystal plate 22 is the optical path B.
Same as ₁ .

The separated light rays L ₁₁ and L ₁₂ are then incident on the liquid crystal rotator 52 of the first group. The electric field components of the light ray L ₁₁ and the light ray L ₁₂ which are orthogonal to each other pass through the liquid crystal plate 55 to which the light ray L ₁₁ is applied with a predetermined voltage and to pass through the liquid crystal plate 56 to which the light ray L ₁₂ is not applied. This makes it parallel to the Y axis. Here, the liquid crystal plate 55 causes the light beam L ₁₁
Is not rotated, but the liquid crystal plate 56 is rotated clockwise as viewed from the incident direction of the light ray L ₁₂ . The polarization state at this time is Z
It is 3.

The light rays L ₁₁ and L in this polarization state
₁₂ propagates as an extraordinary ray in the second birefringent crystal plate 23 while moving in the negative direction of the Y axis. The polarization state at this time is Z4.

These rays L ₁₁ , L ₁₂ parallel to the Y-axis direction
Will then pass through the second group of liquid crystal rotators 53. The electric field components of the light ray L ₁₁ and the light ray L ₁₂ which are parallel to each other are, this time, the light ray L _{11 on the} liquid crystal plate 57 to which no voltage is applied,
The light rays L ₁₂ pass through the liquid crystal plates 58 to which a predetermined voltage is applied, and are orthogonal to each other, resulting in a Z5 state.

The light ray L _{11 is} directed to the third birefringent crystal plate 24.
Becomes an extraordinary ray (E-ray) and the ray L ₁₂ becomes an ordinary ray (O-ray), so that the two rays L ₁₁ and L ₁₂ are spatially separated from each other on the exit end face 24b of the third birefringent crystal plate 24. They are coincident and combined (state of Z6), and emitted from the light ray emission port 30 (light ray L _r ).

As described above, this optical switch 51
According to the first to third birefringent crystal plates 22 to 24 arranged at a predetermined interval along the traveling direction of light rays,
A first group of liquid crystal rotators 52 inserted between the first birefringent crystal plate 22 and the second birefringent crystal plate 23, a second birefringent crystal plate 23, and a third birefringent crystal plate. A second group of liquid crystal rotators 53 inserted between the first and second birefringent crystal plates 2;
The light incident port 28 provided in No. 2 and the light exit ports 29, 30 provided in the third birefringent crystal plate 24 are roughly configured, and therefore, they are configured by using an ordinary optical coupling technique. Therefore, it is possible to eliminate the drawback that the isolation cannot be increased as in the conventional optical switch 1 and the drawback that a very sophisticated optical coupling technique is required. Moreover, since a Faraday rotator or the like that performs non-reciprocal operation is not used, bidirectionality can be obtained.

Further, according to the optical switch 51, the light ray incident from the light ray incident port 28 is emitted from the light ray exit port 29.
So that the liquid crystal plates 55 of the first group of liquid crystal rotators 52 and the second group of liquid crystal rotators 53 are applied to the liquid crystal plates 55 ,. By changing the voltage, the light incident port 28
The light beam entering from the light output port 29 does not go out from the light beam exit port 29, but goes out from the light beam exit port 30 and has a function of switching the optical path, so that the operation as an optical switch can be realized. Therefore, it can be used as a 1 × 2 optical switch.

As described above, according to the optical switch 51, without using the crystal optical rotator or the Faraday rotator,
It is possible to realize an optical path switching type optical switch capable of switching the light emitting port by switching the voltage applied to the liquid crystal plates 55, ....

In the above description, one light incident port and two light emission ports are provided to facilitate understanding of the operation.
Although one 1 × 2 optical switch configuration is adopted, a plurality of light incident ports can be arranged in the Y-axis direction to switch a plurality of channels at the same time. In this case, the light emission port is switched between the adjacent ports. As described above, in the above-described optical switch 51, the number of light beam entrance / exit ports is not limited to that in the above embodiment, and various changes can be made.

FIG. 4 is a perspective view of an optical switch 61 which is a modification of the optical switch 51. The optical switch 61 is different from the optical switch 51 described above in that a lens 62 and an optical fiber 63 are coaxially provided between the first birefringent crystal plate 22 and the light incident port 28, and the third birefringence is provided. Crystal plate 24
The lens 64 and the optical fiber 65 are coaxially provided between the optical fiber 6 and the light emitting port 29, and the lens 66 and the optical fiber 6 are provided between the third birefringent crystal plate 24 and the light emitting port 30.
7 is provided coaxially.

The optical fibers 63, ... Can be applied in either single mode or multimode. Also,
Of course, it is also possible to replace with an optical waveguide capable of confining and propagating light energy.

With this optical switch 61 as well, the same action and effect as those of the optical switch 51 can be obtained, and 1 ×
It can be used as a second optical switch.

(Second Embodiment) FIG. 5 is a perspective view of an optical switch 71 which is an embodiment of the optical switch according to the present invention.

The optical switch 71 includes first to fourth birefringent crystal plates 72 to 75, which are arranged at a predetermined interval along the traveling direction of the light beam, the first birefringent crystal plate 72 and the second birefringent crystal plate 72. Liquid crystal rotator 76 of the first group inserted between the second birefringent crystal plate 73 and the second birefringent crystal plate 73, and the second group inserted between the second birefringent crystal plate 73 and the third birefringent crystal plate 74. LCD rotor 77
And a third birefringent crystal plate 74 and a fourth birefringent crystal plate 75.
Liquid crystal rotator 78 of the third group inserted between the first and second birefringent crystal plates 72, and light incident ports 81 and 82 provided in parallel with each other in the Y-axis direction, and a fourth birefringent Crystal plate 7
5 and light beam emission ports 83 and 84 provided in parallel with each other in the Y-axis direction.

The liquid crystal rotator 76 of the first group is a liquid crystal type polarization rotator capable of rotating each polarization plane by controlling each applied voltage independently.
As shown in FIG. 6, it is composed of four liquid crystal plates 76a to 76d arranged adjacent to each other in the same plane.

The liquid crystal rotator 77 of the second group is composed of one liquid crystal plate 77a. The liquid crystal rotator 78 of the third group, like the liquid crystal rotator 76 of the first group, has four adjacent liquid crystal plates 7 arranged in the same plane as shown in FIG.
8a to 78d.

Like the liquid crystal plates 55, ... Used in the first embodiment, these liquid crystal plates 76a, ... Are rectangular flat transparent cells filled with TN liquid crystal.

The first to fourth birefringent crystal plates 72 to 75 of the optical switch 71 are arranged under the following conditions. First birefringent crystal plate 72 and fourth birefringent crystal plate 75
Is an extraordinary ray of X as the ray propagates in the positive direction of the Z axis.
It is arranged so as to move in the negative direction of the X axis on the -Z plane. The second birefringent crystal plate 73 is arranged so that the extraordinary ray moves in the Y-axis negative direction on the YZ plane as the ray propagates in the Z-axis positive direction. The third birefringent crystal plate 74 is arranged so that the extraordinary ray moves in the Y-axis positive direction on the YZ plane as the ray propagates in the Z-axis positive direction.

Next, the operation and the like of the optical switch 71 will be described with reference to FIGS. 8 and 9. FIG. 8 shows an optical switch 7
1, the light incident port 81 to the light exit port 83
The polarization state and the spatial position of the light ray in the light path C ₁ toward the light incident port 82 and the light path C ₂ in the light path C ₂ extending from the light incident port 82 to the light exit port 84.
1, 82 side).

In the figure, the solid line with an arrow shows the state of the ray of light on the optical path C ₁ , and the broken line with an arrow shows the state of the ray of light on the optical path C ₂ . Hereinafter, these polarization states will be indicated by reference numerals Z1 to Z8.

Here, the liquid crystal plates 76a, 76c, 78
b and 78d are in a state where no voltage is applied (off state), and the liquid crystal plates 76b, 76d, 77a, 78a,
78c is in a state where a predetermined voltage is applied (on state).

Ray L _p incident from the ray incident port 81
Is separated into the ordinary ray L ₁₁ and the extraordinary ray L ₁₂ on the XZ plane by the first birefringent crystal plate 72, and the ray L _s incident from the ray incident port 82 is also the ordinary ray. The light ray L ₂₁ and the extraordinary ray L ₂₂ are separated. The electric field components of these rays L _p and L _s are respectively Y
The state is orthogonal to the axial direction and the X-axis direction (Z2 state).

The light rays L ₁₁ and L ₁₂ and the light rays L ₂₁ and L ₂₂ separated into two are then incident on the liquid crystal rotator 76 of the first group. At this time, since no voltage is applied to the liquid crystal plates 76a and 76c, the electric field oscillation direction of the light passing therethrough is rotated by 90 °. Therefore, the electric field vibration directions of all the light rays L ₁₁ , L ₁₂ , L ₂₁ , and L ₂₂ are parallel to the X axis. The polarization state at this time is Z3.

Rays L ₁₁ , L ₁₂ , L ₂₁ , L ₂₂ parallel to the X axis
Propagates through the second birefringent crystal plate 73 as an ordinary ray. The polarization state at this time is Z4.

These rays L ₁₁ , L ₁₂ , L ₂₁ , L ₂₂ are
Next, the liquid crystal rotator 77 of the second group is passed. At this time, since a predetermined voltage is applied to the liquid crystal plate 77a, the electric field oscillation direction of the light passing through the liquid crystal plate 77a does not rotate (Z5 polarization state). Therefore, these light rays L ₁₁ , L ₁₂ , L ₂₁ , and L ₂₂ are generated by the third birefringent crystal plate 7.
4 also propagates as an ordinary ray, and the polarization state at Z6 is Z
It becomes the same as the state of 3.

These light rays L ₁₁ , L ₁₂ , L ₂₁ , and L ₂₂ are
Next, it will pass through the liquid crystal rotor 78 of the third group. At this time, since no voltage is applied to the liquid crystal plates 78b and 78d, the electric field oscillation direction of light passing therethrough is 90 °.
Rotate. Therefore, the electric field vibration directions of the light rays L ₁₂ and L ₂₂ are rotated by 90 ° and become the Y-axis direction. In this case, the light rays whose electric field oscillation direction rotates by 90 ° are opposite to those in the case of the liquid crystal rotator 76 of the first group. Therefore, ray L ₁₁ and ray L
The electric field oscillation directions of ₁₂ are orthogonal to each other, and the electric field oscillation directions of the light ray L ₂₁ and the light ray L ₂₂ are also orthogonal to each other (Z7 state).

The ray L _{11 is} directed to the fourth birefringent crystal plate 75.
Becomes an extraordinary ray, and the ray L ₁₂ becomes an ordinary ray.
At the exit end face 75b of the birefringent crystal plate 75 of
₁₁ and L ₁₂ are spatially matched and combined (Z8 state),
The light is emitted from the light ray emission port 83 (light ray L _q ). The light rays L ₂₁ and L ₂₂ are also combined by the fourth birefringent crystal plate 75 and emitted from the light ray emission port 84 (light ray L _t ).

[0097] Figure 9 switches the optical path in the optical switch 71, the optical path extending from the light incident port 81 to the light emission port 84 C _3, and light of polarization in the optical path C ₄ respectively directed from the light incident port 82 to the light emission port 83 The state and the spatial position are set to the incident light side (the light ray incident port 81,
82 side).

In the figure, the solid line with an arrow shows the state of the ray of light on the optical path C ₃ , and the broken line with an arrow shows the state of the ray of light on the optical path C ₄ .

Here, the liquid crystal plates 76a, 76d, 78
b and 78c are in a state where a predetermined voltage is applied (on state)
, Liquid crystal plates 76b, 76c, 77a, 78a, 78
d is in a state where no voltage is applied (off state).

Ray L _p incident from the ray incident port 81
Is separated into the ordinary ray L ₁₁ and the extraordinary ray L ₁₂ on the XZ plane by the first birefringent crystal plate 72, and the ray L _s incident from the ray incident port 82 is also the ordinary ray. The light ray L ₂₁ and the extraordinary ray L ₂₂ are separated. The electric field components of these rays L _p and L _s are respectively Y
The state is orthogonal to the axial direction and the X-axis direction (Z2 state).

The light rays L ₁₁ and L ₁₂ and the light rays L ₂₁ and L ₂₂ separated into two are then incident on the liquid crystal rotator 76 of the first group. At this time, since no voltage is applied to the liquid crystal plates 76b and 76c, the electric field oscillation direction of the light passing therethrough is rotated by 90 °. Therefore, the rays L ₁₁ , L
The electric field vibration direction of ₁₂ becomes parallel to the Y-axis, and the light rays L ₂₁ and L ₂₂
The electric field vibration direction of is parallel to the X axis. The polarization state at this time is Z3.

Light rays L ₁₁ and L ₁₂ parallel to the Y axis propagate as moving extraordinary rays in the second birefringent crystal plate 73 while moving in the negative direction of the Y axis, and light rays L ₂₁ parallel to the X axis. , L ₂₂ propagates through the second birefringent crystal plate 73 as ordinary rays. The polarization state at this time is Z4. Therefore, on the emission end face 73a of the second birefringent crystal plate 73, the light ray L ₁₁ and the light ray L ₂₁ , and the light ray L ₁₂ and the light ray L ₂₂ are spatially at the same position in a state where the electric field oscillation directions are orthogonal to each other. .

These light rays L ₁₁ , L ₁₂ , L ₂₁ and L ₂₂ are
Next, the liquid crystal rotator 77 of the second group is passed. At this time, since no voltage is applied to the liquid crystal plate 77a, the electric field oscillation direction of the light passing through the liquid crystal plate 77a rotates clockwise by 90 ° (Z5 polarization state). Therefore, the electric field vibration directions of the light rays L ₁₁ and L ₁₂ are parallel to the X axis, and the electric field vibration directions of the light rays L ₂₁ and L ₂₂ are parallel to the Y axis.

The rays L ₁₁ and L ₁₂ parallel to the X-axis propagate as ordinary rays in the third birefringent crystal plate 74, and the rays L ₂₁ and L ₂₂ parallel to the Y-axis are the third rays. An extraordinary ray propagates through the birefringent crystal plate 74 while moving in the positive direction of the Y axis. The polarization state at this time is Z6.

These light rays L ₁₁ , L ₁₂ , L ₂₁ and L ₂₂ are
Next, it will pass through the liquid crystal rotor 78 of the third group. At this time, since no voltage is applied to the liquid crystal plates 78a and 78d, the electric field oscillation direction of light passing therethrough is 90 °.
Rotate. Therefore, the electric field oscillation direction of the light ray L ₁₁ is 90
Rotate by ° and become parallel to the X axis. Further, the electric field vibration direction of the light ray L ₂₂ is also rotated by 90 ° and becomes parallel to the Y axis (Z7 state).

The ray L _{11 is} directed to the fourth birefringent crystal plate 75.
Becomes an extraordinary ray, and the ray L ₁₂ becomes an ordinary ray.
At the exit end face 75a of the birefringent crystal plate 75 of
₁₁ and L ₁₂ are spatially matched and combined (Z8 state),
The light is emitted from the light ray emission port 84 (light ray L _t ). The light rays L ₂₁ and L ₂₂ are also combined by the fourth birefringent crystal plate 75 and emitted from the light ray emission port 83 (light ray L _q ).

As described above, this optical switch 71
According to the first to fourth birefringent crystal plates 72 to 75 arranged at a predetermined interval along the traveling direction of light rays,
A first group of liquid crystal rotators 76 inserted between the first birefringent crystal plate 72 and the second birefringent crystal plate 73, the second birefringent crystal plate 73 and the third birefringent crystal plate. The second group of liquid crystal rotators 77 inserted between the second group 74 and the third birefringent crystal plate 7
4 and the fourth birefringent crystal plate 75, and a liquid crystal rotator 78 of the third group, and a light incident port 81 provided in parallel with the first birefringent crystal plate 72 in the Y-axis direction. , 82,
Since the fourth birefringent crystal plate 75 and the light beam exit ports 83 and 84 provided in parallel in the Y-axis direction are provided, it is possible to use a conventional optical coupling technique. It eliminates the drawback that the isolation cannot be increased as in the conventional optical switch 1 and the drawback that a very sophisticated optical coupling technique is required. Moreover, since a Faraday rotator etc. that performs non-reciprocal operation is not used,
It can be bidirectional.

Further, according to this optical switch 71, the light ray incident from the light ray incident port 81 is emitted from the light ray exit port 83.
The liquid crystal rotator 76 of the first group, the liquid crystal rotator 77 of the second group, and the liquid crystal rotator 78 of the third group are emitted so that the light beam emitted from the light incident port 82 is emitted from the light beam emission port 84. Of the liquid crystal plates 76a, ... Are set in advance, and the applied voltage of these liquid crystal plates 76a ,. It has a function of switching the optical path that the light rays emitted from the light ray emission port 84 and incident from the light ray incidence port 82 are emitted from the light ray emission port 83 without being emitted from the light ray emission port 84, and realize the operation as an optical switch. be able to. Therefore, it can be used as a 2 × 2 optical switch.

As described above, according to the optical switch 71, without using the crystal rotator or the Faraday rotator,
By switching the voltage applied to the liquid crystal plates 76a, ..., It is possible to realize an optical path switching type optical switch capable of switching the light emitting port.

FIG. 10 is a perspective view of an optical switch 91 which is a modification of the optical switch 71. This optical switch 91
Is different from the above optical switch 71 in that a lens 92 and an optical fiber 93 are coaxially provided between the first birefringent crystal plate 72 and the light incident port 81, and the first birefringent crystal plate 7 is provided.
The lens 94 and the optical fiber 95 are coaxially provided also between the second light beam incident port 82 and the light incident port 82, and the lens 96 and the optical fiber 97 are also provided between the fourth birefringent crystal plate 75 and the light beam emission port 83. The lens 98 and the optical fiber 99 are provided coaxially, and between the fourth birefringent crystal plate 75 and the light exit port 84.
This is the point where and are provided coaxially.

The optical fibers 93, ... Can be applied in either single mode or multimode. Also,
Of course, it is also possible to replace with an optical waveguide capable of confining and propagating light energy.

With this optical switch 91 as well, the same action and effect as those of the optical switch 71 can be obtained, and 2 ×
It can be used as a second optical switch.

[0113]

As described above, according to the first aspect of the present invention.
According to the described optical switch, 3
A plurality of birefringent crystal plates are arranged at a predetermined interval, and the first
A first group of liquid crystals capable of changing the polarization direction of light rays is inserted between the second and third birefringent crystal plates, and between the second and third birefringent crystal plates as well as the first group of liquid crystals. A second group of liquid crystals having the function of (1) is inserted, and at least one light incident port is provided on the first birefringent crystal plate, and a plurality of light emission ports are provided on the third birefringent crystal plate. Therefore, it can be constructed by using the usual optical coupling technology, and the drawbacks that the isolation cannot be made high and the very high optical coupling technology is required unlike the conventional optical switch are solved. . Further, since a Faraday rotator or the like that performs non-reciprocal operation is not used, bidirectionality can be obtained.

Further, according to this optical switch, the directions in which the ordinary ray and the extraordinary ray of the birefringent crystal plate are separated are the same as those of the first and third birefringent crystal plates. The separating direction of the second birefringent crystal plate is the first direction.
And the third birefringent crystal plate is set to be different from the separating direction, and the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate are different from those of the second birefringent crystal plate. The respective polarization directions of the liquid crystals of the first group are set so that they coincide with each other at the incident end face, and the two light beams having the same polarization direction at the emission end face of the second birefringent crystal plate have the same polarization direction. Since the polarization directions of the liquid crystals of the second group are set so as to be orthogonal to each other at the incident end surface of the third birefringent crystal plate, the liquid crystals of the first group and the second group of liquid crystals are formed. By switching the voltage applied to each liquid crystal of the group of liquid crystals, the light ray incident from the light ray incident port i is not emitted from the light ray emission port k, but is emitted from the light ray emission port k + 1.
It has a function of switching the optical path of being emitted from, and can realize an operation as an optical switch. Therefore, it can be used as a 1 × 2 optical switch.

Further, according to the optical switch of the second aspect, four birefringent crystal plates are arranged at a predetermined interval along the traveling direction of the light beam, and between the first and second birefringent crystal plates. A liquid crystal of a first group capable of changing the polarization direction of light rays is inserted into the second group, and a liquid crystal of a second group having a function similar to that of the liquid crystal of the first group is inserted between the second and third birefringent crystal plates. A liquid crystal is inserted, and a liquid crystal of a third group having a function similar to that of the liquid crystal of the first group is also inserted between the third and fourth birefringent crystal plates, and a plurality of liquid crystals are inserted in the first birefringent crystal plate. Since a plurality of light beam emission ports are provided in the third birefringent crystal plate in addition to the light beam incident port, it can be constructed by using a usual optical coupling technique, and it can be constructed by using the conventional optical switch. Of high optical coupling technology The disadvantage that it requires is resolved. Further, since a Faraday rotator or the like that performs non-reciprocal operation is not used, bidirectionality can be obtained.

Further, according to this optical switch, the directions in which the ordinary ray and the extraordinary ray of the birefringent crystal plate are separated are the same in the directions in which the first and fourth birefringent crystal plates are separated. The separating directions of the second and third birefringent crystal plates are also the same, and the separating directions of the first and fourth birefringent crystal plates are the separating directions of the second and third birefringent crystal plates. Respectively, so that the polarization directions of the ordinary ray and the extraordinary ray separated by the first birefringent crystal plate coincide with each other at the incident end face of the second birefringent crystal plate, The respective polarization directions of the liquid crystals of the first group are set, and the polarization directions of the two light rays that are coincident with each other at the exit end face of the second birefringent crystal plate are the same as those of the third birefringent crystal plate. Each of the liquid crystals of the second group is matched so that the incident end faces also match. A polarization direction is set so that the polarization directions of two light rays that coincide with each other on the exit end face of the third birefringent crystal plate are orthogonal to each other on the entrance end face of the fourth birefringent crystal plate. Since the polarization directions of the liquid crystals of the third group are set, the liquid crystal of the first group and the second group of liquid crystals are set.
By switching the applied voltage to some of the liquid crystals of the group of liquid crystals and the liquid crystal of the third group, the light rays incident from the light ray incident port i are not emitted from the light ray emission port k, A light ray emitted from k + 1 and a light ray incident from the light incident port i + 1 is a light ray outgoing port k.
It has a function of switching the optical path of emitting light from the light beam emission port k without emitting light from +1 and can realize operation as an optical switch. Therefore, it can be used as a 2 × 2 optical switch.

As described above, according to the optical switch of the present invention, without using a crystal rotator or a Faraday rotator,
It becomes possible to provide 1 × 2 and 2 × 2 optical switches only with liquid crystal.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical switch according to claim 1 of the present invention.

FIG. 2 is a diagram showing a polarization state and a spatial position of a light ray in an optical path B ₁ of the optical switch of the present invention.

FIG. 3 is a diagram showing a polarization state and a spatial position of a light ray in an optical path B ₂ of the optical switch of the present invention.

FIG. 4 is a perspective view showing a modified example of the optical switch according to claim 1 of the present invention.

FIG. 5 is a perspective view showing an embodiment of the optical switch according to claim 2 of the present invention.

FIG. 6 is a front view showing the configuration of a first group of liquid crystal rotors of the optical switch of the present invention.

FIG. 7 is a front view showing the configuration of a third group of liquid crystal rotators of the optical switch of the present invention.

FIG. 8 is a diagram showing polarization states and spatial positions of light rays on optical paths C ₁ and C ₂ of the optical switch of the present invention.

FIG. 9 is a diagram showing polarization states and spatial positions of light rays in optical paths C ₃ and C ₄ of the optical switch of the present invention.

FIG. 10 is a perspective view showing a modified example of the optical switch according to claim 2 of the present invention.

FIG. 11 is a schematic diagram showing the configuration and operation of an optical switch using a conventional polarization prism or the like.

FIG. 12 is a perspective view showing an optical switch using a conventional reciprocal and non-reciprocal rotator and a liquid crystal plate.

FIG. 13 is a diagram showing a polarization state and a spatial position of a light beam on an optical path A ₁ of a conventional optical switch.

FIG. 14 is a diagram showing a polarization state and a spatial position of a light ray on an optical path A ₂ of a conventional optical switch.

[Explanation of symbols]

51 optical switch 22 First birefringent crystal plate 23 Second Birefringent Crystal Plate 24 Third Birefringent Crystal Plate 28 Light incident port 29,30 Beam exit port 52 First group of liquid crystal rotor 53 Liquid crystal rotor of the second group 55-58 Liquid crystal plate 61 Optical switch 62, 64, 66 lenses 63,65,67 optical fiber 71 Optical switch 72 First birefringent crystal plate 73 Second birefringent crystal plate 74 Third birefringent crystal plate 75 Fourth birefringent crystal plate 76 First group of liquid crystal rotor 77 Liquid crystal rotor of the second group 78 Liquid crystal rotor of the third group 81,82 Ray incident port 83,84 Ray output port 91 Optical switch 92,94,96,98 lens 93,95,97,99 optical fiber

Claims (2)

[Claims] 1. A structure comprising three birefringent crystal plates arranged at a predetermined interval along a traveling direction of a light beam, and varying a polarization direction of the light beam between the first and second birefringent crystal plates. A first group of liquid crystals that can be inserted is inserted, and a second group of liquid crystals having the same function as that of the first group of liquid crystals is inserted between the second and third birefringent crystal plates. The crystal plate is provided with one or more light incident ports and the third birefringent crystal plate is provided with a plurality of light emission ports, and the direction in which the ordinary ray and the extraordinary ray of the birefringent crystal plate are separated is defined by the first And the direction of separation of the third birefringent crystal plate are the same, and the direction of separation of the second birefringent crystal plate is different from the direction of separation of the first and third birefringent crystal plates, respectively. The ordinary ray and the extraordinary ray separated by the first birefringent crystal plate are set. The respective polarization directions of the liquid crystals of the first group are set so that the polarization directions coincide with each other at the incident end surface of the second birefringent crystal plate, and at the exit end surface of the second birefringent crystal plate. 2 that match
An optical switch, wherein the polarization directions of the liquid crystals of the second group are set so that the polarization directions of the light rays of the book are orthogonal to each other at the incident end surface of the third birefringent crystal plate. . 2. A birefringent crystal plate of four sheets is arranged at a predetermined interval along a traveling direction of a light beam, and a polarization direction of the light beam is variable between the first and second birefringent crystal plates. The first group of liquid crystals that can be formed is inserted, and the second group of liquid crystals having the same function as that of the first group of liquid crystals is also inserted between the second and third birefringent crystal plates. The liquid crystal of the third group having the same function as the liquid crystal of the first group is inserted between the birefringent crystal plates, and a plurality of light incident ports are provided in the first birefringent crystal plate and the third birefringent crystal plate is provided. The refraction crystal plate is provided with a plurality of light exit ports, and the birefringence crystal plate separates the ordinary ray and the extraordinary ray in the same direction as the first and fourth birefringence crystal plates are separated from each other. The separating directions of the second and third birefringent crystal plates are also the same, and the first and the second The birefringent crystal plate of No. 4 is set so that the separating direction is different from the separating directions of the second and third birefringent crystal plates, respectively, and an ordinary ray and an anomaly separated by the first birefringent crystal plate are set. The respective polarization directions of the liquid crystals of the first group are set so that the polarization directions of light rays coincide with each other at the incident end surface of the second birefringent crystal plate, and the exit end surface of the second birefringent crystal plate is set. 2 that match in
The respective polarization directions of the liquid crystals of the second group are set so that the polarization directions of the light rays of the book are matched at the incident end face of the third birefringent crystal plate. 2 at the emitting end face
An optical switch, wherein the polarization directions of the liquid crystals of the third group are set such that the polarization directions of the light rays of the book are orthogonal to each other at the incident end surface of the fourth birefringent crystal plate.