JPH0371114A - Optical switch - Google Patents

Abstract

PURPOSE:To offer an optical switch capable of a large deflection point and having high deflection efficiency, a large deflection angle and a large deflection speed by making incident light incident upon an interface between the 1st and 2nd transparent substances from the 2nd transparent substance side with a certain angle. CONSTITUTION:Liquid crystal is applied as the 1st transparent substance 11 and glass is applied as the 2nd transparent substance 12. The refractive index parallel with the major axes of liquid crystal molecules is n1 = 1.73 (when an electric field is impressed) and the refractive index vertical to the major axes is n2 = 1.52 and has positive dielectric constant anisotropy. On the other hand, the glass of refractive index n0 = 1.74 is used as glass having the refractive index n0 larger than the n2. When the incident angle theta of incident light lambdain propagated through the 2nd transparent substance 12 through a mirror 14 upon the interface 13 is set up to 60.9 deg., the incident light lambdain is fully reflected on the interface 13, propagated through the 2nd transparent substance 12 and led out into air through a mirror 18.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical switch that switches the traveling direction of light by applying an electric or magnetic field.

(Prior Art) An optical switch for optical deflection that controls the traveling direction of light is essential as a component of optical information processing, optical exchange, optical memory, optical input/output devices, and the like. This type of optical switch employs various methods such as mechanical deflection, electro-optic deflection, and acousto-optic deflection as means for controlling the deflection.

An optical switch that employs mechanical deflection uses reflection from a mirror with a galvanometer, a rotating prism mirror, or the like, so it has the advantage of high deflection efficiency and a large deflection angle.

In addition, as an optical switch that uses electro-optic polarization,
Pockels effect, where the refractive index of a solid changes due to an electric field;
Alternatively, the Faraday effect, in which the polarization state of light is changed by a magnetic field, is used to separate and polarize two polarized lights by birefringence, and the method is used to separate and polarize two polarized lights by birefringence. Directional coupling type leading wavepath modulators (switches) that utilize optical coupling have been proposed. These have the advantage that the deflection speed is high and the deflection angle can be large.

Furthermore, acousto-optic deflection uses a change in the refractive index of a substance due to ultrasonic distortion.

FIG. 2 is a block diagram of a conventional acousto-optic deflection optical switch using Bragg diffraction using ultrasonic waves.

The basic principle is that as the ultrasonic wave US propagates, the refractive index of the optical crystal 2 changes periodically in accordance with the frequency, depending on the state of the electric field applied to the optical crystal 2 from the high-frequency power source 1. becomes a diffraction grating.

When light λin is incident on the optical crystal 2 in such a state at an angle θ, Bragg diffraction occurs and light with a radiation angle θ is obtained. Using this principle, the optical path of the emitted light λout is switched.

This acousto-optic deflection optical switch has the advantage of relatively high deflection speed.

(Issue 2f1 to be solved by the invention) However, although the mechanical deflection has the above-mentioned advantages, the deflection speed is determined by the mechanical frequency and rotation speed of the drive unit, so there are restrictions on the speed. It has the disadvantage of being accepted.

In addition, those using electro-optical deflection have a fast deflection speed,
Although it is possible to obtain a large deflection angle, the disadvantage is that the deflection point, which is important for parallel processing of light, cannot be set large.

Furthermore, although acousto-optic deflection can obtain a relatively high deflection speed, it has the disadvantage that it is not possible to obtain a large deflection angle, and similarly to electro-optic deflection, it is not possible to set a large deflection point. are doing.

The present invention has been made in view of the above circumstances, and its purpose is to provide an optical switch that can obtain a large deflection point, has high deflection efficiency, and has a large deflection angle and polarization speed. .

(Means for Solving the Problems) In order to achieve the above object, in claim (1), the refractive indexes nl and n2 (nl>
a first transparent material that can be selected from either one of n2), a second transparent material having a refractive index no larger than n2, which is in close contact with the first transparent material, and from the second transparent material side , an input means for inputting light at an angle θ to the interface between the second transparent material and the first transparent material, the angle θ satisfies the following relationship, and either of the following. The relationship was configured to satisfy.

Further, in claim (2), the first transparent material and the second transparent material are each made of a material with a single structure, and a plurality of individually controllable application means are provided.

(Function) According to claim (2), the incident light is directed to the interface between the first transparent material and the second transparent material via the incident means and to the second transparent material.
The light is incident from the transparent material side at an angle θ.

At this time, whether the incident light is totally reflected at the interface or becomes refracted light and proceeds to the first transparent material is controlled by the application state of the electric field or magnetic field by the application means.

That is, by setting the refractive index of the first transparent material to either 01 or n2, the optical path of the incident light is deflected.

According to claim (2), the refractive index of the first transparent material is locally controlled depending on the application state of the electric field or magnetic field by each applying means.

(Example 1) FIG. 1 is a configuration diagram showing a first example of an optical switch according to the present invention.

In FIG. 1, 11 is a first transparent material, which has a refractive index of 01 and n2 (however, n
l>n2). Specifically, for example, when no electric field or magnetic field is applied, the refractive index is set to 02, and when applied, the refractive index is set to nl. As its constituent material, for example, in solid form, KH2P
A material having a large refractive index anisotropy Δn (=nln2), such as electro-optic crystal such as O4°ZnTe, LiNbO3, BaTiO3, etc., is suitable. Furthermore, as a non-solid material, nematic liquid crystal or smectic liquid crystal can be used as a material having relatively large refractive index anisotropy.

12 is a second transparent substance, which has a refractive index nO (no>nl or nl>n
O>n2), and is made of, for example, various glass materials, plastic materials, etc. that do not have refractive index anisotropy.

Reference numeral 13 denotes an interface, which is constructed by having one side of the first and second transparent materials 11 and 12 in close contact with each other.

Reference numeral 14 denotes a mirror as an incident means, for example, an angle (hereinafter referred to as , the incident angle).

The mirror 14 that determines the incident angle θ is formed by vapor-depositing aluminum onto a glass surface.

Transparent electrodes 15 and 16 apply an electric field to the first transparent material 11 when a voltage is applied by a power source 17. When this electric field is applied, the refractive index of the first transparent material 11 is, for example, n
held at l. The transparent electrode 15 is disposed on the lower surface of the first transparent material 11, and the transparent electrode 16 is disposed on the upper surface of the second transparent material 12, and is made of a transparent conductive film such as ITO.

Reference numeral 18 denotes a mirror, and the total reflected light λ8.18 is totally reflected and deflected at the interface 13. is led out into the air via the second transparent material 12 and the transparent electrode 16.

19 is a prism, and a transparent substance 1 of m2 is passed through an interface 13.
The refracted light λRF enters the first transparent material 11 from the refracted light λRF through the transparent electrode 15 and the glass substrate 10, and is led out at a predetermined angle with respect to the air.

Next, the optical path deflection operation with the above configuration is performed by applying liquid crystal as the first transparent material 11 and using the liquid crystal as the second transparent material 11 as described above.
An example in which glass is used as the transparent material 12 will be explained based on FIGS. 3(a) and 3(b).

In addition, specifically, as a liquid crystal, for example, Roche (Roche
), a commercially available nematic liquid crystal material TNO403 is used. The refractive index in the direction parallel to the long axis of the molecules of this liquid crystal is n 1
= 1.73 (when an electric field is applied), the refractive index in the direction perpendicular to the long axis of the liquid crystal molecules is n2d1.52, and it has positive dielectric anisotropy. On the other hand, a refractive index no larger than n2
As the glass having a refractive index no. 1.74, 8940 glass manufactured by Corning Co., Ltd. is used.

FIG. 3(a) shows the state of the liquid crystal molecules 11a when no voltage is applied between the electrodes 15 and 16 (the power source is omitted). The liquid crystal element 11a is homogeneously aligned with its long sleeve substantially parallel to the interface 13 using a well-known alignment treatment technique such as glass surface rubbing. Here, in order to simplify the explanation, the incident light λin is
It is assumed that the S-polarized light has a vibration plane perpendicular to the vibration plane, and the elongated molecules are perpendicular to the vibration plane.

Under these conditions, the refractive index of the liquid crystal viewed from the direction of incidence of the incident light λjn is n2-1.52, and the refractive index no of the 8940 glass is 1.73.

Therefore, the incident angle θ of the incident light λin propagating through the second transparent material 12 through the mirror 14 with respect to the interface 13 is
If the total reflection condition shown by the following equation (1) is satisfied, the incident light λin is totally reflected at the interface 13, and then the second
The light propagates through the transparent material 12 and is led out into the air via the mirror 18.

Next, a voltage is applied between the transparent electrodes 15 and 16 by the power supply 17, and when the electric field applied to the first transparent material 11 is made sufficiently larger than the threshold voltage of the liquid crystal, the liquid crystal molecules 11a , are oriented in the direction of the electric field, and the long axis of the molecule is perpendicular to the interface 13, as shown in FIG. 3(b).

At this time, the vibration plane of the incident S-polarized light is aligned with the long axis of the liquid crystal molecules, so the first
The refractive index of the transparent material 11 is approximately nl-1,73.

Here, if the incident angle θ satisfies the total reflection condition expressed by the following equation (2), the incident light λin becomes refracted light λ8F and propagates through the first transparent material 11 from the interface 13 at a refraction angle φ. do.

As can be seen from Figure 3 (a) and (b), the incident angle θ
under the condition shown in the following equation (3), 60.9° θ< 83
．． io ・If set to (3), the first
By controlling the application of an electric field to the transparent material 11,
Totally reflected light λ3. and the refracted light λRP, the following (4)
An optical path deflection angle A as shown in the formula can be obtained.

A=180-〇-φ...(4)
However, the larger the incident angle θ is, the larger the deflection angle A can be, and the unnecessary reflected light generated at the interface 13 can be reduced in FIG. 3(b).

Note that in the above example, the refractive index no of the second transparent material 12 is
Since n O (1,74) > n 1 (1,73), if the incident angle θ is larger than 83.6°, total reflection will occur regardless of the refractive index anisotropy of the liquid crystal, and the optical path will be deflected. become unable.

However, as the refractive index no of the second transparent material 12, the following equation (5), nl>nO>n2 (5)
If you select a value that satisfies the relationship, the first transparent material (
The refractive index of liquid crystal) 11 is n 1-1.73 (rU!,
In the case of (at the time of application of force), the refracted light is always λRF.

For example, if polycarbonate 1 is used instead of glass as the second transparent material 12, the refractive index is n.

is 1.59, the relationship n>nO is satisfied, and the light becomes refracted light regardless of the incident angle θ, and travels from the interface 13 into the first transparent material 11.

Note that when the refractive index n2 of the first transparent material 11 is 1.52, if the incident angle θ is selected to satisfy the total reflection condition expressed by the following equation (6), the incident light λ1n is totally reflected at the interface 13, further propagates through the second transparent material 12, and reaches the mirror 18.

As described above, according to this embodiment, an optical switch with a large deflection angle and high deflection efficiency can be realized.

Furthermore, since an amorphous material such as liquid crystal is used as the first transparent material, there is no restriction on the incident area of the incident light λin, which has the advantage of allowing a large deflection point, which is important for parallel processing of light. .

Further, if a ferroelectric liquid crystal is used among liquid crystal materials, a deflection speed of 10-4 to 10-6 seconds can be achieved, and a high-speed optical switch can be realized.

(Embodiment 2) 2 Fig. 4 is a configuration diagram showing a second embodiment of the optical switch according to the present invention, and shows an example of the configuration of a multiplex optical switch in which a plurality of optical switches are arranged in parallel and multiplexed. It shows.

In FIG. 4, reference numeral 21 denotes a first transparent substance, which is made of the same material as in Example 1, and has a refractive index of 01 and n2 (nl>n2) depending on the application and non-application of an electric or magnetic field.
).

Reference numerals 22 and 23 denote transparent electrode arrays having a refractive index nO larger than the refractive index n2 of the first transparent material 21.

Each transparent electrode 22a, 23a can be individually controlled from the outside, and a local electric field is applied to the first transparent material 21 depending on whether or not a voltage is applied between each electrode. In FIG. 4, the first transparent material 21 is inserted between the transparent electrode rows 22 and 23, and each transparent electrode 22a, 23a is similar to the second transparent material 12 and the transparent electrodes 15, 16 in Example 1. It also has the functions of In addition, these transparent electrodes 22a, 23
A is formed by vacuum-depositing feed such as ITO or SnO2, and patterning it using photolithography technology.

Reference numeral 24 denotes an interface, and the first transparent electrode 21 and each transparent electrode 22a of the transparent electrode array 22 are in close contact with each other.

Reference numeral 25 denotes a glass prism as an incident means, which allows the incident light λin, which is spatially spread light or a collection of a plurality of light beams to be deflected, to be incident on each transparent electrode 22a at a predetermined angle θ, and , the reflected light λRL totally reflected at the interface 24 is guided into the air.

26 is a glass prism that guides the refracted light λR2 that has proceeded into the first transparent material 21 via the interface 24 into the air.

Note that these glass prisms 25 and 26 are made of glass having approximately the same refractive index as the transparent electrodes 22a and 23a.

In this example, for example, Example 1 is used as the first transparent material.
Similarly, commercially available nematic liquid crystal material TN0 manufactured by Roche
403 as the transparent electrode 22a.

As 23a, SnO2 having a refractive index nO of 1.9 was used.

In this case, when no electric field is applied to the first transparent material (liquid crystal) 21, if the incident angle θ is larger than 53.1', the incident light λ
in is totally reflected.

On the other hand, when applying an electric field to the first transparent material 21, the incident angle θ
is smaller than 65.6°, the incident light λin passes through the interface 24 and becomes refracted light λRP. For example, the incident angle θ is 60
If it is .degree., multiple optical switches can be realized depending on whether or not voltages are individually applied to the transparent electrodes 22a and 23a.

As described above, according to the second embodiment, in addition to the effects of the first embodiment, since the functions of the second transparent material and the electrode are combined in the transparent electrode 22a, the second transparent material Compared to a multiplex optical switch in which electrodes and electrodes are provided separately, it has the advantage of being smaller.

In Examples 1 and 2 above, liquid crystal was used as an example of the first transparent material with variable refractive index, but the invention is not limited to this, and other optical crystal materials and piezoelectric/pyroelectric high Molecular materials and the like can be used similarly.

Moreover, as a means for varying the refractive index of the first transparent material, application of an electric field has been described as an example, but a magnetic material that produces the Cotton-Mouton effect in which the refractive index changes depending on a magnetic field can also be used. Further, the electrode structure, position, and feed for applying the electric field and magnetic field are not limited to those illustrated, and various structures can be selected that apply a desired external force to the first transparent material having a variable refractive index.

Also, regarding the light input means or light extraction means,
In addition to mirrors and prisms, various methods can be selected, such as directly bonding optical fibers.

(Effects of the Invention) As explained above, according to claim (1), the deflection angle is larger and the deflection efficiency is higher than that of the conventional optical switch, and the deflection point, which is important for parallel processing of light, is enlarged. It has the advantage of being able to provide a light switch that can be switched off.

According to claim (2), in addition to the above effects, there is an advantage that a multiplex optical switch capable of processing a plurality of lights in parallel can be realized.

[Brief explanation of drawings]

6. Fig. 1 is a block diagram showing a first embodiment of the optical switch according to the present invention, Fig. 2 is a block diagram of a conventional acousto-optic deflection optical switch, and Fig. 3 is an explanatory diagram of the operation of Fig. 1. FIG. 4 is a configuration diagram showing a second embodiment of the optical switch according to the present invention. In the figure, 10... Glass substrate, 11.21... First transparent material, 12... Second transparent material, 13.24...
Interface, 14...Mirror (incidence means), 15.16...
・Transparent electrode, 17...Power supply, 18...Mirror 19
25.26... Prism, 22.23... Transparent electrode row, 22a, 23a... Transparent electrode.

Claims (2)

[Claims] (1) The refractive index n1 depends on the applied state of the electric or magnetic field.
and n2 (n1>n2); a second transparent material that is in close contact with the first transparent material and has a refractive index n0 larger than n2; incident means for making light incident on the interface between the second transparent material and the first transparent material at an angle θ from the transparent material side of the transparent material, and the angle θ is such that θ>sin^-^1n2 An optical switch that satisfies the relationship: /n0, and satisfies either of the relationships: θ<sin^-^1n1/n0, or n1>n0. (2) The optical switch according to claim (1), wherein the first transparent material and the second transparent material are each made of a material with a single structure, and a plurality of individually controllable application means are provided. .