JPS5890620A - Electrooptic switch - Google Patents

Abstract

PURPOSE:To obtain a compact, inexpensive electrooptic switch by providing a couple of electrode on a surface of photoelectric anisotropic crystal, connecting at least two optical fibers to one end surface crossing the surface at right angles, and providing on the other surface a concave mirror which guides polarized components of light from one optical fiber to the other optical fiber. CONSTITUTION:On a surface of anisotropic dielectric crystal 1 made of PbMoO4 having electrooptic effect, a couple of linear electrodes 2 are provided; and optical fibers 11-13 are connected through an SELFOC lens 4 to one end surface crossing the surface at right angles, and concave mirrors 21-23 are formed in the other end surface. While no AC voltage is applied to the electrodes 2, light projected from the optical fiber 11 for incident travels straight in the crystal 1 through the lens 4, and is reflected by the mirror 23 to illuminate the optical fiber 13. When a voltage is applied, an electric field E is produced in the crystal 1 and two polarized component of the incident light by birefringence are reflected by the concave mirrors 21 and 22 to enter the optical fiber 12. Thus, a compact, inexpensive switch is obtained.

Description

Detailed Description of the Invention The present invention relates to an element that deflects incident light by applying an electric field to a dielectric material that generates an electro-optic effect and forming a non-uniform refractive index distribution in the dielectric material, particularly an anisotropic element. The present invention relates to an electro-optical switch using a dielectric material.

Optical fibers for input and output are optically coupled to opposite end faces of the deflection element, and light from the input optical fiber is made to enter the polarization element from one end face and pass through the deflection element. There is an electro-optic switch that guides light emitted from the other end face to an output optical fiber. By generating an electric field in the deflection element (because light is deflected as it propagates through the deflection element), by applying or not applying an electric field, or by changing the strength of the electric field, the output optical fiber is It is possible to control the light incident on the device, making it possible to switch optical signals.

However, in such an electro-optic switch, it is unavoidable that the light beam incident on the deflection wife spreads while propagating inside the deflection element, and the diameter of the core of the output optical fiber is adjusted to accommodate the spread light beam. Since the diameter of the optical switch is much smaller than the diameter of the optical switch, the loss of optical coupling to the output optical fiber is extremely large, and there is a problem that the optical loss of the entire optical switch cannot be reduced. Since the spread of a light beam is proportional to the optical path length, it is best to make the optical path length as short as possible, but in that case, a dielectric material that can obtain a large deflection angle is required.

However, most dielectrics that can obtain a large deflection angle even with a low applied voltage for generating an electric field are anisotropic dielectrics that are polarization dependent. Generating an electric field in an anisotropic dielectric causes anisotropy in the refractive index, so that the incident light beam is split into two components with different deflection angles, resulting in two beam spots. Since only one polarized component can enter the output optical fiber of an optical switch, a switch using an anisotropic dielectric material reduces the optical coupling to the output optical fiber by half, widening the light beam. Combined, the loss becomes extremely large.

In addition to these problems with electro-optic switches using anisotropic dielectrics, conventional optical switches generally require collimation of light at both ends of the deflection element, which requires lenses, etc. There is a problem in that at least two are required, making it difficult to downsize and reduce the cost.

Furthermore, when providing a changeover switch function, at least two output optical fibers are optically coupled to the other end surface of the deflection element. Therefore, since it is necessary to polarize the light by at least a small amount of the diameter of the optical fiber, there is also the problem that the loss of light increases. In addition, since the output optical fibers are arranged close to each other, there is a problem that a large extinction ratio cannot be obtained. It is an object of the present invention to provide an electro-optical switch that can minimize optical loss, be compact, and be inexpensive.

Hereinafter, embodiments in which the present invention is applied to an electro-optical changeover switch will be described in detail with reference to the drawings.

This changeover switch switches the light from the input optical fiber to the two output optical fibers in accordance with a control signal.

In FIG. 1, a pair of linear electrodes (2) are arranged in parallel at an appropriate distance on the surface of an anisotropic dielectric crystal (1) that generates an electro-optic effect, such as PbMoO4.
ing. An AC power source (3) is connected between these linear electrodes (2).
), an appropriate voltage is applied. The electrode (2) can be formed by depositing aluminum by photolithographic techniques. By applying a voltage between the linear electrodes (2), the crystal (2)
An electric field whose strength varies with its depth (within the depth) is generated.

Since the crystal fi+ is anisotropic, the main axis of the refractive index ellipsoid rotates due to the electro-optic effect, creating anisotropy in the refractive index, and the refractive index changes in proportion to the electric field (6) and its square. Therefore, a refractive index distribution that changes rapidly in the thickness direction of the crystal (1) is obtained.

As a result, if a light beam is incident from one end surface of the crystal (1) perpendicular to the linear electrode (2) at an appropriate depth near the center between the electrodes (2) and parallel to the electrode (2), , this incident beam is divided into two components with polarization components orthogonal to each other, and each polarization component propagates through the crystal (1) in the thickness direction of the crystal (1) as shown in Figure 2. is deflected upward. Since the two polarized light components have different deflection angles due to the influence of the anisotropy of the refractive index, they are divided into two beams and propagated.

Referring to FIGS. 1 to 3, a collimating Selfox lens (4) with a thickness corresponding to 174 wavelengths of incident light is disposed in close contact with the one end surface of the dielectric crystal (1). There is. Three optical fibers Cl1l GZ (1) are arranged so that one end thereof faces the outer surface of the lens (4), and these optical fibers (Ill~ (131) are connected to the crystal (1) through the lens (4). optical fiber Qll.
is for input, and other optical fibers (121 (131 is for output, optical fiber α2 from above) are arranged vertically in the order of (113Q3). These optical fibers 011 to .
1 131 are parallel to each other at least in the vicinity of the crystal, and are also parallel to the linear electrodes (2), and are arranged at the center between the pair of linear electrodes (2). The optical fiber 01) has a central core C11a) and a core (I
The cladding layer (11b) covers the periphery of the optical fiber (IIL).The same applies to the other optical fibers (12 (131).

On the other end surface of the crystal (1) opposite to the one end surface on which these optical fibers are provided, there is a wire at the center between the linear electrodes (2).
Three hemispherical protrusions (241
□□□ (A) is formed and finished with mirror polishing.

Then, thin aluminum films are deposited on these protrusions, respectively, to form three concave mirrors (211@n).

When no AC voltage is applied between the pair of linear electrodes (2), no electric field is generated within the crystal (1). In this case, as shown in Figure 3, the input optical fiber (
The light emitted from il+ is collimated by a lens (4) and then enters the crystal (1), where it may also be deflected.
The light does not split into polarized light components, but spreads out slightly as it travels straight and reaches the concave mirror (23). The light is then reflected by the concave mirror (concave mirror), travels straight while being condensed, enters the lens (4), is collimated, and enters the core of the optical fiber +131. Both optical fibers (II) Positional relationship between Q31 and concave mirror (goods), radius of curvature of concave mirror (23), incident light and concave mirror (
If the direction of 2■ is adjusted in advance, almost the entire amount of light emitted from the optical fiber (11) can be transferred to the optical fiber Q.
31 cores.

When an AC voltage is applied between a pair of linear electrodes (2), an electric field (T) is generated within the crystal (1). In this case, as shown in Figure 2, the light emitted from the optical fiber (11) is collimated by the lens (4), and then is emitted while being slightly flattened in the process of propagating within the crystal (1). Concave mirror (21)@
reach respectively.

The two polarized light components reflected by the concave mirror (2) are then condensed and deflected upward by the electric field again, passing through the lens (4) and being combined into the core of the optical fiber α2. do. Optical fiber αD It is possible to combine the nk-element beam into two polarized components and make almost the entire amount of light enter the optical fiber OX5.

In this way, by controlling the application of the electric field, the light from the optical fiber (11) is transferred to the optical fiber 03 or Q.
It is possible to switch to any one of 31 and make it incident. In this example, the output optical fibers 0 and 03 are
Since the optical fiber a11 is sandwiched between them, a large extinction ratio can be obtained.

The above embodiment is an example of a changeover switch, but it can be simply turned on,
In the case of a switch that only turns off, the optical fiber α2
or Q31, and concave mirror 21) and ■
Either one of the pair or - may be omitted. vice versa,
Multi-point optical switches can also be constructed by increasing the number of optical fibers and concave mirrors or concave mirror pairs. The concave mirror is formed using the other end surface of the crystal (1), but the other end surface may be flattened and a separately prepared concave mirror may be coupled thereto.

As in the above embodiment, it is preferable to use a linear electrode as it is possible to obtain a larger potential gradient, but the shape of the electrode may be circular, rectangular, triangular, comb-shaped or any other shape. Can be adopted. Furthermore, any number of pairs of electrodes other than one pair may be provided, and it is also possible to provide them on both the front and back surfaces of the dielectric crystal. Furthermore, the voltage applied to the electrodes may be not only alternating current but also direct current. - As explained in detail above, in the present invention, an electric field whose strength changes in the depth direction of the dielectric is generated on one surface of an anisotropic dielectric that generates an electro-optic effect. At least one pair of electrodes are provided, and at least two optical fibers are optically coupled to one end face perpendicular to the n1 above-mentioned surface, and when an electric field is generated in the dielectric at the other end face opposite to the one end face, A pair of concave mirror structures are provided that respectively reflect two components of light having different deflection angles, which are incident on the dielectric body from one optical fiber, toward the other optical fiber. By applying a voltage to a pair of electrodes and generating an electric field within the dielectric, the light that has entered the dielectric from one optical fiber is deflected so that it enters or does not enter the other optical fiber. It is possible,
An optical switch can be realized. The light incident on the dielectric is
Even if the dielectric material is anisotropic, the light propagates in two components with different deflection angles, but is reflected by a pair of concave mirror structures and condensed and combined on the way to the other optical fiber. Therefore, even if an anisotropic dielectric material with a low voltage and a large deflection angle is used, loss in optical coupling from the dielectric material to the other optical fiber can be extremely reduced.

In addition, optical coupling with the optical fiber is required only at one end face of the dielectric, and combined with the ease of optical coupling by condensing light with a concave mirror, the collimating system for optical coupling is simple, making it more compact and less expensive. can be achieved. Furthermore, since the light beam travels back and forth within the dielectric, it is possible to obtain a deflection angle twice that of the case where the light beam propagates in only one direction, making it possible to lower the applied voltage and to When there are multiple optical fibers, these optical fibers can be placed apart from each other, which increases the extinction ratio. Since all the optical fibers are ejected in the same direction, mounting on a printed circuit board, etc. is easy, the mounting density can be increased, and maintenance is also simple.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the invention, and FIGS. 2 and 3 are explanatory diagrams showing the principles of deflection and switching. (1)・O・Anisotropic electro-optic dielectric, (2)・φ・Linear electrode, 01)αri αJ・Optical Fino, Inc. Equipment・Concave mirror. Patent applicants: 4 people including Tateishi Electric Co., Ltd.

Claims (3)

[Claims] (1) A pair of electrodes are provided on one surface of an anisotropic dielectric that generates an electro-optic effect to generate an electric field whose strength varies in the depth direction of the dielectric.
At least two optical fibers are optically coupled to each other at one end face +c, perpendicular to the above-mentioned surface; An electro-optic switch is provided with a pair of concave mirror structures that respectively reflect two components of light incident into the body having different deflection angles toward the other optical fiber. (2) At least three first, second and third optical fibers are optically coupled to the one end surface, and the other end surface has:
At least a pair of concave mirror structures that respectively reflect two components having different deflection angles of light incident on the dielectric from the first optical fiber toward the second optical fiber when an electric field is generated; The electro-optic switch according to claim 1, further comprising a concave mirror structure that reflects light from the first optical fiber toward the third optical fiber when an electric field is applied. (3) The electro-optic switch according to claim (1), wherein the electrode is a linear electrode parallel to the light propagation direction.