JPH0792405A - Electric capillary optical switch - Google Patents

Abstract

PURPOSE:To provide an electric capillary optical switch which ensures a high speed operation in spite of miniaturization by providing the switch by a bypassing passage connected to both ends of a slit. CONSTITUTION:Electrodes 1 are respectively arranged in the positions in contact with both ends of the slits 3. The respective electrodes 1 are connected to a power source by wirings. Mercury 2 is, therefore, eventually moved by electric capillarity in the slit 3 when a voltage is impressed between both electrodes 1. A bypassing groove 4 is formed at a glass plate which is a cap. Then, an electrolyte existing in front of the mercury 2 moves to a positive pole side through the bypassing groove 4 and moves backward of the mercury 2 at the time the mercury 2 is moved to a negative pole side by the electric capillarity in the slit 3 when the voltage is impressed between both electrodes 1. The bypassing groove 4 exists on both sides of the slit 3 at this time and, therefore, the electrolyte is eventually divided and moved in two directions and the resistance by viscosity is lowered. As a result, the movement of the mercury 2 is speeded up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrocapillary optical switch for switching optical communication by utilizing the electrocapillary phenomenon.

[0002]

2. Description of the Related Art An example of a conventional electrocapillary optical switch is shown in FIG. The optical switch shown in the figure functions as a 1 × 2 switch. That is, the orthogonal optical waveguides 5 are formed on the planar optical waveguide substrate 6, and the slits 3 enclosing the electrolytic solution 8 and the mercury 2 are obliquely arranged at the intersections thereof, and the electrodes 1 are provided at both ends of the slits 3. Are provided respectively. The mercury 2 is in contact with the electrolytic solution 8 in the slit 3 and is movable. The optical waveguide 5 is connected to the optical fibers A, B and C, respectively.

As the type of the electrolytic solution 8, a solution that does not react with the mercury 2, for example, a dilute sulfuric acid or sodium sulfate aqueous solution can be used.
The mercury 2 functions as a reflecting mirror when it is located at the waveguide intersection in the slit 3, and as shown in FIG.
The optical fiber A and the optical fiber B forming an angle of 0 ° are optically connected via this switch. On the other hand, when the mercury 2 is located inside the slit 3 at a position deviated from the waveguide intersection, the optical fibers A and C, which are located in a straight line, are optically connected.

The movement of the mercury 2 in the slit 3 is caused by the movement of the electrode 1
It is realized by the electrocapillary phenomenon that occurs when a voltage is applied between (JLJackel, S.Hackwood, JJVeselka and G.Be
ni; "Electrowetting switch for multimode optical fi
bers ", Appl.Opt., Vol.22, No.11, pp.1765-1770, 1983).

That is, on the surface of the mercury 2 in the electrolytic solution 8, an electric charge depletion layer called an electric double layer is generated, which functions as a capacitor. Further, since the mercury 2 is positively charged in the electrolytic solution 8, the surface of the mercury becomes an electric double layer surrounded by negative ions of the electrolytic solution 8. This electric double layer also exists between the mercury 2 and the wall of the slit 3, and the mercury 2 is entirely covered with a thin electrolyte solution 8. When a voltage is applied between the electrodes 1,
When an electric current flows through the electrolytic solution 8 and a current flows through the gap between the mercury 2 and the wall of the slit 3, a voltage drop occurs due to the electric resistance of the electrolytic solution 8, and the voltage applied to the electric double layer on the surface of the mercury has a gradient. .

Since the electric double layer functions as a capacitor, if the applied voltage varies depending on the location, the energy stored at each location varies. This difference in energy results in a difference in surface energy and thus causes the surface tension of the mercury surface to tilt along the direction of current flow.
Since the surface tension of the positive electrode side becomes higher than that of the negative electrode side, the mercury 2 moves in the electrolytic solution 8 toward the negative electrode side.

When no current is passed between the electrodes 1, the mercury 2 is fixed to the wall of the slit 3 by static friction and the self-holding property by no power is secured. Especially, when the dimension of the slit cross section is several tens of micrometers or less, the static friction becomes an order of magnitude larger than the force generated by the acceleration due to gravity or collision. Therefore, a special device for fixing the mercury 2, for example, mercury 2 There is no need for a structure in which the slit width of the portion to be held is wide.

[0008]

If the size of the cross section of the slit 3 used in the optical switch is on the order of millimeters, the electrolytic solution 8 in front of the mercury 2 that is pushed away as the mercury 2 moves is It can move to the rear of the mercury 2 through the side surface. At this time, the moving mercury 2 is somewhat deformed due to the movement of the electrolytic solution 8.

However, when the size of the cross section of the slit 3 is less than several tens of micrometers, the mercury 2 is less likely to be deformed. This is because the internal pressure of the liquid droplet has the property of being inversely proportional to the radius of curvature, so in order to deform the small-sized mercury 2,
This is because high pressure is required. Therefore, the slit 3
In the optical switch having a structure in which the electrolytic solution 8 and the mercury 2 are enclosed, if the cross-sectional area of the slit 3 is reduced, the mercury becomes difficult to move, and the switching speed becomes slow, or the switch does not operate. is doing.

Therefore, it was not possible to form a matrix optical switch having a large number of these switches in a small size. The present invention has been made in view of the above-described conventional art, and an object of the present invention is to provide an electrocapillary optical switch that can guarantee high-speed operation even if it is downsized.

[0011]

The electrocapillary optical switch of the present invention which achieves such an object is provided with a slit at a position of blocking an optical waveguide of an optical waveguide substrate, and an electrolyte and mercury are enclosed in the slit, Electrodes in contact with both ends of the slit are respectively arranged, and wiring for applying a voltage is further provided between both electrodes, and when a voltage is applied to both electrodes, the mercury moves in the slit by an electrocapillary phenomenon to move the optical waveguide. In the electrocapillary optical switch for switching between the slits, a bypass groove connected to both ends of the slit is provided, and the electrolytic solution is bypassed to the bypass groove when the mercury moves in the slit. .

Further, the slit is divided into a central portion filled with the electrolytic solution and mercury and both end portions filled with only the electrolytic solution by a narrow portion that prevents passage of the mercury by a capillary phenomenon. You may do it.

[0013]

[Function] Since the bypass groove connecting both ends of the slit is provided, when mercury moves to the negative electrode side due to the electrocapillary phenomenon,
The electrolyte solution in front of the mercury is pushed by the mercury, passes through the bypass groove, and flows around behind the mercury. Therefore, mercury can move without being deformed. Further, since the mercury can move without generating a pressure that is large enough to deform the mercury, the switch can be activated at a lower voltage. With the same voltage, it is possible to perform the switching operation at a higher speed than a switch without a bypass groove.
Therefore, it is possible to reduce the size of the cross section of the slit to several microns or less and integrate it.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. [Embodiment 1] FIGS. 1 and 3 show a first embodiment of the present invention. As shown in both figures, a slit 3 is provided at a position that shields the optical waveguide of the optical waveguide substrate 6, and the slit 3 is filled with an electrolytic solution 8 and mercury 2 and is enclosed by a glass plate 9 as a lid. Electrodes 1 are arranged at positions contacting both ends of the slit 3, and these electrodes 1 are connected to a power source by wiring not shown. Therefore, when a voltage is applied between both electrodes 1, the mercury 2 moves within the slit 3 by the electrocapillary phenomenon.

In this embodiment, the detouring groove 4 is formed in the glass plate 9 which is the lid. The detouring groove 9 is connected to both ends of the slit 3 and has a corridor shape so as to be located on both sides of the slit 3. The detouring groove 4 is formed by the photolithography technique like the slit 3. Since the width of the bypass groove 10 is formed narrower than the width of the slit 3, the mercury 2 does not enter the bypass groove 10. This is because the mercury 2 has a high surface tension of about 450 dyn / cm even in the electrolytic solution 8 and has a property of not getting wet with the glass, and thus it is difficult to enter the narrow space due to the capillary phenomenon.

Therefore, as shown in FIG. 3, when a voltage is applied between both electrodes 1, the mercury 2 moves to the negative electrode side in the slit 3 due to the electrocapillary phenomenon, and the electrolysis in front of the mercury 2 occurs. The liquid 8 moves to the positive electrode side through the bypass groove 4,
Move behind Mercury 2. At this time, since the bypass grooves 4 are located on both sides of the slit 3, the electrolytic solution 8 moves separately in two directions, and the resistance due to viscosity can be reduced. Thereby, the movement of the mercury 2 can be accelerated.

In order to bring the glass plate 9 into close contact with the optical waveguide substrate 6, the slit 3 provided in the optical waveguide substrate 6 is used.
Then, after filling the mercury 2 and the electrolytic solution 8, the glass plate 9 is overlapped and pressed in the electrolytic solution 8. If the pressing force is maintained by using a spring or the like, the glass plate 9 can be kept in close contact with the optical waveguide substrate 6. In many cases, the surface of the optical waveguide substrate 6 is slightly bent for manufacturing reasons, but the optical waveguide substrate 6 can be brought into close contact with each other by pressing together with the glass plate 9 from above and below.

Further, by removing the unevenness due to the bending of the surface of the optical waveguide substrate 6 by polishing, the glass plate 9 can be brought into close contact with the glass plate 9 without applying any pressure. In any case, it is advisable to fix the glass plate 9 to the optical waveguide substrate 6 with an adhesive in a state in which the glass plate 9 and the optical waveguide substrate 6 are in close contact with each other, and to seal with a silicone rubber or the like in order to prevent leakage or evaporation of the electrolytic solution.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention. In this embodiment, the bypass groove 10 is formed on the optical waveguide substrate 6 instead of the glass substrate 9 which is the lid. Other configurations are similar to those of the above-described embodiment. When the detouring groove 10 is provided in the optical waveguide substrate 6 as in the present embodiment, the glass substrate 9 serving as the lid does not need to be provided with any particular structure, and the labor required for processing can be saved.
Since the detour groove 10 can be formed by photolithography at the same time as the slit 3, it is easy to manufacture.

[Third Embodiment] FIG. 5 shows a third embodiment of the present invention. In this embodiment, the mercury 2 cannot contact the electrode 1. That is, the slit 3 is composed of two narrow portions 3a and 3b, and a central portion 3c in which the mercury 2 and the electrolytic solution 8 are enclosed and both end portions 3d and 3 in which only the electrolytic solution 8 is enclosed.
It is divided into e and. The other structure is the same as that of the second embodiment described above, and the detouring groove 10 has the optical waveguide substrate 6
It was created at the same time as the slit 3.

The narrow portions 3a and 3b are passages having a cross-sectional area narrower than the cross-sectional area of the central portion 3c and both end portions 3d and 3e.
It has a feature that does not pass through. Therefore, the mercury 2 can move only within the central portion 3c of the slit 3, and the end portions 3
Since it cannot enter d and 3c, contact with the electrode 1 is avoided. As described above, in this embodiment, since the mercury 2 cannot contact the electrode 1, the mercury 2 does not get wet and stick to the electrode 1. Therefore, the movement of the mercury 2 is not hindered by the electrode 1 and the electrode material You can increase your options.

That is, the mercury 2 has a property of reacting with a metal generally used as an electrode material such as gold, silver and aluminum to form an alloy (mercury amalgam). Therefore, in the structure in which the mercury 2 is in contact with the electrode 1, only a limited metal such as platinum, iron, cobalt, manganese, or nickel, which is hard to react with the mercury 2, can be used as the electrode material.
In the structure in which the mercury 2 cannot contact the electrode 1 as in the present embodiment, the electrode 1 does not react with the mercury 2, so that there is no restriction as an electrode material.

[Embodiment 4] FIG. 6 shows a fourth embodiment of the present invention. This embodiment has a structure in which the mercury 2 cannot contact the electrode 1, but unlike the third embodiment, the bypass groove 4 is formed in the glass plate 9. That is, the slit 3 is divided by the two narrow portions 3a and 3b into a central portion 3c in which the mercury 2 and the electrolytic solution 8 are enclosed and both end portions 3d and 3e in which only the electrolytic solution 8 is enclosed. The other structure is similar to that of the first embodiment.

Also in the present embodiment, as in the third embodiment, since the mercury 2 cannot contact the electrode 1, the mercury 2 does not get wet and stick to the electrode 1, so that the movement of the mercury 2 by the electrode 1 is prevented. Not only is it not hindered, but the choice of electrode materials can be increased. Although the detouring grooves 4 and 10 are provided in either the optical waveguide substrate 6 or the glass plate 9 in the above embodiment, the detouring grooves 4 and 10 are provided in the optical waveguide substrate 6 and the glass plate 9. The structure may be provided on both sides to form an integral groove.

[0025]

As described above in detail with reference to the embodiments, the electrocapillary optical switch of the present invention has the bypass passages connected to both ends of the slit. Even if mercury is moved, the movement of mercury is not hindered by the electrolytic solution. Therefore, the mercury can be easily moved, the switch can be driven at a lower voltage, and when the same voltage is used, the switch operation can be performed at a higher speed. Further, since the bypass groove can be realized by adding a relatively small structure near the slit, the switch does not become extremely large, and the matrix switch in which many electrocapillary optical switches of the present invention are integrated can be made compact. Can be made. Furthermore, if a narrow portion is provided in the slit and a structure in which mercury does not contact the electrode is adopted, a general material such as gold can be used as the electrode material.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a conventional electrocapillary optical switch.

FIG. 3 is a sectional view showing an electrocapillary optical switch according to a first embodiment of the present invention.

FIG. 4 is a plan view showing an electrocapillary optical switch according to a second embodiment of the present invention.

FIG. 5 is a plan view showing an electrocapillary optical switch according to a third embodiment of the present invention.

FIG. 6 is a plan view showing an electrocapillary optical switch according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 electrode 2 mercury 3 slit 4 cover side detour groove 5 optical waveguide 6 optical waveguide substrate 8 electrolyte 9 glass plate 10 optical waveguide substrate side detour groove A, B, C optical fiber

Claims (2)

[Claims] 1. An optical waveguide substrate is provided with a slit at a position that shields the optical waveguide, an electrolyte and mercury are enclosed in the slit, and electrodes that are in contact with both ends of the slit are respectively arranged, and a voltage is applied between both electrodes. When a voltage is applied to both electrodes, the mercury moves in the slit due to an electrocapillary phenomenon to switch the optical waveguide, and in the electrocapillary optical switch, a detour for connecting to both ends of the slit. An electrocapillary optical switch, characterized in that a groove is provided, and when the mercury moves in the slit, the electrolytic solution is bypassed to the bypass groove. 2. The slit is divided into a central portion filled with the electrolytic solution and mercury and both end portions filled with only the electrolytic solution by a narrow portion that blocks passage of the mercury by a capillary phenomenon. The electrocapillary optical switch according to claim 1, wherein: