JPS5952219A - Electrode for liquid crystal optical element - Google Patents

Abstract

PURPOSE:To prevent a liquid crystal optical switch from having a shift in transmission wave optical path, by leading out the lead line of an electrode for orientation control over a liquid crystal layer laminated on a light guide film to the electrode substrate surface opposite to the liquid crystal layer side through a through hole provided at a desired position of the electrode substrate. CONSTITUTION:Through-holes are formed in said electrode substrate 9 of, for example, a 2X2 light guide type liquid crystal switch for a liquid crystal optical element for optical information processing and optical communication at positions (black dot) except light guide optical paths of liquid crystal side electrodes 5, 6, 7, and 8 on the electrode substrate 9. Internal walls of those through-holes are plated chemically with, for example, Cu 10 and then the electrodes 5-8 and their lead lines 12 are connected together by melting and filling an alloy (solder, etc.) 11 consisting essentially of Sn, Pb, etc., having good wettability with Cu 10. Consequently, when voltages are applied from ports I1 and I2 to the liquid crystal layer, guided light is reflected totally by the lower parts of the electrodes 5 and 6 to travel in the order of I1-O2 and I2-O2, and in this case, a shift in optical patch due to the lead lines 12 of the electrodes 7 and 8 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode for a liquid crystal optical element used in optical information processing and optical communication.

As an example of conventional electrodes for liquid crystal optical elements, Japanese Patent Application No. 56-1
The electrodes used in the waveguide type liquid crystal optical switch proposed in No. 67912 will be described below. For convenience of explanation, the operation of the optical switch will also be described. FIG. 1 is a block diagram of a 2×2 waveguide type liquid crystal switch using conventional electrodes for liquid crystal optical elements, and FIG. FIG. 2 is a cross-sectional view taken perpendicularly to the plane of the paper at lines I and -M in FIG. 1; As shown in FIG. 2, this switch consists of a lower electrode 1, a buffer layer 2, an optical waveguide layer 8, a nematic liquid crystal layer 4, and a liquid crystal layer as shown in FIGS. A first electrode 5, a second electrode 6, a third electrode 7, and a fourth electrode 8, which are parallel to each other and have a predetermined angle with respect to the guided light, and an upper part to which lead wires to these electrodes are attached on the contact sides. It consists of an electrode substrate 9. The surfaces of the optical waveguide layer 3 and the upper electrode substrate 9 on the liquid crystal side are subjected to parallel alignment treatment in the X-axis direction in the figure, and when no voltage is applied, the liquid crystal molecules are aligned in the light guide as shown in Figure 2. It is parallel to the wave layer 3 and is oriented in parallel with its long axis facing the X-axis direction.

In the above configuration, let us consider a case where guided light whose electric field vibration surface is within the plane of the optical waveguide layer 3 is incident from the boats ① and ②2. When no voltage is applied, these guided lights travel straight and reach boats M0 and M2. On the other hand, when an alternating voltage is applied to the lower electrode 1 and any of the first to fourth electrodes 8, as shown in FIG. The output becomes smaller and the equivalent refractive index decreases. FIG. 2 shows the situation when voltage is applied to the first electrode 5. As a result, the guided light incident from the port 11 is totally reflected at the lower part of the first electrode 5, and reaches the boat 0□, as shown in FIG.

Now, in this state, when trying to output the guided light incident from boat □2 to boat 0□, the fourth electrode 8
A voltage will be applied to. Then, since a voltage is applied to the liquid crystal layer also at the lower part of the lead portion to the fourth electrode 8, the equivalent refractive index of this part also decreases. Therefore, as shown in FIG. 1, an optical path shift occurs at the lower part of the lead portion to the fourth electrode 8.

As mentioned above, when conventional electrodes for liquid crystal optical devices are used, when trying to assemble a matrix using a waveguide type liquid crystal optical switch, optical path deviation occurs at the electrode leads, and therefore it is difficult to connect optical fibers to the output ports. There is a problem in that the coupling efficiency deteriorates when connecting or installing a light receiver.

Here, we have described the case of constructing the simplest 2 × 2 matrix, but constructing a higher-order matrix of 3 × 8 or more increases the number of times the emitted light crosses the electrode lead part, which increases optical path deviation. , which was virtually impossible.

In order to solve the above-mentioned problem of optical path deviation at the electrode lead portion, the present invention is arranged so that the lead wire of the upper electrode is taken out to the surface of the upper electrode substrate opposite to the surface in contact with the liquid crystal layer. The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a sectional view of an electrode for a liquid crystal optical device according to the present invention. A through hole is formed in an upper electrode substrate 9 made of an insulating material such as glass or ceramic at a portion other than the path of guided light, and this through hole is filled with metal lO-11. The ends of the patterned upper electrode y, that is, the first electrode 5 to the fourth electrode 8, are in contact with the liquid crystal layer side of the through hole filled with metal, and the lead wire 12 is in contact with the other side of the through hole. is connected.

FIG. 8(al) shows the case where the lead wire 12 is taken out as a wire, while FIG. 8(b) shows the case where the lead wire is patterned.

Such an upper electrode structure can be produced, for example, as follows. First, a through hole is made in a desired position of an insulating substrate by a drill or ultrasonic machining. Next, this through hole is filled with metal 10-11, but insulating substrates such as glass and ceramics generally have poor wettability with metal, so even if molten metal comes into contact with the vicinity of the through hole, the metal 10-11 will not penetrate. Does not flow into the hole. Therefore, the inner wall of the through hole may be plated with metal in advance. As the plating method, electroless copper plating is suitable. In this method, when a sample coated with a special paste is immersed in a plating solution, copper is selectively deposited only in the areas where the paste has been coated. Therefore, a special paste is applied to the inner wall (4) of the through hole to deposit copper on the wall surface, and the hole wall is first plated with copper as metal 10. Next, a copper lead wire 12 is passed through this through hole, and a metal 11 that has good wettability with copper, such as tin, lead, or an alloy mainly composed of these (solder, etc.), is melted and brought into contact with the through hole. If so,
The through holes are filled with metal 11 very easily. After that, the surface on the liquid crystal layer side was polished and shaped, and the first electrode 5 was patterned.
~If the fourth electrode 8 is brought into contact, the structure shown in FIG. 3(a) is formed. Also, to make it as shown in Figure 3(b), metal 1
The through holes plated with metal 11 are filled with metal 11, and then both sides of the upper electrode substrate 90 are polished and shaped, and the first electrode 5 is placed on the liquid crystal layer side.
- The fourth electrode 8 may be attached on the opposite side thereof by patterning the lead wire 12.

FIG. 4 shows an example of a waveguide type liquid crystal optical switch using an electrode for a liquid crystal optical element having such a structure. The switch states are I, -0,, I, -〇□ connections as in Fig. 1. As is clear from the comparison with the conventional type shown in Figure 1, the electrode lead wire 1
Since the lead wires 12 are taken out from above the upper electrode substrate 9, the lead wires 12 do not have any influence on the alignment of the liquid crystal, and therefore the structure is such that no optical path deviation occurs at all.

As explained above, if the electrode for a liquid crystal optical device of the present invention is used, the electrode lead wire portion does not have any influence on the liquid crystal alignment, so it is effective when applied to a liquid crystal optical device. In particular, as described above, when used in a waveguide type liquid crystal optical switch, no optical path deviation occurs, so high coupling efficiency can be obtained at the output section, and it is extremely effective in realizing a large-scale matrix switch.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a waveguide type liquid crystal optical switch using conventional electrodes for liquid crystal optical elements, Figure 2 is a cross-sectional view at I and -M of the waveguide type liquid crystal optical switch shown in Figure 1, and Figure 8. 4 is a sectional view of an electrode for a liquid crystal optical device of the present invention, and FIG. 4 is a configuration diagram of an embodiment of a waveguide type liquid crystal optical switch using the electrode for a liquid crystal optical device of the present invention. 1... Lower electrode substrate, 2... Buffer layer, 3...
Optical waveguide layer, 4... Liquid crystal layer, 5... First electrode, 6...
・Second electrode, 7... Eighth electrode, 8... Fourth electrode, 9
...Top electrode substrate. 10...Metal, 11...Metal, 12...Lead wire. Patent applicant Nippon Telegraph and Telephone Public Corporation 1st floor Figure 2 Figure 8 (a) (b, Figure 4)

Claims (1)

[Scope of Claims] L In an electrode for a liquid crystal optical device for controlling the orientation of a liquid crystal layer laminated on an optical waveguide film, a lead wire of a control electrode attached to the liquid crystal layer side of an electrode substrate is 1. An electrode for a liquid crystal optical device, characterized in that the electrode is taken out onto the surface of the electrode substrate opposite to the liquid crystal layer side through a through hole drilled at a desired position of the electrode substrate. & In the electrode for a liquid crystal optical device according to claim 1, the inner wall of the through hole is plated with copper, and the through hole is further filled with tin, lead, or an alloy containing these as main components. An electrode for a liquid crystal optical element characterized by: