JP3110573B2 - Optical switch and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switch used in an optical communication device, an optical transmission device, and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art There are various types of optical switches for switching optical paths. The optical switch shown in FIG. 10 is an example, and is described in JP-A-3-75713. This optical switch is called a mechanical switch, and the free end of an optical fan bar 1 mounted in a cantilever shape is connected to two fixed optical fibers 2 and 3.
To the optical fibers 2, 3
Optically coupled to one of them.

In the prior art, for example, Japanese Patent Laid-Open No.
An optical switch called a waveguide type utilizing characteristics of a dielectric or a semiconductor as described in 194517 is known. FIG. 11 shows an example of the operation principle of this waveguide type optical switch. This is based on the fact that the applied light changes the field distribution of the guided light just before the branch point of the Y-branch optical waveguide 5 formed on the substrate. The optical path is switched accordingly.

[0004] Such mechanical optical switches and waveguide type optical switches have the following technical problems to be solved.

[0005]

First, in the case of a mechanical optical switch, it is necessary to satisfy the accuracy of several μm required for optical coupling at the stage of manufacturing each component and assembling them. There was a problem that production was extremely difficult.

[0006] Further, when an attempt is made to construct a 1 × N optical switch by combining the above-mentioned mechanical optical switches in multiple stages,
An optical fiber must be connected for connection between the optical switches, and there is a problem that the size of the entire switch is increased.

On the other hand, in a waveguide type optical switch, it is easy to realize a 1 × N optical switch by combining in multiple stages. However, the features of this waveguide type optical switch are that the scattering loss at the branch point is large, and that it depends on the wavelength and polarization of the guided light.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an optical switch which uses an optical waveguide as an optical path, and employs a mechanical optical switch using an electrostatic force as an optical path switching method, and a method of manufacturing the same. It is an object.

[0009]

In order to achieve the above object, an optical switch according to the first aspect of the present invention comprises a single elastically deformable conductive movable member supported in a cantilever shape. Moving the movable member to the first position and the second position by electrostatic force.
An electrode disposed in the vicinity of the movable member for driving between the positions; a stop member for stopping the movable member at each of the first position and the second position; A first optical waveguide, a second optical waveguide optically coupled to the first optical waveguide when the movable member is at the first position, and a second optical waveguide optically coupled to the first optical waveguide when the movable member is at the second position. , A third optical waveguide optically coupled to the first optical waveguide.

Further, in the optical switch according to the first aspect of the present invention, a magnetic thin film is formed on the contact surface between the movable member and the stop member, and is self-held when the movable member is at the first position or the second position. It is characterized by having made it.

The electrodes are preferably arranged on both sides of the movable member.

[0012] The stop member may include a second optical waveguide and a third optical waveguide.
It may use a part of the support layer on which the optical waveguide is formed.

By combining such optical switches in multiple stages, an N × M optical switch can be obtained.

[0014] Further, the invention according to claim 5 is characterized in that:
A step of forming a sacrificial layer to be removed later by etching, one elastically deformable conductive movable member supported in a cantilever shape using the sacrificial layer as a mold, and Forming an electrode for driving between a position and a second position, and a stop member for stopping the movable member at the first position and the second position; and providing the first optical waveguide to the movable member. Forming, and forming a second optical waveguide optically coupled to the first optical waveguide when the movable member is at the first position, and when the movable member is at the second position. In addition, a method of manufacturing an optical switch, comprising: forming a third optical waveguide optically coupled to the first optical waveguide; and removing the sacrificial layer by etching.

[0015]

According to the first aspect of the present invention, the movable member can be moved between the first position and the second position by the electrostatic force generated between the conductive movable member and the electrode. For example, when a negative charge is given to the movable member and a positive charge is given to one electrode adjacent thereto, the movable member is attracted in the direction of the electrode by the attraction of the charge. When a negative charge is applied to the electrode, the movable member moves away from the electrode due to repulsion. Since the movable member is supported in a cantilever shape, its free end moves greatly due to electrostatic force.

It is sufficient that at least one electrode is provided. However, when the electrodes are arranged on both sides of the movable member, a suction force acts on one side and a repulsion force acts on the other side. A larger displacement than the electrode is obtained.

Since the first optical waveguide is formed on the movable member, the first optical waveguide is optically connected to one of the second optical waveguide and the third optical waveguide by driving the movable member by electrostatic force. Are combined.

Further, by providing the stop member, the movable member is reliably stopped at predetermined positions (first position and second position) for optical coupling of the optical waveguide. By using a part of the support layer on which the second and third optical waveguides are formed, the stop member simplifies the manufacturing process.

Further, by forming a magnetic thin film on the contact surface between the stop member and the movable member, even when the movable member comes to the first position or the second position, even if the electrostatic force is deenergized. The movable member is held at that position by the magnetic attraction of the magnetic thin film.

Such an optical switch can be manufactured in accordance with the manufacturing method according to the present invention as set forth in claim 5, which is sufficiently performed by an optical integrated circuit manufacturing technology using current silicon semiconductor manufacturing technology. And a complicated assembly process is not required.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show the configuration of an optical switch 10 according to an embodiment of the present invention. FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 3 is a perspective view. In the following description, “left”, “right”, “upper”, and “lower” are based on FIGS. The optical switch 10 in this embodiment has a flat silicon substrate 11, and a silicon oxide layer 12 is formed on the upper surface thereof as an insulating layer. Optical waveguide support layers 13 and 14 made of conductive polysilicon are formed on each of the left and right sides of the upper surface of the silicon oxide layer 12.

The left support layer 14 includes the right support layer 13
A recess 15 is formed in the center of the edge (i.e., the right edge) opposite to. In the center of the left side edge of the right support layer 13, an elongated linear movable member 16 is formed in a cantilever shape. The movable member 16 extends toward the left support layer 14, and its free end is formed in the concave portion 1 of the left support layer 14.
5.

The movable member 16 is made of polysilicon integrally formed with the right support layer 13, and is elastically deformable within a certain range. Therefore, the movable member 16 can swing in a direction parallel to the surfaces of the silicon substrate 11 and the silicon oxide layer 12, but the side wall surface 15
The movable range is limited because its free ends are in contact with a and 15b. Hereinafter, for convenience, the position where the free end of the movable member 16 is in contact with the side wall surface 15a of the recess 15 is referred to as a “first position”, and the position where the free end of the movable member 16 is in contact with the opposing side wall surface 15b is a “second position”.
Called.

On both sides of the movable member 16, electrodes 17a and 17b made of polysilicon are arranged at a predetermined interval. These electrodes 17a and 17b are for moving the movable member 16 by electrostatic force. Electrodes 17a, 17
Since b and the support layers 13 and 14 are formed on the silicon oxide layer 12 which is an insulating material, they are electrically independent.

On the upper surface of the movable member 16, a first optical waveguide 18 made of LiNbO ₃ , glass or the like is formed over the entire length thereof, and the first optical waveguide 18 further extends to the right edge of the right support layer 13. Has been extended. The second optical waveguide 19 and the third optical waveguide 20 are formed on the upper surface of the left support layer 14 so as to extend in parallel with the center line of the first optical waveguide 18. These optical waveguides 18, 19, 2
The positional relationship of 0 is as follows. That is, when the movable member 16 is disposed at the first position, the end face of the first optical waveguide 18 faces the end face of the second optical waveguide 19, and the two optically combine. When the movable member 16 is bent in the opposite direction and is arranged at the second position, the end face of the first optical waveguide 18 faces the end face of the third optical waveguide 20.

FIG. 4 shows the principle of operation of the optical switch 10 having the above configuration. First, when a negative voltage is applied to the electrode 17a and a positive voltage is applied to the electrode 17b while a positive voltage is applied to the movable member 16, the movable member 16 receives a repulsive force from the electrode 17b and an attractive force from the electrode 17a. Accordingly, the first optical waveguide 18 is curved in the direction of arrow A, and its free end is disposed at the first position in contact with the side wall surface 15a of the concave portion 15. In this state, as described above, the first optical waveguide 18
Is optically coupled to the second optical waveguide 19 (FIG. 4A).

When a positive voltage is applied to the electrode 17a and a negative voltage is applied to the electrode 18b, the positively charged movable member 16 receives a force opposite to the above, and is curved in the direction of arrow B, and the free end of the movable member 16 is In contact with the side wall surface 15b. Thereby, the first optical waveguide 18 is optically coupled to the third optical waveguide 20 (FIG. 4).
(B)). When the power supply to the electrodes 17a and 17b is stopped, the electrostatic force is extinguished, and the movable member 16 returns to the neutral position shown in FIG.

In such an operation mode, the support layer 1
The side wall surfaces 15a, 15b of the recess 15 of the fourth function as stop members for the movable member 16, and also function as positioning means for the first optical waveguide 18 with respect to the second or third optical waveguide 19,20. Thereby, a very precise switching operation can be obtained.

In the above embodiment, the recess 15 of the support layer 14 is used as a stop member. However, the stop member may be formed on the silicon oxide layer 12 separately from the support layer 14. Further, two electrodes 17a and 17b are used in order to increase the displacement of the movable member 16 and to minimize external magnetic or electrical influences.
, It is sufficient to have at least one electrode.

The optical switch 10 having the above configuration can be easily manufactured by an optical integrated circuit manufacturing technology using the current silicon semiconductor manufacturing technology. FIG. 5 shows an example of the manufacturing process, which will be described below in order.
In addition, each figure on the left side of FIG. 5 is a plan view of the optical switch, and the right side is a cross-sectional view along the center line of the optical switch.

First, the upper surface of the silicon substrate 11 is thermally oxidized to form a silicon oxide layer 12 (FIG. 5A).

Next, as shown in FIG. 5B, a silicon nitride layer 21 having a predetermined shape is formed on the upper surface of the silicon oxide layer 12 as a sacrificial layer to be removed later by etching. The silicon nitride layer 21 has a protrusion 21a for forming a concave portion of the left support layer 14, and electrodes 17a and 17b.
Through holes 21b and 21c for forming the
Has a groove 21d for forming the same.

Thereafter, polysilicon is stacked on the upper surface of the silicon oxide layer 12 using the silicon nitride layer 21 as a mold. Thereby, the left and right support layers 13 and 14 and the electrode 17 are formed.
a, 17b and the movable member 16 are formed (FIG. 5C). The part formed in this step requires an accuracy of several μm for the purpose of low-loss optical coupling, but this is easily achieved by improving the accuracy of lithography.

Further, as shown in FIG. 5D, first to third positions are set at predetermined positions of the support layers 13, 14 and the movable member 16.
Are formed by vapor deposition, sputtering, or the like.

Finally, when the silicon nitride layer 21 is removed by etching, the optical switch 10 shown in FIGS. 1 to 3 is formed (FIG. 5E).

Since the above steps do not include any assembling steps, a high-precision optical switch can be manufactured.

In the above embodiment, the movable member 16 and the electrode 1
When the energization to 7a, 17b is stopped, the movable member 16 returns to the original neutral position. However, as shown in FIG. 6, the side wall surfaces 15a, 15b of the concave portion 15 of the support layer 14 and the respective side wall surfaces 15a, 15a,
15b and the side of the movable member 16 in contact with the magnetic thin film 3
By forming Oa, 30b, 30c, and 30d, the movable member 16 has a self-holding function. In this case, the magnetic thin films 30a, 30a on the side walls 15a, 15b
If the surface of b is an S pole, the surfaces of the magnetic thin films 30c and 30d on the movable member 16 need to be N poles.

FIG. 7 shows the magnetic thin films 30a, 30b, 30
It is explanatory drawing which shows operation | movement of the optical switch 10 which has c and 30d. In FIG. 7, F _EA and F _EC are electrostatic forces acting on the movable member 16, and F _M1 and F _M2 are magnetic thin films 30 a and 30.
b, 30c, and 30d, the directions of which are shown in FIG.
As shown in FIG. First, in step I, the electrode 1
7a, a positive voltage is applied, and a voltage 17b and the movable member 16 are applied.
When a negative voltage is applied to the movable member 16, the electrode 17
a, a repulsive force is applied from the electrode 17b, and its free end contacts the side wall 15a of the concave portion 15. At this time, the magnetic force F
_M1 is larger than the magnetic force _FM2 . Therefore, even if the energization is stopped in step II, the contact state between the two is maintained by the magnetic force of the magnetic thin films 30a and 30c, and the first optical waveguide 18
Is maintained in a state of being optically coupled to the second optical waveguide 19.

Next, in step III, the electrodes 17a
When a positive voltage is applied to the movable member 16 and a negative voltage is applied to the electrode 17b, the movable member 16 receives a repulsive force from the electrode 17a and a suction force from the electrode 17b. Here, since the magnetic forces F _M1 and F _M2 are determined to be smaller than the total electrostatic force (| F _EA | + | F _EC |) acting on the movable member 16, respectively, in the energized state of Step III, The free end of the movable member 16 is
Contact with the side wall surface 15b of the base member. At this time, the magnetic force F _M2 becomes the magnetic force F
_{Since M1} is larger than _M1 , even when the energization is stopped in step IV, the first optical waveguide 18
Self-holding in a state of being optically coupled to

Although the above embodiment shows the 1 × 2 optical switch 10, an N × M optical switch can be manufactured by combining the 1 × 2 optical switches 10 in multiple stages. FIG. 8 shows an arrangement of the optical switches 10 in the 1 × 8 optical switch 100. Each optical switch 10 in the optical switch 100 has one
The optical waveguides 1 can be manufactured simultaneously on a large number of silicon substrates 110 and further connect the optical switches 10.
20 can also be manufactured on the silicon substrate 110 by an optical integrated circuit manufacturing technique. 8 are electrodes formed on the silicon substrate 110, which are electrically connected to electrodes (not shown) of the predetermined optical switch 10.

Such an optical switch 100 is generally molded of plastic and used in a form as shown in FIG. A matching agent is preferably injected into the plastic mold 150 in order to prevent Fresnel reflection at the waveguide end face due to air. In FIG. 9, reference numeral 160 denotes the electrode 13 of the optical switch 100.
These pins are connected to 0 and have a structure that is convenient to be used by attaching them to an electric board or the like. Further, reference numeral 200
When the connector 190 of the optical fiber 180 is connected to the optical switch, the guide pin 200 of the connector 190 is used.
Is a guide hole to be inserted. This guide hole 170
As shown in FIG. 8, a V-shaped groove 140 formed on a silicon substrate 110 by anisotropic etching is used.
Optical fiber 180 and optical waveguide 12 of optical switch 100
It is desirable to improve the accuracy of optical coupling with zero.

[0043]

As described above, according to the present invention, the conductive movable member is caused to oscillate by the electrostatic force, whereby the first optical waveguide formed on the movable member is moved to the second and third optical waveguides. It can be optically coupled to either one of the wave paths.
Since the switching operation is of a so-called mechanical type, there is no problem such as the dependence of light polarization on the conventional waveguide type.

Further, the movable member and the optical waveguide can be manufactured by using an optical integrated circuit manufacturing technique, and there is no assembling step which causes a decrease in accuracy. As a result, a dimensional error between members is extremely small, and very high accuracy is obtained also in an operation surface.

Further, in this optical switch, since the optical path itself is an optical waveguide, integration is possible. That is, when an N × M type optical switch is manufactured by combining these, it is not necessary to connect the optical switches using an optical fiber, and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of an optical switch according to the present invention.

FIG. 2 is a side view of the optical switch shown in FIG.

FIG. 3 is a perspective view of the optical switch shown in FIG.

FIG. 4 is a plan view showing an operation state of the optical switch shown in FIG.

FIG. 5 is an explanatory diagram showing a manufacturing process of the optical switch shown in FIG.

FIG. 6 is a partial plan view of an optical switch according to the present invention to which a self-holding function is added.

FIG. 7 is an explanatory diagram showing an operation of the optical switch of FIG. 6;

FIG. 8 is a schematic configuration diagram of a 1 × 8 optical switch configured by combining the optical switches of FIG. 1 in multiple stages.

FIG. 9 is a perspective view showing a usage state of a molded 1 × 8 optical switch.

FIG. 10 is a sectional view schematically showing a conventional mechanical optical switch.

FIG. 11 is an explanatory view showing the operation principle of a conventional waveguide optical switch.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Optical switch, 11 ... Silicon substrate, 12 ... Silicon oxide layer, 13, 14 ... Support layer, 15 ... Depression (stop member), 16 ... Movable member, 17a, 17b ... Electrode, 18 ...
1st optical waveguide, 19 ... 2nd optical waveguide, 20 ... 3rd optical waveguide, 30a, 30b, 30c, 30d ... magnetic thin film, 1
00 ... 1x8 type optical switch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-260613 (JP, A) JP-A-4-198911 (JP, A) JP-A-55-26558 (JP, A) 21932 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 26/00-26/08

Claims (5)

(57) [Claims] 1. An elastically deformable conductive movable member supported in a cantilever shape, and an electrostatic force for driving the movable member between a first position and a second position. An electrode disposed in the vicinity of the movable member; a stop member for stopping the movable member at each of the first position and the second position; a first optical waveguide formed on the movable member; A second optical waveguide optically coupled to the first optical waveguide when the movable member is at the first position; and a second optical waveguide optically coupled to the first optical waveguide when the movable member is at the second position. And a third optical waveguide coupled to the optical switch, wherein a magnetic thin film is formed on a contact surface between the movable member and the stop member, and the movable member is in the first position or the second position. Optical switch that is self-holding in some cases 2. The optical switch according to claim 1, wherein said electrodes are arranged on both sides of said movable member. 3. The optical switch according to claim 1, wherein the stop member comprises a part of a support layer on which the second optical waveguide and the third optical waveguide are formed. 4. An optical switch formed by combining the optical switches according to claim 1 in multiple stages. 5. A step of forming a sacrificial layer on a substrate which is later removed by etching, and using the sacrificial layer as a mold, one elastically deformable conductive movable member supported in a cantilever shape. A member and an electrode for driving the movable member between a first position and a second position;
Forming a stop member for stopping the movable member at the first position and the second position; forming a first optical waveguide on the movable member; and the movable member being at the first position. Forming a second optical waveguide optically coupled to the first optical waveguide, and a third optically coupled to the first optical waveguide when the movable member is at the second position. A method for manufacturing an optical switch, comprising: forming an optical waveguide; and removing the sacrificial layer by etching.