KR100398804B1 - Optical switch actuated with multiphase driving voltage - Google Patents

Abstract

The present invention relates to an optical wavelength switch for use in an optical communication network. The optical wavelength switch according to the present invention can be operated at a higher speed than the conventional optical switch element using the electrostatic force even when the driving layer is deflected by the driving voltages of different polarities applied to the upper and lower driving electrodes using a lower driving voltage. In addition, the optical wavelength switch of the present invention can relatively reduce the difference between the voltage applied to the drive layer and the vertical drive electrode, thereby preventing defects caused by the discharge phenomenon between the drive layer and the drive electrode.

Description

Optical Wavelength Switch Driven by Polyphase Driving Voltage {OPTICAL SWITCH ACTUATED WITH MULTIPHASE DRIVING VOLTAGE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength switch used to transmit an optical signal in a desired path in an optical communication network, and more particularly, to an optical wavelength switch driven by a polyphase driving voltage.

Conventionally, in order to establish a communication path of an optical communication network, a method of receiving an optical signal and converting the optical signal into an electrical signal and switching the electrical signal path after switching the electrical signal to an optical signal is used. In this method, the optical signal is converted into an electrical signal and then converted back to an optical signal. Therefore, the transmission efficiency of the optical communication network is degraded and the cost of constructing the network is high. In order to solve this problem, an optical wavelength switch technology has been recently developed to switch an optical signal directly to a desired path without converting the optical signal into an electrical signal. One widely used technique for constructing an optical wavelength switch is to use a micro-electro-mechanical system (MEMS) composed of an array of small mirrors in which the angle of the reflecting surface can rotate at a predetermined angle in response to a drive signal input. . The miniature mirror constituting the MEMS is used to form an optical communication path of a desired shape by rotating by a predetermined angle in response to the input of the drive signal to reflect the incident light input from the input optical fiber to the selected output optical fiber.

Conventional optical wavelength switches in the form of MEMS are typically implemented in the form of cantilever micromirrors and torsion beam micromirrors. The cantilever micromirror has a mirror formed in the form of a cantilever extending from the base, and the mirror is connected to the base by an elastic flexure, and the mirror is bent toward the electrode by the electrostatic force generated by the voltage applied to the driving electrode to enter the mirror. It changes the path of the light. The torsion beam micromirror has a structure similar to the cantilever micromirror, except that the mirror is supported by a pair of torsion beams, which are connected to opposite sides of the mirror and are deformed by rotational forces acting on the mirror. Thus, the torsion beam micromirror may change the path of incident light by rotating about one rotation axis formed by a pair of torsion beams according to the type of driving signal applied thereto.

Conventional MEMS light-wavelength switches in the form of cantilever and torsion beams apply a driving voltage to a mirror driving electrode disposed on the base side on which the micromirror is mounted to generate a rotational force of the mirror by using electrostatic force induced by the driving voltage. However, in the conventional optical wavelength switch, only one driving electrode is disposed on one side of the micromirror, thereby overcoming the elastic force of the cantilever and the torsion beam and rotating the micromirror, and also the micromirror for the driving signal according to the demand for high speed optical switch operation. In order to shorten the response time, relatively high voltage should be applied to the driving electrode. However, when a high voltage is applied to the mirror driving electrode, an arc discharge occurs between the micromirror and the driving electrode, so that the rotation angle of the mirror cannot be accurately controlled and the micromirror or the driving electrode is damaged. In addition, when a high voltage is applied to the driving electrode, it takes time to erase the charged charge between the driving electrode and the micromirror when applying a voltage of opposite polarity to the driving electrode to change the angle of the micromirror. The problem of delayed time is issued. Therefore, there is a need for a new type of wavelength switch device that solves the problems of the conventional MEMS type wavelength switch.

An object of the present invention is to provide an optical wavelength switch having good response characteristics and durability while applying a relatively low driving voltage to the driving electrode in order to solve the problem of the conventional MEMS type optical wavelength switch. In order to achieve the above object, the optical wavelength switch of the present invention arranges a driving layer equipped with a micromirror between a pair of upper and lower driving electrodes, and applies different driving voltages to the upper and lower driving electrodes to electrically connect the driving layer and the upper and lower electrodes. Attraction and repulsion are generated to rotate the drive layer by the combined forces.

1 is an exploded perspective view of an optical wavelength switch according to an embodiment of the present invention.

2 is a perspective view of the optical wavelength switch of FIG.

3 is a cross-sectional view taken along the line A-A 'of FIG.

4 is a perspective view of an optical wavelength switch according to the present invention supporting a drive layer by a pivot structure;

5 is a cross-sectional view of the pivot support of FIG. 4.

<Explanation of symbols for the main parts of the drawings>

10: substrate

11: lower drive electrode

13: upper drive electrode

17: driving layer

20: micromirror

In order to achieve this technical object, the present invention provides a switch substrate, a drive layer rotatably supported by the substrate and including a mirror for reflecting incident light, and a lower drive electrode and an upper drive electrode, respectively, at both ends of the drive layer. A driving voltage pair, wherein the driving layer is biased to a predetermined potential, and at least one of the upper driving electrode and the lower driving electrode of the driving electrode pair has a driving voltage having the same polarity as the voltage applied to the driving layer; Is provided and the other is provided with an optical wavelength switch device to which a driving voltage of 0 V potential or a polarity opposite to the voltage applied to the driving layer is applied. A predetermined voltage is applied to the driving layer, and a driving voltage having a potential having the same polarity as that applied to the driving layer is applied to one of the upper and lower driving electrodes disposed on one side of the driving layer and driving to the other driving electrode. Applying a driving voltage having a voltage of different polarity or a potential of 0 V or a voltage applied to the layer, respectively, obtains a rotational force by the electric repulsive force and the attractive force generated between the drive layer and the up and down drive electrodes. The switch can be operated at high speed as compared with the conventional optical wavelength switch using only the driving electrode of. In addition, the driving speed of the switch can be further increased by installing the vertical driving electrodes on the other side of the driving layer and applying the driving voltage in a pattern opposite to the vertical driving electrodes on the opposite side.

Hereinafter, with reference to the embodiment of the present invention shown in the accompanying drawings the structure and features of the optical wavelength switch element according to the present invention will be described in detail. 1 is an exploded view of an optical wavelength switch according to an embodiment of the present invention. For the purpose of illustration, FIG. 1 illustrates the components of the optical wavelength switch element in a separated state, but the optical wavelength switch of the present invention uses a method of stacking and etching a semiconductor such as silicon with a sacrificial layer refurbished. It should be understood that it is formed as an integral structure. Methods for processing such MEMS structures are described in MA Michalicek, JH Comtois, and HK Schriner, "Design and fabrication of optical MEMS using a four-level planarized surface-micromachined polysilicon5 process," Proc. SPIE , Vol. 3276, pp. 48-55, 1998, and many other documents are known, so a detailed description will be omitted.

Referring to FIG. 1, a substrate 10 formed of a semiconductor such as silicon is provided, and a lower driving electrode 11 and an upper driving electrode 13 are formed of a semiconductor material such as polysilicon on the substrate. The lower driving electrode 11 is formed by depositing a metal layer, doping conductive impurities, or using polysilicon in a predetermined region of the substrate. The lower driving electrode is electrically insulated from the substrate and is connected to a power source (not shown) that applies a predetermined driving voltage when driving the switch. The lower end portion 13A of the upper driving electrode 13 is formed in the outer region 12 of the lower driving electrode of the substrate, and the upper end portion of the upper driving electrode 13 may cover the driving layer 18 as described below. 13B) is formed. It is preferable that the electrode plate of the upper drive electrode 13 has a shape corresponding to the shape of the lower drive electrode 11. The upper driving electrode may also be formed by doping impurities into the silicon or using polysilicon, but it is preferable to form the upper driving electrode with polysilicon that is easy to selectively etch in an etching process of manufacturing a switching device. The upper drive electrode 13 is also electrically insulated from the substrate, and a power supply (not shown) for providing a drive signal of the optical wavelength switch is connected. As described below, the electrode plate 13B of the lower driving electrode 11 and the upper driving electrode 13 controls the driving layer 18 by an electric force generated when a predetermined voltage is applied to the driving layer and the driving electrode. It must have an area sufficient to rotate at an angle.

In the region 14 of the substrate 10, a pair of supports 15 are formed to extend upward from the substrate surface. Inside the pair of support portions 15, a pair of torsion arms 16 are integrally formed with the support portion 15. The rotational modulus of the torsion arm is designed such that the rotation angle of the mirror required for the optical path switching is obtained by the rotational force applied by the drive electrode. The flat drive layer 17 is integrally connected between the pair of torsion arms. In the present embodiment, the driving layer is supported by the torsion arm 16, but if necessary, the driving layer may be supported by an elastic connection structure having various structures such as a spring.

The drive layer 18 is made of a semiconductor material, such as doped silicon or polysilicon, integrally with the support 15, the torsion arm 16, or the like. A mirror yoke 19 is formed at the center of the driving layer, and the micro yoke 20 is mounted on the mirror yoke so that the micromirror also rotates at the same angle as the driving layer as the driving layer rotates. The drive layer generally has a rectangular flat plate shape, but is not limited thereto. As shown in FIGS. 1 and 2, a grating structure 18 including horizontal members and vertical members that cross each other may be formed at the center portion of the driving layer. When the central portion of the drive layer is formed of the lattice structure 18, the mirror yoke 19 and the micromirror 20 are formed at the intersection of the horizontal member and the vertical member. In some cases, only the horizontal member or the vertical member may be formed in the center of the driving layer instead of the lattice structure. The reason for forming the lattice structure or the horizontal / vertical member by patterning the central portion of the driving layer 17 is that the capacitance formed between the upper driving electrode 13, the lower driving electrode 11 and the driving layer inserted therebetween. In order to more precisely control the electrical force acting between them and to facilitate the etching process of the sacrificial layer located between the driving layer and the substrate when manufacturing the switching device. The thickness and width of the horizontal member and the vertical member formed at the center portion of the drive layer can be appropriately adjusted within the limits not deformed by the electrostatic force acting on the drive layer 17 during switch operation.

As shown in Figs. 1 and 2, the drive layer 17 is a semiconductor material such as polysilicon, doped silicon, etc., which has good electron mobility, and is preferably a layer as a lattice structure, a horizontal member or a vertical member in the center. Is patterned to have The drive layer is supported by the support part 15 by an elastic connection part such as the torsion arm 16, and is kept in contact with the up and down drive electrode at a position between the upper drive electrode and the lower drive electrode as shown in FIG. The drive layer is electrically insulated from the substrate, and when the optical wavelength switch operates, a predetermined bias voltage is applied to the drive layer from an external power source as described below. When a different driving voltage is applied to the upper driving electrode 13 and the lower driving electrode 11 while a constant voltage is applied to the driving layer, an electric force is applied between the driving layer and the upper and lower driving electrodes to rotate about the torsion arm. Therefore, the micromirror 20 mounted on the driving layer is rotated. When the drive layer is rotated by an electric force acting by the drive electrode, the drive layer may contact the drive electrode, in particular the upper drive electrode. The upper drive electrode or the drive to prevent discharge due to contact between the drive layer and the drive electrode. An insulating film such as silicon oxide can be formed in the layer.

At the center of the lattice structure (the intersection of the lattice structures in FIG. 1), a mirror yoke 19 for mounting the micromirror 20 is formed. The mirror yoke is made of a material such as polysilicon, and the micromirror mounted on the mirror yoke may have any shape, but is usually formed in a circular or rectangular shape. The size of the mirror is appropriately adjusted according to the width and resolution of the incident beam incident on the switch element, and the reflective surface of the mirror may be formed by depositing a metal such as gold or nickel.

FIG. 2 is a perspective view illustrating an optical wavelength switch structure in which the components shown in the exploded view of FIG. 1 are combined. As shown in FIG. 2, in the non-drive state of the switch, the driving layer 17 and the micromirror 20 are supported to be horizontally spaced from the substrate 10 by the support part 15 and the torsion arm 16. Both sides of the driving layer are inserted in a non-contact state between the electrode plate of the upper driving electrode and the lower driving electrode, respectively. In order to obtain the electric force for rotating the drive layer, it is preferable that a large part of the area of the drive layer in which the grating structure is not patterned is inserted between the upper and lower drive electrodes. In a state in which a driving electrode is not applied to the switch, the driving layer is preferably positioned in parallel with these electrodes at an intermediate point between the upper driving electrode and the lower driving electrode. In addition, the spacing between the drive layer and the upper and lower drive electrodes must be maintained in a range that allows the drive layer to allow the required angle of rotation to switch the incident light to the desired path. Hereinafter, a process in which the switch is operated by applying a voltage to the driving layer and the driving electrode of the optical wavelength switch of FIG. 2 will be described with reference to the accompanying drawings.

3 is a cross-sectional view of an optical wavelength switch cut along the line AA ′ of FIG. 2. As shown in FIG. 3, in the non-driven state of the switch, the driving layer 33 has a pair of lower ends of both ends 33A and 33B of the driving layer, respectively, by the support part 35 and the torsion arm 36 indicated by dotted lines. The driving electrodes 31 and 31 'and the pair of upper driving electrodes 32 and 32' are inserted in a non-contact state and arranged in parallel with these electrodes. When the switch is driven, the driving layer is biased to a constant voltage V _D by an external power supply. For example, the upper driving electrode 32 on the left side of FIG. 3 is biased to a potential V _H having the same polarity as V _D and at the same time, the lower driving electrode. 31 is biased to V _L having a polarity different from that of V _D or having a potential of 0 V. At this time, preferably, V _H may have the same polarity and potential as V _D, and V _L may have a potential of 0 V. In this case, since the driving layer and the vertical driving electrode are driven with only two voltages, V _D and 0 V, the power supply structure and voltage pattern for driving the switch can be simplified. In this state, since the upper driving electrode and the driving layer are biased with the same polarity potential, the left end 33A of the driving layer is subjected to the electric repulsive force directed downward in FIG. 3 by the upper driving electrode 32. In the same manner, since the driving layer and the lower driving electrode 31 have potentials of different polarities from each other, or the lower driving electrode has a potential of 0 V, the left end 33A of the driving layer is formed by the lower driving electrode 31 due to electrostatic induction. 3) is subjected to electrical attraction in the downward direction of FIG. Accordingly, the left end 33A of the driving layer is moved downward in FIG. 3 by the repulsive force by the upper driving electrode and the attraction force by the lower driving electrode to rotate about the torsion arm 36, and thus the driving layer Attached micromirror 34 is rotated counterclockwise in FIG. On the other hand, if the bias voltage of the driving layer is maintained at V _D , and the voltage applied to the upper driving electrode 32 and the lower driving electrode 31 is changed to apply V _L to the upper driving electrode and V _H to the lower driving electrode. An electrical attraction force is applied between the upper driving electrode and the driving layer, and an electrical repulsive force is applied between the driving layer and the lower driving electrode so that the left end of the driving layer receives the upward direction of FIG. 3. The clockwise rotation of FIG. In the embodiment of the present invention, for example, V _H and V _L are applied to the upper driving electrode and the lower driving electrode on the left side of FIG. 3 while the upper driving electrode 32 'and the lower driving electrode 31 on the right side of FIG. When the driving voltage of the left side is changed to 'L', that is, V _L and V _H , respectively, electric attraction force is applied between the upper driving electrode 32 ′ and the right end 33B of the driving layer, and the lower driving electrode ( 31 ') and an electric repulsive force acting between the right end 33B of the drive layer to rotate the drive layer more quickly in the counterclockwise direction of FIG.

The optical wavelength switch according to the present invention generates a rotational force for simultaneously rotating the drive layer by a pair of up and down drive electrodes, so that the difference between the bias voltages of the drive layer and the up and down drive electrodes, that is, V _H -V _D , V _D -V _L Even with a relatively small size, sufficient torque can be obtained to rotate the drive layer quickly, thereby improving the response characteristics of the optical wavelength switch. In addition, the optical wavelength switch of the present invention can effectively double the force for rotating the drive layer by applying a drive voltage of a pattern reversed to each other to the pair of vertical drive electrodes disposed at both ends of the drive layer. In addition, in the optical wavelength switch according to the present invention, since the potential difference between the driving layer and the vertical driving electrode is relatively small, an arc discharge occurs between the driving layer and the driving electrode, thereby preventing the problem of shortening the life of the device.

1 to 3, the drive layer 17 is supported by the support 15 and the pivot arm 16, but the drive layer may be supported in a different manner. In the embodiment of FIG. 4, the drive layer 42 is supported by the pivot support 41 instead of the supports and torsion arms of FIGS. 1 and 2. It is the same as the structure of FIG. The pivot support 41 may be installed below or on both sides of the drive layer 17. The pivot support part 41 may rotate at an angle necessary for switching the incident light to a desired path within a range in which the driving layer 42 does not contact the upper and lower driving electrodes between the lower driving electrode 43 and the upper driving electrode 44. It is desirable to be designed to have a pivoting range of motion that allows it.

5 is a cross-sectional view illustrating the structure of the pivot support 41 of FIG. 4. In FIG. 5, the guide member 52 is formed in a box shape or a cylindrical shape on the substrate 50. A pin joint 51 is inserted in the guide member 52, a joint neck 53 extends from the pin joint through the guide hole of the guide member, and a support plate 54 is connected to the joint connecting member. The support plate 54 is equipped with a drive layer 55 of an optical wavelength switch. In some cases, the driving layer 55 of the wavelength switch may be mounted using a separate member such as a connecting beam instead of being directly mounted to the support plate 54. The pivot structure of FIG. 5 is preferably formed by laminating a polysilicon layer having the sacrificial layer retrofitted and removing the sacrificial layer using etching or the like. An example of such a process is described in US Pat. No. 6,040,935 and the like.

When the driving layer of the optical wavelength switch is rotated by the driving voltage applied to the driving electrode, the pin joint and the supporting plate of the pivot support of FIG. 5 are rotated by the rotation angle of the driving layer. When the pivot support is rotated by a predetermined angle, the lower end of the support plate comes into contact with the guide member to stop the rotation. That is, when the drive layer is supported by the torsion arm, the drive layer continuously rotates at an angle where the rotational force applied by the drive electrode and the elastic force of the torsion arm are in equilibrium, whereas when the drive layer is supported by the pivot support part, The drive layer is rotated by a certain angle limited by the pivot structure. Therefore, the pivot structure has the advantage that the drive layer can have two stable positions when the switch is driven, and also has the advantage that the drive layer can be rotated more quickly because it does not act as an elastic force that prevents rotation during rotation of the drive layer. Have

As a method for supporting the drive layer of the optical wavelength switch of the present invention, in addition to the torsion beam or pivot structure described above, both sides of the drive layer (parts where the torsion beam is connected to the drive layer in FIGS. 1-2) or the center lower part of the drive layer are shown. It is also possible to use a method of supporting the substrate by providing a cantilever-shaped elastic beam in the.

The optical wavelength switch element of the present invention rotates the drive layer on which the micromirror is mounted by using an electric attraction force and a repulsive force acted by a pair of drive electrodes consisting of an upper drive electrode and a lower drive electrode. Even when the potential difference applied is low as compared with the conventional optical wavelength switch element, the optical wavelength switch can be effectively driven, and good response characteristics can be obtained. In addition, since the difference between the voltages applied to the driving layer and the vertical driving electrode can be reduced, it is possible to prevent a discharge phenomenon between them and thereby prevent damage to the device.

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this, Various modifications and modifications based on the technical idea of this invention may belong to the scope of the present invention. For example, in the present specification, an embodiment in which a pair of drive electrodes are provided at one end of the drive layer has been described. However, two or more pairs of drive electrodes may be provided at one end of the drive layer as necessary.

Claims (19)

In the optical wavelength switch device used in an optical communication network, Switch substrates; A drive layer rotatably supported by the substrate and including a mirror to reflect incident light; A drive electrode pair each including a lower drive electrode and an upper drive electrode and disposed at both ends of the drive layer; The driving layer is biased to a predetermined potential, one of the upper driving electrodes and the lower driving electrodes of at least one pair of driving electrodes is applied with a driving voltage having the same polarity as the voltage applied to the driving layer, and the driving of the other An optical wavelength switch device to which a driving voltage of a polarity or 0 V potential is applied to a voltage applied to a layer. The method according to claim 1, And at least one driving electrode pair disposed at opposite ends of the driving layer. The method according to claim 1, The driving voltages respectively applied to the upper driving electrode and the lower driving electrode of the driving electrode pair located at one end of the driving layer are reversed to each other so that the upper driving electrode and the lower driving electrode of the driving electrode pair located at the opposite end are respectively A wavelength switch device applied to the same time. The method according to claim 1, A driving voltage having the same polarity and the same potential as the bias voltage applied to the driving layer is applied to one of the lower driving electrode and the upper driving electrode of the driving electrode pair, and a driving voltage of 0 V is applied to the other electrode. Applied light wavelength switch device. The method according to any one of claims 1 to 4, And an electrode plate on which the lower driving electrode is formed, the upper driving electrode extends from the substrate, and an upper portion of the lower driving electrode covers a portion of the driving layer. The method according to claim 5, And at least a portion of the drive layer is inserted in a non-contact state between the lower drive electrode and the electrode plate of the upper drive electrode. The method according to any one of claims 1 to 4, And the driving layer is rotatably supported between the lower driving electrode and the upper driving electrode while being insulated from the substrate by an elastic support part. The method according to any one of claims 1 to 4, And the driving layer is rotatably supported between the lower driving electrode and the upper driving electrode while being insulated from the substrate by a pivot structure. The method according to any one of claims 1 to 4, And a grating structure, a horizontal member, or a vertical member formed at a central portion of the driving layer. The method according to any one of claims 1 to 4, And the substrate, the driving layer and the vertical driving electrode are formed of a semiconductor material such as silicon or polysilicon. The method according to any one of claims 1 to 4, And a mirror mounted on the yoke formed at the center of the driving layer. The method according to any one of claims 1 to 4, And an insulating layer formed on a surface of the driving layer or the vertical driving electrode. The method according to any one of claims 1 to 4, When a driving voltage is applied to the upper driving electrode and the lower driving electrode of the pair of driving electrodes positioned at one end of the driving layer, the upper and lower driving electrodes generate an electric force that raises or lowers the driving layer with respect to the substrate. And the drive electrode pair located at opposite ends generates an electric force for moving the drive layer in the opposite direction. The method according to any one of claims 1 to 4, And at least two drive electrode pairs disposed at one end of the drive layer. A drive layer comprising a switch substrate, a drive layer rotatably supported by the substrate and including a mirror for reflecting incident light, and a drive electrode pair including lower drive electrodes and upper drive electrodes, respectively, and disposed at both ends of the drive layer; In the method for driving the optical wavelength switch device for optical communication, Biasing the driving layer to a predetermined potential, applying a driving voltage having the same polarity as the voltage applied to the driving layer to one of the upper driving electrodes and the lower driving electrodes of the pair of driving electrodes; And applying a driving voltage having a polarity or 0 V potential opposite to the voltage applied to the driving layer. The method according to claim 15, The driving voltages respectively applied to the upper driving electrode and the lower driving electrode of the driving electrode pair are reversed and applied simultaneously to the upper driving electrode and the lower driving electrode of the driving electrode pair located at the other end of the driving layer. Optical wavelength switch drive method. The method according to claim 15, A driving voltage having the same polarity and the same potential as the bias voltage applied to the driving layer is applied to one of the lower driving electrode and the upper driving electrode of the driving electrode pair, and a driving voltage of 0 V is applied to the other electrode. Optical wavelength switch drive method. The method according to any one of claims 15 to 17, When a driving voltage is applied to the upper driving electrode and the lower driving electrode of the pair of driving electrodes positioned at one end of the driving layer, the upper and lower driving electrodes generate an electric force that raises or lowers the driving layer with respect to the substrate. And the drive electrode pair located at opposite ends generates an electric force for moving the drive layer in the opposite direction to rotate the drive layer. The method according to any one of claims 15 to 17, And at least two drive electrode pairs at one end of the drive layer.