KR100442831B1 - Optical switch and manufacturing method thereof - Google Patents

Abstract

Disclosed are an optical switch and a method of manufacturing the same, which can easily assemble a micromirror and a waveguide, thereby eliminating the need for a separate optical component such as a lens, and facilitating optical alignment.

The disclosed optical switch comprises: at least one input side waveguide through which light is input; A micromirror having at least one incident surface inclined at an angle with respect to the input waveguide; An actuator for moving the micromirror; And at least one output side waveguide for outputting incident light reflected from the micromirror.

Since the optical switch does not need to be separately provided with an optical component such as a lens, it is easy to assemble, and it is possible to test and assemble in a single state instead of a finished state, thereby providing a reliable and easy mass production.

Description

Optical switch and manufacturing method thereof

The present invention relates to an optical switch and a method of manufacturing the same, and more particularly, it is possible to easily assemble the micromirror actuator and the waveguide, so that an additional optical component such as a lens is not required, and the micromirror of the multi-sided mirror can be moved horizontally. The present invention relates to an optical switch and a method of manufacturing the same, which can facilitate optical alignment.

Recently, due to the development of optical communication, research and development of optical switches for switching optical signals to appropriate lines have been actively conducted. OO that can receive a conventional optical signal and convert it into an electrical signal, and then convert the optical signal back to an optical signal and gradually switch the optical signal to an optical signal without converting the electrical signal in the OEO method. The research of the method is in progress.

Optical switch includes TO (thermo-optic) and EO (electro-optic) switches that design the waveguide and change the optical path by applying heat or voltage to change the refractive index of the waveguide, and other mechanical and liquid crystal methods. There is also. Among them, the method of making micromirror using MEMS (MicroElectromechanical System) and switching the optical signal can be made smaller than other methods, and it is preferred because it has less interference with adjacent parts and less optical loss. have.

Among the methods using MEMS, there is a method of switching two-dimensionally by turning off the micromirror in one direction and a three-dimensional method of precisely transmitting an optical signal to a desired position while driving in two directions. By the way, when there are not many switching paths, for example, 16x16 or less, most two-dimensional switching methods are used. Here, the factors that determine the price of the optical switch include the size of the optical switch, the number of manufacturing processes and the ease of assembly.

In the conventional optical switch, there is an on-off switching by driving the micromirror at a right angle. Referring to FIG. 1, a plurality of micromirror actuators 110 are arranged in a two-dimensional matrix form, and light emitted from the optical fiber 143 of the input unit is converted into parallel light through the microlens 145. The parallel light is incident and reflected toward the vertically upright micromirror 131 and then transmitted to the output side optical fiber 148 through the microlens 146 on the output side. That is, the optical switch reflects the optical signal incident by the micromirrors 131a, 131b, 131c, and 131d, which are upright with respect to the substrate 115, by the micromirror 132 which is in a horizontal state. The optical path can be selected by passing an incident optical signal.

By the way, since the optical fibers 143 and 148 have a constant thickness (a diameter of about 125 μm in the case of a short mode optical fiber), an appropriate space is inevitably required for their proper arrangement in two-dimensional space. In addition, in order to arrange the optical paths of the optical fibers 143 and 148 and the micromirror 132, an optical bench must be made, and a lens is used to reduce the loss of light along a long path. However, when the lens is used, since the diameter of the light beam is larger, the arrangement space of the optical fiber is inevitably increased.

In addition, when the micromirror is vertically switched as described above to switch the optical path, it is difficult to accurately control the micromirror vertically. In addition, in order to test the optical performance, the test must be performed while the micromirror is driven with the finished product assembled with the optical switch and the optical bench, so there is no chance of compensation for the defective product, so the defective rate is not suitable for mass production.

2A shows a conventional slide type optical switch, in which a micromirror 155 slidable by an actuator 158 is arranged in a matrix type, and an input optical fiber 150 and a lens are respectively provided on the input and output sides of light. 151 and an output optical fiber 157 are provided. When the micromirror 155 is horizontally moved and positioned on the optical path, incident light is reflected, and when the micromirror 155 is out of the optical path, the light goes straight.

The slide-type structure as described above has a large distance that the micromirror 155 should be moved because the diameter of the light (at least 50 μm) is large when the light from the input optical fiber 150 enters the micromirror 155. However, it is difficult to obtain a sufficient moving distance by a general actuator. In addition, in order to test the optical performance, the defect rate is high because it must be tested in a driving state after manufacturing and assembly are completed.

In addition, in the conventional optical switch, as shown in FIGS. 3A and 3B, the grooves 165 are cross-shaped, and the optical fibers 166 are inserted into the grooves 165, and the microstrip is formed between the grooves 165. The mirror 167 is arrange | positioned so that a slide is possible. In this case, it is not necessary to include an optical component such as a lens, but in manufacturing a vertical micromirror using anisotropic selective etching on a silicon wafer, there is bound to have a large error range depending on the processing conditions during etching. In addition, due to the wavy pattern generated when the vertical micromirror is manufactured using anisotropic selective etching, scattering of reflected light occurs and light loss occurs. In general, when the metal film is applied to the surface of the micromirror, the reflectivity is reduced by about 15-20% due to the reflected light loss due to scattering according to the surface shape.

The present invention has been made to solve the above problems, it is possible to easily assemble the micromirror actuator and the waveguide can be tested in a single state instead of a finished state, there is no need to use optical components such as lenses, and optical alignment is It is an object of the present invention to provide an easy optical switch and a method of manufacturing the same.

1 is a perspective view showing an optical switch vertically driven with a conventional electrostatic power.

2 is a view schematically showing a conventional slide type optical switch.

3A and 3B show a conventional 2x2 optical switch.

4 is a perspective view showing an optical switch according to the present invention.

5A and 5B are diagrams illustrating an operation of an optical switch according to an embodiment of the present invention.

6 is a view showing a comb-type actuator used in the optical switch according to an embodiment of the present invention.

7A and 7B are views for explaining an operating state of an optical switch according to an embodiment of the present invention.

8A and 8B are views illustrating a configuration and an operating state of an optical switch according to another embodiment of the present invention.

9A to 9C are views illustrating a configuration and an operating state of an optical switch according to another embodiment of the present invention.

10A to 10E are views illustrating a manufacturing process of an optical switch according to the present invention.

<Explanation of symbols for main parts of the drawings>

7,8,33,43 ... micromirror, 15,16,17,18,30,35,36,40,43 ... waveguide

20 ... optical fiber, 25,38,48 ... actuator

7a, 8a, 33a, 43a, 43b, 43c ... incident surface

In order to achieve the above object, an optical switch according to a preferred embodiment of the present invention, the first and second waveguide to which light is input; Third and fourth waveguides disposed to face each other at a predetermined distance from the first and second waveguides and outputting light; A first and second waveguide disposed on the plate disposed between the first and second waveguides and the third and fourth waveguides to face each other, the first and second waveguides having an incidence surface and an inclined surface that are inclined with respect to the first to fourth waveguides, respectively; A second micromirror; It is characterized in that it comprises; an actuator coupled to one side of the plate to move the plate horizontally.

The first and second micromirrors are preferably arranged to change the optical path by reflecting the light transmitted from the first and second waveguides in a cross shape.

The actuator is preferably formed integrally with the plate.

The first and second micromirrors are preferably formed in the shape of a triangular prism.

The waveguide, the micromirror and the actuator are preferably arranged in an array structure.

In order to achieve the above object, an optical switch according to a preferred embodiment of the present invention, at least one input side waveguide to which light is input; A micromirror having at least one incident surface inclined at an angle with respect to the input waveguide; An actuator for moving the micromirror; And at least one output side waveguide for outputting incident light reflected from the micromirror.

The micromirror is moved to a step corresponding to the number of the at least one incident surface.

And a waveguide disposed to face the input waveguide.

In order to achieve the above object, an optical switch manufacturing method according to a preferred embodiment of the present invention comprises the steps of: depositing an oxide mask on a wafer; Stacking an actuator SOI or SOG on the oxide mask; Depositing a solid state cost mold on the SOI or SOG and forming a structure for a micromirror through an etching process; Depositing Al over SOI or SOG and removing the oxide mask; Removing the Al layer and depositing a metal layer to form a micromirror and an actuator.

Hereinafter, an optical switch according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

4 and 5A, an optical switch according to an exemplary embodiment of the present invention includes first and second waveguides 15 and 16 to which light is input, and first and second waveguides 15 and 16. And third and fourth waveguides 17 and 18 disposed to face each other at a predetermined interval and outputting light, and the first and second waveguides 15 and 16 and the third and fourth waveguides ( The plates 5 are arranged between 17 and 18.

On the plate 5 a pair of first and second micromirrors 7 and 8 are erected facing each other. The first and second micromirrors 7 and 8 may be in the form of a triangular column having entrance surfaces 7a and 8a and exit surfaces 7b and 8b, respectively. The entrance surfaces 7a and 8a and the exit surfaces 7b and 8b are formed to face each other with a predetermined angle. The output ends 15b and 15b of the first and second waveguides 15 and 16 face the incidence surfaces 7a and 8a of the first and second micromirrors 7 and 8, respectively. Is arranged to. In addition, the input ends 17a and 18a of the third and fourth waveguides 17 and 18 are disposed to face the exit surfaces 7b and 8b. The optical fibers 20 may be further coupled to the first to fourth waveguides 15, 16, 17, and 18 so as to be connected to other components.

On the other hand, one side of the plate 5 is provided with an actuator 25 for horizontally moving the plate (5). The actuator 25 may be, for example, a comb type actuator. As shown in FIG. 6, the comb-type actuator is disposed with the first and second driving electrodes 27 and 28 at the center thereof, and face each other with respect to the first and second driving electrodes 27 and 28, respectively. First and second ground electrodes 29 and 30 are disposed. The first driving electrode 27, the first ground electrode 29, and the second driving electrode 28 and the second ground electrode 30 may each have a comb shape and may be alternately coupled to face each other. . In addition, the first and second driving electrodes 27 and 28 are fixed, and the first and second ground electrodes 29 and 30 are connected to the first and second driving electrodes 27 and 28. It is made to be movable by the electrostatic force by interaction with the. Accordingly, when electrostatic force is generated between the first ground electrode 29 and the first driving electrode 27, the first ground electrode 29 is moved between the first driving electrode 27 and alternately with each other. When the electrostatic force is generated between the second ground electrode 30 and the second driving electrode 28, the second ground electrode 30 is moved between the second driving electrode 27 and alternately with each other. It is located as an enemy.

Here, a slide shaft 35 is connected between the first and second ground electrodes 29 and 30, and plate springs 37 are provided at both sides of the slide shaft 35. Accordingly, when the voltage is released to the first or second driving electrodes 27 and 28, the slide shaft 35 returns to its original position by the restoring force of the leaf spring 37.

One end of the slide shaft 35 is coupled to the plate 5. Therefore, the slide shaft 35 is slid by the electrostatic force generated between the first and second ground electrodes 29 and 30 and the first and second driving electrodes 27 and 28. (5) is moved horizontally, in which the first and second micromirrors (7) (8) are moved horizontally together.

Switching operation of the optical switch according to an embodiment of the present invention is as follows.

As shown in FIG. 5A, light propagated through the first and second waveguides 15 and 16 is respectively incident on the incidence surfaces 7a and 8a of the first and second micromirrors 7 and 8, respectively. Incident. Then, the light reflected from the incident surface 7a of the first micromirror 7 is directed to the exit surface 8a of the second micromirror 8 on the opposite side thereof, and reflected from the exit surface 8a. And enters the fourth waveguide 18. Similarly, light incident from the second waveguide 16 to the incident surface 8a of the second micromirror 8 is reflected toward the exit surface 7b and is reflected by the exit surface 7b. Enters the third waveguide 17.

As described above, the first and second micromirrors 7 and 8 reflect the light from the first and second waveguides 15 and 16 in a cross shape to switch the optical path.

Meanwhile, the state in which the plate 5 is horizontally moved by the actuator 25 is shown in FIG. 5B. As the plate 5 is horizontally moved by the actuator 25, the first and second micromirrors 7 and 8 move together. In this case, the first and second micromirrors 7 and 8 may move away from the optical paths leading from the first and second waveguides 15 and 16 to the third and fourth waveguides 17 and 18. do. Accordingly, the light emitted from the first waveguide 15 goes straight to the third waveguide 17 on the opposite side thereof, and the light emitted from the second waveguide 16 goes to the fourth waveguide on the opposite side ( Go straight to 18).

The optical switch according to the embodiment of the present invention operated as described above has an advantage of easy assembly because of large tolerance of optical alignment. In other words, even when the first and second micromirrors 7 and 8 are not disposed at the exact center position with respect to the incident light i as shown in FIG. This can be passed exactly to the desired path. In other words, if the incident light i only enters the incident surfaces 7a and 8a of the first and second micromirrors 7 and 8, even if the moving position of the micromirror is slightly out of the fixed position, the light advances. Does not affect the path In the figure, R represents the reference line of the exact position of the micromirror for the incident light i. Similarly, even if the first and second micromirrors 7 and 8 are disposed or moved to one side with respect to the incident light i as shown in FIG. 7B, the light can be accurately transmitted in a desired path.

In addition, the 2 × 2 optical switch configured as described above may be arranged in an array structure. In the above configuration, since the input side and the output side are arranged horizontally, such unit optical switches can be easily arranged in an array structure. For example, in the conventional 2x2 optical switch (refer to FIG. 3A), since the input side and the output side are respectively disposed in all directions, it is difficult to arrange in an array structure.

Although the case of the 2 × 2 optical switch has been described above, it is also possible to implement an optical switch having a 1 × N structure. Referring to FIG. 8A, an optical switch according to another exemplary embodiment of the present invention may include a micromirror having an input waveguide 30 and at least one reflective surface 33a inclined at a predetermined angle with respect to the input waveguide 30. 33), an output waveguide 35 for outputting the light reflected by the reflecting surface 33a, and an actuator 38 for horizontally moving the micromirror 33.

The micromirror 33 may be formed in a polygonal column shape. In particular, the micromirror 33 may have a triangular column shape. In this case, the light from the input waveguide 30 may be reflected from the reflection surface 33a, and thus the output waveguide 35 may be formed. Head to). The micromirror 33 may have an isosceles triangle or a right triangle in cross section and protrudes over the plate 42. As described above, when one reflective surface 33a is provided, the output waveguide 35 is provided on an optical path through which the light reflected from the reflective surface 33a travels. In addition, another output side waveguide 36 may be further provided to face the input side waveguide 30. Referring to FIG. 8B, the micromirror 33 is moved by the actuator 38 and transmitted directly to the other output waveguide 36 when it exits the path of travel of light from the input waveguide 30. Accordingly, a 1 × 2 optical switch can be realized.

In addition, as shown in FIG. 9A, an input waveguide 40 is provided, and a plurality of reflective surfaces 43a and 43b (in which the micromirrors 43 are inclined at different angles with respect to the input waveguide 40) 43c). In addition, output side waveguides 45a, 45b, 45c corresponding to the optical paths reflected by the reflective surfaces 43a, 43b, 43c are provided. Unexplained reference numeral 42 denotes a plate and 48 denotes an actuator.

As shown in the above example, the operating state when the micromirror 43 has a plurality of reflective surfaces 43a, 43b, 43c is as follows. The plurality of reflecting surfaces 43a, 43b, 43c are named as a first reflecting surface, a second reflecting surface, and a third reflecting surface in that order for convenience, and each of the output waveguides corresponding to the first to third reflecting surfaces is first to third. We will call it the output waveguide. 9A illustrates that light emitted from the input waveguide 40 is reflected by the first reflection surface 43a and output through the first output waveguide 45a. As shown in FIG. 9B, when the micromirror 43 is moved by the actuator 48 so that the second reflecting surface 43b faces the input side waveguide 40, light is inputted to the input side waveguide 40. If it is transmitted through 40, it is reflected by the second reflecting surface 43b. Then, it is output through the second output side waveguide 45b. In the same way, as shown in FIG. 9C, when the micromirror 43 is appropriately moved so that the third reflecting surface 43c faces the input waveguide 40, an optical signal is transmitted to the third reflecting surface. The third output side waveguide 45c passes through 43c. Here, the actuator 48 may be a comb-type actuator described above.

In the above example, a 1 × 3 optical switch structure having three incidence planes and three output waveguides corresponding thereto is illustrated, but the present invention can be applied to an optical switch having a structure of 1 × N structure with N incidence planes. to be. At this time, the micromirror 43 is moved to a step corresponding to the number of reflective surfaces. That is, when there are three reflecting surfaces, the micromirror 43 is moved in three steps, and the optical path is converted according to each reflecting surface selected to face the input waveguide 40.

Furthermore, another output side waveguide (see 36 of FIG. 8A) may be further provided to face the input waveguide 40 with the micromirror 43 interposed therebetween. At this time, when the micromirror 43 is moved so as to escape the path extending from the input waveguide 40, the light from the input waveguide 40 goes straight to the other output waveguide.

As described above, when the positions of the plurality of reflecting surfaces and the output waveguide corresponding thereto are correctly aligned, optical alignment can be facilitated.

Next, a method of manufacturing an optical switch according to a preferred embodiment of the present invention will be described.

First, as shown in FIG. 10A, an oxide mask 53 is deposited on a wafer 50, and a silicon on insulator (SOI) or silicon on glass (SOG) 55 for a comb-shaped actuator is disposed on the oxide mask 53. )). Next, as shown in FIGS. 10B and 10C, the solid-state cost mold 57 is deposited on the SOI or SOG 55, and then the micromirror shape is patterned and the micromirror structure 50 is formed through an etching process. Form. The solid cost mold 57 may be made of Su-8, for example. Then, an Al layer 63 is deposited on the SOI or SOG 55 as shown in FIG. 10D.

Then, the SOI or SOG 55 and the micromirror for the actuator are removed by removing the oxide mask 53 under the actuator SOI or SOG 55 and the micromirror structure 60 using HF and BHF solutions. The dragon structure 60 is movable. Then, the Al layer 63 is removed and the metal layer 66 made of Ti / Au or Cr / Au is deposited to complete the micromirror 68 and the actuator 67. Reference numeral 69 in FIG. 10E denotes a pad for disposing a power source for driving the actuator.

Meanwhile, as illustrated in FIG. 10D, the waveguide 70 corresponding to the height of the micromirror 68 is separately manufactured using silica or polymer.

As described above, since the micromirror is manufactured using a solid-state mold, the manufacturing process is easier and the verticality and reflectivity of the mirror are improved as compared with a method of depositing a metal film after vertically etching the wafer. In addition, there is an advantage in that the etching direction can be freely determined in etching the solid state cost mold, so that the micromirror can be manufactured in a multi-faced form.

Since the optical switch according to the present invention does not need to be provided with an optical component such as a lens, it is easy to assemble, and it is possible to test and assemble in a single product state rather than a finished product state so that it is reliable and easy to mass produce. In addition, micromirrors are inserted and assembled between the input waveguide and the output waveguide to facilitate optical alignment.

In the manufacturing method of the optical switch according to the present invention, since the micromirror is manufactured using a solid-state mold, the shape of the micromirror can be freely produced, the manufacturing process is simple, the productivity is excellent, and the micromirror is integrally formed on the actuator. The reflectivity and verticality of the micromirror can be improved.

Claims (13)

First and second waveguides through which light is input; Third and fourth waveguides disposed to face each other at a predetermined distance from the first and second waveguides and outputting light; A first and second waveguide disposed on the plate disposed between the first and second waveguides and the third and fourth waveguides to face each other, the first and second waveguides having an incidence surface and an inclined surface that are inclined with respect to the first to fourth waveguides, respectively; A second micromirror; And an actuator formed integrally with one side of the plate to move the plate horizontally. The method of claim 1, And the first and second micromirrors are arranged to switch light paths by reflecting light transmitted from the first and second waveguides in a cross shape. delete The method according to any one of claims 1 to 3, And the first and second micromirrors are formed in a triangular prism shape. The method of claim 4, wherein And the waveguide, the micromirror and the actuator are arranged in an array structure. At least one input side waveguide through which light is input; A micromirror having at least one reflecting surface inclined at an angle with respect to the input waveguide; An actuator for moving the micromirror; At least one output side waveguide for outputting incident light reflected from the micromirror. The method of claim 6, And the micromirror is moved in a step corresponding to the number of the at least one reflective surface. The method of claim 7, wherein And a waveguide disposed to face the input waveguide. The method according to any one of claims 6 to 8, And the micromirror and the actuator are integrally formed. Depositing an oxide mask on the wafer; Stacking an actuator SOI or SOG on the oxide mask; Depositing a solid state cost mold on the SOI or SOG and forming a structure for a micromirror through an etching process; Depositing Al over SOI or SOG and removing the oxide mask; Removing the Al layer and depositing a metal layer to form a micromirror and an actuator. The method of claim 10, HF and BHF solution is used when removing the oxide mask manufacturing method of the optical switch. The method according to claim 10 or 11, wherein The metal layer is an optical switch manufacturing method, characterized in that made of Ti / Au or Cr / Au material. The method according to claim 1 or 6, The actuator is an optical switch, characterized in that the comb-type actuator.