JP2004151647A - Optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To relax the allowable tolerance in manufacturing micro mirrors, to increase the yield and to reduce the cost. <P>SOLUTION: In an optical switch, the optical path of an incident light beam is switched by forming a micro mirror 41 in an upright form on a movable electrode plate 11 arranged opposite to a fixed electrode plate 15, and the micro mirror 41 is moved by electrostatically driving the movable electrode plate 11 in the direction perpendicular to the plate face. The micro mirror 41 is provided with two reflection faces 42 and 43 which emit the incident light beam in an emitting direction which has a predetermined angle with respect to the incident direction by reflecting the incident light beam twice. Even when the micro mirror is manufactured by being rotated from a normal angular position, only a slight offset is generated because the direction of the emitted light beam does not deviate as much as twice the angle, which situation happens in a conventional rectangular solid type micro mirror. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical switch that switches an optical path of a free space propagating light beam.
[0002]
[Prior art]
FIG. 4 shows an example of a conventional structure of this type of optical switch. In this example, the rectangular movable electrode plate 11 has two opposing corners supported by a support beam 12, and these support beams 12 are respectively disposed along two sides of the movable electrode plate 11. The other end is connected and supported by a pair of anchors 14 formed on the substrate 13, respectively.
A fixed electrode plate 15 is disposed on the other surface side of the frame-shaped substrate 13, and the movable electrode plate 11 positioned in the frame of the substrate 13 is opposed to the fixed electrode plate 15 in parallel with a predetermined gap therebetween. In addition, the two support beams 12 can be displaced in a direction perpendicular to the plate surface, that is, in a direction perpendicular to the plate surface of the fixed electrode plate 15.
[0003]
A micro mirror 16 is formed upright at the center of the upper surface of the movable electrode plate 11, and the micro mirror 16 has a rectangular parallelepiped shape.
The optical switch 17 having the above structure is manufactured using a micromachining technology such as photolithography or etching, a technology called MEMS (Micro Electro Mechanical Systems) technology, and the substrate 13 and the fixed electrode plate 15 are formed. A silicon substrate is used, and the movable electrode plate 11, the support beam 12, and the anchor 14 are integrally formed by a polysilicon film.
[0004]
The micromirror 16 is manufactured by sputtering gold (Au) on the surface of a substrate formed by patterning a thick-film type resist by photolithography.
In such an optical switch 17, a voltage is applied between the fixed electrode plate 15 and the movable electrode plate 11 to generate an electrostatic force attracting each other between the electrode plates. The plate 11 is driven to be displaced toward the fixed electrode plate 15, whereby the micromirror 16 can be displaced in a direction perpendicular to the plate surface of the movable electrode plate 11. The optical path of the incident light beam can be switched.
[0005]
4A, reference numerals 21 to 23 denote optical fibers disposed around the optical switch 17, for example, 31 an incident light beam incident on the optical switch 17, and 32 and 33 an outgoing light beams.
When the micromirror 16 is inserted in the optical path, the incident light beam 31 is reflected by the micromirror 16, and the outgoing light beam 32 enters the optical fiber 22. On the other hand, when the movable electrode plate 11 is electrostatically driven and the micromirror 16 is displaced from the optical path, the incident light beam 31 proceeds straight as it is to become the output light beam 33 and is incident on the optical fiber 23 (for example, And Patent Document 1).
[0006]
[Patent Document 1]
JP 2000-121967 A (FIG. 1)
[0007]
[Problems to be solved by the invention]
In the optical switch 17 described above, for example, when the micromirror 16 is formed on the movable electrode plate 11 and the angle formed by the micromirror 16 with respect to the optical axis of the incident light beam 31 shifts, the light coupling efficiency is reduced. There has been a problem in that a drastic reduction is caused and performance is deteriorated.
FIG. 5 shows this state. When the micromirror 16 is manufactured in a state where the micromirror 16 is rotated by an angle δ from a regular position (angular position) shown by a broken line, the emitting direction of the emitted light beam 32 is shown by a broken line. Is shifted from the normal direction by 2δ which is twice the angle δ, and a large loss occurs in the outgoing light beam 32 incident on the optical fiber 22.
[0008]
Therefore, in the conventional optical switch 17, extremely high precision is required for the fabrication accuracy of the micromirror 16, and in this regard, the yield of the optical switch 17 cannot be said to be good and is expensive. Was.
On the other hand, in this type of optical switch, for example, it is conceivable that the back surface of the micromirror 16 having a rectangular parallelepiped shape is also used as a reflection surface, and the optical paths of two incident light beams are simultaneously switched by the reflection surfaces on the front and back surfaces. .
FIG. 6 shows an example of the arrangement of the micromirror and the optical fiber in consideration of such a situation. In this example, the micromirror 16 is arranged at the intersection of two orthogonal axes, and Four optical fibers 21 to 24 are arranged.
[0009]
In this arrangement, first, considering the case where the micromirror 16 is out of the optical path, since the optical fibers 21 and 23 and 24 and 22 have the same optical axis, the incident light beam 31 from the optical fiber 21 is The incident light beam 34 from the optical fiber 24 enters the optical fiber 22, respectively.
On the other hand, when the micromirror 16 is inserted into the optical path, the optical axes of the outgoing light beams 32 and 35, which are reflected by the micromirror 16 and emitted, respectively, when the micromirror 16 is inserted into the optical path, have the thickness t. Therefore, as shown in FIG. 6, an offset of d = (√2 / 2) t is applied to each of the two orthogonal axes, so that the optical axes do not coincide with the optical axes of the optical fibers 22 and 23 and are optically coupled. I could not do it.
[0010]
That is, when a four-port optical switch in which the four optical fibers 21 to 24 are arranged as described above is considered, the thickness (t) of the micromirror 16 causes the through-through (optical fibers 21 → 23, 24 → 22). And all the optical axes of reflection (optical fibers 21 → 22, 24 → 23) cannot be aligned.
In view of these problems, the object of the present invention is to alleviate the rotational tolerance during micromirror fabrication, thereby improving the yield and lowering the cost. It is an object of the present invention to provide an optical switch having a high degree of freedom in switching in that the optical axes can be adjusted.
[0011]
[Means for Solving the Problems]
According to the first aspect of the present invention, the micro mirror is formed upright on the movable electrode plate opposed to the fixed electrode plate, and the micro mirror is displaced by electrostatically driving the movable electrode plate in a direction perpendicular to the plate surface. An optical switch for switching an optical path of an incident light beam, wherein the micromirror has two reflection surfaces for reflecting the incident light beam twice and emitting the light beam at a predetermined angle with respect to the incident direction. It is said.
[0012]
According to the second aspect of the invention, the micro mirror is formed upright on the movable electrode plate facing the fixed electrode plate, and the movable mirror plate is electrostatically driven in a direction perpendicular to the plate surface to displace the micro mirror. Thus, in the optical switch for switching the optical path of the incident light beam, the micromirror reflects the incident light beam twice and emits the light at right angles to the incident direction, and has two reflecting surfaces on both the front and back surfaces. The optical paths of two incident light beams on two orthogonal axes are switched at the same time by the reflection surfaces on the front and back surfaces.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the optical switch according to the present invention, and the same reference numerals are given to portions corresponding to those in FIG. 4, and detailed description thereof will be omitted.
In this example, a rectangular movable electrode plate 11 is supported by four support beams 12 so as to be displaceable in a direction perpendicular to the plate surface. These support beams 12 are respectively derived from both ends of a pair of anchors 14 formed on two opposing sides of a frame-shaped substrate 13, and each of the movable electrodes 12 extends along two sides of the movable electrode plate 11. It extends around the plate 11 in the same direction and is connected to four corners of the movable electrode plate 11.
[0014]
In this example, the micromirror 41 mounted on the movable electrode plate 11 is not a simple rectangular parallelepiped like the conventional micromirror 16, but has a constricted shape at the center, and has constrictions on both front and back surfaces. Two reflecting surfaces 42, 43 and 44, 45 are formed. The reflecting surfaces 42 and 43 and 44 and 45 are in the form of a so-called corner reflector, and the angle θ formed by the reflecting surfaces 42, 43 and 44 and 45 is 135 ° in this example.
The micromirror 41 having the above-described shape is produced by, for example, sputtering Au on the surface of a base formed by patterning a thick-film type resist by photolithography. The height of the micromirror 41 is, for example, about 100 μm, and the overall size (chip size) of the optical switch 46 shown in FIG. 1 is, for example, about 500 μm × 250 μm. The optical switch 46 is manufactured using MEMS technology.
[0015]
FIG. 2 shows how the incident light beam is reflected by the micromirror 41 in the optical switch 46. In the drawing, the broken line shows the state where the micromirror 41 is formed at a regular position (angular position). The progress of the light beam at that time is shown, and the solid line indicates the state in which the micro mirror 41 is manufactured by rotating the micro mirror 41 by an angle δ from the normal angular position and the progress of the light beam at that time.
The incident light beam 31 from the optical fiber 21 is reflected twice by the reflecting surfaces 42 and 43 of the micromirror 41, and the angle θ between the reflecting surfaces 42 and 43 is 135 °. The outgoing light beam 32 is emitted in a direction at 90 ° to the incident direction of the incident light beam 31.
[0016]
Even if the micromirror 41 is manufactured in a state in which the micromirror 41 is rotated by an angle δ from a regular angular position shown by a broken line, the direction of the emitted light beam 32 does not change, that is, as shown in FIG. The situation where the emission direction is shifted by twice does not occur, and the emitted light beam 32 is only slightly offset with respect to the regular position, that is, the optical axis of the optical fiber 22 as shown in FIG. It becomes.
Although FIG. 2 emphasizes the rotation about the center of the thickness of the constricted portion of the micromirror 41 and shows an offset of size s, for example, the 135 ° angle of the two reflecting surfaces 42 and 43 is changed. If the rotation is around the intersection, the offset s may be practically zero for an assumed finite angle δ.
[0017]
On the other hand, in the conventional example shown in FIGS. 4 and 5, if the entire size of the optical switch 17 is about 500 μm × 250 μm, for example, the optical switch 17 in which the end face of the optical fiber 22 is located even when rotated by δ = 1 °. In the peripheral portion of, an offset of 4 μm or more occurs in the same direction as s in FIG. 2, and the combined light amount is completely lost.
As described above, according to this example, a large loss does not occur unlike the related art, and the micromirror 41 has a large rotation tolerance at the time of fabrication.
FIG. 3 is a diagram showing a case where a four-port optical switch is configured by using the reflecting surfaces 42, 43 and 44, 45 on the front and rear surfaces of the micromirror 41 and simultaneously switching the optical paths of two incident light beams. 6, the micromirror 41 reflects twice so that the offset due to the thickness t as in the conventional micromirror 16 can be eliminated. This does not occur, and all optical axes of through (optical fibers 21 → 23, 24 → 22) and reflection (optical fibers 21 → 22, 24 → 23) can be aligned.
[0018]
【The invention's effect】
As described above, according to the optical switch according to the present invention, the rotation tolerance in the manufacture of the micromirror is relaxed, so that the manufacture is facilitated, the yield is improved, and the cost can be reduced accordingly.
In addition, according to the second aspect of the present invention, there is no optical axis deviation even for a four-port optical switch that uses both the front and back surfaces of the micromirror as reflection surfaces and simultaneously switches the optical paths of two incident light beams. An optical switch in which the optical axes of all ports are aligned can be provided, and in that respect, the degree of freedom of switching is high, and a high-performance optical switch is obtained, and an optical switch in which a plurality of optical switches are arranged in an array is provided. The switch array can also be easily configured.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of an optical switch according to the present invention.
FIG. 2 is a view for explaining a change of an emitted light beam due to rotation of a micro mirror in the optical switch shown in FIG. 1;
FIG. 3 is a diagram showing an arrangement and a light beam progression when the optical switch shown in FIG. 1 has a four-port configuration in which both front and back surfaces of a micromirror are used as reflection surfaces.
FIG. 4A is a plan view showing a conventional optical switch, and FIG.
FIG. 5 is a view for explaining a change in an output light beam due to rotation of a micro mirror in the optical switch shown in FIG. 4;
FIG. 6 is a view for explaining an offset caused by the thickness of the micro mirror when the optical switch shown in FIG. 4 has a four-port configuration in which both front and back surfaces of the micro mirror are used as reflection surfaces.

Claims (2)

A micromirror is formed upright on a movable electrode plate opposed to the fixed electrode plate, and the movable electrode plate is electrostatically driven in a direction perpendicular to the plate surface to displace the micromirror, so that the optical path of the incident light beam is changed. In an optical switch for switching,
The optical switch according to claim 1, wherein the micromirror has two reflection surfaces for reflecting the incident light beam twice and emitting the light beam at a predetermined angle with respect to the incident direction. A micromirror is formed upright on a movable electrode plate opposed to the fixed electrode plate, and the movable electrode plate is electrostatically driven in a direction perpendicular to the plate surface to displace the micromirror, so that the optical path of the incident light beam is changed. In an optical switch for switching,
The micromirror has two reflection surfaces on both front and back surfaces for reflecting the incident light beam twice and emitting the light at right angles to the incident direction, respectively.
An optical switch characterized in that the optical paths of two incident light beams on two orthogonal axes are simultaneously switched by the reflection surfaces on the front and back surfaces.

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