Optical switch

• US 20030016906A1
• Filed: 07/16/2002
• Published: 01/23/2003
• Est. Priority Date: 07/18/2001
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: NEC Corporation
• Inventors: Utsunomiya, Motoyasu
• Granted Patent: US 6,795,603 B2
• Time in Patent Office: Days
• US Class Current: 385/18
• CPC Class Codes: B81B 2201/045 Optical switches
• CPC Class Codes: B81B 3/0062 Devices moving in two or more dimensions, i.e. having special features which allow movement in more than one dimension
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841

Abstract

An analog beam-steering free-space optical switch for connecting and switching a plurality of optical signals includes a plurality of optical devices and electrostatic actuators for driving the optical devices. Each optical device is pivotally borne so as to allow rotation around a prescribed center of rotation, and each electrostatic actuator includes the substrate that holds the optical devices and a plurality of driving electrodes that are secured to the substrate. The application of electrostatic voltage between an optical device and the driving electrodes generates electrostatic driving torque for causing the optical device to tilt with respect to the substrate around the center of rotation, whereby the direction of reflection of an optical signal is changed. The plurality of driving electrodes are arranged in a radial pattern relative to the electrode center. Each driving electrode is formed in a shape such that the electrode width of a prescribed outer portion relative to the electrode center decreases with progression toward the outside. In addition, each driving electrode is formed in a shape such that the electrode width of a prescribed inner portion with respect to the electrode center decreases with progression toward the inside. Forming the driving electrodes in this way improves the driving torque characteristic of the micromirror and extends the range of steering angles within which stable positioning can be performed by low-voltage drive.

Claims

1. An optical switch for connecting and switching optical paths of a plurality of optical signals, comprising an optical device and an electrostatic actuator for driving said optical device;

said optical device being pivotally borne so as to allow rotation around a prescribed center of rotation and said electrostatic actuator including a substrate that holds said optical device and a plurality of driving electrodes mounted on said substrate;

wherein

an electrostatic voltage that is applied between said optical device and said driving electrodes generates an electrostatic driving torque for causing said optical device to tilt with respect to said substrate around said center of rotation, whereby the direction of reflection of said optical signal is changed; and

wherein;

said plurality of driving electrodes are arranged in a radial pattern around an electrode center, said electrode center being the orthogonal projection of said center of rotation onto said substrate surface; and

said plurality of driving electrodes are each formed in a shape in which the electrode width of a prescribed outer portion relative to said electrode center narrows with progression toward the outside.

2. An optical switch according to claim 1, wherein:

said optical device includes a micromirror, a mirror frame arranged to surround the circumference of said micromirror, and a frame arranged to surround the circumference of said mirror frame;

said micromirror is pivotally borne by said mirror frame such that said micromirror can rotate around a first rotational axis and such that an elastic restoring force acts against this rotation;

said mirror frame is pivotally borne by said frame such that said mirror frame can rotate around a second rotational axis and such that an elastic restoring force acts against this rotation;

said first rotational axis and said second rotational axis intersect each other on the plane that is parallel to the substrate, this point of intersection making said center of rotation;

said plurality of driving electrodes include a first electrode pair for generating electrostatic driving torque for causing said micromirror to rotate around said first rotational axis and a second electrode pair for generating electrostatic driving torque for causing said mirror frame to rotate around said second rotational axis;

the two electrodes of said first electrode pair are arranged on both sides of a first orthogonal plane, said first orthogonal plane being a plane that includes said first rotational axis and extends perpendicular to said substrate; and

the two electrodes of said second electrode pair are arranged on both sides of a second orthogonal plane, said second orthogonal plane being a plane that includes said second rotational axis and extends perpendicular to said substrate.

3. An optical switch according to claim 2, wherein said first rotational axis and said second rotational axis are mutually orthogonal.

4. An optical switch according to claim 1, wherein each of said driving electrodes is formed in a shape in which the electrode width of a prescribed inner portion thereof with respect to said electrode center narrows with inward progression.

5. An optical switch according to claim 3, wherein each of said driving electrodes is formed in a shape in which the electrode width of a prescribed inner portion thereof with respect to said electrode center narrows with inward progression.

6. An optical switch according to claim 5, wherein the shape of said driving electrodes is a rhombus shape.

7. An optical switch according to claim 5, wherein each of said driving electrodes is an oval having its major axis aligned with a radial direction with respect to said electrode center.

8. An optical switch according to claim 1, wherein a plurality of said optical devices and electrostatic actuators are arranged in an array depending on the number of input and output ports.

9. An optical switch for connecting and switching an optical signal, said optical switch comprising an optical device and an electrostatic actuator for driving said optical device;

said optical device being pivotally borne so as to allow rotation around a prescribed center of rotation;

said optical device including a micromirror, a mirror frame arranged to surround the circumference of said micromirror, and a frame arranged to surround the circumference of said mirror frame;

said micromirror being pivotally borne by said mirror frame such that said micromirror can rotate around a first rotational axis and such that an elastic restoring force acts against this rotation;

said mirror frame being pivotally borne by said frame such that said mirror frame can rotate around a second rotational axis and such that an elastic restoring force acts against this rotation;

said first rotational axis and said second rotational axis intersecting each other on the plane that is parallel to the substrate, and this point of intersection making said center of rotation;

said electrostatic actuator including the substrate that holds said optical devices and a plurality of driving electrodes that are mounted on said substrate;

said plurality of driving electrodes including a first electrode pair for generating electrostatic driving torque for causing said micromirror to rotate around said first rotational axis and a second electrode pair for generating electrostatic driving torque for causing said mirror frame to rotate around said second rotational axis; and

an electrostatic voltage, when applied between said optical device and said first and second driving electrodes, generating an electrostatic driving torque for causing said micromirrors to tilt with respect to said substrate around said center of rotation, thereby changing the directions of reflection of the plurality of optical signals to perform connection and switching of an optical path of said optical signal;

wherein;

said first electrode pair has a pair of circular-segment electrodes of the same size, each having a central angle of approximately 180 degrees, the two electrodes being arranged concentric with an electrode center and confronting each other on both sides of a first orthogonal plane, said electrode center being the orthogonal projection of said center of rotation onto said substrate surface, and said first orthogonal plane being a plane including said first rotational axis and extending perpendicular to the substrate surface;

said second electrode pair has a pair of concentric circular-segment electrodes of the same size, each having a central angle of approximately 180 degrees, the two electrodes being arranged concentric with said electrode center and confronting each other on both sides of a second orthogonal plane, said second orthogonal plane being a plane including said second rotational axis and extending perpendicular to the substrate surface; and

said first electrode pair is arranged concentric to said second electrode pair inside said second electrode pair with respect to said electrode center.

10. An optical switch according to claim 9, wherein wiring for each electrode of said first electrode pair extends in the gap that is provided between the confronting edges of said second electrode pair.

11. An optical switch according to claim 9, wherein said micromirror of said optical device is pivotally borne by first hinge springs on said first rotational axis, said mirror frame is pivotally borne by second hinge springs on said second rotational axis, and the tilt stiffness of said second hinge springs is set stiffer than the tilt stiffness of said first hinge springs.

12. An optical switch according to claim 11, wherein the stiffness ratio of the tilt stiffness of said first hinge springs to the tilt stiffness of said second hinge springs is set to equal the ratio of electrostatic driving torque to be generated by said first electrode pair to electrostatic driving torque to be generated by said second electrode pair when equal driving voltage is applied between said micromirror and said first and second driving electrode pairs.

13. An optical switch according to claim 9, wherein a plurality of said optical devices and electrostatic actuators are arranged in array form depending on the number of input and output ports.