Optical waveguides – With optical coupler – Switch
Reexamination Certificate
2002-03-14
2003-11-18
Patel, Tulsidas (Department: 2839)
Optical waveguides
With optical coupler
Switch
C359S224200
Reexamination Certificate
active
06650806
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of microelectromechanical systems and, more particularly, to a connector microstructure that is compliant, but yet which still allows for the effective transmission of mechanical forces at high operating frequencies.
BACKGROUND OF THE INVENTION
Microelectromechanical (MEM) systems are getting a significant amount of attention in the field of optical switches. MEM technology generally involves the fabrication of small mechanical devices on a silicon substrate, together with electronic circuitry for actuating motion of the mechanical device. Surface micromachining is one type of fabrication technique for MEM systems. Surface micromachining generally entails depositing alternate layers of structural material and sacrificial material on an appropriate substrate, such as a silicon wafer, which functions as a foundation for the resulting microstructures. Various patterning operations may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructures. After the microstructures have been defined in this general manner, the various sacrificial layers are removed by exposing the microstructures and the various sacrificial layers to one or more etchants which “releases” the resulting microstructures from the substrate (e.g., to allow relative movement).
A MEM-based optical system may include multiple mirror microstructures formed on a substrate for making optical connections. Each mirror microstructure may be interconnected with at least one lift assembly, one or more actuators, and one or more displacement multipliers. The lift assembly may be used to raise the mirror microstructure above the plane of the substrate and/or tilt the mirror into an appropriate position to provide a desired optical function. The actuators are attached to the substrate so as to be movable relative thereto, and provide the motive force/displacement that is used to raise/tilt these mirrors. Electrostatic actuators are commonly used in these types of systems. These types of actuators produce a short stroke displacement which may be insufficient to raise/tilt the mirror to a desired level in at least certain instances. Therefore, the noted displacement multiplier(s) is typically disposed between the actuator and its associated lift assembly to increase the displacement provided by the actuator to the lift assembly, and to thereby allow the mirror microstructure to be raised/tilted to a desired degree. One example of a displacement multiplier is disclosed in U.S. Pat. No. 6,175,170.
Displacement multipliers may be designed to produce a relatively large output based upon a relatively small input. However, displacement multipliers can become rather intricate, which increases development costs. Moreover, displacement multipliers often require a significant amount of space on a die. Since there is only a fixed amount of space within a die for fabrication of the microelectromechanical system, the use of one or more displacement multipliers may reduce the mirror density within the die. Although this may be acceptable for certain applications, a higher mirror density may be desirable for other applications. Therefore, it would be desirable to achieve displacement multiplication for a microelectromechanical system in a manner that allows for increased mirror density.
A tether or the like may be disposed within the interconnection between a mirror elevator and the actuator(s). For instance, an actuator or a plurality of actuators may be interconnected with an input to a displacement multiplier, and the tether may interconnect the output of the displacement multiplier with the mirror elevator. This mirror elevator may have a free end that moves away from and toward the substrate, depending upon the direction of the movement of the actuator(s). This then raises and/or tilts a mirror that may be interconnected with the elevator.
One previously contemplated configuration for the above-noted tether was to form the same from a single layer of a structural material in a surface micromachined optical system. This resulted in the tether being flexible.
SUMMARY
Generally, the present invention is embodied in a microelectromechanical (MEM) system having what may be characterized as a lift assembly that is elevatable from a substrate in response to an input displacement that is typically (although not required to be) at least generally parallel with the substrate. The substrate is one that is appropriate for MEM applications. The lift assembly is operable to move an end of an elevation member of the lift assembly at least generally away from or toward the substrate in response to an input displacement, where the movement of the elevation member's free end at least generally away from or toward the substrate is “multiplied” without requiring the use of a separate displacement multiplier. Any appropriate microstructure may be interconnected with this elevation member and for any appropriate application, including without limitation a mirror microstructure for any appropriate optical application (e.g., optical switches, attenuators, multiplexers, and de-multiplexers).
A MEM system of a first aspect of the present invention is preferably fabricated by surface micromachining, although other MEM fabrication techniques or combination of fabrication techniques may be utilized as desired/required. In any case, the MEM system includes: a substrate; any appropriate actuator that is movably interconnected with the substrate in any appropriate manner; a first elevation member that is interconnected with the substrate at a first location (e.g., at one end of the first elevation member, although the first elevation member could be interconnected with the substrate at an intermediate location that is between a pair of its ends) and a free end that is movable at least generally away from or toward the substrate, depending upon the directional movement of the actuator; and a coupling or “tether” that is disposed between and interconnects the actuator to a portion of the first elevation member that is able to move at least generally away from or toward the substrate. Any configuration may be used for this tether. What is important is that the tether attaches to the first elevation member at a location that is between the first location where the first elevation member is interconnected with the substrate and a free end thereof. The benefit of attaching the tether to a location that is between where the first elevation member is interconnected with the substrate and a free end of the first elevation member is that, by adjusting the attachment location along the length of the first elevation member, the displacement of the first elevation member's free end may be altered (i.e., multiplied/amplified) withrespect to the input displacement without requiring the use of a separate displacement multiplier. Since the MEM system of the first aspect does not require the use adisplacement multiplier to produce a multiplied lift for the first elevation member (that is often necessary in various optical applications and possibly others as well), more room on the substrate is available for other microstructures. Accordingly, a higher packing density of microstructures (e.g., mirrors) may be achieved on the substrate.
Various refinements exist of the features noted in relation to the first aspect of the present invention. Further features may also be incorporated in the first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The first elevation member in the case of the first aspect again is interconnected with the substrate at a first location and has a free end that is operable to move at least generally away from the substrate in response to an input displacement. Any type of motion of the free end of the first elevation member may be utilized and in any manner that is at least generally away from or toward the substrate. In one embodiment, the free end
Barnes Stephen Matthew
Miller Samuel Lee
Rodgers Murray Steven
Marsh & Fischmann & Breyfogle LLP
Memx, Inc.
Patel Tulsidas
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