Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-10-08
2001-10-09
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S234000
Reexamination Certificate
active
06300619
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to optical communication systems and, more particularly, to micro-electro-mechanical optical devices.
2. Description of the Related Art
Optical communication systems typically include a variety of optical devices (e. g., light sources, photodetectors, switches, attenuators, mirrors, amplifiers, and filters). The optical devices transmit optical signals in the optical communications systems. Some optical devices are coupled to electro-mechanical structures (e. g., thermal actuators) forming an electro-mechanical optical device. The term electro-mechanical structure as used in this disclosure refers to a structure which moves mechanically under the control of an electrical signal.
Some electro-mechanical structures move the optical devices from a predetermined first position to a predetermined second position. Cowan, William D., et al., “Vertical Thermal Actuators for Micro-Opto-Electro-Mechanical Systems”, SPIE, Vol. 3226, pp. 137-146 (1997), describes one such electro-mechanical structure useful for moving optical devices from predetermined first positions to predetermined second positions.
In Cowan et al., the electro-mechanical structure is a thermal actuator. The thermal actuator is coupled to an optical mirror. Both the thermal actuator and the optical mirror are disposed on a surface of a substrate. The thermal actuator has two beams. A first end of each beam is coupled to the optical mirror. A second end of each beam is attached to the substrate surface.
Each beam of the thermal actuator has two material layers stacked one upon the other. The stacked material layers each have a different coefficient of thermal expansion, with the topmost material layer of each beam having a coefficient of thermal expansion larger than that of the other material layer.
The thermal actuator mechanically moves the optical mirror in response to an electrical signal being applied to the beams. Applying the electrical signal to the beams heats the stacked material layers. Thereafter, upon removal of the electrical signal, the stacked material layers cool. Since the topmost layer of each beam has the larger coefficient of thermal expansion, it contracts faster than the underlying material layer when cooled. As the topmost material layer contracts, it lifts the first end of each beam as well as the optical mirror coupled thereto a predetermined height above the plane of the substrate surface. Additional heating and cooling of the beams does not change the height of the optical device with respect to the plane of the substrate surface. As such, the usefulness of thermal actuators is limited to one-time setup or positioning applications.
Thus, electro-mechanical structures suitable for controlling the movement of optical devices continue to be sought.
SUMMARY OF THE INVENTION
A micro-electro-mechanical (MEM) optical device having a reduced footprint is disclosed. The MEM optical device is disposed on a substrate and includes a support structure for supporting an optical element having an outer edge. The optical element is used to deflect light at a selected angle based upon an amount of tilt imparted to the optical element. The support structure is supported by first and second pairs of beams connected at a first end to the support structure and fixed at a second end to the substrate. The beam pairs are arranged, relative to the optical device, so that the first and second ends of each beam are disposed in close proximity to the optical device. This reduces the amount of substrate surface area required for supporting the MEM optical device. As such, an array having an increased number and yield of devices can be produced in a given substrate size.
In a preferred embodiment, the second ends of the beams in each beam pair are located in close proximity to each other to provide for efficient electrical connection of activation leads to the beams, thereby reducing the amount of substrate surface area required for mapping the leads to the beams.
In another preferred embodiment a stiction force reduction element is included on the optical element as well as on an inner frame used for supporting the optical element. The stiction force reduction element is configured as a plurality of protrusions radially disposed on an outer edge of the optical element and on an outer edge of the inner frame for reducing a region of contact between the substrate and either or both of the inner frame and optical element.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.
REFERENCES:
patent: 5658636 (1997-08-01), Reed et al.
patent: 5903380 (1999-05-01), Motamedi et al.
patent: 5994159 (1999-11-01), Aksyuk et al.
patent: 6116756 (2000-09-01), Peeters et al.
patent: 6137623 (2000-10-01), Roberson et al.
patent: 6137941 (2000-10-01), Robinson
Chen et al.,IEEE, “A Low Voltage Micromachined Optical Switch by Stress-Induced Bending,” pp. 424-428, 1999.*
Cowan et al.,SPIE, “Vertical Thermal Actuators for Micro-Opto-Electro-Mechanical Systems,” vol. 3226, pp. 137-146, 1999.
Aksyuk Vladimir Anatolyevich
Bishop David John
Bolle Cristian A.
Giles Randy Clinton
Pardo Flavio
Lee John R.
Lucent Technologies - Inc.
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