Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-09-13
2003-04-08
Epps, Georgia (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C359S321000
Reexamination Certificate
active
06545796
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to micro-electromechanical systems (“MEMS”) devices. More particularly, the present invention relates to a flexible support element for use in MEMS devices and to articles incorporating the flexible support element.
BACKGROUND OF THE INVENTION
MEMS technology is becoming ubiquitous. MEMS accelerometers, pressure sensors, optical modulators, display devices and even MEMS-based electrical components have been developed for use in a wide variety of applications.
MEMS devices often incorporate structural elements (e.g., plates, etc.) that are supported for movement or that otherwise require separation from other structures in a MEMS device. In some MEMS devices, movable structural elements are supported by support arms that are disposed at the periphery thereof. In other MEMS devices, pedestals that are disposed beneath the structural element provide support therefor.
In U.S. Pat. Nos. 5,673,139 and 5,920,417 (“the '139 and the '417 patents), a MEMS-based television scanning device is described. The device includes a cross-shaped plate having an electrically-conductive material that is supported above four actuator electrodes by a flexible joint. One actuator electrode is disposed underneath each arm of the cross-shaped plate. On application of a voltage to an electrode, an attractive force is induced between the actuated electrode and the overlying arm of the cross-shaped plate. As a consequence, the overlying arm moves towards the actuated electrode.
In one embodiment described in the '139 and the '417 patents, the “flexible joint” is a “flexible shaft” in the form of a solid rod or tube (see, e.g.,
FIG. 8
of either patent showing a cross sectional view of the shaft “32”). To create even a relatively minor amount of flexion in a solid “flexible” shaft requires an undesirably high voltage. In the '139 and '417 patents, the overlying cross-shaped plate itself can flex towards the electrode, so the degree of flexibility of the flexible shaft is not at issue. But in other applications, it is desirable to have a shaft that provides substantially all required flexion to effectuate movement of an overlying plate.
SUMMARY OF THE INVENTION
In accordance with the present teachings, an article comprising a free-standing, hollow micro-tube is disclosed.
The micro-tube, which has a diameter on the order of tens of microns, is typically “free standing” (i.e., supported at only one end thereof). The other end of the micro-tube usually supports a platform or some other structure.
The micro-tube is formed from a cylindrical wall. In some embodiments, the cylindrical wall is created by forming a hole through a substrate material, depositing a material along the perimeter of the hole (ie., on the surface of the surrounding substrate material), and then removing the surrounding material. By virtue of its hollow constitution, the micro-tube offers less resistance to flexing or bending than a solid support structure. Such reduced resistance is particularly advantageous for devices comprising structures that are designed to bend under the action of an applied voltage, since lower bending resistance equates to a lower voltage requirement.
In one specific embodiment of an article comprising a micro-tube, the article is an XY-translation stage. An illustrative XY translation stage includes several electrodes and a platform supported by four micro-tubes. As voltage is applied across a select one or more of the electrodes, an electrostatic force is generated between the stage and the actuated electrode(s). Consequently, the platform moves towards the actuated electrode(s).
In a second specific embodiment of an article comprising a micro-tube, the article is an array of pedestal mirrors. An illustrative pedestal mirror has a reflective platform—a mirror—supported by one micro-tube. Several electrodes are disposed underneath the mirror. As voltage is applied across a select one or more of the electrodes, the mirror “tilts” towards the actuated electrode(s). Moving the mirror in such fashion allows, for example, an optical signal to be selectively directed to any one of several possible destinations (e.g., different waveguides). The array includes a plurality of pedestal mirrors, each of which mirrors are advantageously independently addressable. In one embodiment, the array of pedestal mirrors is used as an optical cross connect in an optical communications system.
REFERENCES:
patent: 5645684 (1997-07-01), Keller
patent: 5673139 (1997-09-01), Johnson
patent: 5920417 (1999-07-01), Johnson
patent: 6051441 (2000-04-01), McDowell et al.
patent: 6199874 (2001-03-01), Galvin et al.
patent: 6319789 (2001-11-01), Carstensen
Agere Systems Inc.
Epps Georgia
Hanig Richard
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