Electrical generator or motor structure – Non-dynamoelectric – Charge accumulating
Reexamination Certificate
2002-03-04
2004-04-20
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Charge accumulating
Reexamination Certificate
active
06724125
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to optical processing using an actuatable structure and, more particularly, to methods and apparatus that facilitate a variety of optical processing functions using a diffractive actuatable optical processor.
DISCUSSION OF THE RELATED ART
Microelectromechanical systems (MEMS) are being employed in an increasing range of applications. The desirability of employing MEMS arises in part because of the ability to batch fabricate such microscale systems with a variety of highly complex features and functionality. Optical processing is one area where MEMS have been used in an increasing number of applications. In particular, MEMS have been used to modulate the intensity of light.
One method of achieving optical modulation using MEMS is by diffractive optical processing. As is conventionally known, the process of diffraction refers to a change in direction and/or intensity of radiation of a given wavelength after the radiation impinges upon a diffracting element (e.g., a reflective diffraction grating).
The process of diffraction results in a number of “orders” of diffracted radiation, wherein each order is diffracted at a particular angle and has a particular intensity, based in part on the wavelength of the radiation and various physical properties of the diffracting element. The mathematical relationships governing the process of diffraction are well-known and may be found in a variety of optics texts, for example.
FIGS. 1A and 1B
are side views of a conventional MEMS diffractive processor
5
illustrating principles of MEMS-based optical processing. In
FIG. 1A
, a grating
10
is illustrated having upper grating elements
12
and lower grating elements
14
. The separation between upper grating elements
12
and lower grating elements
14
, as measured along the path of incoming beam
16
, is equal to one-half of the wavelength of incoming beam
16
. Accordingly, grating
10
acts to reflect incoming beam
16
to generate an output beam along the path of incoming beam
16
.
In
FIG. 1B
, grating structure
10
is actuated using any known MEMS method of actuation (e.g., upper grating element
12
is displaced downward by electrostatic actuation) to achieve a desired separation between upper grating elements
12
and lower grating elements
14
. In
FIG. 1B
the separation, as measured along the path of incoming beam
16
, is equal to one-quarter of the wavelength of incoming beam
16
. Accordingly, grating
10
acts to reflect and diffract incoming beam
16
to form output beams
18
, corresponding to a first order
18
A and a negative first order
18
B of diffraction.
FIG. 1C
is a cross-sectional side view of conventional MEMS optical processor
5
taken along lines
3
C—
3
C of FIG.
1
A.
FIG. 1C
illustrates an exemplary one of upper grating elements
12
, where the ends of upper grating element
12
are fixed to a frame
13
. For efficient operation of a grating (e.g., grating
10
of FIGS.
1
A and
1
B), upon actuation, the separation between upper grating elements
12
and lower grating elements
14
(visible in
FIG. 1B
above) should be a known and fixed value to allow controlled diffraction of an incoming beam; however, conventional grating structures have had limited success in achieving controlled diffraction because actuatable upper grating elements
12
are fixed at the ends, and are otherwise free-standing. Accordingly, grating elements
12
only achieve a desired separation at a limited region
15
of grating element
12
. As a result, conventional MEMS diffractive optical processors have performance issues related to the loss of efficiency arising from the inability to adequately control the MEMS grating structure.
Some additional performance issues relevant to MEMS structures are speed of operation, range of actuation, and physical size of the spatial light modulator. Conventional spatial light modulators suffer from a variety of shortcomings in connection with at least some of the above performance issues. Thus, needs exist for actuatable optical processors having improved control of actuation of grating elements.
SUMMARY OF THE INVENTION
Some aspects of the present invention are directed to actuatable optical processors having improved control of separation of grating elements by using a support structure including an actuation beam to support at least one grating element. Some embodiments of the above aspect of the invention are directed to optical processors for use in optical communications functions. Still other aspects of the present invention are directed to increased functionality of optical communications systems that use actuatable optical processors.
For purposes of the present disclosure, the term “wavelength band” refers to a continuous wavelength spectrum over a particular range of wavelengths (e.g., the optical communications “C” band from 1525 to 1570 nanometers, or the “L” band from 1570-1610 nanometers). Similarly, the term “sub-band” as used herein refers to a fraction of a specified wavelength band, and the term “channel” as used herein refers to a specific relatively narrow sub-band having an optical carrier at a particular wavelength that is modulated to carry information. Accordingly, it should be appreciated that a sub-band (as well as a band) of wavelengths may include one or more channels.
In view of the foregoing, for purposes of the present disclosure, an “optical signal” refers to a signal comprising one or more channels designated by optical carriers having wavelengths in a range of from approximately 0.2 micrometers to 20 micrometers (i.e., from the ultraviolet through the infrared regions of the electromagnetic spectrum). Optical signals including optical carriers corresponding to several channels are commonly referred to as wavelength division multiplexed (WDM) signals. The phrase “optical carrier” as used herein means any information-bearing light beam, independent of any selected modulation scheme.
In some conventional optical communications applications, optical carriers of two or more channels of a given optical signal may be processed differently based on the wavelengths of the carriers. One example of conventional wavelength-based processing of optical signals is referred to as variable optical attenuation, which relates to a controlled attenuation of optical signals across a particular wavelength band (or sub-band). A device that performs this type of function accordingly is referred to as a “Variable Optical Attenuator,” or “VOA.” For purposes of the present disclosure, the abbreviation VOA is used to refer either to the variable optical attenuation function or a device that performs such a function. In VOA, typically optical carriers corresponding to channels lying in a particular wavelength band or sub-band are uniformly attenuated.
Another example of conventional wavelength-based processing is referred to as gain-equalization filtration, and a device that performs this type of function accordingly is referred to as a “Gain-Equalization Filter,” or “GEF.” As above, for purposes of the present disclosure, the abbreviation GEF is used to refer either to the gain-equalization filtration function or a device that performs such a function. In GEF, the attenuation of one or more particular optical carriers corresponding to channels of an optical signal within a particular wavelength band or sub-band is controlled, so as to compensate for wavelength-dependent gain variations of an optical amplifier through which the optical signal passes (e.g., an erbium-doped fiber amplifier).
Yet another example of conventional wavelength-based processing is referred to as optical add/drop multiplexing, and a device that performs this type of function accordingly is referred to as an “Optical Add/Drop Multiplexer,” or “OADM.” As above, for purposes of the present disclosure, the abbreviation OADM is used to refer either to the optical add/drop multiplexing function or a device that performs such a function. In OADM, an optical carrier corresponding to a particular channel of
Deutsch Erik R.
Hung Elmer S.
Senturia Stephen D.
Addison Karen
Dougherty Thomas M.
Lowrie Lando & Anastasi, LLP
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