Optical: systems and elements – Optical modulator – Light wave directional modulation
Reexamination Certificate
2003-05-29
2004-06-29
Ben, Loha (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave directional modulation
C359S238000, C359S243000, C359S244000, C385S016000, C385S017000, C385S018000
Reexamination Certificate
active
06757094
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of optical shutters and switches, and particularly, pertains to optical shutters and switches which operate in the near-infrared and/or visible wavelength regions. More specifically, this invention pertains to optical shutters and switches comprising a reversible transparent-to-reflective optical shutter. This invention also pertains to methods of switching an optical signal from one input path to a selected one of a plurality of different output paths by utilizing the optical shutters and switches of this invention.
BACKGROUND OF THE INVENTION
Throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent specifications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
As the quantity and speed of data communications over fiber optics systems rapidly increases due to the growing demand from Internet usage and other communications, improved all-optical switching systems are of increased interest to overcome the high cost and slow switching speeds of conventional switches. These conventional switches include, for example, various mechanical switches, electro-optic switches, and thermo-optic switches, such as, for example, described in U.S. Pat. Nos. 5,732,168 and 5,828,799, both to Donald. In particular, the increased complexity and cost of switching systems which involve switching from an optical signal to an electrical signal and then back to an optical signal have increased the level of interest in all-optical switches.
An all-optical switch provides switching of an optical signal from one input path to a selected one of a plurality of different output paths without any intermediate conversion of the optical signal to an electrical signal. This is typically accomplished by applying an electrical signal to a switchable element to cause the optical signal to be selectively switched. These electro-optic switches are responsive to the electrical signal to selectively switch the light of the optical signal from the input path to the selected one of the output paths.
A variety of approaches are known for making all-optical or hybrid optical switches, such as, for example, described in U.S. Pat. Nos. 5,905,587 to Maeno, et al.; 5,923,798 to Aksyuk, et al.; 5,970,185 to Baker, et al.; 5,841,912 to Mueller-Fiedler, et al.; 5,091,984 to Kobayashi, et al.; 5,406,407 to Wolff; 5,740,287 to Scalora, et al.; 5,960,133 to Tomlinson; 5,539,100 to Wasielewski et al.; and 5,943,453 to Hodgson.
The need for improved optical switches is increased by the use of wavelength multiplexing which converts the optical signal in the optical fiber into, for example, 16 signals at 16 different wavelengths in a near-infrared range of about 1540 to 1560 nm, as, for example, described in
Bell Labs Technical Journal
, January-March 1999, pages 207 to 229, and references therein, by Giles et al.; and in U.S. Pat. No. 5,959,749 to Danagher et al. The primary function of the optical switch is to add and/or drop optical signals from the multiple wavelengths traveling through the optical fiber. It would be highly desirable to have arrays of optical switches to handle the optical signals from multiple wavelengths per optical fiber and from multiple optical fibers, such as up to 100×100 or greater optical switch arrays. Also, it would be highly desirable if the response time for the optical switch is ultrafast, such as 1 nanosecond or less.
It would be advantageous if an all-optical switching system were available which avoided the complexity and cost of hybrid electro-optic and other switching systems while increasing the speed of the switching times from the millisecond range to the nanosecond or picosecond ranges.
SUMMARY OF THE INVENTION
One aspect of the present invention pertains to an optical shutter comprising an organic free radical compound in which the free radical compound is characterized by forming an oxidized or reduced product having a change in absorption in a near-infrared wavelength region as a result of a photo-induced electron transfer reaction of the free radical compound, wherein the change in absorption is reversible. In one embodiment, the reversible change in absorption is induced by heat. In one embodiment, the reversible change in absorption is induced by radiation selected from the group consisting of ultraviolet radiation, visible radiation, and infrared radiation; and, preferably, the reversible change in absorption is further induced by the presence of oxygen.
In one embodiment of the optical shutter of this invention, the optical shutter further comprises a metallized layer on at least one side of a photon-absorbing layer comprising the free radical compound of the optical shutter. In one embodiment, the metallized layer comprises aluminum.
Another aspect of the present invention pertains to an optical shutter comprising an organic free radical compound, preferably a radical cation compound or a radical anion compound, in which the free radical compound is characterized by forming an oxidized or a reduced product having a change in absorption in a visible and/or a near-infrared region as a result of a photo-induced electron transfer reaction of the free radical compound, wherein the change in absorption is reversible. In one embodiment, the optical shutter is utilized in an optical switch device for a fiber optics communications channel.
Still another aspect of this invention pertains to an optical shutter imageable by photons and having a first state of a low absorption and low reflection at a wavelength and a second state of a high absorption and high reflection at the wavelength, which shutter comprises a photon-absorbing layer, wherein the photon-absorbing layer comprises an organic free radical compound, as described herein, and the photon-absorbing layer is characterized by absorption of the photons by the free radical compound to form a reaction product having a change in absorption at the wavelength and by a reverse reaction of the reaction product to regenerate the free radical compound; and wherein the shutter is characterized by being reversibly imageable between the first and second states. The unique properties of the optical shutter of the present invention may be utilized to prepare a wide variety of extremely compact, picosecond speed optical devices including, but not limited to, optical switches in various arrays comprising one or more of the optical shutters.
Another aspect of the present invention relates to an optical shutter having a first state of transparency and of a low reflectivity at a range of wavelengths and a second state of opacity and of a high reflectivity at the range of wavelengths, which shutter comprises a photon-absorbing layer and a surface layer on at least one side of said photon-absorbing layer, wherein the photon-absorbing layer comprises an organic free radical compound in at least one of the first and second states and is characterized by absorption of photons to form a reaction product having a change in absorption at the range of wavelengths; and wherein the shutter is characterized by being reversibly imageable between the first and second states. In one embodiment, the optical shutter comprises a metallized layer on at least one side of said photon-absorbing layer. In one embodiment, the metallized layer comprises aluminum. In one embodiment, the absorption of photons images the shutter from the first state to the second state, and preferably, wherein the reaction product is the free radical compound. In one embodiment, the absorption of photons images the shutter from the second state to the first state, and preferably, wherein the reaction product is formed from the free radical compound. In one embodiment, absorption of photons reversibly images the shutter between the first and second st
Berger Arthur W.
Carlson Steven A.
Ben Loha
Optodot Corporation
Sampson & Associates P.C.
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