Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-07-05
2002-06-04
Dawson, Robert (Department: 1712)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C252S582000, C204S157150, C428S704000
Reexamination Certificate
active
06400489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to solid-state displacement elements based on a so-called “intercalation phenomenon”, optical elements to which such solid-state displacement elements are applied, and interference filters having solid-state displacement thin films which are fabricated based on the intercalation phenomenon.
2. Description of the Related Art
Research is being carried out diligently on displacement elements in which organic substances are inserted between layers of inorganic layered compounds having layered structures because it is expected that the displacement elements will bring about great advances in the highly advanced mechatronics field, such as for future intelligent robots and microelectronics. Herein, the layered structure refers to a structure in which layers, each composed of densely arranged atoms that are strongly bonded by covalent bonds and the like, are stacked in parallel by weak bonding forces, such as van der Waals' forces, and the inorganic layered compound refers to an inorganic compound having such a structure. Such displacement elements are fabricated based on an intercalation phenomenon. Herein, the intercalation phenomenon refers to a phenomenon in which organic substances corresponding to electron donors or electron acceptors are incorporated or inserted between layers of an inorganic layered compound.
Conventional displacement elements or actuators can be classified according to the structure or the form thereof into, for example, eight groups, i.e., (1) piezoelectric ceramics, (2) polymer gels, (3) shape memory alloys, (4) hydrogen-storing alloys, (5) elements using fluid pressure, (6) electrostatic elements, (7) magnetostrictors, and (8) optical/piezooptical elements.
All of the above techniques are generally well known today. The most important physical properties of the displacement elements or the actuators include displacement (expansion and contraction), generated force, and response speed (control speed). If the above three characteristics can be simultaneously satisfied, that is, if an increase in displacement, an increase in generated force, and shortening of response speed are achieved, development of materials, devices, and various elements will greatly advance. However, under the existing circumstances, it is difficult to obtain displacement elements or actuators which simultaneously satisfy the three characteristics.
For example, although piezoelectric ceramics have excellent generated force and high response speed, the displacement (expansion rate) thereof is 1% or less. Currently, by combining the high-speed response thereof with ultrasonic techniques, ultrasonography, fish detectors, ultrasonic motors, etc. are practically used. However, examples using the displacement are limited to very few applications, such as high-precision actuators which are used for positioning probes of scanning tunneling microscopes (STMs) and atomic force microscopes (AFMs).
Although some polymer gels have a displacement (expansion rate) of several tens of percent to several hundreds of percent, the generated force thereof is significantly low and it is difficult to move heavy objects. Furthermore, it is not always easy to control expansion or contraction. Additionally, since the polymer gels are based on high polymers, the polymer gels are easily affected by heat and are greatly dependent on the operating environment.
Shape memory alloys recover their original shapes by heating after being deformed at low temperatures and, in principle, exhibit thermoelastic martensitic transformation. Therefore, although irreversible plastic deformation does not occur, high/low temperature controlling is required for the use thereof, and twin deformation by lattices is used, and therefore, a large displacement cannot be expected.
Although hydrogen-storing alloys are reversible, the hydrogen-storing alloys are based on the occlusion reaction due to the grain boundary diffusion of atomic hydrogen, thus being disadvantageous with respect to temperatures in the operating environment and responsiveness. Furthermore, the greatest challenge is elimination of heat of the reaction, and it is impractical to obtain small displacement elements or actuators.
Displacement elements or actuators which use fluid pressure are usually composed of composite materials including rubber and fibers, and are driven by air pressure or liquid pressure using the stretching properties thereof. Although such displacement elements or actuators are believed to be suitable for movement in analog form, it is difficult to perform micro-fabrication, and there remain problems with respect to the reduction in size and the integration of the displacement elements or the actuators.
Electrostatic elements are generally fabricated using the fine patterning processes which have been developed for silicon semiconductor devices, and the static electricity Coulomb force is used. Therefore, while the electrostatic elements are advantageous with respect to fine patterning of displacement elements or actuators, there remain problems with respect to the generated force. Furthermore, the greatest challenge is reliability, and because sliding units are included, deterioration easily occurs with time. The electrostatic elements are also easily affected by static electricity.
Magnetostrictors generally use a giant magnetostrictive effect, and materials having a strain of approximately 10
−3
at room temperature (e.g., Tb—Dy—Fe alloys) are known. The magnetostrictors have advantages with respect to displacement, generated force, small mass, etc. in comparison with piezoelectric elements. However, a serious drawback is that an external magnetic field is required for operating a magnetostrictor, and it is a challenge to provide a technique for forming a magnetic circuit in the vicinity of the magnetostrictor. In view of the above, it is difficult to reduce the size and increase the density of the magnetostrictors in comparison with voltage-driven piezoelectric elements.
As optical/piezooptical elements, for example, PLZT exhibiting a photovoltaic effect is known. In the optical/piezooptical elements, electromotive forces are produced by light irradiation based on pyroelectricity of the optical/piezooptical elements, and accordingly the inverse piezoelectric effect occurs, resulting in strain. Although noncontact operation is an advantage, since displacement is caused by inverse piezoelectricity through pyroelectricity, a large displacement cannot be expected, and poling treatment (voltage application) is required to induce displacement, thus giving rise to a problem in the process.
Preferably, displacement elements or actuators include constituents, all of which are solid state. Many organic substances are in a liquid state by themselves, and it is necessary to introduce them into solids without impairing the function of the organic substances. For that purpose, from the point of view of crystallography, it is best that a displacement element or an actuator has an organic molecule as a unit of a crystal structure. By employing such a structure, it is possible to completely prevent atoms and molecules from going in and out in response to the control of the displacement element or the actuator. In order to improve the generated force of the displacement element or the actuator, it is desirable that the displacement element or the actuator has a crystal skeleton similar to that of an inorganic compound. A so-called “intercalation compound” simultaneously satisfies all the conditions described above, in which an organic substance is inserted (intercalated) between layers of an inorganic layered compound having a layered structure. The intercalation compound has both the toughness of the inorganic compound and the flexibility of the organic substance, and is a material which is similar to a biological muscle.
Solid-state displacement elements or actuators using intercalation compounds have been known, for example, from Japanese Unexamined Patent Applicati
Ami Takaaki
Ishida Yuichi
Nagasawa Naomi
Nishimura Teiichiro
Suzuki Masayuki
Dawson Robert
Kananen Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Zimmer Marc S.
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