Optics: measuring and testing – Sample – specimen – or standard holder or support
Reexamination Certificate
1998-03-02
2001-03-06
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Sample, specimen, or standard holder or support
C356S036000, C117S005000, C117S004000, C117S007000, C117S009000, C117S011000
Reexamination Certificate
active
06198530
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to organic films, and more particularly to organic crystalline films.
BACKGROUND OF THE INVENTION
Films of organic crystalline materials can be used in various optical applications. For example, optical waveguides made from organic material include slab waveguides in which light is confined in only one dimension, and 2-D channels of size 1 cm×1 &mgr;m×1 &mgr;m. In addition, cylindrical geometry devices filled inside and outside by a non-linear material and surrounded by an electrical field have been reported.
The growth of thin single crystals is discussed, for example in the reference by K. M. M. Kruse entitled “Apparatus and Method For The Growing Of Single Crystal Specimens Of Organic Substances For Infrared Spectroscopic Investigation,” J. of Physics E. Scientific Instr., vol. 3, pp. 609-14, 1970, Great Britain. The crystals are grown from the melt between NaCl (or KBr) windows held at a distance of about 25 &mgr;m apart by means of a thin spacer (Polyester foil). A temperature gradient is maintained first along a capillary and then along the largest dimension on the NaCl windows, resulting in a clear definition of the crystallizing zone. The crystallizing zone is slowly raised by lowering the cell along the vertical temperature gradient within a heated column.
A second reference by Pech et al. studies the growth of solid benzophenone from its own melt contained in a crucible submitted to a unidirectional temperature gradient. Pech et al., “A New Technique For Determining The Kinetics Of Crystal Growth From The Melt,” J. of Crystal Growth, vol. 43, no. 1, 123-25, 1978. In this reference, a sample was placed in a 1×10×15 mm
3
crucible made of glass plates. Thermal boundary conditions were imposed by two heating blocks fixed to the extremities of the crucible and connected to thermostats. The crucible is fixed to the substage of a microscope so that the moving liquid-solid interface can be maintained in coincidence with the cross-hair reticule of the objective of the microscope.
Another method for producing a crystal film is discussed in the Hattori et al. patent entitled “Method For Producing Organic Crystal Film.” U.S. Pat. No. 5,385,116. In this patent, a crystal film of an organic compound is produced from a molten liquid between a pair of substrates. At least one of the pair of substrates has on a part of a surface thereof a three-dimensional geometrical structure capable of controlling the direction of crystal growth of the organic compound. The other part of the surface having the three-dimensional geometrical structure is smooth.
U.S. Pat. No. 4,793,893 to Thakur et al. entitled “Methods For The Preparation Of Thin Large-Area Single Crystals Of Diacetylenes And Polydiacetylenes” discusses a method for preparing thin large-area single crystals of diacetylene monomer. This method involves forming a liquid layer containing pure diacetylene monomer between two opposed surfaces; applying pressure to the liquid layer disposed between the two opposed surfaces; and crystallizing the liquid layer disposed between the two opposed surfaces while by evaporation the liquid layer is kept under constant pressure to form a thin large-area single crystal of pure diacetylene monomer. This patent also discusses a method for preparing a thin large-area single crystal of pure diacetylene monomer.
Notwithstanding the above mentioned references, there continues to exist a need in the art for improved structures including organic crystals and related methods for forming organic crystals.
SUMMARY OF THE INVENTION
In view of the foregoing background, it is therefore an object of the present invention to provide improved methods and structures for organic crystalline films.
This and other objects, features and advantages according to the present invention are achieved by providing a first plate having a first face. The first face defines a recess which is filled with a material which can be crystallized, and covered with a second plate having a second face. Accordingly, the second face is in contact with the first face and the material in the recess is completely enclosed by the first and second plates. The material within the recess is thereby protected by the plates from chemical and mechanical damage as well as evaporation.
The material in the recess can be crystallized, and the step of crystallization can include the steps of heating the material above a melting temperature, and cooling the material to obtain a homogeneous distribution. The crystallization step can be used to produce a single crystal film of the material in the recess. The single crystal film can provide optical properties that are superior to those of polycrystalline films. In addition, the material can be an organic compound which has non-linear optical properties.
The plates used to contain the material are preferably transparent allowing the material to be visually monitored during the crystallization step. For example, the plates can be formed of fused quartz, which is preferably optically polished to reduce the formation of defects during the crystallization step.
Furthermore, the first face of the first plate preferably defines a groove surrounding the recess. This groove can then be used to contain a portion of the material. For example, if the recess is initially overfilled, or if the material overflows from the recess as a result of thermal expansion, the excess can be contained by the groove. Accordingly, any excess material will be prevented from separating the two plates.
In another embodiment of the present invention, an optical device includes a first plate having a first face which defines a recess, a crystalline material in the recess, and a second plate having a second face wherein the second face covers the first face and crystalline material in the recess. The first face of the first plate may further define a groove surrounding the recess, and a portion of the crystalline material may be contained in the groove surrounding the recess.
The first and second plates are preferably first and second transparent plates such as first and second fused quartz plates. In addition, the second face of the second plate and a surface of the recess opposite the second plate are preferably optically polished. The crystalline material may be an organic compound, and it is preferably a single crystal film.
The methods and structures of the present invention provide an organic single crystal thin film which can be used in non-linear optical applications. The structure can be reproducibly fabricated with relatively little expense. In addition, the thin film in the recess is protected from chemical and mechanical damage, as well as evaporation, by the two plates.
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patent: 3883221 (1975-05-01), Rigrod
patent: 3941482 (1976-03-01), Schneider
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patent: 4419810 (1983-12-01), Riseman
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patent: 5363797 (1994-11-01), Uenishi et al.
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Kovrigin et al, Monitoring the Optical Properties of Nonlinear Crystals, Inserum & Exp. Tech, vol. 14, No. 2, pp. 572-574, Mar. 1971.
K.D. Singer et al., “Measurements of Molecular Second Order Optical Susceptibilities Using dc Induced Second Harmonic Generation”,J. Chem. Phys.,vol. 75, No. 7, Oct. 1, 1981, pp. 3572-3580.
K. M. M. Kruse, “Apparatus and Method for the Growing of Single Crystal Specimens of Organic Substances for Infrared Spectroscopic Investigation”,Journal of Physics E: Scientific Instruments,vol. 3, 1970, pp. 609-614.
S. Pech et al., “A New Technique for Determining the Kinetics of Crystal Growth from the
Patent Law Offices of Heath W. Hoglund
Pham Hoa Q.
University of Puerto Rico
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