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November 2002

The Laboratory
in the News

Commentary by
Leland W. Younker

This Model Can Take the Heat

The Best and the Brightest Come to Livermore

A View to a Kill

Biological Research Evolves at Livermore





Robert J. Deri, Michael D. Pocha, Michael C. Larson, Henry E. Garrett
Compact Multiwavelength Transmitter Module for Multimode Fiber Optic Ribbon Cable
U.S. Patent 6,419,404 B1
July 16, 2002
A compact, multiwavelength transmitter module for multimode fiber-optic ribbon cable. The module couples light from an M x N array of emitters onto N fibers, where the M wavelength may be distributed across two or more vertical-cavity, surface-emitting laser (VCSEL) chips. It combines emitters and multiplexer into a compact package that is compatible with placement on a printed circuit board. A key feature of this invention is bringing together two emitter arrays fabricated on different substrates—each array designed for a different wavelength—into close physical proximity. Another key feature is to compactly and efficiently combine the light from two or more clusters of optical emitters, each in a different wavelength band, into a fiber ribbon.

Luiz B. Da Silva, Bill W. Colston, Jr., Dale L. James
Optical Coherence Tomography Guided Dental Drill
U.S. Patent 6,419,484 B1
July 16, 2002
A dental drill that has one or multiple single-mode fibers used for imaging in the vicinity of the drill tip. Imaging below the surface being drilled is valuable for minimizing damage to vital or normal tissue. Identifying the boundary between decayed and normal enamel (or dentine) would reduce the removal of viable tissue, and identifying the nerve before getting too close with the drill could prevent nerve damage. An improved dental treatment device results from surrounding a drill with several optical fibers that can be used by optical coherence domain reflectrometry to image several millimeters ahead of the ablation surface.

Rodney L. Balhorn, Christopher H. Barry
DNA Attachment to Support Structures
U.S. Patent 6,420,112 B2
July 16, 2002
Microscopic beads or other support structures are attached to nucleic acids (DNA) using a terminal transferase. The transferase adds labeled dideoxy nucleotide bases to the ends of linear strands of DNA. The labels, such as the antigens digoxigenin and biotin, bind to the antibody compounds or other appropriate complementary ligands that are bound to the microscopic beads or other support structures. The method does not require the synthesis of an oligonucleotide probe. The method can be used to tag or label DNA even when the DNA has an unknown sequence, has blunt ends, or is a very large fragment (for example, greater than 500,000 base pairs).

Alan F. Jankowski, Anthony P. Schmid
Flat Panel Display Using Ti–Cr–Al–O Thin Film
U.S. Patent 6,420,826 B1
July 16, 2002
Thin films of titanium–chromium–aluminum–oxygen (Ti–Cr–Al–O) are used as a resistor material. The films are radiofrequency-sputter-deposited from ceramic targets using a reactive working gas mixture of argon and oxygen. Resistivity values from 10 thousand to 10 billion ohm-centimeters have been measured for Ti–Cr–Al–O film less than 1 micrometer thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti–Cr–Al–O as a thin-film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti–Cr–Al–O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat-panel display, or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat-panel displays.

Donald W. Phillion
Constant Volume Gas Cell Optical Phase-Shifter
U.S. Patent 6,421,130 B1
July 16, 2002
A constant-volume gas-cell optical phase shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different from atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume-equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is much the same, a large motion is needed to change the optical phase by the small fraction of a wavelength required for phase-shifting interferometry. This motion can be made to great fractional accuracy.

Stephan P. Velsko, Steven T. Yang
Compact, Flexible, Frequency Agile Parametric
Wavelength Converter

U.S. Patent 6,421,166 B1
July 16, 2002
This improved frequency agile optical parametric oscillator (FA-OPO) provides near on-axis pumping of a single quasi-phase-matched crystal with a tilted, periodically poled grating so that finding a particular crystal that will permit collinear birefringence is not necessary for obtaining a desired tuning range. A tilted grating design and the elongation of the transverse profile of the pump beam in the angle tuning plane of the FA-OPO reduces the rate of change of the overlap between the pumped volume in the crystal and the resonated and nonresonated wave mode volumes as the pump beam angle is changed. A folded mirror set relays the pivot point for beam steering from a beam deflector to the center of the FA-OPO crystal. This setup reduces the footprint of the device by as much as a factor of two over that obtained when using the refractive telescope design.

Scott C. Burkhart
High-Speed Pulse-Shape Generator, Pulse Multiplexer
U.S. Patent 6,421,390 B1
July 16, 2002
The invention combines arbitrary amplitude high-speed pulses for precision pulse shaping for the National Ignition Facility (NIF). The circuitry combines arbitrary height pulses that are generated by replicating scaled versions of a trigger pulse and summing them delayed in time on a pulse line. The combined electrical pulses are connected to an electrooptic modulator that modulates a laser beam. The circuit can also be adapted to combine multiple channels
of high-speed data into a single train of electrical pulses that generate the optical pulses for very high-speed optical communication. The invention has application in laser pulse shaping for inertial confinement fusion, in optical data links
for computers and telecommunications, and in laser pulse shaping for atomic excitation studies. It also can be used to effect at least a 10-fold increase in all fiber communication lines and allows a greatly increased data transfer rate between high-performance computers. The invention is inexpensive enough to bring high-speed video and data services to homes through a supermodem.

Allen T. Christian, Matthew A. Coleman, James D. Tucker
Amplification of Chromosomal DNA In Situ
U.S. Patent 6,432,650 B1
August 13, 2002
Method for amplifying chromosomal DNA in situ to increase the amount of DNA associated with a chromosome or chromosome region. The amplification of chromosomal DNA in situ provides for the synthesis of fluorescence in situ hybridization painting probes from single dissected chromosome fragments, the production of cDNA libraries from low-copy mRNAs, and the improvement of comparative genomic hybridization procedures.

Peter C. Hsu, Erica H. Von Holtz, David L. Hipple, Leslie J. Summers, William A. Brummond, Martyn G. Adamson
Metals Removal from Spent Salts
U.S. Patent 6,436,358 B1
August 20, 2002
A method and apparatus for removing metal contaminants from the spent salt of a molten salt oxidation reactor. Spent salt is removed from the reactor and analyzed to determine the contaminants present and the carbonate concentration. The salt is dissolved in water, and one or more reagents may be added to precipitate the metal oxide and/or metal as metal oxide, metal hydroxide, or salt. The precipitated materials are filtered, dried, and packaged for disposal as waste or can be immobilized as ceramic pellets. More than about 90 percent of the metals and mineral residues (ashes) present are removed by filtration. After filtration, salt solutions having a carbonate concentration of greater than 20 percent can be spray-dried and returned to the reactor for reuse. Salt solutions containing a carbonate concentration of less than 20 percent require further cleanup using an ion exchange column, which yields salt solutions that contain less than 10 parts per million of contaminants.


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