Watching metals melt, nanometer-scale views inside cells

05/02/05

CLEO/QELS/PhAST Meeting to feature state of the art laser and quantum optics results

Washington, DC (May 2, 2005) - Researchers will present new results in the realm of optical science between May 22-27, 2005, in Baltimore, Maryland, at the 2005 Conference on Lasers and Electro-Optics (CLEO), which is being held jointly with the Quantum Electronics and Laser Science Conference (QELS), and the Photonic Applications System Technologies (PhAST) Conference. The meeting is co-sponsored by the Optical Society of America (OSA), the American Physical Society (APS), and the IEEE Lasers & Electro-Optics Society (IEEE/LEOS).

A meeting Press Room will be located in the Baltimore Convention Center in the Pratt Street East Office. The Press Room will be open Sunday, May 22 from 12 p.m. - 4 p.m. and Monday, May 23 - Thursday, May 26 from 7:30 a.m. - 6:00 p.m. Those interested in obtaining a meeting badge for the Press Room should register online at http://www.cleoconference.org/media_center/ or contact OSA's Colleen Morrison at 202-416-1437, cmorri@osa.org.

PRESS LUNCHEON A private press luncheon panel will take place on Tuesday, May 24 at noon in room 333. The press luncheon will convene representatives from the scientific, corporate and analyst communities to discuss the business and science sides of optics, highlight the most intriguing new research in the field, and offer an overarching perspective on significant new developments to be unveiled during CLEO/QELS and PhAST. The panel will also introduce some of the most promising applications for optical technology. To register for the press luncheon contact OSA's Colleen Morrison at 202-416-1437, cmorri@osa.org.

PLENARY SESSION
At two plenary and awards sessions, distinguished speakers will present talks on cutting-edge optics topics. On Monday, May 23 at 6:30 p.m., Arpad Bergh of the Optoelectronics Industry Development Association will discuss the convergence of traditional industry segments --communications, computers and consumer electronics -- and how it may lead to new optoelectronics markets. Shuji Nakamura of the University of California at Santa Barbara will discuss future prospects for solid-state lighting, which promises a much more energy-efficient form of illumination. At the Wednesday, May 25 8 a.m. session, Deborah Jin of JILA/University of Colorado will talk about fermionic condensates, ultracold gases of matter that are enabling researchers to explore some fundamental physics phenomena such as superconductivity. Additionally, Chris Contag of Stanford will show how optical imaging can reveal the factors that cause stem cells either to self-renew (replicate themselves) or differentiate (develop into more specialized cells).

HIGHLIGHTS
Following are a few of the many highlights to be discussed at the conference.

SHEDDING LIGHT ON BRAIN TUMORS AND CLOGGED ARTERIES
Using a practical laser-based fiber-optics system, researchers have developed a minimally invasive technique that can tell the difference between dangerous and less harmful forms of atherosclerotic plaque in 34 human patients. In addition, the same technique distinguished brain tumors from normal tissue in 18 patients. Developed by a team of engineers and surgeons at Cedars-Sinai Medical Center in Los Angeles and the University of Southern California, the system makes use of a technique called "time-resolved laser-induced fluorescence spectroscopy" (TR-LIFS). Using this process, surgeons take a fiber optic probe connected to a laser to access the desired location in the body. There, the probe shines the laser light on tissue, and researchers or physicians record the spectrum of light that the tissue radiates (or "fluoresces") in response. As team member Laura Marcu will report, the fluorescence emission from the tissue can provide information on its chemical composition. This information, for example, can tell physicians whether artery plaque is dangerously inflamed, consisting of foam cells rich in lipids, or if they are less dangerous due to a collagen-rich composition. In the realm of brain surgery, it allows surgeons to determine the boundaries of aggressive brain tumors (glioblastoma) in real-time during surgical procedures. This sensitive optical system removes the need for many biopsies and makes it easier to distinguish between similar types of tissue. With their initial clinical successes, the researchers hope to help fluorescence spectroscopy become a widespread clinical technique. (Presentation CFJ3, "Applications of Time-Resolved Fluorescence Spectroscopy to Atherosclerotic Cardiovascular Disease and Brain Tumors Diagnosis")

WATCHING METALS MELT: INSIGHTS FOR PLANETS, STARS, AND EXTREME STATES OF MATTER
In what may provide deep insights into what goes on inside planets and stars, scientists have captured the first atomic-level view of the melting process, one of the simplest transformations of matter, on the timescale of femtoseconds, or quadrillionths of a second. Rapidly heating metals and watching how their atoms rearrange themselves can provide insights into the extreme conditions inside stars and the interiors of planets as well as the extreme states of matter that approach nuclear fusion temperatures. Demonstrated by a University of Toronto team led by Profesor Dwayne Miller, an intense, ultrafast pulse of laser light melts the target material, followed by a beam of electrons that bounces (or "diffracts") through the material to provide information on the positions of the atoms at any given instant. The experiments are revising scientists' basic knowledge of what happens during rapid melting. Raising the temperature of solid aluminum to approximately 1000 degrees in less than 1 picosecond (a heating rate of more than a million billion degrees per second), the researchers found that the aluminum atoms, initially arranged like oranges in a grocery display, are vigorously shaken off by the laser beam, with the atoms at the corners shaken off first, followed by those closer inside. The researchers have extended their experiments to study the melting of metals, such as gold, which may increase understanding of warm dense states of matter as a prelude to nuclear fusion. (Presentation CTuAA1, "Femtosecond Electron Diffraction: An Atomic-Level View of Condensed Phase Dynamics")

TINY CELL COUNTER MIGHT MAKE CRUCIAL MEDICAL TESTS MORE AVAILABLE
Detecting and counting cells is crucial for clinical diagnosis. Determining the presence and abundance of white-blood cells, for example, is integral for diagnosing cancer and AIDS. Starting out decades ago as a room-sized operation, counting cells is now a tabletop operation but scientists at the University of California at San Diego (UCSD) aim to reduce the size much further, to the point where it could eventually become part of a highly portable, miniature, circuit-based system. Cell counters operate according to a principle known as flow cytometry, the study of cells as they move past detectors in a fluid stream. The hope is to make these often-important cell-counters more available to primary care physicians, potentially enabling patients to get cell counts in the office without having to travel to a lab. Speaking at the CLEO meeting, UCSD's Victor Lien will describe how marrying microfluidics (fluids moving through tiny channels) to photonics produces a thousandfold reduction in size, weight, and cost for performing one of two core functions of flow cytometry: cell detection with very high sensitivity. Instead of mainframe lasers and photodetectors, the UCSD device, which they call a fluidic photonic integrated circuit (FPIC), uses tiny light emitting diodes and silicon detectors for triggering, and then monitoring fluorescence from, passing cells to detect them with 10,000 times better sensitivity than before. The researchers are using their device for detecting stem cells and cancer cells. (Presentation CFF2, "Fluidic Photonic Integrated Circuit (FPIC) for Cytometric Detection")

STUDYING TINY CHANGES IN LIVING CELLS
There have been several ways to study the structure and behavior of organelles, distinct cell structures such as the nucleus and mitochondria. Electron microscopy produces sharp pictures but preparing the specimen to enable viewing necessarily kills the cell. Viewing separate cells at different phases of development can provide a proper time sequence, but this involves much tedious labor. A second method, using fluorescent probes coupled with light microscopes, sometimes saves the cell but can interfere with its normal functioning. A new method, reported by Lev Perelman of Harvard, avoids the forgoing problems by combining the use of tight pinholes to control incoming and collected light (Confocal Microscopy) and analyzing the spectrum of scattered light coming from the sample (Light Scattering Spectroscopy). One builds up a complete image by scanning the microscope across the specimen. The Harvard confocal light scattering spectroscopic (CLSS) microscope achieves pictures of 100-nm organelles with 5-nm accuracy, allowing it to look for clumping of the genetic material known as chromatin, an early sign of cancer, inside the cell nucleus. According to the researchers, this technique has potential applications in such areas as obstetrics/gynecology and drug design. (Paper CThC1, "Application of Confocal Light Scattering Spectroscopic Microscopy to Monitor Subcellular Organelles")

SLOW LIGHT MEANS BETTER TELECOMMUNICATIONS
In the past few years, researchers have slowed down light from its normal speed of 186,000 miles per second to zero velocity. Such a feat may be useful, for example, in using light to make more powerful all-optical versions of computers, memory chips and telecommunications systems. Now, a Cornell-Rochester-Duke team presents a new method of slowing down light, one that is especially practical, as it can be operated over a wide range of wavelengths, including those useful for telecommunications. The method employs a phenomenon known as Brillouin scattering, in which the energy of the optical wave is exchanged with acoustical waves, then re-converted to a lightwave of lower frequency. The researchers use this effect to construct an optical delay, in which a pulse of light is postponed for up to 1.3 times the pulse duration. The technique might be useful for future all-optical systems that store random access memory and perform data synchronization. The system utilizes off-the-shelf components, which reduce its overall cost and allow for straightforward integration with existing telecommunications infrastructure. (Presentation CMCC3, "Tunable All-Optical Delays via Brillouin Slow Light in an Optical Fiber")

PROGRESS TOWARDS COMPOSITE MATERIALS WITH A NEGATIVE INDEX OF REFRACTION FOR VISIBLE LIGHT
A few years ago physicists devised a "metamaterial" -- an artificial composite material made of tiny rods and small split rings -- which had a very curious optical property. Namely, it had a negative index of refraction: Microwave radiation impinging onto the metamaterial's surface bent (refracted) in the opposite direction as it did for ordinary materials. Combining metamaterials with conventional materials might lead to new kinds of cell-phone antennas which could provide better reception and coverage. In addition, a flat panel of metamaterial might enable the construction of a "perfect lens" which can image objects -- at least according to theory -- with limitless detail (resolution). For instance, this would allow for rewritable optical discs with unmatched storage density. The trouble is that the fabrication of metamaterials with a negative index of refraction becomes more difficult as one aims for higher, more practical, frequencies, such as those in the visible spectrum. Now, a collaboration between the University of Karlsruhe in Germany and Iowa State University is reporting a metamaterial designed for electromagnetic radiation at a record high frequency of around 100 terahertz (equivalently, a 3-micron wavelength), in the infrared portion of the electromagnetic spectrum. The material does not yet exhibit a negative index of refraction, and there is no "perfect lensing" of the 3-micron wavelength radiation, but the Karlsruhe-Iowa group is working on this, as well as on metamaterials at even higher frequencies suitable for telecommunications wavelengths. (Presentation JThC1, "Towards Left-Handed Metamaterials at Optical Frequencies")

Source: Eurekalert & others

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