Quantum mirages, space station microscope, and the shortest light pulses ever

Washington, DC, April 23, 2001 ----- North America's largest conference on lasers, electro-optics, and quantum electronics will take place May 6-11, 2001 at the Baltimore Convention Center in Baltimore, Maryland. The combined Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference (CLEO/QELS) features a gathering of the latest research and technology involving lasers, a broad range of electrical and optical devices, and various systems in which the wave nature of atoms and electrons becomes important. Approximately 10,000 attendees are expected. The meeting is sponsored by the Optical Society of America (OSA), the American Physical Society (APS), and the Institute of Electrical and Electronics Engineers (IEEE).

INTRODUCTION
Lasers - When it was introduced in the latter half of the 20th century, the laser was an invention in search of an application. Lasers produced narrow beams of single-color light, made of waves which line up with each other in a perfectly defined, "coherent" fashion. Scientists thought that they would be useful for studying energy jumps in atoms, but other applications remained undetermined. Nowadays, lasers are everywhere - they scan your grocery items at checkout, they play your CDs and DVDs, they perform state-of-the-art laser surgery. And the story of lasers is just beginning, as new applications loom on the horizon. Continuing advances in lasers will help bring about faster Internet transmissions, safer and better ways of detecting diseases such as cancer, new and presently unimagined entertainment applications, and they will continue their original mission of exploring the frontiers of quantum physics.

Quantum Electronics - Much of our present-day technology is based upon the electron, the particle that carries electricity in devices such as stereos and hair dryers. At its most basic level, quantum electronics deals with our modern understanding of the electron in various settings, from the semiconductors which make up computer chips to LEDs (light-emitting-diodes) which illuminate the latest video screens to the lasers that we find everywhere. Whenever the negatively charged electrons accelerate, or shed their energy, or combine with positively charged "holes" in electronic devices, they produce light or some other form of electromagnetic radiation, and therein lies the electron's connection to optical science.

Electro-optics is the study of all of the wavelengths of electromagnetic radiation, from x-rays to the far infrared through the use of electronic and optical devices. Microwave ovens, radios, cell telephones were all made possible through the use of devices which manipulate electromagnetic energy. Just as the spectrum of electromagnetic radiation is infinite, so are the possibilities for electro-optics applications. Wireless communications, solar-energy cells and many other important technologies will depend upon advances in electro-optics.

MEETING PRESSROOM
A pressroom will be located at the conference from Sunday afternoon, May 6 through Thursday afternoon, May 10. A separate room will be available for public relations representatives and others involved with the media to use as briefing and interview space.

On Tuesday, May 8 from 11:30 a.m. to 1:00 p.m., OSA will hold a press luncheon featuring speakers on several topics that will be presented at the meeting. The speakers and location will be announced in a subsequent release. Reporters interested in attending the luncheon should return the reply form at the end of this release or contact Ben Stein (301-209-3091, bstein@aip.org).

PLENARY SESSION
The keynote speakers at this year's CLEO/QELS Plenary Session (Wednesday morning, 8:00-10:45) will address new avenues for laser research, emerging optical component issues, and the physics behind some important quantum devices.

What's In Store For The Fastest Camera In The World? (8:30am)
What are the implications for the fastest camera in the world, which can capture images on the scale of femtoseconds (one millionth of a billionth of a second)? 1999 Nobel Prize winner Dr. Ahmed Zewail will discuss how the new field of femtoscience will change scientists' understanding of everything from chemistry to physics and medicine. Zewail says the ultimate goal of research in this field will be to understand the molecular basis of complex functions and to control such functions at the atomic scale.

The Greater Bandwidth Revolution (9:15am)
Analysts predict that Internet traffic will grow at a rate of 200 - 300% per year for the next several years, a reality that is pushing the telecommunications industry to find a commercially viable way to meet those demands. Dr. Jozef Straus, CEO of JDS Uniphase, will talk about what it will take to meet the public's seemingly insatiable desire for more bandwidth. One possible solution is Dense Wavelength Division Multiplexing or DWDM. DWDM makes fiber optic lines more efficient by allowing several data streams, at different wavelengths, to use the line simultaneously. In his talk Straus will discuss how the industry is working to optimize issues of capacity, reach, flexibility, and reliability in optical networks in order to make optical transmission equipment a commercial success. Straus will also discuss the latest advances in optical components, such as tunable lasers, that are changing the industry and making advances in DWDM possible.

Quantum Mirages (10:00am)
The scanning tunneling microscope (STM) may be used as a tool to directly image the density distribution of the surface state electrons at a particular energy, or to measure their spectrum at a particular point in space. In addition to providing high resolution images of material surfaces, STMs allow researchers to position atoms to form a variety of electron optical structures such as wave guides, reflectors, and resonators known as "quantum corrals." It is possible to perturb the states of a quantum corral by introducing an atom to the corral's interior in such a way that the perturbation has a large effect at a position remote from the perturbing atom. Donald Eigler of IBM's Almaden Research Center will discuss the "quantum mirage," as the effect is known, and touch on some of the information transport and processing properties of the mirage. Eigler will also show how electron devices may exploit wave optics to do things that conventional electronics devices cannot.

HIGHLIGHTS OF THE TECHNICAL SESSIONS

---Monitoring Coronary Stents with OCT
Wire mesh tubes, known as stents, keep arteries open following balloon catheter treatments to expand coronary vessels clogged with plaque. Between 20 and 30% of patients suffer from restenosis - the growth of new tissue within the stent that may again clog arteries - within six months after the placement of a stent. Often, the status of coronary stents is monitored with intravascular ultrasound, but the diagnostic tool lacks resolution to clearly reveal emerging difficulties. Now, Brett Bouma (617-726-9007, bouma@helix.mgh.harvard.edu) and coworkers at the Wellman Laboratories of Photomedicine and Department of Pathology at Harvard Medical School have developed an Optical Coherence Tomography (OCT) catheter to provide improved images of stented arteries. OCT is a technique similar to ultrasound, but uses infrared light rather than acoustic waves to generate images with 10 micron resolution. The group collected OCT pictures of implanted stents by briefly flushing blood from arteries with saline solution, providing two-second windows to image stent complications such as prolapse or herniation. Bouma will report on a preliminary study of OCT catheter imaging and the potential of the technology to provide improved diagnostics following treatments for atherosclerosis, the leading cause of death in western industrialized countries. (Paper CTuY3)

---Nanoshells for Novel Drug Delivery and Immunoassays
Nanoshells are tiny, layered spheres that provide new opportunities for biotechnological procedures ranging from cancer therapy to medical testing and drug delivery. The spheres are tailored to absorb specific colors of light by controlling the thickness of the nanoparticles' layers. Nanoshells engineered to absorb light in the near infrared spectrum hold particular promise for medical applications because such wavelengths penetrate several centimeters into the human body. Naomi Halas (713-348-5611, halas@rice.edu) of Rice University will report on optically active nanoparticles combined treated with a thermoresponsive polymer to release drugs in response to near infrared irradiation(Paper CThF6). In another talk (CThF7), Halas will describe rapid imunoassays that use nanoshells as detection substrates - antibodies that adhere to nanoshell surfaces remain active and have been detected in whole blood via near infrared, surface-enhanced Raman spectroscopy.

---Space Station Microscope
The International Space Station will contain a state-of-the-art microscope with some new features never previously available on a space mission. The microscope will be used initially for four materials science experiments, some of which may ultimately identify useful materials that can be grown in a low-gravity environment. Biology experiments are envisioned as well. In addition to giving an overall view of the microscope (Poster CWA29), Andrew Resnick of Logicon Federal Data in Ohio (216-925-1151, aresnick@cleveland.feddata.com) will present, for the first time, a discussion of a specific module for the microscope, known as laser "tweezers" (Talk CWN5). Never before have laser tweezers been flown in space. Also known as "optical tweezers," laser tweezersf light to hold and move microscopic particles, in this case as small as 2 microns diameter, less than half the size of a red blood cell. The tweezers can measure how a particle resists flow and how it reacts to its environment, for example to low-gravity forces. Resnick's talk will include preliminary performance characteristics of the laser tweezer unit. Resnick's poster will include other first-time-ever features on a space microscope, such as a confocal design, which reduces out-of-focus images and increases the amount of detail that can be seen in samples.

---Computing with Interference
Computers as we know them do their jobs by using particles (electrons) to move around inside computer chips and carry out the desired tasks. But now, a University of Rochester group led by Ian Walmsley (716-275-0312, walmsley@optics.rochester.edu) has constructed a simple optical system that performs a database search in a way that cannot be emulated in any particle-based computer (Paper QWB3). In their demonstration, the researchers use the "wavelike" side of light's personality: in other words, its ability to act as a wave with peaks and valleys. Different waves can overlap, or "interfere" to produce new patterns of peaks and valleys. Preparing a single pulse of light containing a rainbow spectrum of colors, the researchers store different bits of information in different colors. The interference process works such that the color in the beam with the desired bit of information travels its own way, towards a specific detector, enabling the researchers to read out the information and determine the location of the desired item in the database. While this demonstration is not any faster than traditional database searches, it is the largest database search ever (50 items) with wave interference. Advanced versions of optical searches could employ principles of modern quantum physics, potentially providing insights into quantum computing, which promises astronomically faster database searches.

---Brighter Light from Semiconductor Lasers
The breakthrough for everyday applications with lasers, such as CDs and DVDs, was triggered by the ability to make them with cheap, efficient, easily manufactured semiconductor materials, such as gallium arsenide (GaAs) and indium phosphide (InP). A state-of-the-art laser design, known as the Vertical-External-Cavity Surface-Emitting Laser (VECSEL), recently enabled Sandia researchers to produce semiconductor lasers exceeding 1 Watt.of power, yielding record brightnesses in the light from this class of laser. For comparison, a laser in a typical CD player has a power of less than a milliwatt (a thousandth of a watt). Much brighter semiconductor lasers open up new applications, such as faster optical networks with all-optical switching, lasers that use fiber optics to synchronize different parts of ultra-fast computer chips, or even a home-theater with a laser display. Record-power pulses from these lasers have just been achieved by Reto Haring of the Swiss Federal Institute of Technology in Zurich (011-41-1-633-2181, haring@iqe.phys.ethz.ch) and his colleagues. (Paper CMB1.) The researchers combine the bright power from a VECSEL with a Semiconductor Saturable Absorber Mirror (SESAM), a very fast light switch chops the laser beam into pulses, rather than a continuous stream of light. In such a pulsed mode, the average power is somewhat reduced, but the peak power reaches now a level of 30 W. Focused on a spot 1 micron in diameter, this is about ten billion times brighter than the sun. Moreover, the potential of this new type of laser is by far not exhausted yet. The researchers believe that such lasers will soon deliver several billion pulses per second with an average power of several watts.

---Femtosecond Lasers to Manipulate the Machinery of Life
Understanding the role of individual sub-cellular structures is one of the major challenges in modern cell biology research. To pin down the role played by each part of a cell, researchers disturb a sub-cellular structure and observe the effect on a particular cellular function. Unfortunately, it's often difficult to determine which structures are effected using conventional biochemical and genetic techniques. Tightly focused, femtosecond laser pulses provide a new method to probe the machinery of life by depositing energy in sub-micrometer volumes inside cells, thereby destroying individual structures. Nan Shen (617- 495-9616, nshen@physics.harvard.edu) will report on research at Harvard University involving actin fibers inside a human fibroblast cell precisely severed with a train of femtosecond laser pulses. In future work, the researchers plan to use the technique to study signal transduction in live cells. (Paper CThF5)

---Ultra-Slow Light Pulses in a Solid
Recently, Harvard researchers slowed and stopped light in atomic vapors. Although these were impressive demonstration experiments, most potential applications require that this capability be present in the solid state. To this end, Philip Hemmer of the Air Force Research Laboratory, Hanscom AFB (Philip.Hemmer@hanscom.af.mil) and Selim Shahriar of MIT have succeeded in slowing light's group velocity (the velocity at which it transmits information) to glacial speeds in a crystal doped with the metallic element praseodymium (Pr). The observed optical group velocities are close to what has been achieved in a vapor, and are well below the sound velocity in this material. The demonstration of sub-sonic light speeds is important for potential applications in information storage. Among the latest results to be presented in CLEO/QELS are data showing the delay of individual optical pulses, which were recently obtained with the assistance of post-doctoral associate Alexey Turukhin of MIT. The slowing of individual pulses is the first key step toward the demonstration of stopped light in a solid, which has potential application as a high-fidelity memory for quantum computing. (Paper QMC1)

---The Attosecond Barrier May Be Within Reach
Having recently produced the world's shortest pulses of electromagnetic radiation--an x-ray pulse lasting 1.8 femtoseconds, or 1.8 quadrillionths of a second, Ferenc Krausz of the Vienna Institute of Technology (011-43-1-58801-38711, ferenc.krausz@tuwien.ac.at) and colleagues in an Austria-Germany-Canada collaboration are working intensively to produce even shorter pulses, and will provide an up-to-date report on the status of the project at the time of the meeting. (Paper CMJ1) Their goal is to produce pulses lasting less than 1 fs, putting them on the scale of attoseconds, where one attosecond is a billionth of a billionth of a second. Researchers could use attosecond-scale pulses as a stroboscope for investigating ultra-fast processes such as the rearrangement of electrons within an atom. The researchers are confident that their techniques for achieving their present record will allow them to reach their goal shortly. The team achieved the short pulses by sending a longer-duration pulse of infrared photons into a noble gas, which converts bunches of infrared-light photons into single X-ray photons that constitute the shorter pulse. Measuring the ultra-short duration of the pulse became feasible thanks to a newly developed method, one that enables researchers to measure events on a time scale shorter than it takes for the infrared-pulse-producing laser to generate a light wave with a single peak and valley (i.e., undergo a single oscillation).

These items were prepared by Ben Stein, James Riordon, and Rory McGee of the American Institute of Physics in cooperation with the Optical Society of America and the respective speakers.
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CLEO/QELS Meeting, May 6-11, 2001
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