Researchers from around the world presented new results in optics, photonics and their applications at the 2006 CLEO/QELS meeting, held May 21-26, 2006, in Long Beach, California. The meeting is co-sponsored by the Optical Society of America (OSA), the APS Division of Laser Science, and the IEEE Lasers & Electro-Optics Society (IEEE/LEOS).
Three plenary talks featured a mixture of speakers and topics. Don Boroson of MIT Lincoln Lab explained technology that could allow spacecraft to transmit high rates of data via light waves, rather than with conventional radio waves, and how this space technology will influence future laser communications systems. David Payne of the University of Southampton described how lasers that use fiber optics to generate beams may move into many niches that traditional laser designs currently occupy. Richard E. Slusher (Lucent Technologies Inc.) discussed how light's quantum properties are being exploited for use in powerful new encryption, computing, and communications technologies.
Terahertz Biochip for Drug Detection. A Taiwan research collaboration has built a tiny biochip that can instantly identify illicit drugs such as cocaine and amphetamines in their natural powdered form. Researchers simply deposit powder in its natural form into a small, rectangular glass-and-plastic biochip containing some electronic components.
Inside the biochip, a small transmitter beams electromagnetic radiation in the terahertz (THz) range, to which biomolecules are very sensitive. By recording how much radiation the powder absorbs over a range of THz frequencies, the researchers obtain distinctive chemical fingerprints of the biomolecules that make up the powder.
Using this method, the researchers were able to distinguish powders of cocaine and amphetamine from powders of potato starch, flour, and lactose. In addition, the drug's distinctive THz signatures makes them possible to detect even if they were mixed in with an additional ingredient such as flour.
Forensics is not the only application for the terahertz biochip: researchers also believe it may be very useful for molecular biology applications, such as studying the folding patterns of proteins, which would be helpful for designing new drugs.
High-Speed Terahertz Imagers. In an approach that has already improved nondestructive evaluation of the space shuttle and can potentially bring about better detection of weapons and explosives for homeland security, David Zimdars of Michigan-based Picometrix presented a fast and practical real-world system for terahertz (THz) imaging. THz imaging employs a band of electromagnetic radiation between the microwave and infrared spectrum to penetrate objects and look inside them.
NASA engineers have already used the Picometrix design to peer through the layer of spray-on foam insulation on the external fuel tanks of the space shuttle Discovery and inspect it for defects. The terahertz imager is also fast enough for monitoring certain high-speed industrial processes.
The researchers expect it to be possible to develop much faster versions of this system for homeland security applications, such as airline screening of passengers and luggage.
Probing Planetary Atmospheres. In an advance that enables heightened monitoring of planetary atmospheres, for the first time researchers have designed new lightweight laser instruments that make it practical to routinely measure concentrations of atmospheric gases in situ, or in their natural environments. Measuring these gases more widely and frequently will give atmospheric researchers much richer information for studying weather, climate change, and other phenomena on Earth and other planets and moons.
The instruments, known as tunable mid-IR laser spectrometers, produce light in the mid-infrared region, a part of the spectrum to which all atmospheric gases respond in a distinctive fashion.
Using a laser spectrometer on NASA's high altitude WB-57 spacecraft, Christopher Webster of the Jet Propulsion Laboratory and his colleagues have made the first-ever in situ measurements of different water isotopes in and out of the clouds from the troposphere to the stratosphere. This information is providing a wealth of data on the still incompletely understood origin of cirrus clouds, the wispy masses that play a major role in warming Earth.
Record-Breaking Tabletop Microscope. Using state-of-the-art extreme ultraviolet laser technology, Courtney Brewer of Colorado State University and her colleagues have built a tabletop optical imaging system that can reveal details smaller than 38 nanometers in size, a world record for a compact light-based optical microscope. The microscope can keenly inspect nanometer-scale devices designed for electronics and other applications. It will also be capable of catching subtle manufacturing defects in today's ultra-miniaturized computer circuits, where defects just 50 nm in size that were once too small to cause trouble could wreak havoc in the nanometer scales of today's computer chips.
Other state-of-the-art optical microscopes have achieved resolutions as low as 15 nm, but they required the use of large particle accelerators called synchrotrons. This more compact and less expensive system has the potential to become more widely available to researchers and industry.
Orbital Tomography. Electrons orbiting an atomic nucleus are often depicted concretely but incorrectly as little planets circling a miniature sun in crisp trajectories. Quantum mechanics provides a more accurate (but still metaphorical) picture: the electrons can't be depicted directly. Rather, only the probability of their being at certain places near the nucleus can be rendered and even then only as cloudlike blobs. Researchers never had access to actual images of electron clouds–they only calculated them in theory. Thanks to breakthroughs with ultrashort laser pulses, these orbitals can now be imaged directly.
David Villeneuve of the National Research Council of Canada and his colleagues have helped pioneer a method in which a femtosecond laser pulse rips electrons from the periphery of molecules. These electrons, feeling the electric field of the pulsed light, are first repelled but then very quickly recalled to their home molecule by the strong fields of the same pulse which, in its quick cycling, reverses direction. The electrons can then recombine into the parent molecule, and in the process emit extreme ultraviolet light of their own, light which can be used to perform a type of "tomographic" imaging of the molecule, or more particularly its orbitals. Thus the electron is used to image its own domain.
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