By Patricia Daukantas

In this age of instant telecommunications and social media, one of the reasons why people still attend professional conferences is to run into old friends and catch up with them. I certainly experienced this at CLEO:2011 as I ran into OSA staff members, OPN contributors and past OSA presidents at various sessions and the conference reception.

It’s also gratifying to see people I’ve written about for OPN in the past and learn about their current work. For example, last year I wrote in the Scatterings column about a three-dimensional, near-infrared “invisibility cloak” created by a team at the Karlsruhe Institute of Technology (KIT) in Germany. This week at CLEO, Joachim Fischer of KIT reported that his group has pushed the technology to the edge of the visible realm by making a 3-D cloak that works for 700-nm light.

To build their near-IR cloak, the KIT researchers used a fabrication technique called direct laser writing to build a tiny “woodpile” photonic crystal. Because a visible-light cloak would require even finer detail, the team incorporated stimulated-emission-depletion (STED) fluorescence microscopy into the laser-writing fabrication process. The resulting cloak worked not just with monochromatic light from a Ti:sapphire laser, but also with a white-light source passed through a red filter.

“Seeing the cloaking action with one’s own eyes is an amazing experience,” the KIT team wrote in the CLEO proceedings. We couldn’t agree more. Their paper, with Fischer as the lead author, is now available in the “Early Posting” section of Optics Letters.

This blog can’t possibly cover everything that has been happening at CLEO this week. If you hunger for more information, point your browser to the CLEO social media hub and drink in the postings. The OSA booth at CLEO has a Legislative Action Center station where attendees can express their views about U.S. science funding issues, and you don’t have to be onsite to use that website, either. Finally, the CLEO:2011 proceedings will be published on OSA’s Optics InfoBase in the near future.

CLEO/QELS, Lasers, CLEO

By Patricia Daukantas

This year’s CLEO conference features such a wide array of interesting scientific findings and technological applications that it’s hard to know where to begin this blog post. So I’ll just dive right in.

The Dawn of "Nuclear Photonics"

Ever heard of “nuclear photonics”? It may sound like a bit of an oxymoron, since photonic inventions and techniques, such as laser spectroscopy, are associated with physics on the atomic level. However, if the folks at Lawrence Livermore National Laboratory (U.S.A.) have their way, super-high-energy beams with laser origins could solve some extremely practical national-security problems.

According to Livermore scientist Chris Barty, researchers at the lab are learning how to make tunable gamma-ray beams by Compton scattering of laser beams off relativistic electrons. The Livermore people call these “mono-energetic gamma rays,” or “MEGa-rays.”

At the 2-MeV photon energy range, MEGa-ray beams would be at least 15 orders of magnitude brighter than synchrotron light, which has its maximum brightness between 10 and 100 keV. Such brilliant beams have the energy to probe not just atoms, but the nuclei within those atoms.

Nuclear resonance fluorescence (NRF) is analogous to the more familiar atomic resonance fluorescence, but it depends on the number of protons and neutrons in the nucleus, so that it can ferret out the spectral signature of isotopes. The narrowband MEGa-rays could selectively excite NRF transitions, and, with the appropriate detector, could provide precise assays of the isotopic content of, and isotopic distribution within, bulk material.

Although no NRF imaging has been done yet, simulations indicate that MEGa-rays could someday help detect highly enriched uranium in the 48 million cargo containers that enter the United States annually, Barty said.

Today, two U.S. laboratories and one in Japan have second-generation MEGa-ray sources for proof-of-principle experiments, Barty said. The next step is to miniaturize the technology – it needs to be able to fit into a truck to be practical for homeland security applications. Livermore is building a nuclear photonics lab for creating a next-generation source that combines compact X-band linac technology from the SLAC National Accelerator Laboratory with Livermore’s high-power diode-pumped lasers.

Second Plenary Session

CLEO traditionally has two plenary sessions, and the 2011 conference was no exception. While Monday night’s plenary talks told of technological applications, the Wednesday morning speakers addressed fundamental science.

Mordechai (Moti) Segev of Israel outlined the pioneering work that he and his colleagues have done in Anderson localization of light. A fellow CLEO blogger, James Van Howe, summed up his talk better than I could have done. I liked how Segev, instead of ending his speech with a list of “conclusions,” listed the possibilities for future research in his field. These open questions include localization in honeycomb lattices, localization with entangled photons, sub-wavelength localization of light and solitons in disordered media.

Likewise, Susumu Noda of Japan presented a thoroughly detailed account of photonic crystal theory and experiments as they have developed over the past 20 years. Although photonic crystals occur in nature – as in the scales on the wings of a beautiful blue butterfly – human-made crystals were still in the microwave regime in the early 1990s. Progress has indeed come very rapidly.

CLEO/QELS, Lasers, CLEO, OSA nuclear photonics, Anderson Localization, CLEO, CLEO:2011, photonic crystals, Moti Segev, Susumu Noda, optics, Optics and Photonics News

By Patricia Daukantas

The weather outside the Baltimore (U.S.A.) Convention Center has been varying wildly, from warm and summery to cool and rainy. Indoors, however, the atmosphere of the CLEO:2011 conference was steadily abuzz with exciting applications of the latest photonics technologies.

Ultraviolet LEDs Can Disinfect Water

Although CLEO is primarily a laser conference, some tracks focused on other photonics technologies, such as photovoltaics and quantum computing. Following a joint symposium on semiconductor ultraviolet (UV) lasers and LEDs, a session reviewed several practical applications of UV LEDs.

One task for which these devices are particularly suited is the removal of harmful germs and other contaminants from drinking water. Gordon Knight, a research manager at Trojan Technologies (Canada), explained that UV light penetrates the cell membranes of bacteria, viruses and protozoa and permanently alters their DNA so the critters can’t reproduce and infect humans. UV rays can also break down organic contaminant molecules, as long as the molecular absorption spectrum matches the output of the UV sources.

Water treatment specialists are primarily interested in the UV-C spectrum (200 to 280 nm), in which the peak absorption spectrum of germ DNA falls, Knight said. The industry’s workhorse has been the low-pressure mercury arc lamp, which has a strong emission peak at 254 nm. However, solid-state UV sources could be more energy-efficient and could maintain their steady output for five times longer than the mercury lamps.

Although some technical challenges remain in the development of UV-C LEDs--namely, cost and the need to boost individual chip output above 5 mW--Knight is confident that these sources will provide efficient instant-on operation for future water treatment devices, both in municipal plants and perhaps even in household-sized systems.

IARPA: An Opportunity, Not a Misspelling

You’ve heard of DARPA, but what about IARPA? The Intelligence Advanced Research Projects Agency, a new branch of the U.S. government’s spy agencies, recently started searching for “high-risk, high-payoff” research programs to boost America’s intelligence-gathering efforts.

According to IARPA official Michael C. King, the agency is especially interested in significant advances in techniques to gather biometric data from distant, moving human subjects. Successful proposals require not just a good idea, but also a capable leader to guide the research project. One U.S. team followed King’s talk with a discussion of their own technique for so-called “standoff biometric identification” of people. According to Brian C. Redman of Lockheed Martin (U.S.A.), Fourier transform profilometry involves bouncing fringes from an 808-nm laser off the subject, capturing it and its two-dimensional fast Fourier transform, then doing an inverse transform and merging it with the original data. The laser pulses are eye-safe and, with a duration of 100 microseconds, short enough to freeze motion at a brisk walking speed of 1.5 m/s. The near-infrared light can even “see” through most sunglasses, Redman said.

Applied optics, Biomedical optics, CLEO/QELS, Energy, Lasers, Lasers, CLEO, OSA, Photovoltaics lasers, cleo, the optical society, optics & photonics news, quantum computing, biomedical optics, photovoltaics

By Patricia Daukantas

Every scientific advancement has a story behind it. Telecommunications fibers and optical coherence tomography (OCT) are no different. Donald Keck and James Fujimoto--the first two CLEO:2011 plenary speakers--did a great job of telling those true tales.

Donald Keck, a retired Corning Inc. (U.S.A.) scientist who participated in the development of the first low-loss optical fiber, attributed the telecom boom to a “syzygy” of rapid-fire technological developments four decades ago. In addition to that first practical fiber, the earliest computer-network experiments, the room-temperature laser chip and the computer chip all appeared between 1969 and 1971.

Evoking the original notion of the laser as a “solution looking for a problem,” Keck drew chuckles by reminding the audience of schemes for laser cutting of trees, laser-made nipples for baby bottles and Arthur Schawlow’s “laser eraser” for typists. Early proposals for laser telecommunications--by sending light beams down 2-in.-wide coaxial cables--were not much more practical.

Fortunately, British government researchers asked Corning for help in creating glass fibers with attenuation below 20 dB/km, at a time (1966) when the best silica fiber suffered from signal loss of 1,000 dB/km. Drawing upon glass research from the 1930s to the 1950s, Keck and his Corning colleagues started tracking down and eliminating the sources of optical loss in fiber.

Their initial fiber-drawing equipment was crude--including a household vacuum cleaner--but effective. When Keck tested the first fiber with a loss of only 17 dB/km, he was so impressed that he wrote in his lab notebook, “Whoopee!” However, in 1970 an Applied Physics Letters reviewer initially rejected the Corning team’s paper because, Keck said, “it lacked believability.”

Today’s single-mode fibers fulfill Keck’s 1972 prediction of operation with losses of 0.2 dB/km or less at the 1,550-nm wavelength. Progress in telecommunications has come rapidly, especially after the 1984 court-ordered breakup of the old Bell-System AT&T, which created “a lot of fiber-hungry ‘baby Bells,’” Keck said. With the development of fiber that can bend around sharper corners without introducing losses, the industry is poised to use fiber in ways traditionally associated with copper wire.

OCT: Joining Optics and Clinical Science

OCT is a method of imaging using echoes of light--the optical analogue of ultrasound, said James Fujimoto of the Massachusetts Institute of Technology (U.S.A.). In terms of resolution and tissue penetration, OCT bridges the gap between ultrasound and confocal microscopy.

Although Michel A. Duguay and A.T. Mattick first suggested the technique in a 1971 Applied Optics article, the first demonstration of OCT, performed on a cadaver eye, was published two decades later, according to Fujimoto. Since then, progress has come rapidly, with the technique’s extension to living tissue and the commercial development of OCT equipment for clinical use. Today, spectral domain interferometric techniques have improved both the speed and sensitivity of OCT. High-speed CCD cameras and volumetric data-rendering techniques have added to OCT’s ability to track dynamic processes such as capillary blood flow.

OCT is now moving beyond ophthalmic procedures into the world of intravascular imaging, where the technique can identify unstable arterial plaques and guide the medical treatment of those dangerous blood-flow blockers.

Fujimoto said that there has been a huge increase in intravascular OCT procedures in the last three years. The development of tiny fiber-optic catheters and the Fourier-domain mode-locked (FDML) laser have helped make this possible.

Finally, Fujimoto drew the audience’s attention to one of this CLEO’s postdeadline papers, which reports a record imaging speed for OCT using a swept single-mode vertical-cavity surface-emitting laser (VCSEL). OCT promises to be an exciting technological field to watch in the near future.

Applied optics, Biomedical optics, CLEO/QELS, Fiber optics, Lasers, Lasers, CLEO CLEO, CLEO2011, lasers, laser, fiber optics, biomedical optics, Donald Keck, James Fujimoto, optics, photonics, Optics & Photonics News, Patricia Daukantas, OPN

By Patricia Daukantas

CLEO:2011, the annual laser conference organized by OSA and other scientific societies, got off to a strong start today with a full range of sessions on pure laser physics and applications of the technology. Here are a few highlights from Monday‘s sessions:

• Could lasers make your automobile burn gasoline more efficiently than spark plugs do? Researchers from Japan and Romania have developed all-ceramic micro-lasers that could zap the insides of car-engine cylinders with multiple sub-nanosecond pulses to ignite a lean mixture of fuel and air. The speaker for the group, Takumori Taira of Japan’s Institute for Molecular Science, declined to predict when laser-powered cars will hit the market. The team’s research has been getting a lot of press, including a mention by a New York Times blogger.
• Although General Electric Corp. may be more famous for manufacturing light bulbs, appliances and jet engines, the company has made several important contributions to laser technology. In his talk on laser materials processing, Marshall G. Jones of GE Global Research (Niskayuna, N.Y., U.S.A.) recalled that Robert N. Hall of GE invented the semiconductor injection laser--forerunner of the innards of all laser printers and CD players--and Joseph P. Chernoch devised the face-pumped laser in 1972. Today, GE is more concerned with laser drilling, welding and cladding techniques for manufacturing components of locomotives and turbines. Its scientists are developing fiber lasers that meld the high stability of Nd:YAG lasers with the high efficiency and sharp focusing ability of CO₂ lasers.
• It’s taking awhile, but eventually the European Space Agency will launch Aeolus, a wind-lidar satellite containing the first ultraviolet laser to fly in space. Dutch physicist Martin Endemann explained that the transmitter assembly for the 355-nm laser must last for 5 billion shots over 39 months in orbit without significant degradation or coating damage. His team found that the system needed to contain low levels (0.2 mbar) of oxygen in order to keep the UV optical components from darkening. The laser should be ready to be installed in the satellite next year, pending a successful extended vacuum-chamber test this fall.

Tonight is the first of two plenary CLEO plenary sessions, this one featuring Donald Keck and James Fujimoto, both highlighted in OPN for May 2011, along with their fellow plenary speakers Moti Segev and Susumu Noda.

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