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

I can’t let my coverage of FiO/LS end without mentioning the wonderful talk that OSA Honorary Member Arthur Ashkin gave at the special symposium organized in his honor.

Ashkin, now 88 years old and retired from Alcatel-Lucent/Bell Laboratories (U.S.A.), pioneered the notion of moving microparticles with laser light, back in the days when lasers were the new thing on the lab bench. His work formed the basis for optical tweezers and, eventually, the atom-cooling and laser-trapping work that garnered three other OSA Honorary Members their Nobel Prize in 1997.

In his autobiographical speech, Ashkin--who still has traces of the accent of his native Brooklyn, N.Y.--showed his warm and sometimes mildly self-deprecating humor. Yes, he said, he holds degrees from “all these fancy schools” like Columbia and Cornell universities, but it took him seven years just to get his bachelor’s degree.

That wasn’t entirely of his own doing. As he entered Columbia, World War II was starting and the university, whose physics department had people like Sidney Millman, Willis Lamb and Polykarp Kusch, founded a radiation laboratory with, as Ashkin put it, “all this new equipment free from the government.” Millman taught the new undergraduate about magnetrons – “glass, brass and sealing wax” – and then Ashkin got drafted at age 19.

“I’m a sophomore, how important can I be to the war effort?” Ashkin asked rhetorically. But the folks at Columbia got him into the Army’s enlisted reserve, so that he could work as a staff member, and he eventually built a megawatt magnetron.

Once Ashkin got to Cornell as a graduate student, he said, he took no solid-state physics or optics courses. “All I took was nuclear physics because there were all these guys from Los Alamos [the Manhattan Project, which built the first nuclear weapons],” he said. He took the first quantum mechanics class taught by the then-future Nobel Prize winner Richard P. Feynman. Ashkin added: “The stories I could tell, if I had the time…”

Once hired at Bell Labs, he was told he could do anything he wanted to do, but he still ended up working on microwave tubes for a while. “At Bell Labs they wanted you to do great work, but you had to find your own way,” he said.

In the late 1960s, Ashkin attended a talk about “runners” and “bouncers,” or tiny balls moving around due to heating. That got him thinking about radiation pressure, and he started thinking about moving even tinier particles with the light from laser beams, and then experimenting in earnest.

By the time Ashkin was writing his first paper on the subject, he was wondering whether the laser beams could trap atoms, molecules and microscopic living things. “So I put all that into the paper and got credit for it,” he added. His first experiments with trying to move bacteria around killed them--he dubbed it “opticution”--but eventually he and his colleagues learned how to keep them alive while moving them with infrared beams.

You can read more about Ashkin’s pioneering efforts in a March 2010 feature article in OPN.

Like a good entertainer, Ashkin knows how to leave his audiences wanting more. He wound up his talk by saying that during his 15-year retirement, he has been experimenting with solar power, and he thinks he has found away of getting energy from the Sun more cheaply than burning fossil fuels.“I’m writing a paper for Science, and if I tell you about it they won’t publish it,” he concluded. “So stay tuned.”

The Newest OSA Honorary Member

At its meeting during FiO/LS, the OSA board of directors selected James P. Gordon as the Society’s newest Honorary Member. Regular readers of OPN may recall his article for the May 2010 issue of OPN--the special “Lasers at 50” issue--in which he described his work on the first maser with another OSA Honorary Member, Charles H. Townes.

2010-10 October, Applied optics, Biomedical optics, Frontiers in Optics, Optics history fio, optics history, optical manipulation, optical tweezers, optical history, lasers

By Patricia Daukantas

Halloween is the season of ghosts, goblins and vampires … so why not add some spooky quantum entanglements to the mix? On a cloudy, damp morning in Rochester (N.Y., U.S.A.), the plenary speakers at OSA’s 94th annual meeting, Frontiers in Optics, took the audience on a tour of Bell inequalities, wild biomolecules and other scientific treats.

This year’s Ives Medalist, OSA 2007 President Joe Eberly, used elementary trigonometric identities (remember those?) to demonstrate a seeming contradiction in a thought experiment about a polarizing interferometer. Eberly, a longtime professor at the University of Rochester, solved the conundrum by showing that the photons were entangled in what is now known as a Bell state.

Measuring degrees of photon entanglement is one of Eberly’s recent interests. He noted that Erwin Schrödinger introduced the notion of entanglement in 1935 -- and, 75 years later, scientists still don’t have a lot of quantitative answers about it. This is “a guarantee of permanent employment for a physicist,” he said, generating a ripple of chuckles among the audience.

One of the two winners of the American Physical Society’s Arthur M. Schawlow Prize, Henry Kapteyn of JILA (University of Colorado, U.S.A.), paid homage to the award’s namesake. “It was clear he liked to point lasers at things and blow them up, and that’s mostly what we do,” he said. Fortunately, most of the high-energy (and soft-X-ray) lasers he talked about haven’t exploded, and he predicted that there are excellent prospects for generating hard X-ray laser beams from tabletop devices in the near future. His wife and co-prize-winner, Margaret Murnane of JILA, will speak at tonight’s APS Laser Science banquet.

Plenary speaker Steven Block, a professor of physics and biology at Stanford University (U.S.A.), took the audience on a tour of “riboswitches,” non-coding messenger RNA strands that control gene expression by changing their structure when they selectively bind to a signal molecule. In evolutionary terms, this is probably the earliest form of molecular control at the cellular level, but it was poorly understood until scientists could start manipulating the molecules with optical tweezers. (Attendees of CLEO/QELS 2010 in May might remember Block’s blues mandolin performance.)

The final plenary speaker, Alain Aspect of the Institut d’Optique (France), gave a history lesson on the Hanbury Brown and Twiss interferometry experiment of the mid-1950s and its relevance to modern-day quantum optics.

Checking the Efficacy of Breast-Cancer Therapy

Can oncologists deduce the efficacy of breast-cancer treatment as early as one day after the start of chemotherapy? According to Albert Cerussi of the Beckman Laser Institute (U.S.A.), this can happen, thanks to a technique called diffuse optical spectroscopic imaging (DOSI).

Traditional “adjuvant therapy” for breast cancer calls for surgery first, followed by a round of chemotherapy. Oncologists are now moving to “neo-adjuvant therapy,” in which the chemo comes first -- making it even more important to monitor the patient’s response to the powerful drugs.

DOSI works in the near-infrared window of 650 to 1,000 nm; those wavelengths penetrate tissue relatively well, although the photons take a “random walk” through the tissue (hence the “diffuse” part of the imaging). Instead of getting the black-and-white patterns of a traditional mammogram, DOSI provides spectral information about tumor biomarkers such as oxygenated and deoxygenated hemoglobin.

Researchers first studied DOSI at the midpoint of chemotherapy, when oncologists usually assess the patient and decide whether to switch therapies. But the researchers from Beckman and the Chao Family Comprehensive Cancer Center (both part of the University of California at Irvine) found that they could detect changes in the biomarkers one week and even one day after the start of chemotherapy.

According to Cerussi, scientists are even studying whether the technique could predict whether chemo will help a particular patient even before the treatment starts, but they are still trying to understand the biological process behind that. In the near future, researchers will look for additional biomarkers, shrink the size of the equipment, and join a clinical trial involving four other cancer centers.

(Note to readers of OPN’s Twitter feed, @OPNmagazine: Cerussi’s talk was the one I chose out of eight simultaneous invited talks at the start of the afternoon sessions. It was a tough call -- the other topics included luminescent solar concentrators, laser refractive surgery for cataracts and long-term monitoring of buried fiber-optic cables.)

Industrial Physics Forum

This event, sponsored by the Corporate Associates of both OSA and the American Institute of Physics, drew large crowds to several talks -- particularly the one by quantum cascade laser pioneer Federico Capasso of Harvard University. On Monday, the forum covered a range of biomedical and environmental applications of lasers.

An Earth-observing lidar satellite called CALIPSO (for “Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations”) has been in orbit since April 2006, and Carl Weimer (Ball Aerospace, U.S.A.) reviewed its ongoing engineering and science results.

As I described in an OPN article last year, CALIPSO is part of an “A-Train” of environmental satellites in the same orbit, with roughly 15 minutes of spacing between them. Its dual-wavelength (532 and 1,064 nm) lasers collect data in a 70-m-wide “curtain” from ground level to about 40 km altitude.

So far, the satellite has collected 6.6 terabytes of data from 2.6 billion laser shots, Weimer said. Its estimated particle sizes within cloud distributions provide important input for scientists’ models of global atmospheric circulation.

The Industrial Physics Forum is concluding this morning with sessions on lasers’ applications in metrology and other “frontiers of physics” areas.

The Day Ahead: Tuesday

This afternoon, brand-new OSA Honorary Member Arthur Ashkin will speak first at a symposium honoring his pioneering work with optical tweezers. The FiO/LS exhibit hall will open, and OSA student chapters will kick off their lesson plan competition. Two other events of particular interest to young professionals are a public-policy forum and the Minorities and Women in OSA (MWOSA) tea. Finally, we’ll all learn who won the OSA officer elections for 2011.

2010-10 October, Applied optics, Biomedical optics, FiO/LS, Lasers OSA, university of rochester, fio, biomedical optics, industrial applications, Patricia Daukantas, the Optical Society, quantum entanglement, CALIPSO, LaserFest

By Patricia Daukantas

Whoops – yesterday I forgot to note that a second OSA member is among the 23 winners of the annual “genius grant” from the John D. and Catherine T. MacArthur Foundation.

OSA member Nergis Mavalvala, a physics professor at the Massachusetts Institute of Technology (U.S.A.), has done significant research at the intersection of optics, quantum physics and gravity. MacArthur Fellows receive $500,000 over five years with no strings attached.

When Mavalvala, now 42, was still a graduate student, she developed a prototype laser interferometer for detecting gravity waves. The principles of that instrument were later incorporated into the Laser Interferometer Gravitational-Wave Observatory (LIGO).

The MacArthur Foundation has put a brief biography and video of Mavalvala online. OPN published more information on LIGO in the May 2008 issue and the July 1995 issue.

2010-09 September, Applied optics, Astrophysics, Lasers interferometry, astrophysics, awards, women, ligo

By Patricia Daukantas

A Cornell University (U.S.A.) scientist specializing in on-chip nanophotonics devices has won a $500,000 “genius grant” fellowship from the John D. and Catherine T. MacArthur Foundation.

OSA Fellow Michal Lipson, associate professor of electrical and computer engineering at Cornell, is one of 23 award recipients in diverse fields ranging from astrophysics to sculpture, theater and jazz. MacArthur Fellows receive $500,000 over five years with no strings attached.

The 40-year-old Lipson received the award for “working at the intersection of fundamental photonics and nanofabrication engineering to design silicon-based photonic circuits that are paving the way for practical optical computing devices,” according to the foundation’s website. She was named an OSA Fellow in 2008 for “outstanding contributions to the field of silicon nanophotonics, including the development of high-bandwidth modulators and low-power nonlinear optical devices.”

The MacArthur Foundation has put a brief biography and video of Lipson online. I wrote about her work in the November 2006 Scatterings column (four-wave mixing within a broadband light amplifier) and also in January 2008 (a microfluidic device that used light to sort tiny particles).

2010-09 September, Applied optics, Biomedical optics, OFC/NFOEC nanotechnology, awards, OSA Fellows, women, photonics, silicon photonics

By Christina Folz, OPN Managing Editor

On August 6, the Air Force Office of Scientific Research (AFOSR) continued the 2010 LaserFest celebration with its own event highlighting everyone's favorite technology this year. The event showcased the work of three OSA Fellows--Alan Willner, who works on optical communications at the University of Southern California; Margaret Murnane, who is studying high-peak-power physics with lasers at the University of Colorado, and Richard Miles, a Princeton professor who spoke about the role of lasers in aerospace. Two other laser experts--Robert Jones and Gary Teraney--described the important role that lasers are playing in the defense industry and in medicine. Each of the participants had been funded by AFOSR as grad students and went on to become distinguished leaders in the laser field.

For those who missed the event, or who simply sought more info, yesterday the AFOSR held a "bloggers roundtable" moderated by Howard Schlossberg, the program manager at AFOSR, to discuss the event and answer additional questions about the state-of-the art in laser technology. Schlossberg was joined by several of the event participants, including Willner and Miles.

And for those who missed THAT (including this humble blogger), you're in luck: A podcast and transcript of the roundtable are posted on the Department of Defense's blog. 

Schlossberg emphasized the importance of solid-state lasers in particular as pivotal to modern laser research and technology. "The primary emphasis by us and by others as well is in solid-state lasers, either on bulk solids, slabs pumped with semi-conducted lasers, or in optical fiber lasers," he said. He also called medical and materials processing two of the biggest application areas of lasers these days.

And don't worry--LaserFest is far from over. "At meetings, they'll have demonstrations and displays," Schlossberg said. "If you get on the LaserFest website, you'll see some of the terrific movies of early times." 

Party on!  

2010-08 August, Applied optics, Laserfest, Lasers, Optics history Laserfest, lasers, defense, AFOSR, technology, OSA, OSA Fellows, optics, optics history

By Patricia Daukantas

The Deepwater Horizon oil spill, which has been raging since April 20 in the Gulf of Mexico, has the potential to pollute the region’s air as well as the water. Various optical technologies are tracking air quality in the region.

For example, one miniature fiber-optic spectrometer has been set up in southern Mississippi near the Gulf coast to measure levels of benzene, toluene, sulfur dioxide and other substances. Real-time data is being posted online at http://fenceline.org/test/map.php. According to this report, Argos Scientific custom-configured the monitoring station using the spectrometer from Ocean Optics. A second Argos system is going to the University of North Alabama for future studies of Gulf-area samples.

For a more complete picture of air quality around the Gulf Coast, see the U.S. Environmental Protection Agency’s page at http://www.epa.gov/bpspill/air.html, which provides some actual data files. You can also get real-time ozone and particulate-matter information from http://www.airnow.gov and http://gulfcoast.airnowtech.org. None of these sites, however, really get into details about the sensors and/or spectrometers that collected these data.

So far, the air out there doesn’t look too bad. Let’s hope it doesn’t get any worse.

2010-06 June, Applied optics, Miscellaneous Optics spectroscopy, disasters, atmospheric optics, energy

By Patricia Daukantas

As a high-school graduation gift, I got my first “real” camera – a 35-mm single-lens reflex, rather than a fixed-focus Instamatic for snapshots – and began to learn the artistic joys and challenges of manipulating the depth of field. What, in a scene, did I want to focus on? Sometimes I wanted to keep both foreground and background objects sharp and clear, but I couldn’t, especially when the ambient light level forced me to use a large aperture.

Now, researchers based at the University of Toronto (Canada) say that they’ve developed a new type of video camera that will keep high-resolution near- and far-field images in focus simultaneously.

This “Omni-focus Video Camera” is actually an array of color video cameras that are each focused at a different distance. The images from each of these video cameras are fed into a component invented by OSA Fellow – and frequent OPN contributor – Keigo Iizuka. This component, the “Divcam” (for Divergence-ratio Axi-vision Camera), performs real-time mapping of the distances between the pixels and the objects in the scene. Software developed by another Canadian scientist, David Wilkes, selects individual pixels from all the available camera outputs on the basis of the distance information and puts together a single image that is “omni-focused.”

The researchers say that the camera could have many different applications that could use greater depth of field, ranging from TV studio cameras to laparoscopic medical procedures.

The new camera isn’t commercially available yet, but the university recently announced it to the media. According to Iizuka, who is the principal investigator of the project as well as a Toronto engineering professor, the team last week submitted a comprehensive article about the camera to a scientific journal.

In the meantime, here are a couple of illustrations of the technology (photo credits: University of Toronto).

Above: Comparison between the Omni-focus Video Camera (a) and a conventional video camera (b). Note that the fingerprints are recognizable in (a).

Above: The eye of one sewing needle is captured through the eye of a second needle – 1.17 m in front of it.

2010-05 May, Applied optics, Imaging, Photography imaging, video, video camera, applied optics, photography, camera, lenses, divcam, image mapping

By Patricia Daukantas

What do lasers have to do with Robin Hood and the Sheriff of Nottingham? They turn out to have a rather “deep” connection, if you’ll pardon the pun.

The University of Nottingham – yes, that Nottingham – has begun to survey the hundreds of sandstone caves under the English city with laser-scanning equipment. One of those caves is believed to be the dungeon in which the Sheriff of Nottingham imprisoned Robin Hood (if, of course, you believe that the do-gooding outlaw actually existed in medieval times).

The British Geological Survey mapped the caves in the 1980s, but Nottingham officials would like to use the laser-scanning data to create virtual representations of the caves to increase their tourist potential. In other words, visitors would be able to explore the caves without experiencing the associated “health and safety issues,” as the BBC report put it.

The Nottingham Caves Survey has its own website at which it explains the laser scanning procedure.

We’re all about to be inundated with everything “Robin Hood,” as the Ridley Scott movie by that name is readied for a debut next week. In this month of the laser’s 50^th anniversary, it’s interesting to contemplate the intersection of modern optical history with the legends of yore.

2010-05 May, Applied optics, Miscellaneous Optics, Optics and pop culture lasers, laser scanning, nottingham, robin hood, mapping, optical history