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!  

By Patricia Daukantas

For the past decade, astronomers have used laser guide star (LGS) adaptive-optics systems to remove the blurring caused by atmospheric turbulence above ground-based telescopes. Such systems, however, have always faced one restriction: an extremely narrow field of sharp viewing.

A team from the University of Arizona (Tucson, U.S.A.) has managed to widen that sharp field by developing a five-laser guiding system for the MMT telescope on Mount Hopkins in southern Arizona. The astronomers report on their system in the August 5 issue of Nature.

Michael Hart, of the university’s Steward Observatory, and colleagues wanted to study aging star clusters at near-infrared wavelengths (1.25 to 2.2 μm). One such cluster, dubbed M3, nearly fills the 110-arcsecond-wide field of the MMT’s infrared camera.

The researchers arranged five 4-W, 532-nm pulsed lasers in a pentagon and projected them from a small telescope behind the MMT’s adaptive secondary mirror. A combination of three sensors detects the aberrations in the Rayleigh-backscattered light coming back to the telescope, estimates the aberration from ground-level turbulence and directs the secondary mirror to correct the aberrations.

On a night when the native “seeing,” or point-spread-function diameter of stellar images, at the MMT was only 0.7 arcseconds, the astronomers improved it to 0.3 arcseconds over a 2-arcminute-wide field of view – roughly the same as the Hubble Space Telescope gets with its most recent upgrades, but with a bigger aperture to gather more light.

Astronomers are now developing a similar system for the Large Binocular Telescope on Arizona’s Mount Graham.

By Patricia Daukantas

Last week, Charles H. Townes passed yet another milestone: he turned 95 years old.

Townes, now of the University of California at Berkeley (U.S.A.), is of course most famous in the optics community for his fundamental contributions to laser theory:

• The development of the first maser with James Gordon and Herbert Zeiger in 1953, as Gordon recounted in a recent OPN feature article; and
• The principles behind the optical maser, or laser, published by Townes and his brother-in-law, Arthur Schawlow, in December 1958.

Along the way, he’s worked at Bell Labs and three prominent universities, served on various U.S. government committees and think tanks, held a Guggenheim Fellowship and a Fulbright Scholarship, and won the Templeton Prize for contributing to the understanding of religion.

As we’ve noted in past OPN blog posts, Townes is still active in astrophysical research. So far in 2010, he and his colleagues have published two articles relating to Berkeley’s Infrared Spatial Interferometer, a three-telescope system with high spectral resolution. This year, which is the 50^th anniversary of the first working laser, he’s been invited to speak at many scientific conferences, including a special historical symposium at CLEO/QELS 2010.

We should also note that 2010 marks two other milestones for Townes. It was 40 years ago, in 1970, that Townes was named an OSA Honorary Member. And it was 50 years ago that Townes, along with 14 other physicists, chemists, engineers and physicians, was named a representative of “U.S. Scientists” for Time magazine’s 1960 “Men of the Year” (now "Person of the Year") issue. Townes and bubble-chamber inventor Donald A. Glaser are the two surviving members of that august ensemble.

Townes and his wife of 69 years, Frances, have four daughters. We wish him a Happy Belated Birthday and much joy with his family.

By Patricia Daukantas

Thanks to a NASA environmental-studies satellite that uses lidar technology, scientists have produced a first-of-its-kind map of tree-canopy heights around the world. The study will help climate researchers gain new insights into the rate of carbon recycling through global forests.

According to a paper coming out in Geophysical Research Letters, Michael Lefsky of Colorado State University (U.S.A.) used lidar data taken by ICESat, part of NASA’s Earth Observing System mission, to measure the height of forest trees. The ICESat instrument known as the Geoscience Laser Altimeter System, or GLAS, measured the time-of-arrival distance between laser pulses reflected off the ground and those reflected off treetops.

Unfortunately, due to problems with its lasers, GLAS was able to perform direct sensing of only 2.4 percent of Earth’s total forest cover. Lefsky thus combined the lidar data with additional data from the imaging spectrometers aboard two other NASA satellites, Terra and Aqua.

I wrote about ICESat in my “Lidar in Space” article in the June 2009 issue of OPN. In February 2010, NASA ended ICESat’s science mission after the third and final GLAS laser failed. Last week, the U.S. space agency fired ICESat’s thrusters one more time to lower its orbit, and sometime in the next couple of months, the satellite will re-enter the atmosphere, where most of it is expected to burn up before it could reach the ground.

A second-generation laser altimeter mission, ICESat 2, is still in the early phases of development, with a launch tentatively scheduled for late 2015.

By Patricia Daukantas

A smorgasbord of recent developments in U.S. energy policy, astrophysics and the deep sea:

• The barren desert that once hosted hundreds of nuclear fission explosions will become a testing ground for collecting energy from that ultimate source of fusion power, the Sun. The U.S. Department of Energy has announced it is creating a solar energy demonstration zone at the Nevada Test Site. U.S. Energy Secretary (and OSA Honorary Member) Steven Chu recently signed an agreement with his counterpart at the Interior Department, which owns the land. The 25 square miles of desert, which is away from the regions of the test site that actually saw nuclear explosions, will host demonstrations of concentrated solar power (CSP) technologies.

• The Hubble Space Telescope’s master repairman has gotten himself a second ground-based gig. John Grunsfeld, who has made three space trips to fix and upgrade the 20-year-old orbiting instrument, will be a research professor of physics and astronomy at Johns Hopkins University in Baltimore, Md., U.S.A. Grunsfeld, an astrophysicist by training, now serves as deputy director of the nearby Space Telescope Science Institute.

• Finally, I stumbled upon this nifty Q&A with Emory Kristof, the National Geographic contributing photographer-in-residence whose photographs appeared in the cover story of OPN’s October 2005 issue. You can also check out his photo gallery, “Discovering the Titanic,” and some of his images are included in “Milestones in Underwater Photography” as well.

By Patricia Daukantas

Since we’re just past the summer solstice in the Northern Hemisphere, it seems appropriate that solar-powered vehicles are sailing through the news.

First of all, the University of Michigan’s solar car team, based in Ann Arbor (U.S.A.), won last week’s American Solar Challenge road race through heartland America, from Tulsa, Okla., to Naperville, Ill.

Michigan was one of 17 competing teams, mostly from the United States, but also representing Canada, Germany and Taiwan. The University of Minnesota (U.S.A.) finished in second place and the Hochschule Bochum – Bochum University of Applied Sciences (Germany) came in a strong third, less than 10 minutes behind Minnesota.

Although the winner’s elapsed racing time was just under 28 hours and 15 minutes, the race took a full week to complete, because of the mandatory checkpoints and overnight stops along the winding route.

Check out the photos of the Michigan car and its rivals in the links above – from the front, the Michigan vehicle looks to me like one of the UFOs from sci-fi movies of the 1950s, and from the side, it looks a bit like a small boat on wheels. Plus, the tiny compartment for the driver ensures that the car will never become the family sedan of the future. Still, one can’t argue with success.

Another solar-vehicle race – this one for high school students – will take place July 18-25 on steeper American terrain (Fort Worth, Texas, to Boulder, Colo.). Twenty-two teams have applied to take part in the Hunt-Winston School Solar Car Challenge. Yes, the drivers of the cars actually do have to have their driver’s licenses. But it’s still amazing what these teenagers can do.

Finally, the Japan Aerospace Exploration Agency, or JAXA, has deployed a solar sail in outer space. Its unpiloted satellite, IKAROS, was launched six weeks ago and had to “stretch its wings” once it got several million kilometers away from Earth. JAXA will monitor the output of the thin-film solar cells and learn how to maneuver with the combined force of radiation pressure on the sails and the energy generated from the photovoltaic sail. The agency explains how the sail was deployed and has a website with other details of the mission.

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.

By Patricia Daukantas

Instead of a long blog post, I’m going to post links to several optics-related news items that caught my eye this week.

• A German photonics scientist, Michael Grätzel, has won the Millennium Prize of the Technology Academy Finland for his role in developing dye-sensitized solar cells that mimic photosynthesis. Grätzel heads the Laboratory of Photonics and Interfaces at the Ecole Polytechnique Fédérale de Lausanne, Switzerland. A Web graphic illustrates the principle behind these so-called Grätzel cells, which have been recently commercialized.

• NIST Tech Beat, a website of the U.S. National Institute of Standards and Technology, writes about a recent Optics Express article describing a “dark-pulse” laser. It’s a semiconductor infrared laser that makes dips in light intensity, instead of bursts of light. The scientists at NIST and JILA in Boulder, Colo. (U.S.A.) say that the technology may be useful in signal processing and optical networking.

• A multinational team has used pump-probe spectroscopy to measure electron localization in H₂ and D₂ molecules on the attosecond scale. Of course, this work would not be possible without the development of attosecond lasers. G. Sansone et al. report on this work in the June 10 issue of Nature.

• Finally, Light Reading reports on the impact World Cup fever is going to have on worldwide network traffic. And you thought you were the only one waiting for that “buffering” message to go away so that you can watch your favorite team online….

By Patricia Daukantas

Two telescope-building astronomers who have won OSA awards for optical engineering are among this year’s winners of the Kavli Prize for Astrophysics.

The Kavli Prizes, worth $1 million each, are bestowed every two years in the fields of astrophysics, neuroscience and nanoscience – areas that didn’t really exist when the Nobel Prizes were founded.

Jerry Nelson, J. Roger P. Angel and Raymond N. Wilson shared the astrophysics prize for their contributions to the technology behind some of the world’s largest telescopes.

Nelson, of the Center for Adaptive Optics at the University of California at Santa Cruz (U.S.A.), served as project scientist for the twin 10-m-aperture Keck Telescopes on Hawaii’s Mauna Kea. These telescopes use his design of lightweight hexagonal mirror segments with active controls to keep the optics perfectly aligned. His pioneering design is being used in other large telescopes now under construction. An OSA member, Nelson received the 1996 Joseph Fraunhofer Award/Robert M. Burley Prize from OSA for his contributions to optical engineering.

Angel, director of the Steward Observatory Mirror Lab at the University of Arizona, took a different approach to the design of large, lightweight telescope mirrors: casting them as a single unit in a giant spinning furnace that cools slowly. The resulting mirrors have a near-parabolic top surface and a honeycomb structure underneath. He received OSA’s Fraunhofer Award/Burley Prize in 2007 for his body of work, which includes fiber-fed spectroscopy and solar photovoltaic technology.

The third winner of the astrophysics Kavli Prize, Raymond N. Wilson, formerly of the European Southern Observatory in Germany and Imperial College London in England, developed the computer-controlled actuation system for active optics, which is used in many of the world’s largest observatories.

Five scientists from U.S. universities and industrial research centers shared the Kavli Prizes in nanoscience and neuroscience. The Norwegian Academy of Science and Letters made the prize announcement this morning. Funding for the prizes comes from comes from the Kavli Foundation.

By Patricia Daukantas

To wind up OPN’s coverage of CLEO/QELS 2010, I would like to spotlight some of the interesting things that I didn’t get a chance to write about during the conference.

Weather Guy to Lidar Specialists: Please Help

A meteorologist at California State University at Chico (U.S.A.) presented a list of opportunities for lidar researchers to help improve his group’s technology for studying atmospheric aerosols.

Shane D. Mayor uses a direct-detection infrared lidar instrument dubbed REAL (for Raman-shifted Eye-safe Aerosol Lidar) to study how particulate matter moves with air currents. He has participated in several simulations of bacterial agent plumes – this knowledge could be important in the case of a biological weapons attack.

REAL operates at 1,543 nm, which Mayor said is in the “sweet spot” between shorter-wavelength retinal hazards and insufficient detector performance above 2 µm. The 1.5-µm zone also offers such desirable qualities as low molecular scattering, low background radiation from the sky, and compatibility with telecom components. Mayor and a colleague designed a Raman shifter for converting the REAL Nd:YAG laser output from 1,064 nm to 1,543 nm (Appl. Opt. 46, 2990).

Unfortunately, the flashlamps on REAL’s pump laser need replacement every 20 million shots or 23 days – at $200 each, that amounts to $6,350 per year, Mayor noted. Also, the CSU-Chico lidar setup requires a tractor-trailer for transportation, but Mayor’s goal is to shrink that down to fit in a more mobile van.

Mayor listed a number of ways that optical scientists could help improve REAL. They include:

• Reduce or eliminate flashlamp replacement.
• Increase efficiency by reducing power consumption and waste heat.
• Further reduce the mass of the beam steering unit mirrors, which are now 14 kg each.
• Develop a high-precision pulse energy monitor that can measure shots to ± 1 percent.
• Figure out how to monitor beam divergence continuously on the fly.

What Makes Counterfeit Money Funny?

Can measuring the intrinsic fluorescence lifetime of U.S. paper money distinguish between phony bills and the real thing? Researchers from Yale University (U.S.A.) believe that this technique could be used for forensic identification of counterfeit money.

The key, according to biomedical engineers Michael J. Levene and Thomas Chia, is that the paper for all U.S. currency comes from a single source. Although the exact “recipe” for that paper is secret, it has a very consistent fluorescence lifetime “signature” that differs from that of other types of papers made from wood, cotton and linen pulp. U.S. currency ink is essentially non-fluorescent, although the serial numbers on bills scatter light. (Inks on some non-U.S. currency, like the Mexican 100-peso note, do fluoresce, so that could be important in detecting foreign fakes.)

The researchers used a custom-built two-photon microscope, with an excitation wavelength of 735 nm, to study U.S. currency – mostly $100 banknotes, since they are the highest-valued bills targeted by counterfeiters. (They also tested some lower denominations as a control group.) They also tested three kinds of counterfeit bills provided to them by investigators: digital scans onto printer paper, counterfeit bills printed on cotton-linen-blend paper, and so-called “bleached” low-denomination bills that were illicitly reprinted with a higher denomination.

Levene and Chia didn’t know the exact provenance of the counterfeit money. “They [investigators] don’t like us to hold onto the bills for more than a few hours and won’t tell us much about where they came from, and we’re not going to make our own,” Levene said.

All the genuine currency notes had consistent short- and long-lifetime components to their fluorescence. The printer-paper fakes had only the longer-lifetime component. Other counterfeit bills had noticeably shorter long-lifetime components.

The testing group included bills dating back to the 1970s, and because the United States has been using the same paper supplier for so many decades, the two-component intrinsic fluorescence lifetime signature is “remarkably consistent” over the years, Levene said.

Small and Big Lasers

Qi Qin of the Massachusetts Institute of Technology (U.S.A.) and colleagues at two other labs built a tunable terahertz “wire laser” whose cavity is much narrower than its operating wavelength. The researchers tuned the laser by moving either a metal or dielectric “plunger” outside the laser cavity. (The gold plunger shifted the wavelength shorter and the silicon plunger made the operating wavelength longer.)

The group’s first design, as reported in the original CLEO proceedings, achieved 137 GHz of tuning centered on 3.8 THz. To get rid of the static friction that made the plunger stick and jump, they designed a MEMS-type plunger made up of layers of gold, silicon and silicon dioxide. The revised laser, only 10.5 µm wide, registered a total shift of 330 GHz between 3.85 and 4.2 THz, or about 8.5 percent. Such lasers could be used to detect explosives, which have spectroscopic “fingerprints” in the terahertz range, according to Qin.

On the opposite end of the laser size spectrum, Textron Defense Systems (U.S.A.) is building a 100-kW laser as part of the Pentagon’s Joint High Power Solid State Laser Program. Invited speaker Alex Mandl traced the history of Textron’s efforts from its initial “membership in the kilowatt club” (1.2 kW achieved in February 2004) to its laser’s performance of more than 100 kW in final government tests (exactly how much more, he couldn’t divulge).

Textron calls its technology ThinZag because the beam path inside the laser zigzags through a comparatively thin slab of ceramic (not crystalline) Nd:YAG material. The final laser configuration consists of six ThinZag 15-kW-class lasers in series (yes, 15 × 6 = 90, but again, there may have been other technological tweaks to get it over the 100-kW mark).

Social Media and Postdeadline Papers

I would like to tip my hat to the four CLEO/QELS bloggers – Jim van Howe, Ksenia Dolgaleva, Xiaoyu Miao and David Nugent – who have been contributing to the conference’s social media hub. If you haven’t done so already, please check out their coverage of CLEO/QELS.

Van Howe, a professor at Augustana College in Rock Island, Ill. (U.S.A.), blogged about a couple of postdeadline papers I missed because the room was full and the entryway was clogged. (The paper numbers, though, were QPDA5 and QPDA6.) Since those papers seemed to generate a lot of buzz, I’ll summarize them here.

The group that presented QPDA5, from Yale University (U.S.A.), said that an arbitrary body can be made perfectly absorbing at discrete frequencies, thanks to the interaction of optical absorption and wave interference. “It is thus the time-reversed process of lasing at threshold,” A. Douglas Stone and colleagues wrote.

In QPDA6, Evgenii Narimanov of Purdue University and two colleagues from Norfolk State University (all U.S.A.) found a new approach to the “blacker than black” phenomenon of radiation absorption: something called hyperbolic metamaterials. Hyperbolic dispersion means that a metamaterial has negative electric permittivity in the direction perpendicular to its surface and positive electric permittivity parallel to its surface. The researchers tested their ideas by building an experimental array of silver nanowires.

In the postdeadline session where I did find a space to put myself, Aleksandr Biberman of Columbia University (U.S.A.) described his group’s demonstration of a 40-Gbps electro-optic switch for photonic networks-on-chip (paper CPDA11). Such CMOS-compatible switches will be needed as more photonic networks are built inside the computer as well as between computers. Biberman worked with researchers from both Columbia and Cornell University (U.S.A.).