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

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

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.

By Patricia Daukantas

2008 is shaping up to be a really long year – especially with the addition of a “leap second” to the last day of the year, as announced by the U.S. Naval Observatory (USNO) in Washington, D.C. But how do the world’s timekeepers know that our calendars, already tweaked by a leap day every four years, need such a small adjustment?

As it turns out, the Naval Observatory and its colleagues in the international scientific community increasingly rely on optical technology to distinguish between the time based on the rotation of the Earth and the time based on the atomic standard. (After all, the second is defined as exactly 9,192,631,770 times the period of a certain hyperfine transition of the cesium-133 atom.) The leap second will keep the two kinds of time synchronized.

USNO is responsible for monitoring the variations in Earth’s rotation. Its time scale is governed by a combination of 52 atomic clocks – 16 hydrogen masers and 36 cesium clocks. The observatory’s Time Service, a member of the International Earth Rotation and Reference Systems Service, has provided data on past leap seconds, ongoing variability of the Earth's rotation and other cool facts about time measurement.

The observatory has been working on cesium fountain clocks and rubidium fountain clocks and recently dedicated a new Master Clock Facility building for its present and future time technology.

Posted by Christina Folz, OPN Managing Editor 

The Nov. 11 Kojo Nnamdi show on NPR featured a fascinating interview with OSA member Tung H. Jeong, professor emeritus at Lake Forest College. Jeong discussed the technology of holograms as part of the show's "Tech Tuesday" segment. Jeong was asked about CNN's use of a so-called "holographic" technology when it beamed 3D images of its guests into the network's studio on election night. Jeong pointed out that those images were not actual holograms--and explained why. In fact, he said, "there is no relationship between the two except showing images." Jeong was later joined by physicist Hans Jurgen Kreuzer of Dalhousie University in Nova Scotia. The two described how the field of holography is advancing to include new applications in data storage, cellular manipulation, and holographic 3D TV. Regarding the latter: Because everyone would have to wear their own special glasses to see the holographic images, a key advantage is that "you don't have to fight for the remote," Jeong said.

By Patricia Daukantas

The clock is ticking down to the launch of the Large Hadron Collider (LHC), the massive international particle-physics experiment in Europe. The collider’s host, CERN, has its hands full with debunking rumors that the LHC is going to cause the end of the world.

Seems as if a small but vocal crowd believes that LHC will generate a tiny black hole that will keep sucking matter inward until it devours the entire planet Earth (mass: 6 × 10²⁴ kg). Court cases have been filed on both sides of the Atlantic Ocean to try to stop the LHC research; two Nobel laureates sided with the government to continue the experiments in one such lawsuit.

LHC defenders argue that there is no such physical theory that actually predicts the growth of microscopic black holes into macroscopic, planet-guzzling monsters. In a column called “Inside Science Research,” the American Institute of Physics (AIP) points out that if black holes really do evaporate as predicted by Cambridge University's Stephen Hawking, an attometer-sized black hole would survive for only a billionth of an attosecond – such a brief time period that there isn’t even a standard SI prefix to describe it.

In a more technical article written for scientists, Michael Peskin of the Stanford Linear Accelerator Center reviews a Physical Review D paper that found no evidence that black holes on the scale of 10¹² electron volts (TeV) could create damage over time scales shorter than the lifespan of Earth. Since our planet has already been around for 4.5 billion years and the Sun has enough nuclear fuel to last at least another 5 billion years, I’m not worried that the world as I know it will vanish while I’m sleeping tonight.

The “first beam” of the LHC – analogous to “first light” for a telescope – is set for early Wednesday at 3:30 a.m. EDT in the United States or 9:30 a.m. CET for most of Europe.

To celebrate the arrival of the LHC, the Boston Globe published a stunning Web photo essay showing off the various component instruments. And some young scientists at CERN assembled this “Large Hadron Rap” song that’s garnered more than 1.6 million YouTube downloads already.

By Patricia Daukantas

Most OSA members, I’m sure, are aware that negative-refractive-index metamaterials have been a hot topic of research for the past few years. Although scientists have found success making materials “invisible” to microwaves, several teams have been racing to extend these materials into the optical range – a development that would have much more interesting applications.

This week, two new papers from a California-based team hit the news wires. The researchers, based at the University of California at Berkeley and Lawrence Berkeley National Laboratory, made a prism out of optically negative-index metamaterial that closely resembles layers of tiny fishnets, according to the letter that appeared in Nature.

Xiang Zhang’s group made their metamaterial out of a stack of alternating layers of silver and magnesium fluoride; the size of the “fishnet” cells was on the order of a few hundred nanometers. The scientists tested the prism’s refractive index at near-infrared wavelengths from 1,200 to 1,800 nm and found that the index went to zero at around 1,475 nm.

In the brief Science paper, Zhang and colleagues reported on a different experiment that refracted red light via an aluminum-oxide array of nanometer-sized holes filled with silver. Negative refraction, however, happened only for transverse magnetic polarized light, not for transverse electric polarized light.

Journalistic interest, of course, is driven by the age-old human dream of invisibility, never mind the cloak and cloaking devices in the Harry Potter and “Star Trek” tales. Fortunately, some of the news coverage took pains to explain that practical devices made from negative-index metamaterials are still many years in the future.

By Patricia Daukantas

Several interesting news stories recently crossed my computer screen. One involves a useful optical illusion and another an LED landmark.

First comes an Associated Press story via CNN.com about a test of fake speed bumps that look real to oncoming motorists. The pseudo-bumps are really flat plastic with embedded glass beads to make them reflective at night, but they are colored to look like three-dimensional pyramids sitting in the middle of the road. The U.S. National Highway Traffic Safety Administration (NHTSA) is testing these and other “calming” devices to see if they really do slow down speeding cars. You can read about the “Heed the Speed” program on NHTSA's Web site (the details are in this section).

Second, a public television station in Boston, Mass., is having trouble with its giant outdoor LED screen. Last September, WGBH-TV installed a 30- by 50-foot (9.1- by 15.2-m) LED video screen on the outside of its headquarters, where it would be visible to passersby on a major highway. However, the Boston Globe reported that some of the LEDs go dark when the screen gets too warm. Repairs may take a couple of months.

Finally, several news services have reported that dozens of partygoers suffered partial vision loss from a laser light show gone awry near Moscow, Russia.