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It's a golden year for lasers

Berkeley Lab
Wim Leemans of Berkeley Lab's Accelerator and Fusion Research Division works on
a 40-terawatt laser that could blaze a trail for a new breed of particle accelerator.

Fifty years after the first laser was demonstrated, engineers are celebrating the golden anniversary, marveling over how a once-feared "death ray" now touches almost every aspect of our lives, and setting the stage for future breakthroughs.

The push to invent the laser (which is actually an acronym for "light amplification by stimulated emission of radiation") actually started out in the 1950s as a quest to build a better radar system. First, scientists came up with gadgets to amplify microwave beams, known as masers, and then the technology was extended to light wavelengths.

Although there's been a historical debate over who is most properly credited as the inventor of the laser, the clearest milestone came on May 16, 1960, when Hughes Research Laboratories' Theodore Maiman demonstrated a solid-state device that used a flashlamp coiled around a ruby crystal to produce coherent pulses of red light.

It didn't take long for the laser to take its place in pop culture as a powerful beam weapon - perhaps most famously in the classic 1964 movie "Goldfinger," where James Bond nearly gets burned in his boxers. In real life, however, laser power is used more often to mend rather than rend - for example, by repairing torn retinas, tweaking out-of-shape corneas or eliminating cancerous tumors.

The reason the laser plays such a powerful role in technology isn't just because of its power. Most laser-based technologies play off the fact that the photons in the light beams move in lock step and keep their focus. That makes lasers ideal for sending precisely modulated messages over long distances - to the moon and back, for instance - or for reliably reading off the messages contained in DVDs, bar codes or biological cells.

"Almost all real-time information now, more or less, is encoded using the laser," said Thomas Baer, executive director of the Stanford Photonics Research Center. Even wireless communication networks are knit together on the ground using fiber-optic networks, which rely on lasers to encode and boost data transmissions as they streak across the world.

Baer said the devices and services that rely on lasers - ranging from optical fiber to grocery scanners to cheap laser pointers - are thought to play a role in more than $3 trillion worth of commerce yearly.

The laser's glorious past is being marked this year with LaserFest, a yearlong array of activities organized by the Optical Society, the American Physical Society, SPIE and the IEEE Photonics Society. But we're not just talking about history here.

"Even 50 years after the invention of the laser, new applications are being patented at a phenomenal rate," Baer said. Patent data searches show that the term "laser" ranks as the third most popular keyword, right behind "engine" and "computer."

As part of the LaserFest celebration, Baer and other laser researchers outlined some of the innovations ahead over the weekend in San Diego at the annual meeting of the American Association for the Advancement of Science:

Lasers and energy:

The biggest spotlight for laser power falls on the National Ignition Facility at Lawrence Livermore Lab in California, where researchers are working toward producing the world's first controlled nuclear fusion burn. The plan calls for zapping a small pellet of hydrogen isotopes with 192 precisely focused laser beams, as I explained last month. During his AAAS talk, NIF principal associate director Edward Moses emphasized that although the campaign to produce a break-even reaction is due to begin this year, actually attaining that goal might take a year or two.

Turning laser fusion into a commercially viable operation is an even greater challenge: Moses showed an animation in which fusion-fuel targets are shot into the ignition chamber 10 times a second, with each blast yielding 10 times as much energy as NIF is expected to produce (that is, 200 megajoules vs. 20). Although the task looks daunting, Moses expressed confidence that a demonstration power plant could be built in 10 to 15 years.

"If there's a will, the way is 15 to 20 years to be on line with power," Moses told journalists.

In the shorter term, there may be a laser in your car engine sometime soon: Engineers have been developing a fuel-ignition system that relies on laser light instead of spark plugs.

Lasers and medicine:
Baer said researchers are developing techniques that use lasers to shed light on cellular activity. One approach relies on shaped laser pulses to penetrate into moles deep enough to see the potential signs of skin cancer. Laser holography can also be applied to the search for cancer deep within tissue.

Yet another laser technique can detect the early signs of Alzheimer's disease: Drops of a special fluorescent dye are placed into the eye, and then the eye is illuminated with a pulse of blue laser light. If the dye lights up, that indicates the presence of beta amyloid, a protein linked to Alzheimer's that shows up in the eye years before other symptoms of the disease emerge.

Lasers and computers:
If computer manufacturers can make the switch from electronics to laser-based photonics, that would dramatically reduce the cost and power requirements for mobile phones, computers and other gadgets.

"A new optical USB protocol has just been demonstrated, which means that in just a year or two, we will have 10-gigabit-per-second bidirectional optical connections on our laptops, allowing much faster communications to displays, memory and the Internet," John Bowers, director of the Institute for Energy Efficiency at the University of California at Santa Barbara, said in a LaserFest roundup.

Lasers are also blazing a trail in heat-assisted magnetic recording, a technology that could increase the storage capacity of disk drives by a factor of 20 or more.

Lasers and materials science:
Scientists have come up with a new type of laser apparatus to check the composition of a material by blasting off just a microscopic piece of it and analyzing the plume that's given off. Laser-induced breakdown spectroscopy, or LIBS, could be used to look for E. coli bacteria in spinach, to determine whether a powder contains ordinary mold or anthrax spores, to help art experts authenticate or restore a painting, or to see what substances are contained in a dinosaur fossil.

Meanwhile, Livermore Lab is developing a laser light source that produces mono-energetic gamma rays, or MEGa-rays for short. Livermore Lab's Christopher Barty says such rays could spot the signature of nuclear material even if it's hidden behind 3 feet (1 meter) of steel - which would be ideal for detecting smuggled uranium, or analyzing the composition of nuclear fuel as well as nuclear waste.

Lasers and the subatomic world:
Berkeley Lab's Wim Leemans is leading a team of researchers who are trying to develop a new type of accelerator that pumps up subatomic particles with laser light rather than microwaves. He compares laser plasma wakefield acceleration to the effect that a motorboat's wake has on a lake. If the laser energy is tuned just right, electrons riding the laser waves can be accelerated to higher energies over a very short distance. Small-scale, laser-based accelerators may not rival the Large Hadron Collider anytime soon, but they may open the door to new applications in medical imaging and radiation therapy.

Lasers and weapons:
Although it didn't come up at the AAAS meeting, the concept of using the laser as a military weapon had its latest tryout this month, when the U.S. Air Force knocked down a test missile with an airborne laser. At the time, the military called the test a success, but since then there have been indications that the current technology is just not ready for prime time. New Scientist reports that the Air Force is going "back to the drawing board" with next-generation alkali lasers. Hmm, I wonder what that portends for Dr. Evil's plans for laser world domination....

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