Killer lasers: on the cutting edge
It can be hard for science to live up to the imaginations of science-fiction writers. There aren't many people zipping around on jet packs, and there's no human outpost on Mars. At least, not yet.
Lasers are a different story. First demonstrated 50 years ago, they are involved in building every car and airplane, in delivering every telephone call and email. They sequence DNA, and they fix people's eyesight. They help audiences follow tedious PowerPoint presentations, and they make heavy metal rock shows wicked awesome.
True, they don't shoot enemies out of the sky, but that, at long last, is coming — along with dozens of new applications for lasers as researchers develop new materials and techniques to generate different types of beams that can be more powerful and precise.
Last year, Northrop Grumman demonstrated a high-powered laser that is powerful enough for battle but made of materials that are compact and easy to transport, based around a novel formulation of the common laser material neodymium-doped yttrium aluminum garnet, or "nd:YAG."
Now the laser is being tested by the U.S. navy on board ships and by the army at its White Sands Missile Range in New Mexico. Dan Wildt, Northrop's vice-president of directed energy systems, says that if the military decides to begin using these weapons, they could be in the field by the middle of the decade.
"Laser" is an acronym for "light amplification by stimulated emission of radiation." A substance (a crystal or a gas, usually) is hit with energy, usually light or electricity, which stimulates the molecules to emit electromagnetic radiation (X-rays, ultraviolet radiation, visible light, infrared radiation, etc.) that is amplified and shot out in a beam.
Einstein predicted the stimulated emission part in 1917, and 50 years ago on May 16, 1960, Theodore Maiman demonstrated the first working laser at Hughes Research Labs.
What makes a laser so useful is that it is extremely neat, clean and sharp — the light is all the same wavelength and it is said to be coherent. "An orchestra warming up, that's like an incandescent light," explains Thomas Baer, executive director of the Stanford Photonics Research Center at Stanford University. "When the first violinist tunes to A, that's the laser."
(Baer is also a director of the Optical Society of America, which is staging a year-long celebration of the 50th anniversary of the laser with the wonderfully geeky name "Laserfest.")
The orderliness of lasers is what makes them useful for things like storing and relaying information —that's why they can transmit voice and data signals around the world through fibre-optic cables. And it allows manufacturing engineers to focus lasers extremely tightly into blades that never dull.
Will for weapons
The U.S. military has long wanted to develop lasers it could use as weapons on the battlefield. Lasers are fast — they travel at the speed of light. They can be precise — they could take out a radar installation on a building without levelling the building. And, as long as you have power, they won't run out of ammo.
But until recently, the only way to make lasers powerful enough to blow something tough into pieces was to use a chemical laser, which produces its energy through a chemical reaction. They are cumbersome and the logistics of supplying chemicals and disposing of waste makes them impractical.
The invention that led to Northrop Grumman's laser was made in 1995 by the Japanese researcher Akio Ikesue and others. They showed that a laser could be produced with a ceramic instead of a crystal, which has led to the development of new, extremely powerful lasers that are only now becoming a reality. (Northrop Grumman declined to comment on the laser's composition.)
While there are only a handful of types of crystals that can be used for lasers, materials scientists can bake any manner of ceramic that can produce lasers of different wavelengths, power and efficiency.
"We've opened a whole new class of laser materials," says Robert Byer, a professor in the applied physics department at Stanford. "From a researcher's point of view, I'm a kid in a candy store."