Lasers are inherently cool. A pointer that shoots a red beam in a perfectly straight line more than 1,500 feet costs less than $10. When choreographed to “Dark Side of the Moon,” lasers can transport a bunch of aging rockers in a Lasarium back to high school circa 1973. And, at least in the movies, they can be used to blow up just about anything.
With these images firmly in tow, we trekked to the laser labs at the Palo Alto Research Center. If there is one technology in which the propeller heads at PARC are expert it is lasers. Red ones, violet ones, blue ones, invisible ones-they’ve got them all in their lab on a beautiful hillside above downtown Palo Alto.
We were keen to see some. We figured there might be laser duels in the parking lot, smoldering scraps of metal incinerated by giant lasers, maybe even Pink Floyd cranked in the PARC cafeteria.
No dice. “We don’t blow things up,” a PARC public relations woman said shortly after our arrival.
Fine, blowing things up isn’t everything. There was plenty more to see and learn from PARC’s own Dr. Laser (our moniker, not his), Noble Johnson.
After a brief stroll down PARC’s spotless halls, we were led into a small, dark conference room where Johnson and two of his laser-obsessed colleagues were waiting.
Johnson has a military bearing that doesn’t seem to fit with his jeans and white tennis shoes. It might be his short haircut or buffed arms. We sit down with Chris Chua [pronounced chew-ah] and Michael Kneissl [kuh-nee-sul], and Johnson turns out the lights. Here comes the Floyd!
Nope. Instead, Noble slaps a transparency onto an overhead projector. The only noise accompanying him is the whir of the machine’s internal fan. With Chua and Kneissl jumping in, Johnson patiently explains the basics of lasers, actually an acronym for “light amplification by stimulated emission of radiation.” Though informative, the presentation is definitely no trip to the Lasarium. No one even uses a laser pointer.
Starting in the 1970s, PARC engineers like Johnson pioneered the laser printer for Xerox, and continue to feed the company with faster and higher resolution arrays of lasers for printing. Once PARC’s parent, Xerox cut the research center loose when it fell on hard times and couldn’t find a buyer for its onetime Wunderkind. As of January, PARC was left to fend for itself. It still has strong ties to Xerox, but it’s chief goal is to sell its technology to third parties. For PARC to survive, Noble and his colleagues must find a way to commercialize their research, something at which PARC has been notoriously unscuccsessful.
To understand where lasers are going, it helps to understand where they have been. Most lasers work by sending electrical current into some medium. The medium can be a gas, liquid or a crystal. The added energy sends atoms in the medium into an excited state. When the atoms return to their normal state they shed the excess energy in the form of photons-particles of light. By focusing these photons into a precise beam you get a laser. The earliest optical lasers were developed more than 40 years ago and used ruby. But other materials were being researched from the beginning, and gas and other less precious semiconductor lasers were demonstrated.
Noble and the PARC engineers specialize in semiconductor lasers, which use layered crystals formed from material like gallium nitride and gallium arsenide. Semiconductor lasers have several advantages over their gas counterparts: They use relatively little energy, they are durable and, most importantly, they are cheap. The development of inexpensive semiconductor lasers emitting red or infrared light opened the door to mass-market CD players, DVD players, laser printers and a slew of other devices.
Depending on the medium used, the resulting lasers come in different wavelengths, and with lasers wavelength is everything. Send current through a layered material containing gallium nitride crystal and the resulting laser is blue. So what? Well, the wavelength of a blue laser is smaller than a red or infrared laser, meaning it takes up less space. And that’s a big deal.
DVDs and CDs have microscopic pits on their surfaces that correlate to digital data’s 0s and 1s. Like the phonograph needles of old, lasers read the pits. A blue laser can read pits that are four times smaller than those read by red lasers. With a marketplace full of blue laser-based readers, you could quadruple the content on a DVD. It would also allow you to fit a single movie in the data-intensive high definition television standard onto a DVD, a pending government requirement. Optical data devices could also be made much smaller, and blue lasers are the key to it all.
“That is one of the near-term applications that is happening right now,” says Johnson, who heads up blue laser research at PARC. “No one would be surprised that within the next few years these blue laser devices will start hitting the market, and that’s a multi-billion dollar [consumer electronics] industry.” Labs at consumer device giants like Sony, Sharp and Philips have been spending a good deal of money to figure out blue lasers. If PARC solves the riddle first, it could theoretically license its technology to any or all of the consumer device makers. Xerox is depending on PARC to adapt blue lasers to printing.
But blue is not the only future for lasers at PARC. Another area of research is vertical cavity surface emitting lasers or VCSELs essentially arrays of tiny lasers that shoot beams from the surface of a chip. PARC researchers have built a VCSL on which they have crammed 14,000 lasers. That is one laser every three microns. A human hair is about 77 microns thick.
PARC’s VCSL is the world’s smallest and densest laser array. Chua fires it up in his lab, and we look at it through a magnifying monitor. Tiny orange lights flash on and off in seemingly random order. It’s like looking at a very tiny Christmas tree under a microscope.
There are plenty of issues to be worked out, like how to monitor the thousands of lasers to make sure they are all working in tandem, but the concept has been proven, and Chua says the applications are numerous. In printing, for example, the Holy Grail is one laser per pixel. Writing data could occur simply by turning a laser on and off.
VCSLs could also be used as optical interconnects, transferring data over short distances via laser. In computers, arrays of lasers could replace coaxial cables and remove one of computer hardware’s most irksome bottlenecks: the transfer of data from board- to- board or chip- to- chip within a computer.
PARC’s research in the ultraviolet and near-ultraviolet spectrum also has important applications, ranging from cheap semiconductor lasers that could perform water purification to lasers that are the brains of a bio-agent warning system, the latter being developed with $8.4 million in DARPA funding.
Many bio-molecules, friendly and unfriendly-like anthrax-absorb light in the UV range and start to glow under the beam of a laser. The goal is to shrink an expensive, energy- sucking gas laser that now fits in the back of a truck, down to the size of a soda can. Johnson is part of the team that has four years to get it done. “Give us some time,” he says, laughing when questioned about the team’s progress. “We only just got the grant in June.”
Other applications for UV semiconductor lasers are farther out: No one has found the right material to make a UV semiconductor laser. If such a laser can be developed, it would “lend itself to all sorts of new things and more compact systems,” says Kneissl. “It might be DNA, proteins or other areas of genetics. U.V. and near UV semiconductor lasers can bring us closer to true lab- on- a- chip concepts.”
As he talks, Kneissl fiddles with a blue-violet laser. Packed in a black alloy casing, the beam is beautiful to look at as it scoots around the spotless lab filled with racks of electronic equipment. “Don’t look directly at the beam,” he warns. “It’s not safe for that yet.”
Finally something dangerous. Could we have stumbled onto a secret government project to create real light sabers? Stay tuned.
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