A Post on the Light Side

Stephen DeAngelis

January 29, 2010

Fear of the dark has always gripped men’s souls. I’m sure that our earliest ancestors worshiped fire as much for its light as its warmth. The old adage “it’s always darkest before the dawn” instills in us both a sense of fear about the dark and sense of comfort about the light. When we finally see a solution to a particular problem, we finally “see the light.” When the world stagnated during the middle ages, it was the age of darkness. The creation of the electric light was heralded as man’s triumph over darkness. Over the past couple of hundred years, mankind has learned a lot more about light. But it was only 50 years ago that magic of Light Amplification by Stimulated Emission of Radiation (or LASER) was discovered [“Laser light proves to have many uses in business, health, communications,” by How and Why, Washington Post, 19 January 2010]. There are few people in the developed world whose lives aren’t daily touched by lasers. The article calls the discovery of laser “one of the most portentous events in the history of science.” It continues:

“Like many a transformative development, it was met initially with thunderous public indifference, although there were a few mutterings about ‘death rays.’ A number of techno-pundits regarded the upstart gizmo as basically a glorified parlor trick, a ‘solution looking for a problem,’ as Charles Townes, who won the Nobel Prize for pioneering the idea, later wrote. Half a century later, lasers check out our groceries, read and write CDs and DVDs, guide commercial aircraft, enable eye surgery and dental repairs, target weapons, provide worldwide communications, survey the planet, print documents, cut fabric for clothing and metal for tools, make powerful pointers for PowerPoint slides and are now poised to ignite nuclear fusion, among scores of other uses.”

In past posts, I have often voiced support for basic science as well as applied science. The laser was a result of basic scientific research that obviously has created solutions in fields of human endeavor that were never dreamed of by those who first fiddled around with it. As the article says, “Who knew?” It continues:

“Certainly not Albert Einstein, who had predicted the laser effect way back in 1917. By then, physicists understood that virtually all the light you see is produced by a process called spontaneous emission. Zap a few atoms with the right amount of energy — including energy from light itself — and their electrons will absorb the energy and jump up to excited levels, the original ‘quantum leap.’ But they won’t stay there. That’s because, as the parent of any teenager can tell you, it is the natural tendency of things in this universe to preferentially seek the lowest energy condition, which is why water always flows downhill, shoelaces never re-tie themselves and your check is still in the mail. So the excited electrons soon drop back to lower levels; in the process, they spontaneously shed the surplus energy in the form of photons, the smallest individual units, or quanta, of light. The size of the drop determines the wavelength of the emitted photon. That’s how light emerges from a flickering campfire, the surface of the sun, the bulb in a lamp or the screen of your TV.”

According to the article, Einstein predicted “that there could be a second, very different kind of emission in certain types of materials — not spontaneous, but stimulated.” The light emitted in this excited or stimulated state would be quite different than normal light.

“It would work like this: Suppose that you had already excited the electrons in the material’s atoms until they were trembling on the brink of emitting photons. But before they did so, what would happen if you whacked those atoms with incoming photons from another source that were exactly equal in energy to the ones the electrons were about to emit? In that case, Einstein figured, instead of absorbing the incoming photon, each atom would be stimulated to give off a photon identical in every way to the incoming photon while leaving the original unchanged. Not only would the emitted photon be precisely the same wavelength as the one that stimulated it, but its wave peaks and troughs would be perfectly in phase (a condition called coherence) and it would be traveling in the same direction. Those twin photons would then fly off to stimulate more nearby atoms, which would emit yet more photons in a glowing profusion of luminous clones.”

You can see how that description of a laser could produce “thunderous public indifference.” It was, however, an idea that a theoretical physicist could love.

“By the mid-1950s, scientists had identified several excellent materials and had recognized that putting a mirror on each side of the laser medium would drastically increase the output, reflecting the photons back and forth, and producing more stimulus and more emissions on each transit. If one of the mirrors was partially transparent, a stream of photons would emerge from that end — the now familiar laser beam. Finally in May 1960, Theodore Maiman, a physicist at Hughes Research Laboratories, constructed the first laser that emitted light in the visible range. Today there are dozens of designs exploiting all three of the distinctive properties of laser light. The narrowly defined wavelength allows a laser scanner at the grocery store to bounce its beam off a bar code and read the result when the store lights are on. Indeed, the outputs of different lasers are so sharply differentiated that you can run signals from a bunch of them through the same fiber optic cable simultaneously and still separate them easily at the end. The unidirectional tightness of laser light makes it ideal for surveying because, unlike a flashlight beam, it doesn’t diverge much over distances. Even really long distances: Laser light from the surface of the Earth, bouncing off a reflector placed on the lunar surface by Apollo astronauts, has revealed that the moon is receding from our planet by about an inch and a half a year. Finally, the beam’s coherence makes it stunningly powerful. A laser drawing a couple of kilowatts (slightly more than your home hair dryer) can cut through an inch of carbon steel. But that’s nothing compared with another device you own, along with every other American taxpayer. Out in California, researchers at the Department of Energy’s National Ignition Facility are about to concentrate 192 laser beams totaling 500 trillion watts on a capsule of hydrogen the size of a pencil eraser. If it works, the power of the lasers will shove the hydrogen atoms together hard enough to ignite nuclear fusion, creating (if you could see it) a microscopic star — and with it, some people believe, the prospect of limitless energy for society using the same energy source that fires up the sun. One of these days. Perhaps.”

The article concludes by calling the laser “civilization’s leading light,” and, because of the breadth of its utility, it probably is. However, despite the fact that lasers can create amazing nighttime light shows, when it comes to replacing darkness with light, lasers fall short. In a previous post entitled LED to the Future, I discussed how light emitting diodes (or LEDs) are being touted as the future of the lighting industry because of the energy they can save. LEDs, however, remain almost prohibitively expensive for household use. Fluorescent bulbs remain the energy-saver bulb of choice; but makers of incandescent bulbs haven’t given up. They are hoping that new innovations will help them make a comeback [“Incandescent Bulbs Return to the Cutting Edge,” by Leora Broydo Vestel, New York Times, 5 July 2009]. Vestel reports:

“When Congress passed a new energy law [several] years ago, obituaries were written for the incandescent light bulb. The law set tough efficiency standards, due to take effect in 2012, that no traditional incandescent bulb on the market could meet, and a century-old technology that helped create the modern world seemed to be doomed. But as it turns out, the obituaries were premature. Researchers across the country have been racing to breathe new life into Thomas Edison’s light bulb, a pursuit that accelerated with the new legislation. Amid that footrace, one company is already marketing limited quantities of incandescent bulbs that meet the 2012 standard, and researchers are promising a wave of innovative products in the next few years. Indeed, the incandescent bulb is turning into a case study of the way government mandates can spur innovation.”

Innovations generally don’t come cheap — at least in the beginning — and the new incandescent bulbs are no different. According to Vestel, “the first bulbs to emerge from this push, Philips Lighting’s Halogena Energy Savers, … sell for $5 apiece and more, compared with as little as 25 cents for standard bulbs.” The up-front cost, however, is offset by long-term savings. The new bulbs are 30 percent more efficient than older bulbs and last about three times as long. According to Vestel, even though the new bulbs meet the 2012 standard they are not as efficient as fluorescent bulbs. On the other hand, the new incandescent bulbs don’t suffer from slow start-up times or hazardous mercury content. Here’s how the new bulbs work:

“Normally, only a small portion of the energy used by an incandescent bulb is converted into light, while the rest is emitted as heat. Deposition Sciences applies special reflective coatings to gas-filled capsules that surround the bulb’s filament. The coatings act as a sort of heat mirror that bounces heat back to the filament, where it is transformed to light. While the first commercial product achieves only a 30 percent efficiency gain, the company says it has achieved 50 percent in the laboratory. No lighting manufacturer has agreed yet to bring the latest technology to market, but Deposition Sciences hopes to persuade one.”

Vestel reports that technologies similar to those used by Deposition Sciences are being worked on by “the big three lighting companies — General Electric, Osram Sylvania and Philips — … as is Auer Lighting of Germany and Toshiba of Japan.” Vestel continues:

“A wave of innovation appears to be coming. David Cunningham, an inventor in Los Angeles with a track record of putting lighting innovations on the market, has used more than $5 million of his own money to develop a reflective coating and fixture design that he believes could make incandescents 100 percent more efficient.”

Lasers, even though they aren’t used to provide light, may play a role in reinvigorating the incandescent bulb. Vestel explains:

“Both Mr. Cunningham and Deposition Sciences have been looking into the work of Chunlei Guo, an associate professor of optics at the University of Rochester, who announced in May [2009] that he had used lasers to pit the surface of a tungsten filament. ‘Our measurements show that the treated filament becomes twice as bright with the same power consumption,’ Mr. Guo said.”

Others are also conducting research:

“A physics professor at Rensselaer Polytechnic Institute, Shawn-Yu Lin, is also seeing improved incandescent performance by using a high-tech, iridium-coated filament that recycles wasted heat. ‘The technology can get up to six to seven times more efficient,’ Mr. Lin said.”

Why all of this interest in incandescent bulbs? Vestel reports that “despite a decade of campaigns by the government and utilities to persuade people to switch to energy-saving compact fluorescents, incandescent bulbs still occupy an estimated 90 percent of household sockets in the United States.” The reason, of course, is that “old-style incandescents have the advantage of being remarkably cheap.” The cheapest bulbs, however, are going to be hard to find after the new 2012 standard kicks in. Even more innovation in lighting is likely to result from a contest offering a significant prize for developing a better bulb [“Build a Better Bulb for a $10 Million Prize,” by Eric A. Taub and Leora Broydo Vestel, New York Times, 24 September 2009]. The “L Prize” is being offered by the U.S. Department of Energy “to the first person or group to create a new energy-sipping version of the most popular type of light bulb used in America.” Taub and Vestel report that a winner may already have submitted the winning bulb. Philips claims that it has developed an LED light bulb that uses one-sixth the energy of a standard 60-watt incandescent bulb. If true, the new bulb exceeds the requirements of the prize. Taub and Vestel report that the $10 million is not the biggest prize the company could win.

“The $10 million is almost beside the point. More important, the contest winner will receive consideration for potentially lucrative federal purchasing agreements, not to mention a head start at cracking a vast consumer marketplace. The L Prize has garnered significant attention in the lighting industry because 60-watt incandescent lamps represent 50 percent of all the lighting in the United States, with 425 million sold each year. The Energy Department says that if all those lamps were LED equivalents, enough power would be saved to light 17.4 million American households and cut carbon emissions by 5.6 million metric tons annually.”

Philips LED light bulb might win the contest, but it won’t win the hearts, minds, and pocketbooks of consumers until the price of LED lights can be significantly reduced. Even though LED lights save money in the long-term, most people opt for near-term bargains over long-term savings.