Legendary physicist and Nobel laureate Charles H. Townes, who passed away at the age of 99 in Oakland, California recently, leaves behind a world that’s richer for the huge array of applications based on his brainchild, the laser, for the process of light amplification by stimulated emission of radiation.
Today lasers dominate our lives as few other inventions have, with applications in everything from surgical instruments, bar code readers, CD players and satellites.
At a time when the concept of laser existed only in the minds of sci-fi writers (who conjured up death rays for their heroes to fight evil with), young Townes sat down on a Washington park bench and had what he calls “divine inspiration”. It occurred to him that he could amplify microwaves and build what was essentially a sensitive atomic clock.
It was a eureka moment, not unlike the one a schoolboy named Albert Einstein once had when he thought of riding a light beam on his way back from school and turned Newtonian physics on its head. Amplification of microwaves led Townes to lasers that work by exciting gas atoms and forcing them to give up their energy in the form of an intense flash of light.
For something so powerful, lasers are based on simple principles, and can actually be devised as a gadget to fit in the palm of your hand, consisting nothing more than a small rod of synthetic ruby crystal.
Since scientists knew about electromagnetic waves for a long time, many of them must have kicked themselves for not developing the laser earlier. Townes’s genius lay in realising that if he could somehow make light waves ‘coherent’ (all with the same wavelength, and moving in phase), they would travel in step like marching soldiers.
A beam of light usually spreads out as it traverses long distances, but coherent light will have its beams almost parallel all the way, so that you could bundle them into a ray hundreds of times finer than the human hair. Thus lasers can cut steel plates with the same ease with which they destroy tumours in surgical operations. And just like radio waves they can carry enormous volumes of radio and TV transmissions and telephone conversations simultaneously.
Extraterrestrial life, or the search for it, was almost an obsession with Townes. At an age when most scientists retire to write their memoirs, Professor Townes (“Charlie” to friends and family) believed there was a lot of science left in him to do as he prepared for his next great adventure.
“I always wanted to do serious astronomy, and I devote much time to that now,” he told this writer in an interview in 2008. He shared the idea that astronomy could be in for the next big thing if all went well with the Search for Extraterrestrial Intelligence (SETI) launched by the University of California, Berkeley.
In fact, SETI itself is based on an idea Townes first suggested in the 1960s that instead of listening to signals from space, astronomers should start looking for them. Just as astronomers eavesdrop on the heavens with radio telescopes to discern the equivalent of a “hello” amid the crackle and hiss of radio waves, Townes and his team started to religiously look for laser flashes in outer space. “Actually, it’s also easy to send laser messages into space to other civilisations,” he said.
Rigging up a laser device of, say, one megawatt (the same level of power that a TV station uses) to an optical telescope is an excellent way to transmit signals to nearby stars. But Townes’s suggestion that alien intelligences might use powerful laser flashlights to contact Earth seemed so “embarrassingly simple” in the 1960s that astronomers didn’t give it much thought. Townes, though, believed that the gas clouds between stars are natural microwaves amplified by the stimulated emission of radiowaves, or masers — the forerunners of the laser — that emit intense radiation in all directions, and ET signals shouldn’t be too difficult to spot.
Townes knew it was a shot in the dark, but then it was a similar situation when he invented the laser, too. Even many Nobel laureates had pooh-poohed his idea of the maser before Townes developed it in 1954.
“They didn’t seriously think it’d work,” Professor Townes once recalled. He had felt the same also about finding that first whisper from space, saying: “You just have to look hard enough.”
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Corrections and Clarifications
This article was edited to reflect the following correction:
The full form of laser is light amplification by stimulated emission of radiation — not “ simulated ” — as the Open page article, The man behind the laser saga, and more (Feb. 8, 2015), said.
