杏吧原创

THIS is a story about the laser 鈥� and no, we haven鈥檛 misspelled it in the title. Lasers produce intense beams of light of a single wavelength by exciting atoms, ions or molecules in a substance and then using photons to stimulate them to release their extra energy as other, identical photons. The word laser stands for 鈥渓ight amplification by the stimulated emission of radiation鈥�, and was coined in 1957 by Gordon Gould, then a doctoral student at Columbia University in New York. Strictly speaking, however, Gould got the name wrong.

How so? In 1959, a year before anyone had built a laser, physicist Arthur Schawlow pointed out that since the amplification is achieved by bouncing the photons back and forth within a resonant cavity, the process would be better described as 鈥渓ight oscillation鈥�. Thus the correct acronym is 鈥渓oser鈥�. It鈥檚 a moot point, and Schawlow was a playful soul, but his joke carried a barb: this was the beginning of a 30-year war over who invented the laser.

鈥淗e was a playful soul, but this 鈥榣oser鈥� joke carried a barb鈥�

It was Albert Einstein who, in 1917, first proposed that photons might stimulate the emission of light from excited atoms or molecules. However, the idea was of purely academic interest until the early 1950s, when Charles Townes, then a physics professor at Columbia University, stimulated ammonia molecules to generate microwaves in a device he called a 鈥渕aser鈥�, standing for 鈥渕icrowave amplification by the stimulated emission of radiation鈥�. (The maser was an oscillator too, but nobody seems to have thought of calling it a 鈥渕oser鈥�.)

While puzzling over how to take the next logical step and extend the maser principle to light, Townes talked to Gould about light sources. This got Gould thinking. Within a few weeks he had sketched out plans for stimulating light from atoms in a gas and bouncing the light back and forth between a pair of mirrors to generate a beam. Notebook in hand, he went to a patent attorney. Meanwhile, Townes teamed up with Schawlow at Bell Labs to come up with essentially the same design as Gould, which they called an 鈥渙ptical maser鈥�. The race to make the laser was on.

Who won? Surprisingly, none of them did. It was Ted Maiman, a physicist at Hughes Research Laboratories in California, who in 1960 built the first device. But that didn鈥檛 stop the battles over who invented it. Initially Gould won credit only for the word, and for a few years 鈥渓aser鈥� was politically incorrect terminology at Bell Labs, although eventually they went along with everyone else. Townes and Schawlow received the initial patent, and Gould lost a series of patent decisions, until the tide turned in the 1970s. He eventually collected four key US patents, and when he died last year aged 85, he was a multimillionaire.