His inventions are all around us
SCIENTIST KEPT SUCH A LOW PROFILE, HIS 2016 DEATH GOT LITTLE NOTICE
Robert N. Hall’s legacy can be found at almost every checkout counter — that little red blinking laser scanner that reads bar codes on milk cartons, boxes of light bulbs, price tags dangling from a new jacket and just about everything else that can be bought in a store.
A product of his inventive labour can also be found in most kitchens nowadays: the microwave oven.
Yet for all the widespread familiarity of what Hall wrought as a remarkably inventive physicist, his death, at 96, on Nov. 7, 2016, gained little notice. An announcement paid for by his family appeared in two upstate New York newspapers — The Times Union of Albany and The Daily Gazette of Schenectady — and General Electric, in a company publication, published a remembrance a month later. But otherwise the news of Hall’s death did not travel far.
His daughter, Elaine Schulz, said he died of complications of pneumonia. The New York Times learned of Hall’s death while editing this obituary, which had been written in 2012.
Hall left his fingerprints far and wide. He built the first solid-state laser in 1962. Nearly 20 years earlier, during the Second World War, he designed a magnetron to jam enemy radar that, thanks to a melting candy bar, was adapted to create the microwave oven.
Another of his inventions makes it possible to control the high-voltage DC current that runs things like electric locomotives. His gamma ray detector is used in nuclear research. And his laser not only promotes faster checkouts, channel surfing and pointers; it also enables fibre optics to carry data.
It’s probably fair to say, however, that when he invented his laser in 1962, Hall could never have imagined the uses to which it would one day be put, for he was not a consumer product developer. He was an experimenter who spent his entire career at what is now GE Global Research, a General Electric research laboratory, in Niskayuna, N.Y., outside Schenectady.
Lasers had been invented in 1960, but they were bulky, complex affairs built around simulated rubies or chambers full of a gas that could be “excited” into giving off light, the rays of which bounced between mirrors until they were concentrated into a single beam.
Hall’s laser device, by contrast, was a single, small solid-state semiconductor piece that had to be cooled to the temperature of liquid nitrogen — more than 300 degrees Fahrenheit below zero — making it an unlikely candidate for consumer uses. Once the principle of a tiny, solid laser was established, however, others refined it.
By Hall’s account, in a videotaped 2010 interview, the laser had its origins in a fellow scientist’s teasing. Since Hall had “invented all kinds of things,” he recalled his colleague saying, “Why didn’t I invent a semiconductor laser?” His earlier inventions, after all, had earned him the freedom to do what he wanted at the G.E. laboratory and a small team to help him do it.
Hall was skeptical at first that he could build a semiconductor laser, but after reading others’ research, he concluded that it was possible. Based on published experiments, he settled on gallium arsenide as the most promising medium.
Using semiconductors the size of “a grain of salt,” he said, he polished their parallel faces to mimic the mirrors used in existing lasers. Current was introduced at the ends of the semiconductors. In only a few months, he and his team had produced a working solid laser.
Hall was already well known among colleagues for purifying germanium, the primary material in the early diodes that were used in solid-state electronics. He discovered that freezing a piece of germanium would leave impurities at one end, giving him the purest germanium yet produced.
Advancing that work, he began adding the element indium to the germanium, and discovered that the resulting semiconductor could control heavy loads of current.
But he also found that the existing explanation of how electrons moved through semiconductors was not matching his calculations. So he devised a new explanation for the process, which is now known as Hall-Shockley-Read recombination.
Hall began working at the G.E. lab after graduating from the California Institute of Technology in 1942. With the Second World War in progress, he soon designed a type of magnetron that could jam enemy radar. Shortly afterward, an engineer at Raytheon standing near one of the devices noticed that it had melted a candy bar in his pocket. Raytheon engineers used the discovery to develop the microwave oven.
After the war, Hall returned to Caltech for a doctorate. With the encouragement of his advisers, who were excited by the atomic age, he began studying nuclear physics. He received his Ph.D. in 1948.
Hall would never enter the field professionally. But though he never did nuclear research, a classmate did, and it was through him that Hall learned that nuclear physicists were bedevilled by a problem with the germanium used in devices that detected the gamma rays given off by radioactive activity — rays that are deadly at high exposures.
Hall reasoned that he could solve the problem by purifying germanium to the point where no more than one-millionth of a millionth part would be impure — an unheard-of level. Few believed that that was possible, but Hall succeeded, creating the detector that is used worldwide today.
Hall held more than 40 patents in the United States. He was awarded the Marconi Prize in 1989 and was inducted into the National Inventors Hall of Fame in 1994. He retired from the G.E. lab in 1987.
Robert Noel Hall was born on Dec. 25, 1919, in New Haven, Conn.
He said he became interested in science as an 11-year-old when an uncle, an early aircraft-engine designer, took him to a science fair.
In a 2012 interview for this obituary, he talked about the pleasure he took in a life of science.
“You see there is a problem to be solved,” he said, “and you think about it, and you solve it, and it’s a thrill.”