April 13, 2024

Herbert Kroemer, Nobel laureate who developed laser technology, dies at 95

Herbert Kroemer, a Nobel Prize-winning physicist who led the development of a new type of semiconductor, leading to Information Age advances at the heart of everything from barcode scanners, CD players, and cell phones to satellite communications and networks of fiber optics, died March 8 at 95.

His death was announced by the University of California at Santa Barbara, where he taught for nearly 50 years. A statement from the school’s dean, Henry T. Yang, did not say where or how he died, but credited Dr. Kroemer with “transforming UC Santa Barbara into a leader in engineering and materials science.”

A German-born researcher with a thick white beard and strong skepticism of scientific authority, Dr. Kroemer received a share of the Nobel Prize in physics in 2000 for his development of semiconductor heterostructures, layered devices that have proven fundamental to advanced lasers and high speed transistors. .

He shared his half of the prize with Russian physicist Zhores Alferov, who worked independently but in parallel on developing the devices; the other half went to Jack Kilby, a researcher at Texas Instruments who played a central role in the invention of the integrated circuit, or microchip.

Together, their work “established a stable foundation for modern information technology,” the Nobel committee said.

Dr. Kroemer began his scientific career in research laboratories in West Germany and the United States in the mid-1950s, shortly after the creation of the transistor. The device helped usher in the development of modern electronics, replacing the vacuum tube as an electronic switch and amplifier. Although it would typically be constructed from a single material, usually silicon, Dr. Kroemer proposed creating a faster transistor using a kind of sandwich, or heterostructure, made up of different materials.

In 1963, he applied his research on heterostructures to lasers, which had been invented just three years earlier but only worked at low temperatures and in short pulses. Kroemer developed a way around these problems, creating the basic principle of a device known as a double heterostructure laser, the basis of the first commercial semiconductor laser.

The devices “are used worldwide in fiber optic networks and made the internet possible, transforming the world,” said his colleague John Bowers, director of the Energy Efficiency Institute at UC Santa Barbara, in a tribute.

“It was a question of making something possible that without heterostructures simply could not have been done,” Dr. Kroemer told the New York Times after winning the Nobel Prize. Without the structures, he added, “there would be no CD or CD players,” no LED lights and countless other electronic devices.

Kroemer started out as a theoretical physicist – his first employer, a telecommunications laboratory run by the German Post Office, insisted that he stay away from research equipment for fear of breaking something – and said that when he developed the idea of ​​the heterostructured laser, he was only interested in in the fundamental science behind the concept.

“I didn’t really care what the uses were,” he told IEEE Spectrum, the flagship magazine of the Institute of Electrical and Electronics Engineers.

But his bosses at Varian Associates, a Silicon Valley research firm, refused to grant him resources to develop the technology, “on the grounds that ‘this device could not have any practical applications,’” ​​he recalled in his Nobel lecture. Other researchers, including Alferov, built and refined the first heterostructured lasers.

“It was really a classic case of judging a fundamentally new technology not by the new applications it could to createbut only for what it can do for existing applications,” said Dr. Kroemer in his talk, calling on institutions to focus less on the question of what cutting-edge science might be “good” for.

“The problem is widespread, as old as the technology itself,” he added, noting that the double heterostructure laser “was simply one more example in a long chain of similar examples. Nor will it be the last.”

The eldest of three children, Herbert Kroemer was born in Weimar, Germany, on August 25, 1928. His father was a civil servant and his mother was a homemaker. Neither of them had a high school education nor had much interest in science. Still, they sought to encourage Dr. Kroemer’s natural affinity for mathematics, physics, and chemistry, including purchasing him an encyclopedia of some 20 volumes.

Looking for additional reading material as a teenager during World War II, Dr. Kroemer went to the library twice a week, browsing the science section and becoming fascinated by “the realization that, from a small set of fundamental laws, it was possible to draw very, very broad conclusions,” as he put it in an oral history.

After graduating from high school in 1947, he enrolled at the University of Jena, where he studied with physicist Friedrich Hund during the post-war Soviet occupation of the city. As the social climate became increasingly repressive, lecture attendance declined; some of his more liberal colleagues disappeared without explanation.

“You never know whether they fled to the West or ended up in the German branch of Stalin’s Gulag,” he recalled in an autobiographical essay.

While working for the Siemens company in Berlin during the summer of 1948, Dr. Kroemer decided to resettle in West Germany, securing a seat aboard a return flight from the Berlin airlift. He enrolled at the University of Göttingen and received a doctorate in physics in 1952, writing his dissertation on the effects of “hot electrons” in transistors.

Dr. Kroemer conducted some of his early heterostructure research at RCA Laboratories in Princeton, NJ, and settled in California in 1959, joining Varian Associates in Palo Alto. He moved there with his wife, Marie Louise, and their young children, including a 2-year-old daughter, Sabine, who drowned in a swimming pool shortly after her arrival, according to a report in the local Peninsula Times Tribune.

His wife died in 2016. Information about the survivors was not immediately available, but they had five children, according to IEEE Spectrum.

Dr. Kroemer joined the faculty at the University of Colorado in 1968 and moved to UC Santa Barbara in 1976, eventually holding joint appointments in the department of electrical and computer engineering and the department of materials. He received one of Germany’s highest government honors, the Grand Cross of the Order of Merit, in 2001, and was awarded the IEEE Medal of Honor the following year.

After receiving the Nobel Prize, Dr. Kroemer gained a burst of attention, which he tried to ignore. “You receive a lot of invitations where you know very well that you are being invited to decorate. Those I generally turn down,” he told a UC Santa Barbara interviewer. “But there is one type of invitation that I feel I can give back to society – invitations to speak to students,” whom he spoke to in primary and secondary schools.

“Society has been good to me,” he said, “and this is one way I can pay it forward.”

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