An analogy would be the striking of a tuning fork: When it is struck gently, you hear a pure tone; but when it is struck hard, you hear the harmonics. Similarly, when matter is struck with an intense enough laser beam, you get a light harmonic, which is a nonlinear optical effect.
Dr. Bloembergen shared the 1981 Nobel Prize in Physics with Arthur Schawlow, a physicist from Stanford University, and Kai M. Siegbahn, of Sweden.
His major contribution to the development of the laser was the creation of a three-level pumping system, which made it much easier to pump atoms from their ground state to a higher energy state, allowing the device to operate continuously.
The pumping scheme was originally designed for the laser’s predecessor, the maser, which amplified microwaves instead of light. It offered a much more practical and easier way of making lasers.
“He was one of the major intellectual forces in the explosion of science and applications related to the laser,” said John Armstrong, a retired IBM research director who worked as a postdoctoral student in Dr. Bloembergen’s lab in the 1960s. “There are a thousand applications of lasers, not only in surgery but in all forms of manufacturing and all forms of diagnostics for material properties.”
Before his major advancements in nonlinear optics and laser development, Dr. Bloembergen found early success as a pioneer in nuclear magnetic resonance spectroscopy, a method of detecting the faint magnetism of the atomic nucleus, which is used to study molecular structures and measure magnetic fields.
His doctoral thesis, “Nuclear Magnetic Relaxation,” explored what controlled the shape of spectral lines, which can occur when atoms in their excited state emit radiation. It was used to produce a paper published in 1948 with his Harvard colleagues Edward M. Purcell and Robert V. Pound that became one of the most cited works of physics and was turned into a widely read book in the field.
“That was a giant contribution to spectroscopy that covers every field of science,” said Eli Yablonovitch, a physicist at Berkeley who completed his doctorate under Dr. Bloembergen. “The Nobel committee could have mentioned any of these three things, or could have mentioned others, and it would have been equally noteworthy.”
Nicolaas Bloembergen, who was often called Nico, was born on March 11, 1920, in Dordrecht, the Netherlands, the son of Auke Bloembergen, an executive at a fertilizer company, and Sophia Maria Quint Bloembergen. He was the second of six children.
Growing up he yearned for academic challenges. At age 12 he attended a prestigious municipal gymnasium in Utrecht, where he learned chemistry, mathematics and Latin. But it was physics that he found most challenging, and most worthy of pursuit.
He graduated from the municipal gymnasium as valedictorian in 1938, giving his speech in white tie and tails. Little did he know that he would wear the exact same suit to accept, at 61, a Nobel Prize in Stockholm many years later.
He entered the University of Utrecht to study physics. There, he took an experimental physics course with Leonard S. Ornstein, who allowed him to assist a graduate student with his Ph.D. research project. That led to Dr. Bloembergen’s first publication of a scientific paper in 1940.
That same year Adolf Hitler launched a massive airborne invasion westward. Without warning, German troops parachuted into Holland and took control of the nation.
The next year, Dr. Ornstein, a Jew, was removed from the university at the same time that Jewish students were expelled. (Dr. Ornstein died six months later from what Dr. Bloembergen had said was stress and malnutrition.)
Though Dr. Bloembergen was not Jewish, he was still a potential target for deportation or even death; the Nazis were deeply suspicious that any student could be part of the Dutch resistance.
Despite studying under German occupation, he received the Dutch-equivalent of a bachelor’s degree in 1941 and the equivalent of a master’s degree in 1943, mere weeks before the Nazis closed the University of Utrecht. After graduating, Dr. Bloembergen spent the next two years hiding from the Nazis, including during the “hunger winter” of 1944, when food was scarce and many died of malnutrition.
“I remember eating bitter tulip bulbs to fill my stomach. They were hard and indigestible despite of hours of boiling,” he wrote in his book, “Encounters in Magnetic Resonances: Selected Papers of Nicolaas Bloembergen.” “I read through the book ‘Quantum Theorie des Elektrons und der Strahlung,’ by H. A. Kramers, by the light of a storm lantern.”
The Allied forces liberated Holland in 1945, and Dr. Bloembergen later left the shambles of Europe for the United States. He enrolled in Harvard and worked under Dr. Purcell on nuclear magnetic resonance. Dr. Purcell would win the Nobel Prize in Physics in 1952 for his work with NMR.
Dr. Bloembergen would go on to say that it was his good fortune to have arrived at the lab six weeks after Dr. Purcell and his colleges detected NMR in condensed matter. He had come upon a field that was ripe for discovery.
Dr. Bloembergen returned to the Netherlands to earn his doctoral degree at the University of Leiden, in 1948, and defend his thesis.
While there he met Huberta Deliana Brink, whom he called Deli. During the war she had been in a Japanese concentration camp in Indonesia, where she was born. Dr. Bloembergen returned to Harvard in 1949 and she followed shortly after. They married in Amsterdam on June 26, 1950, beginning a 67-year marriage. Both became citizens in 1958. She survives him.
In addition to his wife and his son, he is survived by two daughters, Antonia Bloembergen and Juliana Dalton, and two grandchildren.
Dr. Bloembergen became a professor at Harvard in 1951 and stayed there until his retirement in 1990. He received the National Medal of Science from President Gerald R. Ford in 1974. After retiring from Harvard, he moved to Tucson and became a professor emeritus at the University of Arizona, College of Optical Sciences, in 1991, though he would not accept a salary.
In 2010, for his 90th birthday, his friends, family and scientists he had mentored — the “Nicolettes,” as one colleague called them — gathered at the university for an optical sciences symposium followed by a tennis tournament.
“He was so well loved by colleagues and especially former students and postdocs,” Dr. Wyant said.
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