Nicolaas Bloembergen The Nobel Prize in Physics 1981

autobiography

Lasers have come a long way since the first ruby crystal in the 1960's, Nobel prize-winning physicist Nicolaas Bloembergen told a University of Arkansas audience Thursday night, translating into a $20 billion market today. "In the 1960's, it was considered a solution looking for a problem," Bloembergen said of the first laser development. "Now, it's different. Now there are many problems solved by lasers." Bloembergen, professor emeritus at Harvard, pioneered work on nuclear magnetic resonance with Edward Purcell and Robert Pound, as well as development of energy transfer schemes. He was awarded the Nobel Prize for physics in 1981 for his work on nonlinear spectroscopy and optics. Bloembergen spoke to a full house in Giffels Auditorium in Old Main. His presentation, "Lasers: Physics Impacting Your Life" was part of the Robert D. Maurer Lecture Series, named after the physics department alumnus and inventor of the first telecommunications-grade optical fiber. The lecture was sponsored by the physics department.

The word "laser," Bloembergen explained, is an acronym for "light amplification by stimulated emission of radiation." Because of the nature of the light amplification process, he said, light rays go in the same direction at the same frequency, and a coherent phenomenon occurs. Lasers have some common characteristics, including a high chromaticity (of color and wavelength), directionality (relating to direction in space), and high intensity and power. With the directional quality of lasers, he noted, distances such as from the Earth to the moon can be measured to within one inch of accuracy. On a large scale, they can be used to see changes in distance from one point on the Earth to another, detecting possible shifts in tectonic plates. On a smaller scale, they can be used to align underground or underwater pipelines and tunnels, such as the tunnel under San Francisco Bay.

The directionality of lasers also enables laser communication. Lasers can focus onto an area of an optical fiber of one micrometer squared, or as Bloembergen explained, "one thousandth of a cross-section of a human hair, if you can imagine that," making them practical in large cities where there is no more room to lay copper cables for communication. "One optical fiber can carry 400,000 simultaneous telephone conversations," he noted, "so it can do more than 100,000 copper wires."

There are now more than a dozen optical fibers from the East coast to Europe, with a similar number extending across the Pacific. Lasers are also important in the development of optical discs for mass storage requirements, Bloembergen said, and in the automotive industry for heat treatment of metal cylinders in combustion engines, as well as laser beam welding systems. Lasers can also cut materials like paper, textiles, and diamonds, and one of their most interesting uses, he said, is in medicine. They have many uses in surgery, such as to repair detached retinas or remove port wine stains, and their use is cleaner, with less blood loss, and more precision than standard surgical instruments.

Bloembergen sees laser use increasing in scientific applications, and said there is an "enormous push" now for high-powered, semiconductor lasers. Bloembergen has authored two monographs, "Nuclear Magnetic Relaxation" and "Nonlinear Optics," and published more than 300 papers in scientific journals. He was president of the American Physical Society, and has won a number of national and international awards, including the Lorentz Medal of the Royal Dutch Academy of Sciences and the U.S. National Medal of Science. A reception followed his presentation

My parents, Auke Bloembergen and Sophia Maria Quint, had four sons and two daughters. I am the second child, born on March 11, 1920, in Dordrecht, the Netherlands. My father, a chemical engineer, was an executive in a chemical fertilizer company. My mother, who had an advanced degree to teach French, devoted all her energies to rearing a large family. Before I entered grade school, the family moved to Bilthoven, a residential suburb of Utrecht. We were brought up in the protestant work ethic, characteristic of the Dutch provinces. Intellectual pursuits were definitely encouraged. The way of life, however, was much more frugal than the family income would have dictated. At the age of twelve I entered the municipal gymnasium in Utrecht, founded as a Latin school in 1474. Nearly all teachers held Ph.D. degrees. The rigid curriculum emphasized the humanities: Latin, Greek, French, German, English, Dutch, history and mathematics. My preference for science became evident only in the last years of secondary school, where the basics of physics and chemistry were well taught. The choice of physics was probably based on the fact that I found it the most difficult and challenging subject, and I still do to this day. My maternal grandfather was a high school principal with a Ph.D. in mathematical physics. So there may be some hereditary factor as well. I am ever more intrigued by the correspondence between mathematics and physical facts. The adaptability of mathematics to the description of physical phenomena is uncanny.

My parents made a rule that my siblings should tear me away from books at certain hours. The periods of relaxation were devoted to sports: canoing, sailing, swimming, rowing and skating on the Dutch waterways, as well as the competitive team sport of field hockey. I now attempt to keep the body fit by playing tennis, by hiking and by skiing. Professor L.S. Ornstein taught the undergraduate physics course when I entered the University of Utrecht in 1938. He permitted me and my partner in the undergraduate lab, J.C. Kluyver (now professor of physics in Amsterdam) to skip some lab routines and instead assist a graduate student, G.A. W. Rutgers, in a Ph.D. research project. We were thrilled to see our first publication, "On the straggling of Po-a-particles in solid matter", in print (Physica 7, 669, 1940).

After the German occupation of Holland in May 1940, the Hitler regime removed Ornstein from the university in 1941. I made the best possible use of the continental academic system, which relied heavily on independent studies. I took a beautiful course on statistical mechanics by L. Rosenfeld, did experimental work on noise in photoelectric detectors, and prepared the notes for a seminar on Brownian motion given by J.M.W. Milatz. Just before the Nazis closed the university completely in 1943, I managed to obtain the degree of Phil. Drs., equivalent to a M.Sc. degree. The remaining two dark years of the war I spent hiding indoors from the Nazis, eating tulip bulbs to fill the stomach and reading Kramers' book "Quantum Theorie des Elektrons und der Strahlung" by the light of a storm lamp. The lamp needed cleaning every twenty minutes, because the only fuel available was some left-over number two heating oil. My parents did an amazing job of securing the safety and survival of the family.

I had always harbored plans to do some research for a Ph.D. thesis outside the Netherlands, to broaden my perspective. After the devastation of Europe, the only suitable place in 1945 appeared to be the United States. Three applications netted an acceptance in the graduate school at Harvard University. My father financed the trip and the Dutch government obliged by issuing a valuta permit for the purchase of US$ 1,850. As my good fortune would have it, my arrival at Harvard occurred six weeks after Purcell, Torrey and Pound had detected nuclear magnetic resonance (NMR) in condensed matter. Since they were busy writing volumes for the M.I.T. Radiation Laboratory series on microwave techniques, I was accepted as a graduate assistant to develop the early NMR apparatus. My thorough Dutch educational background enabled me to quickly profit from lectures by J. Schwinger, J.H. Van Vleck, E.C. Kemble and others. The hitherto unexplored field of nuclear magnetic resonance in solids, liquids and gases yielded a rich harvest. The results are laid down in one of the most-cited physics papers, commonly referred to as BPP (N. Bloembergen, E.M. Purcell and R.V. Pound, Phys. Rev. 73, 679, 1948). Essentially the same material appears in my Ph.D. thesis, "Nuclear Magnetic Relaxation", Leiden, 1948, republished by W.A. Benjamin, Inc., New York, in 1961. My thesis was submitted in Leiden because I had passed all required examinations in the Netherlands and because C.J. Gorter, who was a visiting professor at Havard during the summer of 1947, invited me to take a postdoctoral position at the Kamerlingh Onnes Laboratorium. My work in Leiden in 1947 and 1948 resulted in establishing the nuclear spin relaxation mechanism by conduction electrons in metals and by paramagnetic impurities in ionic crystals, the phenomenon of spin diffusion, and the large shifts induced by internal magnetic fields in paramagnetic crystals. During a vacation trip of the Physics Club "Christiaan Huyghens" I met Deli (Huberta Deliana Brink) in the summer of 1948. She had spent the war years in a Japanese concentration camp in Indonesia, where she was born. She was about to start her pre-med studies. When I returned to Harvard in 1949 to join the Society of Fellows, she managed to get on a student hospitality exchange program and traveled after me to the United States on an immigrant ship. I proposed to her the day she arrived and we got married in Amsterdam in 1950. Ever since, she has been a source of light in my life. Her enduring encouragement has contributed immensely to the successes in my further career. After the difficult years as an immigrant wife, raising three children on the modest income of a struggling, albeit tenured, young faculty member, she has found the time and energy to develop her considerable talents as a pianist and artist. We became U.S. citizens in 1958. Our children are now independent. The older daughter, Antonia, holds M.A. degrees in political science and demography, and works in the Boston area. Our son, Brink, has an M.B.A. degree and is an industrial planner in Oregon. Our younger daughter, Juliana, envisages a career in the financial world. She has interrupted her banking job to obtain an M.B.A. in Philadelphia.

In this family setting my career in teaching and research at Harvard unfolded: Junior Fellow, Society of Fellows 1949 - 1951; Associate Professor 1951- 1957; Gordon McKay Professor of Applied Physics 1957 - 1980; Rumford Professor of Physics 1974 - 1980; Gerhard Gade University Professor 1980 present. While a Junior Fellow, I broadened my experimental background to include microwave spectroscopy and some nuclear physics at the Harvard cyclotron. I preferred the smaller scale experiments of spectroscopy, where an individual, or a few researchers at most, can master all aspects of the problem. When I returned to NMR in 1951, there were still many nuggets to be unearthed. My group studied nuclear quadrupole interactions in alloys and imperfect ionic crystals, discovered the anisotropy of the Knight shift in noncubic metals, the scalar and tensor indirect nuclear spin-spin coupling in metals and insulators, the existence of different temperatures of the Zeeman, exchange and dipolar energies in ferromagnetic relaxation, and a variety of cross relaxation phenomena. All this activity culminated in the proposal for a three-level solid state maser in 1956. Although I was well aware of the applicability of the multilevel pumping scheme to other frequency ranges, I held the opinion - even after Schawlow and Townes published their proposal for an optical maser in 1958 - that it would be impossible for a small academic laboratory, without previous expertise in optics, to compete successfully in the realization of lasers. This may have been a self-fulfilling prophesy, but it is a matter of record that nearly all types of lasers were first reduced to practice in industrial laboratories, predominantly in the U.S.A.