Nicolaas Bloembergen

Nicolaas Bloembergen, a Dutch–American physicist, was born on March 11, 1920, in Dordrecht, Netherlands. His father worked as a chemical engineer and executive, and he was one of six siblings; his brother Auke became a legal scholar. Bloembergen began studying physics at Utrecht University in 1938, earning a C.Phil. in 1941 and a doctorandus in 1943. When German authorities closed the university during the occupation, he spent two years in hiding.

After World War II, in 1945, he left the Netherlands to pursue graduate studies at Harvard University under Edward Mills Purcell. Through Purcell, Bloembergen became part of an academic lineage that includes J. J. Thomson, Lord Rayleigh, Ernest Rutherford, Owen Richardson, and Purcell himself—all Nobel laureates. He was also influenced by John Van Vleck and Percy Bridgman. Six weeks before Bloembergen arrived, Purcell and his students Torrey and Pound had discovered nuclear magnetic resonance (NMR); Bloembergen was hired to build the first NMR machine. His NMR systems are precursors to modern MRI machines. This work sparked his interest in masers, introduced in 1953, which preceded lasers.

In 1947, Bloembergen returned to the Netherlands and submitted his doctoral thesis, *Nuclear Magnetic Relaxation*, at Leiden University. He had completed preliminary exams in the Netherlands, and Cornelis Jacobus Gorter offered him a postdoctoral position there. He received his Ph.D. in 1948 and stayed as a postdoc for about a year.

In 1949, Bloembergen returned to Harvard as a junior fellow of the Society of Fellows. He became an associate professor in 1951, Gordon McKay Professor of Applied Physics in 1957, Rumford Professor of Physics in 1974, and Gerhard Gade University Professor in 1980. He retired from Harvard in 1990. He also served as a visiting professor at the University of California, Berkeley (1964–1965), and later as a visiting scientist at the University of Arizona’s Optical Sciences Center (1996–1997), becoming a professor there in 2001. He was a board member of the *Bulletin of the Atomic Scientists* and honorary editor of the *Journal of Nonlinear Optical Physics & Materials*.

By 1960, Bloembergen was experimenting with microwave spectroscopy at Harvard. He modified Charles Townes’s maser and, in 1956, developed a crystal maser more powerful than the standard gaseous version. With the advent of the laser, he helped develop laser spectroscopy, which enables precise atomic observations. After second-harmonic generation was demonstrated in 1961, Bloembergen studied how high-intensity photon beams reveal new structures in matter—coining the term “nonlinear optics.” He reflected in a 1990 Dutch newspaper interview: “We took a standard textbook on optics and for each section we asked ourselves what would happen if the intensity was to become very high.” His theoretical work showed how to combine two or more laser beams in the visible range to produce a single laser beam with different frequencies in the infrared and ultraviolet, broadening the frequency band of laser spectroscopy.

Bloembergen shared the 1981 Nobel Prize in Physics with Arthur Schawlow and Kai Siegbahn for work that “has had a profound effect on our present knowledge of the constitution of matter” via laser spectroscopy. He was singled out for founding nonlinear optics by mixing laser beams to produce light of a different wavelength.

In 1948, Bloembergen met Huberta Deliana “Deli” Brink while on vacation with his university’s Physics Club. She traveled with him to the United States in 1949 on a student hospitality exchange; he proposed upon arrival, and they married in Amsterdam in 1950. They became naturalized U.S. citizens in 1958 and had three children. Bloembergen died on September 5, 2017, at an assisted living facility in Tucson, Arizona, from cardiorespiratory failure at age 97. His wife died on June 19, 2019.

A Dutch biography was published in 2016, and an English one in 2019. On March 11, 2020—what would have been his 100th birthday—a team at the University of New South Wales published a *Nature* article demonstrating a first-time success.