Nicolaas Bloembergen in 1995. (Harvard University)

Nicolaas Bloembergen, a Dutch-born American scientist who ate tulip bulbs to survive during World War II and went on to win the Nobel Prize in physics, died Sept. 5 at a retirement community in Tucson. He was 97.

His son, Brink Bloembergen, who confirmed the death, said the cause was cardiorespiratory failure.

Over a much-honored career that included 40 years on the faculty of Harvard University, Dr. Bloembergen became a pioneer and major contributor in three significant areas of physics, all of which have significant applications in daily life.

He was one of the pioneers in the development of nuclear magnetic resonance (NMR) techniques, which have become invaluable to modern medicine for creating images of the tissues of the body.

A paper published by Dr. Bloembergen and co-authors on the subject of NMR was said for many years to be one of the most quoted articles in the physics literature. Published in the Physical Review, it was by Dr. Bloembergen, Edward M. Purcell and Robert V. Pound and relied heavily on Dr. Bloembergen’s doctoral thesis.

In physicists’ shorthand the paper was known as “BPP.”

Dr. Bloembergen was also recognized for making important advances in the development of the maser, a device similar to the laser but that amplifies microwaves rather than light waves.

He was one of three physicists awarded the Nobel Prize in 1981, along with Kai M. Siegbahn of Sweden and Arthur L. Schawlow of the United States. The Swedish Academy cited Dr. Bloembergen for his work in nonlinear optics. Of all his accomplishments, it appeared that Dr. Bloembergen was proudest of his pioneering work in nonlinear optics. The field has important applications in modern optical communications, among other areas.

Dr. Bloembergen, who once described physics as the science that explains “the how and why of things,” can be seen as part of a generation of scientists trained in Europe before World War II who later came to the United States. Many arrived before the war. Their contributions helped put the United States at the forefront of scientific discovery.

Nicolaas Bloembergen was born March 11, 1920, in Dordrecht, the Netherlands. His father was a chemical engineer and executive. His maternal grandfather was a high school principal with a doctorate in mathematical physics.

Dr. Bloembergen began to concentrate on physics not because he found it easy but because he considered it “the most and difficult and challenging subject.”

He enrolled at the University of Utrecht in 1938 and obtained the equivalent of a bachelor’s degree (in 1941) and master’s degree (in 1943) before the Nazis shut down the institution. He later went into hiding and endured such privation that he recalled the winter of 1944 as the “hunger winter.”

Concealed from the Nazis, with food almost impossible to find, he ate tulip bulbs. They required long preparation and provided little nourishment, he recalled. But they staved off the worst hunger pangs by filling his stomach.

After the defeat of the Nazis in 1945, Dr. Bloembergen was accepted into graduate school at Harvard, where he worked on NMR under Purcell, one of his two co-authors on the often-cited 1948 Physical Review paper, and a 1952 Nobel laureate.

Certain laboratory techniques, he said, he found difficult to master. But he once wrote, “I found that many abilities can be acquired by perseverance.”

Dr. Bloembergen received his PhD in physics at the University of Leiden in his home country in 1948. This was said to have come about because he had completed preliminary qualifications there. The next year, he returned to Harvard, where he remained on the faculty until retiring in 1990.

He was said to have never missed a class in his four decades on the faculty at Harvard, where he was known for his kindness towards students. He became a naturalized U.S. citizen in 1958.

In later years, he joined the faculty of the University of Arizona.

Survivors include his wife of 67 years, the former Huberta Deliana Brink of Tucson; and three children.

The title of Dr. Bloembergen’s PhD thesis was “Nuclear Magnetic Relaxation.” In this context, relaxation refers to a change in the energy state of a magnetic system composed of the spins of atomic nuclei. The spins of electrically charged particles, such as protons in the nucleus, create circulating electric currents, permitting individual nuclei to be treated as subatomic magnets.

In the process of relaxation, these nuclear magnets, which line up with or against a fixed magnetic field return to their original positions. In NMR spins that have lined up in one direction may flip to the opposite direction in response to an oscillating electromagnetic field.

The frequency at which the nuclei respond is the resonant frequency. It can be used to find out about atoms, molecules and the substances they compose and the environments in which they exist.

Edward Purcell was one of the first to demonstrate NMR in certain materials, and at Harvard, Dr. Bloembergen became his first graduate student. “It was my good fortune to arrive at the right time at the right place,” Dr. Bloembergen later said of coming to Harvard. .

Following his NMR work, Dr. Bloembergen devoted his attention to the amplification of microwave energy and the device for producing this effect, the maser. The word is the acronym for microwave amplification by stimulated emission of radiation.

The device was a forerunner of the better-known and more widely used laser, in which the L stands for light.

With the ability to create extremely intense light beams, it was possible to open up the barely known areas of nonlinear optics and nonlinear spectroscopy.

In nonlinear processes, the consistent correspondence between signal and response breaks down. An increase in the intensity of one no longer creates an equivalent increase in the other. One of Dr. Bloembergen’s major contributions was enabling these nonlinear effects to be understood.

If for any of his scientific accomplishments, his son said, he wanted to be remembered as the father of nonlinear optics.

Despite the seriousness with which he approached his work, Dr. Bloembergen was not without wit and humor. After his retirement at Harvard, he was made professor emeritus. He described his change in status this way: “A professor can do as he pleases, but a professor emeritus can do as he damn well pleases.”