Nicolaas Bloembergen (born 11.03.1920) is an American physicist and a member of the National Academy of Sciences (1960). He was born in Dordrecht (Netherlands). He graduated from the University of Utrecht (1943). In 1947—49 he worked at the University of Leiden. Since 1949 he has worked at Harvard University (professor from 1957).
His research was in the field of nuclear magnetic and electron paramagnetic resonance, quantum electronics, non-linear optics and laser spectroscopy. In 1956 he proposed using the three-level method to create radio-frequency quantum amplifiers based on paramagnetic crystals (paramagnetic masers), and he gave a design for a continuous-wave solid-state maser. He recommended single crystals of gadolinium ethyl sulfate as the working substance of a maser (the maser he proposed was built in 1957).
In 1948, together with E. Purcell and R. Pound, he introduced the concept of a spin temperature higher than the lattice temperature, and with the same colleagues he laid the foundations of the microscopic theory of relaxation in liquids. In 1949 he introduced the idea of spin diffusion.
Independently of J. Weber he developed quantum counters (1959). He proposed using a zero-field maser as a frequency standard (1960). With P. Pershan, and independently of N. Kroll and R. V. Khokhlov, he worked out the optics of non-linear media (1962) and discovered a number of the laws of non-linear optics. In 1962 he developed the theory of the non-linear interaction of four light waves (in particular the theory of third-harmonic generation) and the theory of stimulated Raman scattering. He observed experimentally the second harmonic of a ruby laser on reflection from a semiconductor crystal of gallium arsenide (1963), stimulated Raman scattering in a field of picosecond light pulses, and stimulated concentration scattering (1970). Independently of A. Pavlov he detected narrow two-photon resonances (1974), and so originated the method of Doppler-free two-photon spectroscopy. He studied the multiphoton dissociation of molecules in a strong infrared field. In 1981 he was awarded the Nobel Prize for his contribution to the development of laser spectroscopy.
The National Medal of Science (1974) and others.