Bloembergen , Nicolaas

(1920–) Dutch–American physicist

Bloembergen was born in Dordrecht in the Netherlands and was educated at the universities of Utrecht and Leiden, where he obtained his PhD in 1948. He moved to America soon afterward, joined the Harvard staff in 1949, and served from 1957 as Gordon McKay Professor of Applied Physics; from 1974 to 1980 he was also Rumford Professor of Physics. He became Gerhard Gade university professor in 1980, a post he held until his retirement in 1990.

In the mid 1950s Bloembergen introduced a simple yet effective modification to the design of the maser. First built by Charles Townes in 1953, the early maser could only work intermittently: once the electrons in the higher energy level had been stimulated they would fall down to the lower energy level and nothing further could happen until they had been raised to the higher level once more. Bloembergen developed the three-level and multilevel masers, which were also worked on by Nikolai Basovand Aleksandr Prokhorov in the Soviet Union. In the three-level maser, electrons are pumped to the highest level and stimulated. They consequently emit microwave radiation and fall down to the middle level where they can once more be stimulated and emit energy of a lower frequency. At the same time more electrons are being pumped from the lowest to the highest level making the process continuous. Bloembergen has worked extensively on nonlinear optics – i.e. on effects produced by high intensities of radiation. He has particularly investigated the use of lasers to excite or break particular bonds in a chemical reaction. For his work he shared the 1981 Nobel Prize for physics with Arthur Schawlow (and Kai Siegbahn).

Bloembergen wrote Nuclear Magnetic Relaxations (1948) and Nonlinear Optics (1965).