Boris Ivanovich Stepanov ( born 28.04.1913) is a Soviet physicist and an academician of the Academy of Sciences of the Byelorussian SSR (1953). He was born in Leningrad. He graduated from Leningrad University (1936). In 1936 —53 he was at the State Optical Institute (head of a laboratory from 1951), and from 1953 at the Institute of Physics of the Academy of Sciences of the Byelorussian SSR (director from 1957), where he is also head of a department, and professor at Byelorussian University.
His research concerned spectroscopy, luminescence and quantum electronics. He developed the theory of anomalies in the electronic-vibrational-rotational spectra of diatomic molecules (1939), the theory of vibrational spectra of polyatomic molecules (1948), and the quantum-mechanical theory of the luminescence of complex molecules (1955). In 1957 he formulated the universal relation between the absorption and emission spectra of complex molecules (the Stepanov relation). He developed the foundations of the spectroscopy of negative light fluxes (1959) and simple probabilistic methods of calculating the optical properties of laser systems (1964). Together with A. N. Rubinov and V. A. Mostovnikov he discovered a new class of lasing compounds — organic dyes (1964), and together with A. S. Rubanov and E. V. Ivakin the phenomenon of wavefront reversal in four-wave interaction (1970). His research also concerned non-linear optics, laser spectroscopy, optical holography and the history of optics.
Hero of Socialist Labour (1973). USSR State Prizes (1950, 1972, 1982). State Prize of the Byelorussian SSR (1974). S. I. Vavilov Gold Medal (1967). Honoured Worker of Science of the Byelorussian SSR (1967).