Petr Petrovich Feofilov (13.04.1915 —24.04.1980) was a Soviet physicist and a corresponding member of the USSR Academy of Sciences (1964). He was born in Solvychegodsk. He graduated from the Leningrad Polytechnic Institute (1939). From 1939 he worked at the State Optical Institute.
His work was in the field of physical optics, the spectroscopy of the condensed state and quantum electronics. He studied the luminescence of solutions of complex organic compounds and of crystals. He established the connection between the degree of polarisation of luminescence and the symmetry of the structure of the luminescing molecules, and developed the method, proposed by S. I. Vavilov, of determining the multipole character of elementary emitters. He was the first to detect polarised luminescence of cubic crystals. He developed a method of studying fast processes (USSR State Prize, 1949). He created a new scientific direction — the polarised luminescence of molecules and crystals.
He carried out a series of studies of the properties of artificial single crystals, in particular of single crystals activated by ions with unfilled shells. He obtained and studied many new activated crystalline systems of interest for quantum electronics. He detected the phenomenon of giant spin memory in some crystals with rare-earth activators, the photo-transfer of an electron between activator ions, and the phenomenon of cooperative sensitised luminescence. He developed a new direction in the spectroscopy of crystals — the study of cooperative effects. He constructed a theory and created the foundations of a number of methods of studying the latent anisotropy of crystals. For a series of works on the creation of new optical methods of studying complex impurity centres and defects in crystals he was awarded the USSR State Prize in 1975.
Chief editor of the journal “Optics and Spectroscopy” (from 1977). The S. I. Vavilov Gold Medal (1970).