Arkadiusz Henryk Piekara (born 12.01.1904) is a Polish experimental physicist and a member of the Polish Academy of Sciences. He was born in Warsaw. He graduated from the University of Warsaw (1927). In 1928-39 he worked as a physics teacher at a secondary school in Rydzyna, in 1937 —46 at the University of Kraków, in 1946—52 he was professor at the Higher Technical School in Gdańsk, in 1952—65 professor and director of the Institute of Experimental Physics of the University of Poznań, and in 1965—74 professor at the University of Warsaw (in 1966 —67 also director of the Institute of Physics of the Polish Academy of Sciences).
His research was in solid-state physics, the physics of liquids, magnetism, spectroscopy, optics, quantum electronics and nonlinear optics. Together with S. Kielich he predicted (1958—59) induced birefringence and a change in the dielectric and magnetic permeabilities of a medium under the influence of powerful laser radiation. In 1966 — 68 he explained the effect of the self-collimation of light, and in 1971 —74 the increase in the refractive index of a medium under the action of a laser pulse.
State Prize of the Polish People's Republic (1955). The M. Smoluchowski Medal (1976).