Prof. Antonsen was a National Research Council postdoctoral fellow at the Naval Research Laboratory in 1976-1977, and a research scientist in the Research Laboratory of Electronics at MIT from 1977 to 1980. In 1980 he moved to the University of Maryland where he joined the faculty of the Departments of Electrical Engineering and Physics in 1984. He currently holds a joint academic appointment as Professor of Physics and Professor of Electrical Engineering; his research is in the Institute of Research for Electronics and Applied Physics. Prof. Antonsen has held visiting appointments at the Institute for Theoretical Physics (UCSB), the Ecole Polytechnique Federale de Lausanne, Switzerland, and the Institute de Physique Theorique, Ecole Polytechnique, Palaiseau, France. He was selected as a Fellow of the Division of Plasma Physics of the American Physical Society in 1986.
The theory of magnetically confined plasmas, the theory and design of high power sources of coherent radiation, nonlinear dynamics in fluids, and the theory of the interaction of intense laser pulses and plasmas.