Matter in ultrastrong laser fields

An analysis is made of the physical principles of stimulated emission of laser pulses with extremely high power (up to 10¹⁵ W) and of very short duration (less than 1 ps). Relationships governing the interaction of such pulses with matter are discussed. It is shown that the phenomena that occur on exposure of transparent media and condensed targets to high-power ultrashort laser pulses are different in kind. Qualitatively new physical effects, whose appearance is related to nonlinear (including relativistic) effects in the laser-beam electric field are given special attention. The results of recent experiments and studies planned for the future are considered in conjunction with a theoretical analysis.