ABSOLUTE AND CONVECTIVE SUPERRADIANCE - DYNAMICS AND MACROSCOPIC QUANTUM FLUCTUATIONS

Classical and quantum dynamics of superradiance in macroscopic samples of active media is discussed. Along with the usual convective instabi lity, the absolute instability is analyzed as the basis of the superra diance phenomenon. Various regimes of superradiance in a conducting in verted two-level medium immersed in the plasma under and out of the co ndition of plasma-dipole resonance are described and compared. It is s hown that the absolute instability of long-wavelength high-frequency p olarization waves results in the pulsed generation of strong nonradiat ing electric fields. The remarkable phenomenon of macroscopic manifest ation of quantum fluctuations in the observable parameters of superrad iance is described. A general method of the quantization of unstable n ormal modes in the systems of coupled partial modes with opposite-sign energies is developed. Delay-time statistics of the superradiance pul se is examined in detail. New experiments for the observation of the o utlined effects in the nonequilibrium activated semiconductors and par tially ionized gases, e.g., in impulsive discharge, in the infrared ra nge are proposed and appropriate estimates are provided.