Free induction decay with radiation damping I. General treatment

Emmanuel I. RASHBA

A theory of the free induction signal from biexcitons and bound excitons is presented. The simultaneous existence of the exciton continuum and a bound state is shown to result in a new type of time dependence of the free induction. The optically detected signal increases in time and oscillates with increasing amplitude until damped by radiative or dephasing processes. Radiative decay is anomalously fast and can result in strong picosecond pulses. The expanding area of a coherent exciton polarization (inflating antenna), produced by the exciting pulse, is the underlying physical mechanism. The developed formalism can be applied to different biexciton transients.

Masakazu Kunitomo, T. Endo, Shunsuke Nakanishi +1 more

Klaus Bratengeier, H.‐G. Purucker, A. Laubereau

Frank C. Spano, W. S. Warren

We numerically investigate optical dephasing from as many as 500 interacting two-level absorbers by making the semiclassical approximation on the radiation–matter interaction which includes retarded dipole–dipole coupling and superradiant coupling. We calculate the superradiant decay rate following single pulse optical excitation, the photon echo decay and the fluorescence. By carrying out an expansion to the second order in time we demonstrate a fundamental difference between the homogeneous free-induction decay and photon echo decay which is due to radiation damping. We show that an echo sequence is capable of reversing superradiant damping in some cases. Specific computations for pentacene doped mixed molecular crystals, where ‘‘domains’’ of resonant impurities are likely to exist, are presented and compared with experimental results.

Daniel Abergel, Alain Louis‐Joseph, Jean‐Yves Lallemand

In this paper, the dynamics of a magnetization undergoing a radiation-damping based feedback radio-frequency field is investigated both theoretically and experimentally. It is shown that due to the presence of T1 relaxation the evolution equations predict the existence of self-sustained maser pulses. This phenomenon is a consequence of the competition between two different processes, namely, T1 relaxation and a precession about a magnetization-dependent radio-frequency field. Experiments show the existence of periodic revivals of the free induction decay over unusually long periods of time, on the order of tens of seconds.

Juha Javanainen