Quantum beats in excitons in Cu2O

A theoretical study is carried out of quantum beats (QB) in the time-dependent intensities of absorption of a test pulse and of spontaneous luminescence in a Cu2O crystal under conditions of double optical resonance. It is assumed that pumping is effected by a CO2-laser pulse which dynamically couples the exciton levels Is(Gamma(5)(+)) and 2p(Gamma(4)(-),Gamma(5)(-), Gamma(3)(-)Gamma(2)(-)) and splits them into two or three pairs of quasi-energy levels. The frequency of the test pulse is in resonance with the frequency Gamma(5)(+) Of the exciton. The corresponding intensities for various directions of the electric vector of the pump field E-L, the polarization vector xi and the wave vector q of the test pulse are obtained. The frequency of the quantum beats is twice the Rabi frequency, which for different values of E-L, xi and q contains different sets of matrix elements of the dipole transitions between the levels Is(Gamma(5)(+)) and 2p(Gamma(4)(-),Gamma(5)(-),Gamma(3)(-)Gamma(2)(-)) Thus, by measuring the period of the quantum beats it is possible to determine the unknown matrix elements of the indicated transitions. (C) 1997 American Institute of Physics.