Excitation mechanism of additional signals of photon and electron spin echo

Edward A. Manykin, I. Ya. Polishyuk, Alexander L. Burin +1 more

Игорь Сергеевич Осадько

Abstract For more than 70 years spin and photon echo excited by micro- and nanosecond pulses have been the subject of research by various scientific groups. Bloch equations are the mathematical basis in these studies. However, Bloch equations cannot describe echo signals if excitation of the electron-vibrational system is realized by short femtosecond pulses. Only theory for density matrix, which is more general than the Bloch equation approach, is able to describe femtosecond relaxation of polarization and decay of femtosecond echo signals. This work gives an overview of the resent results obtained in developing such a general theoretical formalism.

L. Langer, S. V. Poltavtsev, I. A. Yugova +6 more

We report on magnetic field-induced oscillations of the photon echo signal from negatively charged excitons in a CdTe/(Cd,Mg)Te semiconductor quantum well. The oscillatory signal is due to Larmor precession of the electron spin about a transverse magnetic field and depends sensitively on the polarization configuration of the exciting and refocusing pulses. The echo amplitude can be fully tuned from the maximum down to zero depending on the time delay between the two pulses and the magnetic-field strength. The results are explained in terms of the optical Bloch equations accounting for the spin level structure of electrons and trions.

Cheng Li, Xiangyang Yu

William L. Wilson, Gerhard Wäckerle, M. D. Fayer

A theory is presented describing the proposed phonon perturbed photon echo experiment. This experiment is a combination of picosecond time scale stimulated Raman pumping and photon echo experiments. The theory demonstrates that the phonon perturbed photon echo can directly measure electronic excitation–phonon coupling matrix elements by observing the influence of a well defined coherent phonon wave on the photon echo signal. The theory predicts that the echo pulse area (integrated intensity) is reduced. The size of this change is related to the strength of the excitation phonon coupling. In addition, a realistic estimate is made of the size of the effect, and it is shown that the experiment is feasible with available laser equipment.

R. Boscaino, F. M. Gelardi