New Photon-Echo Phenomena in a Localized-Electron Phonon System

Valentin I. Prokhorenko, Rienk van Grondelle, R. J. Dwayne Miller

Masaki Aihara

It is predicted that a new type of photon echo appears in a strongly coupled localized-electron-phonon system with a broad homogeneous spectral width. These echoes arise because of the reversibility of the decay of the phonon wave packet, and their formation is independent of the inhomogeneous broadening of spectral line due to the spatial crystalline field inhomogeneity.

Masashi Ban, Toshihico Arimitsu

The localized electron-phonon model, which was proposed by Takagahara, Hanamura and Kubo (THK), is extended by including the change of frequency and is treated analytically to obtain the response function and the photon echo signal. Our treatment also gives an analytical expression for the integrand of the transient emission spectrum of the second order optical processes in a localized electron-phonon system which was treated by THK in terms of the eigenvalue problem of the relaxation operator.

V. A. Moskalenko, Xi-Fu Wang, Wang Zhi-Xing +1 more

James L. Skinner

We calculate the photon echo decay for a strongly coupled electron–phonon system, without making unrealistic assumptions about excitation pulse durations. We find that asymptotically, the photon echo decay is exponential, and we provide a formal expression for the decay rate 1/T2 which is independent of pulse duration. In contrast to the usual results, our expression for 1/T2 is nonperturbative in the electron–phonon interaction. We calculate the dependences of the echo amplitude on pulse power and duration, finding that the strong electron–phonon coupling modifies the simple two level system result. We also focus on the relationship between the zero phonon line shape in the homogeneous optical absorption spectrum, and the photon echo decay rate. We find that the zero phonon line shape is Lorentzian, with width 1/πT2. We show that the usual optical Bloch equation approach to analyzing time-domain experiments, which normally is only applicable if the electron–phonon coupling is weak, can be extended to the case of strong coupling. These strong coupling Bloch equations are adequate for analyzing the time dependence, but not the pulse power and duration dependences, of time-domain experiments. Our results indicate that within the Condon approximation, electron–phonon coupling cannot explain the very low temperature anomaly of recent photon echo experiments on impurities in molecular crystals.

Stephan W. Koch, Yiping Z. Hu, Rolf H. Binder