Non-Markoffian effects in the laser

Tomohei Sasada

The non-Markoffian effect on superradiance from an assembly of many harmonic oscillators is investigated based on a theory recently developed by Bonifacio, Schwendimann, and Haake. A superradiance master equation is solved exactly by introducing the coherent state basis. It is show how the retardation effect, which takes into account a dynamical role of the photon field played during the radiating processes, modifies the shape and Poissonian statistics of superradiant pulses obtained from the Markoffian approach.

Alfred M. Levine, Abraham G. Kofman, Reuven Zaibel +1 more

Stig Stenholm

Yuichi Fujimura, Tomoya Akiyama, Takashi Y. Nakajima +2 more

We develop a theory of quantum beats in molecular fluorescence taking into account collision effects (such as pure dephasing due to elastic collision) without invoking the Markoff approximation. Model calculations of the time dependent fluorescence from molecules with two excited levels are performed in order to see how the non-Markoffian character in the collision process exerts influence upon the quantum beat pattern. It is suggested that if the pure dephasing between the excited states is a Markoffian ‘‘the degree of modulation of the beats’’ decreases exponentially with time; if it is in the static limit the degree of modulation of the beats decreases as a Gaussian function (the non-Markoffian behavior in the quantum beats). A given case can be classified as either Markoffian or non-Markoffian, depending on the relative magnitudes of the collision duration time τc, the beat frequency ω, and the coupling strength v which is characteristic of the pure dephasing process. The Markoff approximation holds only if the condition ω<v<1/τc is satisfied; the non-Markoffian behavior appears in the quantum beat pattern when ω>v, even if v2τ2c<1 .

A. P. Kazantsev, Gregory I. Surdutovich

Subir K. Bose, David T. Ng

Non-Markoffian effects in the Josephson-radiation linewidth are investigated by using the projection-operator formalism of Mori. The memory function as well as the frequency are calculated in perturbation theory. We develop formal expressions for these to order ${\ensuremath{\lambda}}^{4}$, $\ensuremath{\lambda}$ being a perturbation parameter, and discuss the simpler results valid to order ${\ensuremath{\lambda}}^{2}$.