Theory of photon echoes in dressed atoms

Youhong Huang, Fucheng Lin

Li Yongfang

Using the method of the Bloch vectors,the physics mechanism of the photon echo is analyzed with both the dressed state and quantum interference theory,and the physics picture for the interaction between light and atoms is given in detail.The dynamic process for the quantum information storage and that of the recall with the photon echo is discussed under adiabatic condition.The results show that the photon information is stored in the medium during the first pulse,and when v and w of the Bloch vectors are inversed during the second pulse,the information reappears as the photon echo.The process of the photon echo is virtually the process of photon information storage and recall.

In F

There are two side-bands in addition to the central fluorescence from dressed atoms in a strong pump field. When two fairly intense pulses at one of the two sideband frequencies are applied to the dressed atoms at time t and t + T, with pulse areas of π/2 and π respectively, an echo is emitted at time T after the second pulse. It is discovered that in addition to the echo with frequency of the applied pulse, there exists another echo at the other frequency of the two side-bands.

Yea-Hwang Uang

Kauzya Okamura

Ruwang Sung, P. R. Berman

The interaction between an intense radiation field and atoms that undergo collisions in an atomic vapor is studied. With the assumption that velocity-changing collisions are state independent and weak, we obtain an analytic expression for the time-dependent density-matrix elements by solving a quantum-mechanical transport equation using a dressed-state approach. Our analytical calculation is used to predict the form of the signal in an extended-pulse photon echo. The results show good agreement with an experiment carried out by Yodh et al. [Phys. Rev. Lett. 53, 659 (1984)]. It is found that the decay rate of the echo signal decreases rapidly with increasing duration of the second pulse in the pulse excitation sequence. A comparison between theory and experiment is presented and a physical interpretation of the results is given.