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M. Sahrai Research Institute for Applied Physics, The University of Tabriz, Tabriz, Iran

The effect of the spontaneously generated coherence on the dynamical behaviors of the dispersion and the absorption. M. Sahrai Research Institute for Applied Physics, The University of Tabriz, Tabriz, Iran e-mail: sahrai@tabrizu.ac.ir. Outlines. The effect of SGC EIT

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M. Sahrai Research Institute for Applied Physics, The University of Tabriz, Tabriz, Iran

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  1. The effect of the spontaneously generated coherence on the dynamical behaviors of the dispersion and the absorption M. Sahrai Research Institute for Applied Physics, The University of Tabriz, Tabriz, Iran e-mail: sahrai@tabrizu.ac.ir

  2. Outlines • The effect of SGC • EIT • Subluminal and superluminal light propagation • Model and equations • Results • Conclusion

  3. Spontaneously Generated Coherence (SGC)

  4. Kocharovskaya (1988) S. E. Hariss (1989). (Sr Atom) Bare State Dressed State Electomagnetically induced transparency (EIT)

  5. Harris experiment (Na) Transmission Refractive Index 60MHZ Subluminal

  6. In the experiment of L. J. Wang (2000, Atom Na) Supeluminal

  7. and and For the absorptive medium, The dispersion is normal and so For the gain medium, The dispersion is anomalous and so From the Lorentz model

  8. G. S. Agarwal, T. Nath dey, S. Menon, Phys. Rev. A 64, 053809(2001) Switching from subluminal for superluminal light propagation

  9. 1) M. Sahrai, H. Tajalli, K. T Kapale, and M. S. Zubairy, Phys. Rev. A, 70, 023813 (2004) 2) M. Sahrai, H. Tajalli, J. Opt. B Quantum semiclassical Opt. 7, 168 (2005) 3) M. Sahrai, M. Mahmoudi, and R. Kheradmand, Doi: 10.1016/ J. Phys. Lett. A, 2007. 03. 014

  10. Direct pumping Indirect Pumping M. Mahmoudi, M. Sahrai, and H. Tajalli,, Physics Letter A, 357, 66 ( 2006).

  11. M. Mahmoudi, M. Sahrai, H. Tajalli, J Phys B: At. Mol. Opt. Phys. 39, 1825 (2006). The Model and Equations

  12. .

  13. Steady State behavior

  14. For the realistic example, we consider the sodium transition, The transition rate, dipole moment and atom density are The probe field with is applied to the The coupling field is applied tothe leading to .

  15. Comparing of the numerical (solid) and analytical (dashed) results: Real (a) and imaginary (b) parts of susceptibility as a function of probe field detuning, c) group index as a function of probe field detuning.

  16. Dynamical behavior

  17. Conclusion 1) The transient optical process in a three-level Lamda medium has been investigated when driving field is switched on. It is shown that the absorption and the dispersion properties of the medium not only depend on the Rabi-frequency of the driving field, but they depend on the relative phase between applied fields as well. 2) We show that when only SGC is introduced, the medium does not phase dependent, but in the presence of SGC and incoherent pumping field the medium exactly is phase dependent. 3) Therefore, the slope of dispersion can change from positive to negative just by the change of relative phase between applied fields. This is an important technique to control the propagation of the light pulse from subluminal to superluminal. 4) In fine, EIT three-level medium can be used as an optical switch in which the propagation of a light pulse can be controlled with another pulse. It is interesting to use the optical switch for quantum computation and quantum communication.

  18. Tabriz Thanksfor your attention

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