خانه :: اساتید :: اخبار

بازدید:21966   بروزرسانی: 13-11-1397

Mohammad Mahmoudi

علایق پژوهشی

1-Interaction of Intense Laser Field with Free Charged Particle

We  are studying  the quantum behaviour of  free charged particle in intens laser field with Prof. Ch. H. Keitel in  Max-Planck Insititute for Nuclear Physics, Heidelberg, Germany and  Prof. Yousef I Salamin in Pysics Department of American University of Sharjah.
Quantum signatures of a free electron in interaction with a continuous wave radiation field are investigated by looking for negativies in the Wigner function of the system. The electron wave function in the radiation field is calculated fully analytically by solving the appropriate Scrodinger equation in the Krammers-Henneberger frame. It is found that pronounced quantum signatures show up already for a laser peak field of magnitude     to  and a frequency   However, the nonclassical behavior gets lost if interaction with the radiation field is taken in the dipole approximation.

2-Coherent Control of the group velocity of light in dispersive mediums.

We investigate the phase dependence of group velocity in three-level Λ type atomic medium. We show that the slope of dispersion can change from positive to negative just by the changing of relative phase between coupling and probe fields. The effect of spontaneously generated coherence (SGC) on the controlling of light propagation is also investigated. We show that in the presence of SGC, the group velocity of probe field is phase dependent, while in the absence of this coherence the phase dependence of group velocity will cancel. Moreover, we show that using lower-level coupling field makes the system phase sensitive.
We studies the effects of incoherent pump field and Spontaneously Generation Coherence (SGC) on the phase control of dispersion and absorption spectra of a weak probe field. The effect of relative phase between probe and coupling fields on the group velocity is then discussed. It is shown that the phase dependence of group velocity, not only depends on the existence of SGC, but also it depends on the existence of the incoherent pump field. We show that for the weak probe field, and in the presence of SGC, the existence of incoherent pump field is necessary condition to phase control of dispersion, absorption, and group index

3-Coherent Population Trapping in open multi level quantum systems

At the phenomenon of the CPT , particles (atoms molecules and ions) are not excited by light from long lived energy quantum levels (ground or metastable levels) to the upper level under the condition of optical resonance. This phenomena is caused by the presence of special superposition of quantum states, that don’t interact with radiation in such multilevel system. CPT can be used in ultra-high resolution spectroscopy, laser frequency stabilization, cooling of atom, laser without inversion and other important field of physics.