Oscilações de Rabi em redes ópticas não lineares.

Abstract

Abstract An optical lattice is a periodic array produced by the superposition of two or more counter-propagating laser beams which interfere and create a spatial periodic intensity pattern. An important difference between a solid state crystalline lattice and an optically induced lattice is that the latter have a longer coherence time which permits the observation of coherent phenomenon such as Bloch oscillations. Recently, an interesting effect has been reported in the literature, which is the analogue of Rabi oscillations in two level systems driven by an external optical field: an optical beam composed by pair of frequencies, resonants with the high symmetry points of the Brillouin zone, propagating through an optical lattice exhibits oscillations of the Fourier ways between the frequencies due to the coupling with the lattice. Therefore, in the optical case the field plays the role of the matter, while the lattice plays the role of the driving field which couples the frequencies. Based in this result, the objective of this paper is to investigate the influence of self-defocusing in the optical Rabi oscillation. We have shown, through numerical calculation of the wave nonlinear equation, that in the self-defocusing optical lattice, these oscillations go disappearingare. The result of the disappearance of the oscillations of Fourier can be understood considering that self-defocusing promotes an addition of phases in the ways that were resonant - kB and kB, in different way, form that the basic difference between kB and - kB will not be plus a vector of the reciprocal net, and as consequence the oscillations of optic Rabi disappear, therefore the coupling with the net requires this condition in the resonant frequencies.