RESUMEN
An incident cw laser beam polarized along the y direction induces a four-wave mixing oscillation polarized along the x direction in a linear cavity containing a sodium cell. The interaction of the incident field with the standing wave induces the generation of a reflected field. Reflectivities of as much as 20% inside the cell and response times shorter than 100 ns have been observed.
RESUMEN
We have studied the four-wave-mixing oscillation obtained when a cell containing sodium and a buffer gas is enclosed in a ring cavity. The beat frequency Deltanu between the two counterrotating beams is shown to depend on the intensity difference (I(1) - I(2)) between the two pump beams. The curve giving Deltanu as a function of (I(1) - I(2)) is a gyrotype curve, which suggests some possible application for optical gyros.
RESUMEN
We investigate degenerate four-wave mixing on the 607.4-nm line of neon using crossed-polarized beams. We show that the line shape changes dramatically in the presence of a magnetic field. Narrow resonances are observed, which are interpreted as level-crossing resonances in the energy diagram of the dressed atom.
RESUMEN
We demonstrate the phenomenon of directed diffusion in a symmetric periodic potential. This has been realized with cold atoms in a one-dimensional dissipative optical lattice. The stochastic process of optical pumping leads to a diffusive dynamics of the atoms through the periodic structure, while a zero-mean force which breaks the temporal symmetry of the system is applied by phase modulating one of the lattice beams. The atoms are set into directed motion as a result of the breaking of the temporal symmetry of the system.
RESUMEN
We report a theory of amplified reflection in degenerate four-wave mixing that includes Gaussian distribution of intensity in the incoming beams and different intensities for the two pumping beams. In the Kerr limit, we obtain an analytical solution that may explain previous experimental observations.
RESUMEN
We report the first direct observation of Brillouin-like propagation modes in a dissipative periodic optical lattice. This has been done by observing a resonant behavior of the spatial diffusion coefficient in the direction corresponding to the propagation mode with the phase velocity of the moving intensity modulation used to excite these propagation modes. Furthermore, we show theoretically that the amplitude of the Brillouin mode is a nonmonotonic function of the strength of the noise corresponding to the optical pumping, and discuss this behavior in terms of nonconventional stochastic resonance.
RESUMEN
We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal, Phys. Rev. Lett. 78, 4709 (1997)]; C. Jurczak, Phys. Rev. Lett. 77, 1727 (1996)]], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance.
RESUMEN
We report the photometric observation of a polychromatic laser guide star (PLGS) using the AVLIS laser at the Lawrence Livermore National Laboratory (LLNL). The process aims at providing a measurement of the tilt of the incoming wave front at a telescope induced by atmospheric turbulence. It relies on the two-photon coherent excitation of the 4D5/2 energy level of sodium atoms in the mesosphere. We used two laser beams at 589 and 569 nm, with a maximum total average output power of approximately 350 W. For the purpose of photometric calibration, a natural star was observed simultaneously through the same instrument as the PLGS at the focus of the LLNL 50-cm telescope. Photometric measurements of the 330-nm return flux confirm our previous theoretical studies that the PLGS process should allow us at a later stage to correct for the tilt at wavelengths as short as approximately 1 microm at good astronomical sites. They show also that, at saturation of two-photon coherent absorption in the mesosphere, the backscattered flux increases by a factor of approximately 2 when the pulse repetition rate decreases by a factor of 3 at constant average power. This unexpected behavior is briefly discussed.