Fast phase-modulated optical lattice for wave packet engineering
We investigate experimentally a Bose Einstein condensate placed in a 1D optical lattice whose phase is modulated at a frequency large compared to all characteristic frequencies. As a result, the depth of the periodic potential is renormalized by a Bessel function which only depends on the amplitude of modulation, a prediction that we have checked quantitatively using a careful calibration scheme. This renormalization provides an interesting tool to engineer in time optical lattices. For instance, we have used it to perform simultaneously a sudden $\pi$-phase shift (without phase residual errors) combined with a change of lattice depth, and to study the subsequent out-of-equilibrium dynamics.