  We report on a generic cooling technique for atoms trapped in optical
lattices. It consists in modulating the lattice depth with a proper frequency
sweeping. This filtering technique removes the most energetic atoms, and
provides with the onset of thermalization a cooling mechanism reminiscent of
evaporative cooling. However, the selection is here performed in quasi-momentum
space rather than in position space. Interband selection rules are used to
protect the population with a zero quasi-momentum, namely the Bose Einstein
condensate. Direct condensation of thermal atoms in an optical lattice is also
achieved with this technique. It offers an interesting complementary cooling
mechanism for quantum simulations performed with quantum gases trapped in
optical lattices.
