  The study of low density, ultracold atomic Fermi gases is a promising avenue
to understand fermion superfluidity from first principles. One technique
currently used to bring Fermi gases in the degenerate regime is sympathetic
cooling through a reservoir made of an ultracold Bose gas. We discuss a
proposal for trapping and cooling of two-species Fermi-Bose mixtures into
optical dipole traps made from combinations of laser beams having two different
wavelengths. In these bichromatic traps it is possible, by a proper choice of
the relative laser powers, to selectively trap the two species in such a way
that fermions experience a stronger confinement than bosons. As a consequence,
a deep Fermi degeneracy can be reached having at the same time a softer
degenerate regime for the Bose gas. This leads to an increase in the
sympathetic cooling efficiency and allows for higher precision thermometry of
the Fermi-Bose mixture.
