  We have developed an optical lattice clock that can operate in dual modes: a
strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation
of the Sr-Yb optical lattice clock is achieved by alternately cooling and
trapping $^{87}$Sr and $^{171}$Yb atoms inside the vacuum chamber of the clock.
Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical
configurations, respectively, resulting in a small distance of the order of 100
$\mu$m between the trapped Sr and Yb atoms. The $^{1}$S$_{0}$-$^{3}$P$_{0}$
clock transitions in the trapped atoms were interrogated in turn and the clock
lasers were stabilized to the transitions. We demonstrated the frequency ratio
measurement of the Sr and Yb clock transitions by using the dual-mode operation
of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the
uncertainty of the blackbody radiation shift in the frequency ratio
measurement, because both Sr and Yb atoms share the same blackbody radiation.
