  A frequency-stabilized light source emitting at 556 nm is realized by
frequency-doubling a 1112-nm laser, which is phase-locked to a fiber-based
optical frequency comb. The 1112-nm laser is either an ytterbium (Yb)-doped
distributed feedback fiber laser or a master-slave laser system that uses an
external cavity diode laser as a master laser. We have achieved the continuous
frequency stabilization of the light source over a five-day period. With the
light source, we have completed the second-stage magneto-optical trapping (MOT)
of Yb atoms using the 1S0 - 3P1 intercombination transition. The temperature of
the ultracold atoms in the MOT was 40 uK when measured using the time-of-flight
method, and this is sufficient for loading the atoms into an optical lattice.
The fiber-based frequency comb is shown to be a useful tool for controlling the
laser frequency in cold-atom experiments.
