  In the optomechanical cooling of a dispersively coupled oscillator, it is
only possible to reach the oscillator ground state in the resolved sideband
regime, where the cavity-mode line width is smaller than the resonant frequency
of the mechanical oscillator being cooled. In this paper, we show that the
dispersively coupled system can be cooled to the ground state in the unresolved
sideband regime using an ancillary oscillator, which is coupled to the same
optical mode via dissipative interaction. The ancillary oscillator has a
resonant frequency close to that of the target oscillator; thus, the ancillary
oscillator is also in the unresolved sideband regime. We require only a single
blue-detuned laser mode to drive the cavity.
