  We theoretically investigate the spectrum of the fluorescence from triple
quantum-dot molecules and demonstrate that it is possible to use tunneling to
induce dark states. Unlike the atomic system, in quantum-dot molecules we can
use tunneling to create the dark states and control fluorescence emission,
requiring no coupling lasers. And interesting features such as quenching and
narrowing of the fluorescence can be obtained. We also explain the spectrum
with the transition properties of the dressed states generated by the coupling
of the laser and the two tunneling. The quenching of the fluorescence is due to
the tunneling induced dark states, while the narrowing of the central peak is
due to the slow decay rate of the dressed levels.
