  We propose an all-optical switch constructed from a two-mode optical
resonator containing a strongly coupled, three-state system. The coupling
allows a weak, continuous wave laser drive to incoherently control the
transmission of a much stronger, continuous wave signal laser into (and
through) the resonator. We demonstrate that in this simple setup the presence
of a control drive with one tenth the power of the signal drive can induce near
complete reflection of the signal, while its absence allows for near complete
transmission. The switch can also be operated as a set-reset relay with two
control inputs that efficiently drive the switch into either the reflecting or
the transmitting state.
