  We report all-optical switching due to state-filling in quantum dots (QDs)
within a Mach-Zehnder Interferometric (MZI) switch. The MZI was fabricated
using InGaAsP/InP waveguides containing a single layer of InAs/InP QDs. A
1530-1570 nm probe beam is switched by optical excitation of one MZI-arm from
the top. By exciting below the InGaAsP bandgap, we prove that the refractive
index nonlinearity is only due to the QDs. The switching efficiency is 2
rad/(microW absorbed power). Probe wavelength insensitivity was obtained using
a broad distribution of QDs.
