All-optical switching in a quantum dot switch

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. By exciting below the InGaAsP bandgap, we prove that the refractive index nonlinearity is entirely due to the QDs. The switching efficiency is 5 rad/(µW absorbed power). Probe wavelength insensitivity was obtained using a broad size distribution of QDs