Ultrafast, high-contrast, polarization-insensitive all-optical switch by using spin-polarization in low-temperature-grown MQWs

Summary form only given. Ultrafast all-optical switches will be of great importance to our future´s high-bit-rate optical communication systems. We have previously reported a surface-reflection type ultrafast all-optical switch with a response time of 250 fs. The device is basically a saturable absorber that relies on a carrier-induced change in the excitonic absorption of InGaAs/InAlAs MQWs. To achieve ultrafast operation MQWs were grown at a low-temperature of 200/spl deg/C and were doped with Be. Furthermore, large optical nonlinearity was achieved by introducing compressive strain into the MQWs, adopting reflection geometry and using a DBR with 1% reflectivity. We describe here successfully enhanced on/off ratios of the device by using spin polarization.