Saturation intensity in InAs quantum dot and its application to all-optical switches

All-optical switches using optical nonlinear (ONL) materials, promising for future OTDM systems, require both ultrafast and low optical-power operations. Symmetric-Mach-Zehnder (SMZ)-type all-optical switches are very attractive because they can operate in ultrafast response time of minimum 200 fs without limitation of the lifetime of the ONL materials composing the SMZ-interference waveguides. Therefore, the operation power of the SMZ switches can be reduced without any response delay by using the materials with larger optical nonlinearity than ever, resulting in simultaneous achievement of the above requirements. Quantum dots (QDs) are promising candidates for large ONL materials due to their delta-function-like densities of states. However, the optical nonlinearity, especially the saturation intensity, of self-assembled QDs has been hardly reported so far. In this paper, we measured the saturation intensity in self-assembled QD and estimated the reduction of SMZ-switch operation-power