large enhancement of optical nonlinearity using quantum dots embedded in a photonic crystal structure for all-optical switch applications

摘要

All-optical switches using optical nonlinear (ONL) materials, promising for future OThM/WDM 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 without limitation of the lifetime of the ONL materials. Therefore, the operation power of the SMz switches can be reduced without any response delay when using the materials with larger optical nonlinearity than ever, resulting in simultaneous achievement of the above requirements. For the purpose, we have proposed the use of the saturation absorption of quantum dot (QD) embedded in photonic crystal (PC)-waveguide (WG) as an origin of large optical nonlinearity. In this paper, the design of the operation-power reduction of the SMZ-switch is revealed under a realistic operation condition, based on the measured saturation intensity (Is) in an InAs QD and simple assumptions of power enhancement effect in a PC-WG.