Title: Advanced quantum dot and photonic crystal technologies for integrated nano-photonic circuit

By: Prof. Kiyoshi Asakawa(National Institute of Materials Science (NIMS) & University of Tsukuba, Tsukuba, Japan)

Date: May 29, 2008

Abstract:

    Two kinds of nano-photonic technologies, i.e., GaAs-based two dimensional photonic crystal (2DPC) slab waveguides (WGs) and InAs-based quantum dots (QDs) were developed for key photonic device structures in the future advanced telecommunication systems. For an ultra-fast digital photonic network, an ultra-small and ultra-fast symmetrical Mach–Zehnder (SMZ)-type all-optical switch (PC-SMZ) has been developed in the first stage. In the second stage, the PC-SMZ is now evolving into a new functional key device, i.e., an ultra-fast all-optical flip-flop (PC-FF) device that is essential for the digital photonic network. Through the two stages, two important techniques were developed so far. One is a new simulation method, i.e., topology optimization method of 2DPC WGs with wide/flat bandwidth, high transmittance and low reflectivity. Another is a new selective-area-growth method, i.e., metal-mask MBE method of InAs QDs. This technique contributes to achieving high-density and highly uniform InAs QDs in a desired area such as an optical nonlinearity-induced phase shift arm in the PC-FF. For a quantum information system, a single photon qubit composed of a QD ensemble, or desirably single QD, embedded in a PC-based high-Q cavity has been studied as an application of the PC/QD-combined nano-photonics. Purcell effect specific to the photon-localized system has been observed so far. As a unique site-controlled QD technique, a nano-jet probe (NJP) method has also been developed for positioning a single QD at the centre of the PC high-Q cavity. All these results will pave the way for implementation of innovative photonic devices in the advanced ultra-fast photonic network system.