“…In particular, a semiconductor optical amplifier (SOA) is a very attractive and promising nonlinear element, and a large number of all-optical logic gate devices using SOAs have been reported [3][4][5]. So far, we have investigated the optical logic gate device integrated with an SOA and ring resonators [6,7], in which the SOA utilized a highly-stacked quantum dot (QD) structure, and we analytically indicated the potential of the device for ultra highspeed all-optical logic gate operation at 160 Gb/s [8][9].…”