Feasibility Study on Ultrafast Nonlinear Optical Properties of 1.55-µ m Intersubband Transition in AlGaN/GaN Quantum Wells

The feasibility of the intersubband transition (ISBT) in Al(Ga)N/GaN quantum wells (QWs) as a device mechanism for ultrafast optical switches is theoretically investigated. The 1.55-µ m ISBT is shown to be feasible because of its large conduction band discontinuity. The intersubband relaxation time at 1.55-µ m is estimated to be 80 fs, which is about 30 times shorter than that in InGaAs QWs. The third order nonlinear susceptibility is estimated to be 1.6×10-15 m2 V-2 for N=1×1018 cm-3. These characteristics suggest that the ISBT in nitride QWs is a promising mechanism for multi-terabit/s optical switches.