Ultrafast Intersubband Relaxation Dynamics And Coherent Nonlinearity In Gan/Ain Multiple Quantum Wells

We have investigated the ultrafast coherent dynamics of the intersubband transition in GaN/AlN multiple quantum wells, using a spectral resolved two-color pump-probe technique. We have found a significant spectrum change as a function of the delaytime tau. For negative delaytimes corresponding to tau < 0, coherent spectrum oscillations have been observed. At tau similar to 0, asymmetric dispersion has been observed. For positive delaytimes, tau > 0, no measurable spectrum change has been observed. From the analysis of these results, we have estimated that intersubband transitions dephasing time is more than 100 fs measured at room temperature.