ABSTRACT
Energy relaxation time of short wavelength (~ 2.5 μm) intersubband transition (ISB-T) in n-doped InGaAs / AlAs quantum wells is directly observed for the first time. Pump & probe measurements with a time resolution of ~ 100 fs are performed at room temperature to investigate the recovery time of the induced ISB absorption saturation. The intersubband energy relaxation time in 2.5 μm ISB-T is shown to be 2.7~3.5 ps. Theoretical analysis reveals that not only intersubband longitudinal optical phonon scattering but also intrasubband energy relaxation has an important role in the carrier relaxation process in the short wavelength ISB-T.
