Enhancement of coherent longitudinal optical phonon oscillations in a GaAs/AlAs multiple quantum well due to intersubband energy tuning under an electric field

摘要

We have demonstrated the generation of intense coherent longitudinal optical (LO) phonon oscillations with use of intersubband energy tuning by application of electric field. The coherent LO phonon in a GaAs/AlAs multiple quantum well was investigated in detail as a function of electric field by using a reflection-type pump-probe technique. In the case that the intersubband energy is tuned to the LO phonon energy of GaAs by the electric field owing to a quantum confined Stark effect, the amplitude of the coherent LO phonon is intensively enhanced by a factor of 23 in comparison with the amplitude in a low electric field regime. This enhancement is caused by the coupling between the coherent LO phonon and the longitudinal polarization due to the impulsive interference between excitons with different subbands.