Effects of pumping on propagation velocities of confined exciton polaritons in GaAs/Al_xGa_(1-x)As double heterostructure thin films under resonant and non-resonant probe conditions

摘要

We report the effects of excitation of exciton polaritons on their propagation in GaAs (110nm)/ Alo.3Gao.7As double heterostructure thin films by measuring the cross-correlation signal, which was recorded as the intensity of the second harmonic light generated by the gate pulse and the probe pulse reflected from the sample. When the probe energy is tuned at the lowest exciton energy, the signal profile changes due to the appearance of nonlinear dispersion. On the other hand, the signal profile shows a complicated change under the non-resonant probe condition, in which the energy is the center energy of two exciton states. These results originate from a change in the propagation velocity of the exciton polariton due to the pump.