Observation of coherent hybrid intersubband-cyclotron modes in a quantum well

We report on the coherent excitation of hybrid intersubband-cyclotron modes in a high-mobility semiconductor quantum well by ultrafast optical pulses. Pump-probe experiments were performed in the reflection geometry at 7 K in tilted magnetic fields, which mix motions in-plane and along the growth direction and lead to hybrid modes. The modes observed in the pump-probe experiments are all consistent in frequency and selection rules with spontaneous Raman scattering data on the same samples.