Interaction between intersubband Bernstein modes and coupled plasmon-phonon modes

In a quasi-two-dimensional (2D) electron system under a perpendicular magne tic field, we have observed resonant interaction between intersubband Berns tein modes and coupled intersubband-plasmon-LO-phonon modes. By changing pa rameters of the 2D electron system, a transition from strong to weak regime s of coupling between the plasmon and LO phonon was considered. In the stro ng-coupling regime, we have observed a double-resonance splitting of the fi rst intersubband Bernstein mode with both intersubband-plasmon-LO-phonon mo des, whereas in the weak-coupling regime only a single resonance splitting with the intersubband-plasmon-like mode has been found.