Magnetic field control of intersubband polaritons in narrow-gap semiconductors

We investigate theoretically the polariton coupling between the light confined in a planar cavity and the intersubband transitions of a two-dimensional electron gas confined in semiconductor quantum wells in the presence of a vertical magnetic field. We show that in heterostructures made of nonparabolic semiconductors, the polaritons do not fit a two-level problem, since the cavity photons couple to a nondegenerate ensemble of intersubband transitions. As a consequence, the stationary polariton eigenstates become very sensitive to the vertical magnetic field, which thus plays the role of an external parameter that controls the regime of light–matter interactions. At intermediate field strength, we predict that the magnetopolaritons have energy dispersions ideally suited to parametric amplification.