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 non-parabolic semiconductors, the polaritons do not fit a two-level problem, since the cavity photons couple to a non-degenerate 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 magneto-polaritons have energy dispersions ideally suited to parametric amplification.