  Nanoscale light-matter interaction in the weak-coupling regime has been
achieved with unique hyperbolic metamaterial modes possessing a high density of
states. Here, we show strong coupling between intersubband transitions (ISBTs)
of a multiple quantum well (MQW) slab and the bulk polariton modes of a
hyperbolic metamaterial (HMM). These HMM modes have large wave vectors (high-k
modes) and are normally evanescent in conventional materials. We analyze a
metal-dielectric practical multilayer HMM structure consisting of a highly
doped semiconductor acting as a metallic layer and an active multiple quantum
well dielectric slab. We observe delocalized metamaterial mode interaction with
the active materials distributed throughout the structure. Strong coupling and
characteristic anticrossing with a maximum Rabi splitting (RS) energy of up to
52 meV is predicted between the high-k mode of the HMMand the ISBT, a value
approximately 10.5 times greater than the ISBT linewidth and 4.5 times greater
than the material loss of the structure. The scalability and tunability of the
RS energy in an active semiconductor metamaterial device have potential
applications in quantum well infrared photodetectors and intersubband
light-emitting devices.
