Intersubband polaritons have been recently observed in reflectance
measurements . Nowadays a considerable effort is devoted to the
conception and realisation of devices operating in the strong
coupling regime. In this context, the vacuum Rabi splitting has been
observed in intersubband photodetectors , and electrically injected
polariton emission has been realised in a cavity organic LED .
In this seminar I will describe our results on the observation of
polariton emission and detection in a semiconductor intersubband
device. The latter is a GaAs/Al0.45Ga0.55As quantum cascade
structure, emitting at 7.6µm, embedded in a planar microcavity . The
light confinement takes place between an Al0.95Ga0.05As layer and a
metal contact, which also assures the electrical injection. Circular
mesas are etched to define the region where the current is flowing.
The main motivation of this work is to create new light sources
operating in the strong coupling regime, such as polariton lasers and
emitter with enhanced spontaneous emission rate.
In conclusion I will present some idea, in the THz range, on how to
achieve the ultra-strong coupling regime. In this wavelength range
the vacuum Rabi splitting is comparable to the photon energy coupled
to the system .