  Terahertz emission between exciton-polariton branches in semiconductor
microcavities is expected to be strongly stimulated in the polariton laser
regime, due to the high density of particles in the lower state (final state
stimulation effect). However, non-radiative scattering processes depopulate the
upper state and greatly hinder the efficiency of such terahertz sources. In
this work, we suggest a new scheme using multiple microcavities and exploiting
the transition between two interband polariton branches located below the
exciton level. We compare the non-radiative processes loss rates in single and
double cavity devices and we show that a dramatic reduction can be achieved in
the latter, enhancing the efficiency of the terahertz emission.
