  We revisited the intersubband polaritonics - the branch of mesoscopic physics
having a huge potential for optoelectronic applications in the infrared and
terahertz domains - and found that, contrary to the general opinion, the
Coulomb interactions play crucial role in the processes of light-matter
coupling in the considered systems. Electron-electron and electron-hole
interactions radically change the nature of the elementary excitations in these
systems. We show that intersubband polaritons represent the result of the
coupling of a photonic mode with collective excitations, and not
non-interacting electron-hole pairs as it was supposed in the previous works on
the subject.
