Photovoltaic probe of cavity polaritons in a quantum cascade structure

The strong coupling between an intersubband excitation in a quantum cascade structure and a photonic mode of a planar microcavity has been detected by angle-resolved photovoltaic measurements. A typical anticrossing behavior, with a vacuum-field Rabi splitting of $16\mathrm{meV}$ at $78\mathrm{K}$ , has been measured, for an intersubband transition at $163\mathrm{meV}$ . These results show that the strong coupling regime between photons and intersubband excitations can be engineered in a quantum cascade optoelectronic device. They also demonstrate the possibility to perform angle-resolved midinfrared photodetection and to develop active devices based on intersubband cavity polaritons.