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 meV at 78 K, has been measured, for an intersubband transition at 163 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. (C) 2007 American Institute of Physics.