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Light-matter strong coupling regime

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The aim of this research axis is the realization of mid- and far-infrared emitters operating in the light - matter strong coupling regime without population inversion (beyond the laser paradigm). They are based on the strong coupling between an intersubband excitation of a two-dimensional electron gas and a cavity mode. The quasi-particles issued from this coupling are called intersubband polaritons .1 We demonstrated the first mid-infrared emitter based on intersubband polaritons and showed that the polariton states are populated resonantly with the energy of the electrons in the injector.Retour ligne automatique
In order to achieve the strong coupling regime in the THz range, we have realized metal dielectric metal microcavities (see figure 1a). In these systems, light is confined in a highly subwavelength semiconductor layer, sandwiched between two metal layers, the top one textured in a periodic grating of patches or stripes (see figure 1a and 1c). The insertion of doped quantum wells between the two metal layers allowed the first observation of the strong and ultra-strong coupling2 regime in the mid and THz range. We demonstrated that the coupling energy can be up to 50% of the intersubband excitation energy, as shown in fig. 1b.

The experimental work on the ultra-strong coupling regime has been accompanied by a detailed theoretical study of the interaction between a cavity mode and a two-dimensional electron gas. We have shown that the collective character of the intersubband excitation is a key element to understand the origin and the physical properties of the ultra-strong coupling regime.

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