Microcavity exciton-polaritons (polaritons) are light-matter quasi-particles arising from the strong coupling of photons and quantum well excitons in a semiconductor microcavity. Polaritons are composite bosons with µm-sized thermal de-Broglie wavelengths (λdB) of several µm at temperatures of a few Kelvin. A gas of polaritons transitions to a collective single quantum state (an atomic Bose-Einstein-like condensate, BEC) when their λdB exceeds the average inter-particle distance. Own to the long λdB, a polariton BEC can be confined in µm-large intra-cavity traps produced by a lateral modulation of the cavity spacer thickness during the growth process (see figure).
The project aims at the exploitation of novel photonic functionalities based on the coherent acoustic modulation of confined polariton condensates. We are developing for that purpose structured microcavities with 2D and 3D polariton traps (as well as trap arrays), which simultaneously confine stimulated GHz phonons, as shown in the figure. The traps have dimensions down to 1 µm and support confined polariton BECs characterized by the emission linewidth below 100 µeV. In addition, we established a process for the piezo-electric generation of bulk vibrations with frequencies of up to 20 GHz. Phonon frequencies above 100 GHz will be excited by optical ps-pulses in collaboration with our Argentinian partners. The strong acousto-optic coupling in the proposed structures will be exploited for the coherent optical control of vibrations as well as for the manipulation of polariton BECs by phonons.
This project is a collaboration between the Paul-Drude-Institute and the Institute Balseiro, Bariloche, Argentina. It is supported by the Deutsche Forschungsgemeinschaft (DFG) and the Argentinian Conycet in the framework of the grants 646033 and 646034, "Coherent acousto-optical interactions in structured polariton microcavities”.