Coherent surface acoustic phonons governed by structured light for modulation of planar exciton-polariton waveguides in space and time

• Applicant: Dr. Anton Samusev
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 529710370

Ultrafast acousto-optics deals with ultrashort optically-excited strain pulses of picosecond duration represented by wavepackets of coherent acoustic phonons of GHz to THz frequencies. When applied to a semiconductor, the dynamical strain gives rise to energy shifts of the electronic, excitonic, and photonic resonances. This in turn can be employed for the ultrafast and highly efficient modulation of reflected, scattered, or emitted light. Such all-optical devices, where light is manipulated by light through acoustic phonons are of both applied and fundamental interest. On one hand, such systems are capable of transferring and storing information even at the quantum limit. On the other hand, within this concept, phonon-related microscopic properties of various systems can be addressed and respective underlying mechanisms can be revealed. In this project, we will study planar semiconductor slabs supporting resonant hybrid states originating from the strong coupling of high oscillator strength exciton to optical guided modes, i.e. guided exciton-polaritons. The excitonic response of the chosen structures (multiple InGaAs quantum wells embedded in GaAs slab and thin crystalline CsPbBr3 perovskite film) will allow us to maximize the strain-induced optical effects. Mutual interaction and free-space outcoupling of guided exciton-polaritons in these systems will be induced through coherent surface acoustic phonons giving rise to complex quasiparticles – surface exciton-phonon-polaritons. Within the project, we will comprehensively study their spatial and temporal dynamics. The most remarkable characteristics of exciton-polaritons – high optical nonlinearity and high temporal and spatial coherence – will be further boosted through phonon-mediated polariton dispersion engineering. Specifically, we will for the first time realize a high-Q polaritonic bound state in the continuum and the regime of exceptional-point-driven polariton lasing both enabled by coherent surface acoustic phonons. We believe that these studies will significantly contribute to the development of ultrafast on-chip active and passive acousto-optical devices.

• DFG Programme: WBP Position