Wavefront shaping with 2D excitonic metasurfaces Large-area, atomically-thin optical elements leveraging exciton resonances

Optical metasurfaces offer ultracompact manipulation of light through resonant light scattering by dense arrays of nanoparticles. While efficient, these conventional metasurfaces are static after nanofabrication limiting their applications in upcoming applications where dynamic manipulation of light fields is essential. This thesis explores exciton resonances in monolayer 2D semiconductors as novel resonant tunable building blocks in atomically thin metasurfaces. The thesis is comprised of five chapters covering three overarching topics. First, a comprehensive summary of metasurface physics and established mechanism for active metasurfaces is presented to set the stage. Second, a detailed temperature dependent study of light focusing by an atomically thin lens directly demonstrates the intricate link between the optical function of the lens and the temporal exciton decay dynamics. Third, electrical tuning of the exciton resonance is leveraged to demonstrate dynamic and selective beam steering in an interleaved metagrating optoelectronic device. A fundamental numerical study of light scattering by individual and arrays of nanoribbons is used to explain the results and highlights novel design rules for phase and amplitude engineering in such atomically thin 2D excitonic metasurfaces. The thesis combines fundamental studies with prototype device demonstrations to emphasize the direct relevance of these novel 2D metasurfaces in applications of transparent optical elements.