Nanoparticles composed of high refractive index semiconductors can support electric and magnetic multipolar Mie-type resonances that can be tuned by the nanoresonator design . Furthermore, such semiconductor nanoresonators can exhibit very low absorption losses at optical frequencies. Based on these properties, semiconductor nanoresonators represent versatile building blocks of functional photonic nanostructures with tailored optical response.
This talk will review our recent advances in controlling the generation and propagation of light with metasurfaces composed of high-index semiconductor nanoresonators. Such metasurfaces can impose a spatially variant phase shift onto an incident light field, thereby providing control over its wave front with high transmittance efficiency . However, there are two important limitations: most semiconductor metasurfaces realized so far are passive, and their optical response is permanently encoded into the structure during fabrication. This talk will concentrate on strategies to integrate emitters into the metasurfaces and to obtain dynamic control of the metasurface optical response.
In particular, two approaches for active tuning of the metasurface response will be discussed, namely integration of the metasurface into a nematic-liquid-crystal cell  and ultrafast all-optical tuning based on the nonlinear optical response of the constituent semiconductor materials. Furthermore, I will show that Mie-resonant semiconductor metasurfaces allow for spatial and spectral tailoring of spontaneous emission from various types of emitters.
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