Electrically tunable hybrid-2D metasurfaces

Recent advances in nanophotonics have made it possible to control visible light on the subwavelength scale using optically resonant nanostructures and metasurfaces. Yet, so far, they have remained passive due to the limited tunability of natural materials. This thesis introduces electrically tunable hybrid-2D metasurfaces as a platform for active control of visible light. The central idea is to combine exciton resonance tuning in high-quality heterostructures based on monolayer semiconductors with the strong field enhancement provided by nonlocal dielectric resonances. Using this approach, we demonstrate free-space amplitude modulation by electrically tuning the system between the strong and weak coupling regimes, reaching 9.9 dB reflectance modulation and a 48.9 percent absolute change in reflectance at room temperature. The platform is then extended to complex-amplitude modulation, that is, independent control over both the reflection amplitude and the full phase range from 0 to 360 degrees. By operating near critical coupling and using two separate electrical control channels, our devices achieve complex-amplitude modulation and reconfigurable beam steering. Finally, a spatiotemporal coupled-mode theory framework is developed to capture the impact of finite sizes on the performance of footprint-limited nonlocal metasurfaces. The model describes linewidth broadening and interference effects that emerge when the device size approaches the modal propagation length, and its predictions are validated experimentally. Together, these results establish electrically tunable hybrid-2D metasurfaces as a uniquely versatile platform for achieving strong and tunable light-matter interactions in 2D quantum materials, which can be leveraged to study and control light at the nanoscale.