Congratulations to Qitong on his successful thesis defense!

Title: Improved light-Field Control and Lightmatter Interaction for Device Applications via Optically Resonant Nanostructures


Starting from the 1970s, great efforts have been made to miniaturize bulky optical devices. This progress accelerated significantly over the last decade due to the emerging field of metasurfaces. These planar nanophotonic devices, made from judiciously engineered, subwavelength-thick optical nanoresonators, are capable of controlling the amplitude, phase, polarization, and spectral properties of light waves with subwavelength resolution, and therefore have the potential to replace a wide range of bulk optical elements with flat optics.

Here, we go one step further to explore the emergent properties of optical nanoresonators beyond the concept in conventional optics. The radiative nature of optical resonances results in emerging collective modes in nanoresonator arrays beyond the description of the renowned chemical bonding model, leading to tremendous degrees of freedom for manipulating the light fields. Given the dimension of these flat optical elements becoming compatible with on-chip electronics, we now foresee an unprecedented opportunity to boost the performance and enable novel functionalities in integrated devices by bridging the gap between optics and electronics using metasurfaces. The carefully engineered local
photonic environment created by optical nanoresonators can selectively interact with quantum states in a broad range of material systems, probing and extracting the quantum information as needed.

In this thesis, I will specifically illustrate how to leverage the above-mentioned emergent properties of optically resonant nanostructures to achieve the improved control over the emission, propagation, and absorption of the light fields at the nanoscale. Eventually, it leads to three representative device applications: a transparent spectro-polarimetric silicon nanowire photodetector, a comprehensive metasurface optofluidic platform for dynamic control of light fields, and an efficient monolayer semiconductor free-space electro-optical modulator operating at room temperature. These works validate the crucial role that optical nanoresonators play in revolutionizing various optical and optoelectronic devices that may find use in real-world applications. The underlying physics behind these applications further reveals the opportunity to employ optical nanoresonators as a tool to probe the fundamental nature of complex physical systems.