UCLA

Optical devices play a vital role in modern technology facilitating communication, sensing, imaging, and energy conversion across various disciplines. These devices rely on strong interaction between light and the underlying materials to achieve control of light at nanoscale. The conventional dielectric materials, including Si and InP, although widely used, are limited by their optical material properties and can hardly further induce stronger light-matter interactions for enabling better device performance.Emergent layered van der Waals materials exhibit unique optical properties and thus can offer opportunities for building more advanced photonic devices. In particular, light can efficiently couple with the intrinsic material resonances to form half-light, half-material hybridized states, yielding a greatly enhanced light-matter interaction. My dissertation project focuses on understanding how the coupling between light and material resonances modifies the optical responses in nano-structures made of van der Waals materials, especially transition metal dichalcogenides and hexagonal boron nitrides, and the profound implications it brings to the device performance. By combining theoretical analysis with experimental characterization techniques, in this thesis we examine the dynamics of light-matter interactions within optical nanostructures made of bulk TMDCs and hBN, especially in the vicinity of intrinsic material excitations. We provide a numerical modelling of key integrated photonic components made of bulk form of layered van der Waals semiconductors, paving the way for using a more advanced material platform to complement today’s Si and InP photonics technologies. Moreover, we also theoretically examine the limits of optical confinement in van der Waals materials. Due to the coupling between light and intrinsic excitons, these materials possess strongly modified dielectric permittivity, allowing light to be efficiently confined to very small spots; well beyond diffraction limit with greatly concentrated optical fields. These results are of paramount interest for creating more advanced integrated optical systems with higher integration density and more efficient electro-optic modulation. In addition to theoretical analysis, we also adopt state-of-the-art material characterization, nanofabrication, and optical measurement techniques to experimentally demonstrate the functional nanophotonic devices made of multilayer van der Waals materials in both near- and mid-infrared bands. The nanofabrication processes we develop allows creating compact, deeply subwavelength nanostructures out of exfoliated van der Waals material thin films with smooth, less tilted sidewalls compared to previously reported work. Furthermore, we use far- and near-field optical characterization techniques to examine the functionalities realized by these novel van der Waals photonic devices. The findings in this dissertation work can provide a guideline for designing, fabricating, and characterizing advanced optical systems made of novel van der Waals materials, paving the way to achieving high precision optical sensing, nanoscale opto-mechanics, small footprint optical interconnects, and tunable thermal radiation and imaging.