Integrated Metamaterials and Nanophotonics in CMOS-Compatible Materials

Abstract

This thesis explores scalable nanophotonic devices in integrated, CMOS-compatible platforms. Our investigation focuses on two main projects: studying the material properties of integrated titanium dioxide (TiO2), and studying integrated metamaterials in silicon-on-insulator (SOI) technologies. We first describe the nanofabrication process for TiO2 photonic integrated circuits. We use this procedure to demonstrate polycrystalline anatase TiO2 ring resonators with high quality factors. We measure the thermo-optic coefficient of TiO2 and determine that it is negative, a unique property among CMOS-compatible dielectric photonic platforms. We also derive a transfer function for ring resonators in the presence of reflections and demonstrate using full-wave simulations that these reflections produce asymmetries in the resonances. For the second half of the dissertation, we design and demonstrate an SOI-based photonic-Dirac-cone metamaterial. Using a prism composed of this metamaterial, we measure its index of refraction and unambiguously determine that it is zero. Next, we take a single channel of this metamaterial to form a waveguide. Using interferometry, we independently confirm that the waveguide in this configuration preserves the dispersion profile of the aggregate medium, with a zero phase advance. We also characterize the waveguide, determining its propagation loss. Finally, we perform simulations to study nonlinear optical phenomena in zero-index media. We find that an isotropic refractive index near zero relaxes certain phase-matching constraints, allowing for more flexible configurations of nonlinear devices with dramatically reduced footprints. The outcomes of this work enable higher quality fabrication of scalable nanophotonic devices for use in nonlinear applications with passive temperature compensation. These devices are CMOS-compatible and can be integrated vertically for compact, device-dense industrial applications. It also provides access to a versatile, scalable and integrated medium with a refractive index that can be continuously engineered between n = −0.20 and n = +0.50. This opens the door to applications in high-precision interferometry, sensing, quantum information technologies and compact nonlinear applications.