Low-loss tellurium oxide devices integrated on silicon and silicon nitride photonic circuit platforms

Abstract

Silicon (Si) and silicon nitride (Si3N4) have become the dominant photonic integrated circuit (PIC) material platforms, due to their low-cost, wafer-scale production of high-performance circuits. However, novel materials can offer additional functionalities that cannot be easily accessed in Si and Si3N4, such as light emission. Tellurium oxide (TeO2) is a novel material of interest because of its large linear and non-linear refractive indices, low material losses and large rare-earth dopant solubility, with applications including compact low-loss waveguides and on-chip light sources and amplifiers. This thesis investigates the post-processing integration of TeO2 devices onto standardized Si and Si3N4 chips to incorporate TeO2 material advantages into high-performance PICs. Chapter 1 introduces the state-of-the-art functionality for various integrated photonic materials as well as methods for integrating multiple materials onto single chips. Chapter 2 presents the development of a high-quality TeO2 thin film fabrication process by reactive RF sputtering, with material refractive indices of 2.07 and optical propagation losses of <0.1 dB/cm at 1550 nm. Chapter 3 investigates a conformally coated TeO2-Si3N4 waveguide platform capable of large TeO2 optical confinement and tight bending radii, characterizing fiber-chip edge couplers down to ~5 dB/facet, waveguide propagation losses of <0.5 dB/cm, directional couplers with 100% cross-over ratio, and microresonators with internal Q factors of 7.3 × 105. In Chapter 4 a spectroscopic study of TeO2:Er3+-coated Si3N4 waveguide amplifiers was undertaken, with internal net gains of up to 1.4 dB/cm in a 2.2-cm-long waveguide and 5 dB total in a 6.7-cm-long sample demonstrated, predicted to reach >10 dB could 150 mW of pump power be launched based on a developed rate-equation model. Chapter 5 demonstrates TeO2-coated microtrench resonators coupled to silicon waveguides, with internal Q factors of up to 2.1×105 and investigates environmental sensing metrics of devices. Chapter 6 summarizes the thesis and provides avenues for future work.