Physically Realistic Air-Trench Modelling For Enhancing Thermal Characteristics of Heated Micro-Ring Resonators

To facilitate enhancing the design the heated micro-ring resonators (MRR), a thermo-electrical model that incorporates a physically realistic etching step has been developed. The etching model is used to define the extent of air-trenches below a heated MRR structure. The model is based on the diffusion equation and distinguishes the regions where substrate material is removed during device fabrication. The simulations reveal the extent to which air trenches can increase thermal resistance of the device and enhance its tuning efficiency. It is found that there is a critical sized air trench below which no benefit is found in terms of the MRR tunability. However, tuning efficiency is exponentially enhanced when the amount of material removed from under the MRR increases above this critical amount. For the heated MRR example considered, the tuning efficiency is ~0.1 nm/mW without air trenches, but it becomes 20X larger at the etched-through extreme.