we demonstrate that it is possible to obtain Kerr bistable memory in a whispering-gallery-mode cavity with an add-drop system but it is impossible with a side-coupled system when the thermo-optic effect is present.
We quantitatively analyze the performance of optical memories based on Kerr bistability in microcavites. We model a silicon nitride microring and a silica toroid microcavity, and examine the performances of these cavities in an actual situation where there is a thermo-optic effect. Numerical simulations based on coupled mode theory and the thermal diffusion equation reveal that an input power of 1.8 W is necessary to achieve a Kerr bistable memory in a silicon nitride microring, while that of only 1.7 mW is necessary in a silica toroid microcavity. This result shows that the use of silica toroid microcavity is advantageous when we want to demonstrate a Kerr bistable memory operation with a reasonably low input power. In addition, we quantitatively investigate the trade-off between the required input power and the response speed of the device.