Bistability engineering in ring-coupled Mach-Zehnder interferometers for efficient all-optical switching

We propose a two-ring structure that can generate an ultra-narrow resonance which may be used, together with the Mach-Zehnder interferometer (MZI), to engineer bistability switching with low switching threshold and reasonably high extinction ratio (ER) and modulation depth (MD). The two-ring MZI (2RMZI) is also compared with the conventional one-ring MZI (1RMZI). A flexible optimization scheme has been developed and can be used to obtain maximum ER and MD. Complementary relationship between switching threshold, sensitivity to loss and optical bandwidth are discussed for the two types of devices.