MMI-based ultra linear electro-optic modulator with high output RF gain

A compact modulator with both ultra-linearity and high output RF gain is proposed and analyzed theoretically. It is implemented by a combination of a 1 × 2 multimode interference (MMI) coupler and an integrated Mach–Zehnder interferometer (MZI) modulator consisting of a microring and a phase modulator (PM). Due to the application of MMI coupler, traditional direct current (DC) bias circuits can be omitted, leading to reduced device complexity and increased device stability. Besides, this design shows a feature of maintaining both large output RF gain (1.1, 1.96 times larger than MZI and ring-assisted MZI (RAMZI) respectively) and high linearity performance (spurious-free-dynamic-range (SFDR) value is 133.5 dB and linearity range m is 84.4%) simultaneously.