An equivalent circuit model of thin film lithium niobate Mach-Zehnder modulators with T-rail travelling wave electrodes

T-rail electrodes has emerged as a promising candidate for increasing the electro-optical modulator(EOM) bandwidth, compared to traditional travelling wave electrodes. We demonstrate an equivalent model of thin film lithium niobate (TFLN) Mach-Zehnder modulators with T-rail electrodes, utilizing the distributed capacitance and conformal mapping techniques to calculate the microwave refractive index, RF characteristic impedance, microwave loss. The validity of the values extracted from the equivalent circuit model is confirmed by their agreement with finite element method (FEM) simulations. We analyze various influential parameters affecting modulator performance to enhance design efficiency and achieve a 3dB bandwidth of approximately 120 GHz.