Mach–Zehnder modulator based on a tapered waveguide and carrier plasma dispersion in photonic crystal

Abstract

Electro-optic modulators with wide bandwidth and low loss are necessary as the demand for high-speed integrated communication systems increases. We propose a Mach–Zehnder modulator based on photonic crystal. A tapered structure based on photonic crystal is introduced to suppress the cascading loss between the nanowire waveguide and photonic crystal waveguide at the input and output. We design and optimize a photonic crystal bent waveguide to reduce the reflection loss at each corner. The parameters of the Mach–Zehnder modulator are calculated using the three-dimensional finite-difference time-domain method. The numerical results show that the insertion loss and extinction ratio at the operating wavelength of 1550 nm are 0.22 and 15.2 dB, respectively. The 3 dB bandwidth can reach up to 72 GHz. This Mach–Zehnder modulator has the advantages of low loss and small size (47.8×11.6×0.22µm), which can be applied in photonic integrated systems.