High-performance thin-film lithium niobate electro-optic modulator based on etching slot andultrathin silicon film.

Abstract

An electro-optic modulator (EOM) is an indispensable component to connect the electric and optical fields. Here, we propose a high-performance, thin-film lithium niobate-based EOM, where the modulation waveguide is formed by an etching slot on the lithium niobate film and the deposit of an ultrathin silicon film in the slot region. Therefore, a small mode size and high mode energy can be simultaneously achieved in the LN region with a high EO coefficient, which will be beneficial to increase the EO overlap and gradually decrease in the mode size. Further, we employed a waveguide structure to construct a typical Mach-Zehnder interference-type EOM. According to the requirements of high-speed traveling wave modulation, we conduct the index matching, impedance matching, and low-loss operation. From the results, the key half-wave voltage length product and 3dB modulation bandwidth are, respectively, 1.45Vcm and 119GHz in a modulation length of 4mm. Moreover, a larger 3dB bandwidth also can be achieved by shortening the modulation length. Therefore, we believe the proposed waveguide structure and EOM will provide new ways to enhance the performance of LNOI-based EOMs.