Mid-infrared barium titanate electro-optic modulators based on a germanium-on-silicon platform

Abstract

Mid-infrared electro-optic (EO) modulation efficiency and high-frequency performance of barium titanate (BTO) modulators on a germanium-on-silicon platform are investigated. Leveraging its exceptional Pockels coefficients, BTO exhibits remarkable EO modulation capabilities in both transverse-electric (TE) mode for a-axis growth and transverse-magnetic (TM) mode for c-axis growth. At the wavelength of 3.8 µm, the V π ⋅L for a-axis oriented BTO (TE polarization) is 1.90 V·cm, and for c-axis oriented BTO (TM polarization), it is 2.32 V·cm, which have better performance than those of the Pockels effect based EO modulators from literature. In addition, the high-frequency EO response of the modulator is simulated, and a 3-dB EO bandwidth of 62.82 GHz with the optimized traveling wave electrodes is achieved, showing promise in the high-speed MIR applications such as free-space optical communications.