All-optical tunable terahertz modulator based on a BiFeO3/Si heterostructure

An all-optical tunable terahertz modulator based on a BiFeO 3 /Si heterostructure is proposed. Optical and transmission properties of the BiFeO 3 /Si sample are characterized by the terahertz time-domain spectrometer. Under an external optical pumping, the modulator demonstrates an optical power-dependent modulation effect. A maximum modulation depth of 91.13% can be acquired when the optical pumping power is 700mW in the observed frequency. Due to the separation and localization of photogenerated carriers caused by the BiFeO 3 /Si heterostructure, the conductivity of the device can be changed and finally resulting in a modulation of the incident terahertz wave. In addition, the photoconductive property of the BiFeO 3 thin film on Si substrate is investigated to further explore and interpret the working mechanism of the proposed modulator.