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

An all-optical tunable terahertz modulator based on a BiFeO3/Si heterostructure is proposed. Optical and transmission properties of the BiFeO3/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 BiFeO3/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 BiFeO3 thin film on Si substrate is investigated to further explore and interpret the working mechanism of the proposed modulator.