We report an active broadband terahertz modulator based on Fe3O4 nano-particles/Si structure, for which, the effects on it’s interface were measured in a THz time-domain spectroscopy system. As high as 92% modulation depth was achieved at an external excitation laser of 3.6 W/cm2. This phenomenon can be explained by the accumulation of carriers in the interface of hybrid structure, which induce the intense absorption of terahertz transmission. The Fe3O4 nano-paricles thin film on Si substrate was easily attained by spin-coating widely commercial ferrofluids. The superior performance of this device on THz wave modulation compared to other terahertz modulators based on nano-materials and the ease of fabrication both illustrate that a promising method to modulate THz transmission has been realized.
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