Magnetically controlled terahertz modulator based on Fe3O4 nanoparticle ferrofluids

A multifunctional terahertz (THz) wave modulator fabricated from Fe₃O₄ nanoparticle ferrofluids and metamaterials was characterized in externally applied magnetic fields. Specifically, modulation depths and frequency shifts by the wave modulators were examined. A 34% THz amplitude modulation depth was demonstrated and the absorption peak of the metamaterial induced a frequency shift of 33 GHz at low magnetic field intensities. It is anticipated that this device structure and its tunable properties will have many potential applications in THz filtering, modulation, and sensing.