Terahertz Magnetic Modulator based on Magnetically-Clustered   Nanoparticles
  Random orientation of liquid-suspended magnetic nanoparticles (Ferrofluid) gives rise to zero net magnetic orientation. An external magnetic field tends to align them into clusters, leading to a strong linear dichroism on a propagating wave. Using 10 nm-sized Fe3O4, we experimentally realize a polarization-sensitive magnetic modulator operating at terahertz wavelengths. We reached a modulation depth of 66% using a field of 35 mT. The proposed concept offers a solution towards fundamental terahertz magnetic modulators. 
Mostafa Shalaby, Marco Peccianti, Yavuz Ozturk, Ibraheem Al-Naib,   Christoph P. Hauri, and Roberto Morandotti
physics.optics