Terahertz wave generation via optical rectification from multiferroic   BiFeO3
  We detected broadband coherent terahertz (THz) emission from multiferroic BiFeO3 after illuminating a high-quality bulk single ferroelectric domain crystal with a ~100 fs optical pulse. The dependence of the emitted THz waveform on the energy and polarization of the optical pulse is consistent with the optical rectification mechanism of THz emission. The THz emission provides a sensitive probe of the electric polarization state of BiFeO3, enabling applications in ferroelectric memories and ferroelectric domain imaging. We also report room-temperature THz optical constants of BiFeO3. 
D. Talbayev, Seongsu Lee, S.-W. Cheong, A. J. Taylor