Terahertz wave generation via optical rectification from multiferroic BiFeO3

Abstract

We detected broadband coherent terahertz (THz) emission from multiferroic BiFeO 3 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 BiFeO 3 , enabling applications in ferroelectric memories and ferroelectric domain imaging. We also report room-temperature THz optical constants of BiFeO 3 .

Photoexcitation of gigahertz longitudinal and shear acoustic waves in BiFeO3 multiferroic single crystal

“…As a result using femtosecond laser pulses, it was shown that coherent terahertz electromagnetic waves emission is possible. 12,13 More interestingly, it was shown that actually the emitted terahertz radiation reflects the ultrafast modulation of the spontaneous polarization of BFO which offers approaches to readout in nonvolatile random access memories and ferroelectric domain imaging systems. In addition, such pump-probe technique allows access to the photo-induced coherent acoustic phonons dynamics 18 which provides access to the determination of the elastic properties and also provides insight on the coupling of phonons and light.…”

“…8 Besides, because BFO has a small bandgap (in contrast to normal ferroelectrics), properties such as visible-light photovoltaic effect, 9,10 photostriction properties, 11 or THz electromagnetic wave generation by laser illumination have been recently explored. 12,13 The mechanisms behind these properties are not fully understood yet as some traps arising from defects or Schottky barriers at electrode interface can affect the experimental observations. 10,13 Nevertheless, it is believed that light excitation allows injection of photocarriers whose motion is driven by the built-in electric field linked to the large polarization of BFO.…”

“…12,13 The mechanisms behind these properties are not fully understood yet as some traps arising from defects or Schottky barriers at electrode interface can affect the experimental observations. 10,13 Nevertheless, it is believed that light excitation allows injection of photocarriers whose motion is driven by the built-in electric field linked to the large polarization of BFO. As a matter of fact and in addition to magnetic and/or electric field, light appears as a powerful tool to probe and tune BFO multiferroic properties as well as an original way for the discovery of unrevealed yet phenomena.…”

“…More specificaly, ultra-fast optical pump-probe spectroscopy can bring insights into the fundamental microscopic dynamics, important in many applications, that are at the origin of functional properties of various materials such as metals, 14 semiconductors, 15 collossal magnetoresistive manganites, 16 superconductors, 17 or multiferroics. 12,13,18 Such technique was used to investigate the model multiferroic BFO. As a result using femtosecond laser pulses, it was shown that coherent terahertz electromagnetic waves emission is possible.…”

Multi-stimuli manipulation of antiferromagnetic domains assessed by second-harmonic imaging

“…Lastly, it is interesting to note that an intense light can also apply an electric field, by virtue of the optical rectification process 24 . This stems from the second-order nonlinearity also giving rise to the SHG signal.…”