Strong Terahertz Radiation via Rapid Polarization Reduction in Photoinduced Ionic-To-Neutral Transition in Tetrathiafulvalene-p-Chloranil.

Terahertz lights are usually generated through the optical rectification process within a femtosecond laser pulse in noncentrosymmetric materials. Here, we report a new generation mechanism of terahertz lights based upon a photoinduced phase transition, in which an electronic structure is rapidly changed by a photoirradiation. When a ferroelectric organic molecular compound, tetrathiafulvalene-p-chloranil, is excited by a femtosecond laser pulse, the ionic-to-neutral transition is driven and simultaneously a strong terahertz radiation is produced.

Ultrafast magnetization modulation induced by the electric field component of a terahertz pulse in a ferromagnetic-semiconductor thin film.

High-speed magnetization control of ferromagnetic films using light pulses is attracting considerable attention and is increasingly important for the development of spintronic devices. Irradiation with a nearly monocyclic terahertz pulse, which can induce strong electromagnetic fields in ferromagnetic films within an extremely short time of less than ~1 ps, is promising for damping-free high-speed coherent control of the magnetization. Here, we successfully observe a terahertz response in a ferromagnetic-semiconductor thin film.

Dynamical magnetoelectric effects in multiferroic oxides.

Multiferroics with coexistent ferroelectric and magnetic orders can provide an interesting laboratory to test unprecedented magnetoelectric (ME) responses and their possible applications. One such example is the dynamical and/or resonant coupling between magnetic and electric dipoles in a solid. As examples of such dynamical ME effects, (i) the multiferroic domain wall dynamics and (ii) the electric dipole active magnetic responses are discussed with an overview of recent experimental observations.

Terahertz radiation by an ultrafast spontaneous polarization modulation of multiferroic BiFeO3 thin films.

Terahertz (THz) radiation has been observed from multiferroic BiFeO3 thin films via ultrafast modulation of spontaneous polarization upon carrier excitation with illumination of femtosecond laser pulses. The radiated THz pulses from BiFeO3 thin films were clarified to directly reflect the spontaneous polarization state, giving rise to a memory effect in a unique style and enabling THz radiation even at zero-bias electric field. On the basis of our findings, we demonstrate potential approaches to ferroelectric nonvolatile random access memory with nondestructive readability and ferroelectric domain imaging microscopy using THz radiation as a sensitive probe.

Effect of charge ordering and disordering on terahertz radiation characteristics of magnetoresistive Pr0.7Ca0.3MnO3 thin films.

Terahertz (THz) radiation from voltage-biased photoswitching devices made on magnetoresistive manganite Pr0.7Ca0.3MnO3 have been investigated for thin films grown under different conditions.