The relaxation processes of electrons and spins systems following the absorption femtosecond optical pulses in ferromagnetic nickel have been studied using magneto-optical pump-probe techniques. magnetization film drops rapidly during first picosecond, but different electron spin dynamics are observed for delays range 0--5 ps. experimental results adequately described by a model including three interacting reservoirs (electron, spin, lattice).

It is shown that the laser induced ultrafast demagnetization of ferromagnetic films results in emission a terahertz electromagnetic pulse. This has been detected from Ni using free-space electro-optic sampling. The radiated electric field E(t) explained by Maxwell equations (radiation time dependent magnetic dipole), and expected to be proportional second derivative magnetization d2M/dt2, as measured far field. technique opens appealing perspectives context measuring understanding spin...

The thermalization of electrons in copper nanoparticles embedded glass is investigated using femtosecond pump-probe spectroscopy. time dependent induced transmission enhanced near the surface plasmon resonance nanoparticles, as opposed to static one obtained with thermomodulation measurements. In addition, a slowing process electron cooling lattice temperature observed at resonance. These observations show importance quasiparticle collisions confined metallic structures.

We have characterized by pump-probe polarimetry the time-dependent dielectric tensor in a CoPt3 ferromagnetic film excited 20 fs laser pulses. It is shown that, after thermalization time of electrons (approximately 50 fs), dynamics real and imaginary parts Voigt vector are identical. In addition, their relative variation 10 times larger than that diagonal elements tensor, which allows one to infer spins dominate magneto-optical response. During process, temporal behavior opens new questions...

We show that the many-body interactions among excitons govern temporal line shape of coherent (free induction decay) emission from semiconductor quantum walls. At low exciton densities, they become dominant contribution to emission.

We report about the existence of magneto-acoustic pulses propagating in a 200-nm-thick ferromagnetic nickel film excited with 120 fs laser pulses. They result from coupling between magnetization and longitudinal acoustic waves associated to propagation lattice deformation induced by femtosecond The are detected both front back sides film, using time-resolved magneto-optical Kerr technique, measuring time dependent rotation ellipticity. show that pulse couples efficiently is strong enough...

We have measured the real space trajectory of ultrafast magnetization dynamics in ferromagnetic metals induced by femtosecond optical pulses. Our approach allows observation initial change modulus and orientation magnetization, occurring within a few hundreds femtoseconds, as well its subsequent precession damping around effective field. The role magnetocrystalline anisotropy shows up reorientation during electron-lattice relaxation. In addition, we propose model which takes into account...

The behavior of carrier-carrier screening is investigated in a GaAs-GaAlAs quantum-well structure by measuring the band-to-band polarization dephasing with femtosecond photon echoes. variation electron-hole-polarization time carrier concentration reveals two-dimensional character short-range between interacting carriers.

Abstract The study and control of magnetic materials using ultrashort laser pulses is great interest both from a fundamental point view for potential applications in the technology information communication. In this review state art experimental theoretical works field Ultrafast Magnetization Dynamics described, with particular emphasis on dynamics nanostructures. elementary physical mechanisms involving spin when exciting nanostructures femtosecond optical are considered. variety methods...

A joint theoretical and experimental investigation is performed to understand the underlying physics of laser-induced demagnetization in Ni Co films with varying thicknesses excited by 10 fs optical pulses. Experimentally, dynamics spins studied determining time-dependent amplitude Voigt vector, retrieved from a full set magnetic nonmagnetic quantities on both sides films, absolute time reference. Theoretically, ab initio calculations are using density functional theory. Overall, we...

We have measured the magnetization dynamics of an epitaxial ${\mathrm{CoPt}}_{3}$ alloy film using a magneto-optical pump-probe Kerr setup with 120 fs laser pulses. At high pump fluence, is driven from ferro- to paramagnetic state characteristic time comparable pulse duration. The associated demagnetization occurs within thermalization electrons Fermi distribution. These results demonstrate feasibility ultrafast devices.

Fast magnetization changes can be achieved in a ferromagnet using optical pulses. Such which are due to an increase of the spin temperature above Curie point generally induced by elevation lattice pico-nanosecond pulses [1,2]. In this case, electron and phonon population equilibrium, delay between dynamics has been attributed phonons interactions. As reported paper, initial hot distribution created femtosecond induce ultrafast heating via electron-spin collisions. It is shown that first...

We study the effect of Coulomb correlations on ultrafast optical dynamics small metal particles. demonstrate that a surface-induced dynamical screening electron-electron interactions leads to quasiparticle scattering with collective surface excitations. In noble-metal nanoparticles, it results in an interband resonant $d$ holes plasmons. show this size-dependent many-body manifests itself differential absorption for frequencies close plasmon resonance. particular, our self-consistent...

Femtosecond magneto-optical measurements detect the formation of a spin-excited state in vanadium–chromium Prussian blue analogue, which is molecule-based magnet.

The electron dynamics is studied in silver nanoparticles of different sizes embedded either a silicate glass or porous alumina matrix, using time-resolved optical spectroscopy. femtosecond pump–probe measurements, made under various conditions excitation, reveal that the energy relaxation faster as particle size decreases. For particles with identical and excitation conditions, time found to be for clusters matrix. influence surface acoustic modes heat conductivity matrix on discussed.

A new method to measure and analyze the time spectrally resolved polarimetric response of magnetic materials is presented. It allows us study ultrafast magnetization dynamics a CoPt3 ferromagnetic film. The analysis pump-induced rotation ellipticity detected by broad spectrum probe beam shows that magneto-optical signals predominantly reflect spin in ferromagnets.

We investigate the temporal evolution of instantaneous frequency ultrashort-pulse four-wave mixing in GaAs/${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum-well structures. find that coherent light emitted by excitons exhibits a complex phase behavior which depends critically on density and central exciting pulses. Depending excitation conditions, we observe nonlinear shifts within one ultrashort pulsed emission or quantum beats. In latter case...

This paper describes the synthesis and X-ray optical characterization of conjugated soluble polymers in which planarity backbone has been improved by intramolecular H bonds. The solubility was enhanced increasing number alkyl chains on aryl group. electron density phenyl ring also modified amino ester groups, introducing electron-donor or electron-acceptor increase polarizability. have synthesized polycondensation using a palladium-catalyzed coupling reaction, between bromoaryl an...

We investigate the interaction of femtosecond laser pulses with spins including relativistic corrections. The time-ordered magneto-optical signals corresponding to a pump-probe configuration are calculated in case one electron submitted magnetic field and evolving eight levels fine structure hydrogenlike atom. Our simulations explain origin coherent response ultrafast spin dynamics ferromagnets excited by intense as recently reported Ni CoPt${}_{3}$ ferromagnetic thin films. detailed...