Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation

Spintronic Sources of Ultrashort Terahertz Electromagnetic Pulses

Spintronic terahertz emitters are novel, broadband and efficient sources of terahertz radiation, which emerged at the intersection of ultrafast spintronics and terahertz photonics. They are based on efficient spin-current generation, spin-to-charge-current and current-to-field conversion at terahertz rates. In this review, we address the recent developments and applications, the current understanding of the physical processes as well as the future challenges and perspectives of broadband spintronic terahertz emitters.

Fundamentals of Scanning Surface Structuring by Ultrashort Laser Pulses: From Electron Diffusion to Final Morphology

Industrial use of ultrashort-pulse surface structuring would significantly increase by an effective utilization of the average laser powers available currently. However, the unexplained degradation of surfaces processed with numerous pulses at high average laser power makes this difficult. Based on a systematic experimental study, the structure formation underlying such surface degradation was investigated. We presented a hierarchical structural formation model that bridges the gap between laser-induced periodic surface structures and surface degradation. Contrary to expectations based on prev…

Interaction of thin tungsten and tantalum films with ultrashort laser pulses: calculations from first principles

The interaction of ultrashort laser pulses with thin tungsten and tantalum films is investigated through the full-potential band-structure calculations. Our calculations show that at relatively low absorbed energies (the electron temperature $T_e$$\lesssim$7 kK), the lattice of tantalum undergoes noticeable hardening. The hardening leads to the change of the tantalum complete melting threshold under these conditions. Calculations suggest that for the isochorically heated Ta film, if such hardening really occurs, the complete melting threshold will be at least 25% higher. It is also shown that …

非晶原子层沉积MoS$_2$薄膜的超短脉冲激光退火

Ultrashort Pulse Laser Annealing of Amorphous Atomic Layer Deposited MoS$_2$ Films

本文提出利用超短脉冲激光退火实现低温原子层沉积的非晶MoS$_2$薄膜结晶化，详细分析了加工参数对薄膜形貌的影响，展示了激光退火诱导的自组织图案转变，并对比了不同退火方式的效果。

Glass tube cutting with aberration-corrected non-diffracting ultrashort laser pulses

The separation of complex inner and outer contours of glass articles with curved surfaces using ultrashort pulsed lasers is reported. Single-pass, full-thickness modifications along the entire substrate are achieved using a processing optics that allows for beam shaping of non-diffracting beams and, additionally, for aberration compensation of phase distortions occurring at the curved interface. The glass articles finally separated by thermal stress or via selective etching meet the demands of the medical industry in terms of micro-debris, surface quality and processing speed.

Magnetization switching by ultrashort acoustic pulses

It is shown theoretically that a single a few picoseconds long acoustic pulse can reverse magnetization in a magneto-strictive material Terfenol-D. Following giant magneto-elastic changes of free energy density the magnetization vector is kicked out of a local in-plane energy mininum and decays into another minimum. For acoustic pulse duration significantly shorter than magnetization precession period $τ_{ac}$<<$T_{prec}$, the switching threshold is determined by the {\it acoustic pulse area}, i.e. pulse integral in time domain, similar to coherent phenomena in optics. Simulation results are s…

Thermal response of double-layered metal films after ultrashort pulsed laser irradiation: the role of nonthermal electron dynamics

The thermal response of a Cu-Ti double-layered film is investigated after laser irradiation with ultrashort pulses (pulse duration τp=50fs, 800nm laser wavelength) in submelting conditions by including the influence of nonthermal electrons. A revised two-temperature model is employed to account for the contribution of nonthermal electron distribution while the variation of the optical properties of the material during the laser beam irradiation is also incorporated into the model. Theoretical results can provide significant insight into the physical mechanism that characterize electron dynamic…

Generation of exchange magnons in thin ferromagnetic films by ultrashort acoustic pulses

We investigate generation of exchange magnons by ultrashort, picosecond acoustic pulses propagating through ferromagnetic thin films. Using the Landau-Lifshitz-Gilbert equations we derive the dispersion relation for exchange magnons for an external magnetic field tilted with respect to the film normal. Decomposing the solution in a series of standing spin wave modes, we derive a system of ordinary differential equations and driven harmonic oscillator equations describing the dynamics of individual magnon mode. The external magnetoelastic driving force is given by the time-dependent spatial Fou…