All-optical switching on a nanometer scale — ScienceDaily


Ultrafast light-driven management of magnetization on the nanometer size scale is vital to realize aggressive bit sizes in subsequent technology knowledge storage expertise. Researchers at Max Born Institute in Berlin and of the massive scale facility Elettra in Trieste, Italy, have efficiently demonstrated the ultrafast emergence of all-optical switching by producing a nanometer scale grating by interference of two pulses within the excessive ultraviolet spectral vary.

The physics of optically pushed magnetization dynamics on the femtosecond time scale has change into of nice curiosity for 2 primary causes: first, understanding the elemental mechanisms of nonequilibrium, ultrafast spin dynamics and, second, the potential utility within the subsequent technology of knowledge expertise with a imaginative and prescient to fulfill the necessity for each sooner and extra power environment friendly knowledge storage units. All-optical switching (AOS) is among the most attention-grabbing and promising mechanisms for this endeavor, the place the magnetization state might be reversed between two instructions with a single femtosecond laser pulse, serving as “0s” and “1s.” Whereas the understanding of the temporal management of AOS has progressed quickly, information on ultrafast transport phenomena on the nanoscale, essential for the conclusion of all-optical magnetic reversal in technological purposes, has remained restricted because of the wavelength limitations of optical radiation. A sublime option to of overcoming these restrictions is to scale back the wavelengths to the acute ultraviolet (XUV) spectral vary in transient grating experiments. This method is predicated on the interference of two XUV beams resulting in a nanoscale excitation sample and has been pioneered on the EIS-Timer beamline of the free-electron laser (FEL) FERMI in Trieste, Italy.

Now, researchers from the Max-Born-Institute, Berlin and the FEL facility FERMI have excited a transient magnetic grating (TMG) with a periodicity of ΛTMG = 87 nm in a ferrimagnetic GdFe alloy pattern. The spatial evolution of the magnetization grating was probed by diffracting a time-delayed, third XUV pulse tuned to the Gd N-edge at a wavelength of 8.3 nm (150 eV). As AOS reveals a strongly non-linear response to the excitation, one expects attribute symmetry adjustments of the evolving magnetic grating distinct from the preliminary sinusoidal excitation sample. This data is straight encoded within the diffraction sample: in case of a linear magnetization response to the excitation and no AOS, a sinusoidal TMG is induced and the second diffraction order is suppressed. Nevertheless, if AOS happens, the grating form adjustments, now permitting for a pronounced second order diffraction depth. In different phrases, the researchers recognized the depth ratio between the second and first order (R21) as a fingerprint observable for AOS in diffraction experiments.

In future transient grating experiments with considerably smaller periodicities all the way down to <20 nm, ultrafast lateral transport processes are anticipated to equilibrate the excitation gradients inside a number of picoseconds and can subsequently outline the elemental spatial limits of AOS.

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