Progress with EUV and x-ray transient gratings

August 1, 2021
  • Following the first successful demonstration of EUV pump / EUV probe transient grating measurements at FERMI to which our group contributed [1], two new important new results have been obtained and published [2,3].
  • In collaboration with colleagues from Siegen and Stockholm as well as the local team at FERMI, we made the first observation of transient nanoscale gratings of magnetization, see Fig. 1 below [2].
  • We have done the first EUV pump / EUV probe experiment in the reflection geometry and measured 50 GHz surface acoustic waves in SrTiO[3].
  • Reflection mode measurements greatly expand the range of possible samples  (otherwise samples must be in the form of ultrathin membranes in order to be able to transmit the EUV probe). 
  • In collaboration with collaegues from Paul Scherrer Institut and others,  we have made the first transient grating experiment with hard x-ray excitation at SwissFEL [4]. 

[1]. F. Bencivenga et al., “Nanoscale transient gratings excited and probed by extreme ultraviolet femtosecond pulses,” Sci. Adv. 5, eaaw5805 (2019). 

[2] D. Ksenzov et al.,  “Nanoscale transient magnetization gratings created and probed by femtosecond extreme ultraviolet pulses,” Nano Lett. 21, 2905−2911 (2021).

[3] A. A. Maznev et al., “Generation and detection of 50 GHz surface acoustic waves by extreme ultraviolet pulses,” Appl. Phys. Lett. 119, 044102 (2021).

[4] J. R. Rouxel et al.,  “Hard X-ray transient grating spectroscopy on bismuth germinate,” Nat. Photonics 15, 499–503 (2021). 


Figure. 1  Transient gratings of magnetization. (a) The concept of the experiment. The sample is kept in a homogeneous magnetization state by the external field H, which is larger than the coercive field. The two EUV pump pulses generate a nanoscale spatial modulation of the temperature, producing a transient magnetization grating in the sample. The dynamics of the magnetization grating are monitored via transient diffraction (dashed arrows) of a timedelayed probe pulse, tuned to a magnetic absorption edge. After each FEL shot, the sample is returned to the initial magnetic state by the field H. (b) Images of the transient diffraction signal collected with a CCD camera at different pump−probe delays are indicated in the individual panels. (c) EUV TG signal from a 9 nm-thick film of CoGd alloy as a function of the time delay between the pump and probe pulses recorded  with and without an external magnetic field. The  period of the magnetization grating is 44 nm.