RESUMO
Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have enormous benefits for ultrafast science. These novel sources promise to become indispensable tools for the investigation of structural dynamics on the femtosecond time scale, with spatial resolution on the atomic scale. Here, we demonstrate the use of laser-wakefield-accelerated electron bunches for time-resolved electron diffraction measurements of the structural dynamics of single-crystal silicon nano-membranes pumped by an ultrafast laser pulse. In our proof-of-concept study, we resolve the silicon lattice dynamics on a picosecond time scale by deflecting the momentum-time correlated electrons in the diffraction peaks with a static magnetic field to obtain the time-dependent diffraction efficiency. Further improvements may lead to femtosecond temporal resolution, with negligible pump-probe jitter being possible with future laser-wakefield-accelerator ultrafast-electron-diffraction schemes.
RESUMO
It was recently proposed that ionization-induced self-compression could be used as an effective method to further compress femtosecond laser pulses propagating freely in a gas jet [He et al., Phys. Rev. Lett. 113, 263904 2014]. Here, we address the question of the homogeneity of the self-compression process and show experimentally that homogeneous self-compression down to 12fs can be obtained by finding the appropriate focusing geometry for the laser pulse. Simulations are used to reproduce the experimental results and give insight into the self-compression process and its limitations. Simulations suggest that the ionization process induces spatio-temporal couplings which lengthen the pulse duration at focus, possibly making this method ineffective for increasing the laser peak intensity.
