Relativistic surface-plasmon enhanced harmonic generation from gratings
  The role of relativistic surface plasmons (SPs) in high order harmonic emission from laser-irradiated grating targets has been investigated by means of particle-in-cell simulations. SP excitation drives a strong enhancement of the intensity of harmonics, particularly in the direction close to the surface tangent. The SP-driven enhancement overlaps with the angular separation of harmonics generated by the grating, which is beneficial for applications requiring monochromatic XUV pulses. 
Luca Fedeli, Andrea Sgattoni, Giada Cantono, Andrea Macchi
physics.plasm-ph