A plasmon enhanced attosecond extreme ultraviolet source
  A compact high repetition rate attosecond light source based on a standard laser oscillator combined with plasmonic enhancement is presented. At repetition rates of tens of MHz, we predict focusable pulses with durations of ~< 300 attoseconds, and collimation angles ~< 5 degrees. Attosecond pulse parameters are robust with respect variations of driver pulse focus and duration. 
Mattia Lupetti, Matthias F. Kling, and Armin Scrinzi
physics.optics quant-ph