A Cubic Micron of Equilibrium Pair Plasma?
  Is it possible to create a small volume of equilibrium pair plasma in the laboratory with an intense laser pulse? No. The required power would exceed 10^{18} W. The number of seed particles required to absorb the laser energy would approach the number of pairs in the desired plasma, and their radiation in a visible laser field would occur at extremely high frequencies. 
J. I. Katz