Laser heating of air plasmas seeded by ultrashort pulse filaments

The air plasma produced by an ultrashort pulse laser filament can be used as a source of seed electrons for subsequent heating and breakdown by a higher energy long pulse laser. In this way, the threshold intensity for breakdown can be effectively lowered, raising the possibility of producing a bright, hot air plasma at a remote location. The physics of this process is examined experimentally and numerically. The experiment utilizes a 500 fs, 100 mJ pulse from a Nd: glass laser to produce the seed plasma, and a 50 ns, 1 J pulse from a Nd:YAG laser to heat the air. Radially resolved hydrodynamics calculations with detailed air chemistry are carried out to support the experiment.