Remotely induced atmospheric lasing

A method for remotely generating a laser pulse in the atmosphere, comprising:

• at time t1, firing a first laser pulse into the atmosphere, the first laser pulse being a pulse from an ultrashort pulse laser (USPL) and being configured to generate a plasma filament at a predetermined location in the atmosphere through ionization of O2 and N2 molecules in the atmosphere, the plasma filament containing a plurality of free electrons generated as a result of the ionization;
• and
• at time t2>t1, firing a second laser pulse into the atmosphere, the second laser pulse being an intense pulse and being configured to form a heater beam that overlaps at least part of the plasma filament so as to thermalize at least some of the free electrons in the plasma filament;
• wherein the thermalized electrons collide with other electrons and the O2 and N2 molecules in the filament to collisionally excite a plurality of N2 molecules in the filament, create a population inversion of excited N2 molecules and cause lasing, the lasing being the result of the C3Πu→B3Πg(v=0→0) transition of the N2 in the filament.