Patent ID: 8665923

Claim:
A method for remotely generating a laser pulse in the atmosphere, comprising: at time t 1 , 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 O 2 and N 2 molecules in the atmosphere, the plasma filament containing a plurality of free electrons generated as a result of the ionization; and at time t 2 >t 1 , 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 O 2 and N 2 molecules in the filament to collisionally excite a plurality of N 2 molecules in the filament, create a population inversion of excited N 2 molecules and cause lasing, the lasing being the result of the C 3 Π u →B 3 Π g (v=0→0) transition of the N 2 in the filament.