High energy THz generation from meter-long two-color filaments in air

High energy THz emissions from meter-long, two-color femtosecond laser-induced filament in air are demonstrated at a distance of over 10 m from the laser. The THz emission is linearly proportional to the N2 fluorescence inside the filaments under the same excitation condition; this provides a sensitive method to monitor the THz energy from a distance.