Enhancement of third harmonic emission by interaction of two colored filament with droplet in air

Numerical simulations are performed to investigate the third harmonic emission from femtosecond laser filament, center of which is blocked by a droplet. It is shown that sudden stop of fundamental laser filament induced by the droplet leads to the enhancement of third harmonic emission. The diffraction on droplet leads to the increase of third harmonic energy in background reservoir which can be survived after the dissipation of filament.