Enhancement of third-harmonic emission from femtosecond laser filament screened partially by a thin fiber

The third-harmonic (TH) emission characteristics from femtosecond laser filament, the center of which is screened by a thin metallic fiber, are experimentally investigated. The intensity of the TH emission has been enhanced for 1 order of magnitude by comparing with the undisturbed filament. The physical mechanism of the TH enhancement is analyzed to be the diffraction of the TH emission on the fiber and a redistribution of laser energy during the reconstruction of the two-colored filament. These two factors can release a part of the TH energy from the filament core into the background and keep more TH energy after the termination of filament.