Noncollinear interaction of femtosecond filaments with enhanced third harmonic generation in air

We demonstrate that the interaction between two intense femtosecond filaments noncollinearly crossed in air results in third harmonic generation of more than two orders enhancement in energy conversion as compared with that from a single filament. The dependences of the third harmonic generation on the noncollinear crossing angles, input intensity ratios, and input pulse polarizations are investigated.