| Self-guided propagation of ultrashort intense laser pulses in air is demonstrated to induce filament channels with the advantage of energy-stability and high-quality beam profile due to the counterbalance between Kerr self-focusing and plasma-defocusing. However, filament can not be functioned as waveguide to keep energy propagate in a long distance due to the influence of experimental condition and environment. Therefore, the application of filament is limited by these factors. Recently, two-beam interaction is considerate as an efficient candidate process for the filament control to elongate the filament distance. In addition, the third harmonic generation is also enhanced. It will be beneficial to the laser long-distance propagation and the development of UV laser.With filament as the research object, this thesis is mainly focused on influence of the strong interaction between filaments on the filament propagation, enhancement of third harmonic energy conversion and the effect of multi-dimension waveguide. Mainly include the following:1. The filament control is achieved in the way of filament interaction to fulfill the elongation of filament and the two-order enhancement of third harmonic energy conversion. In the experiment, the process of third harmonic generation could be controlled by changing the noncollinear crossing angles, input intensity ratios, and input pulse polarizations. In addition, this technology can also be applied to the filamentation process of few-cycle pluses to fulfill the enhancement of broadband third harmonic. It provides a new and effective way to achieve the few-cycle femtosecond laser pulse in UV domain.2. The wavelength-scale periodic plasma waveguide array is achieved by adjusting the spatiotemporal overlap of laser pulse in the filament interaction region. The diameter and spatial distribution of plasma waveguide array can be adjusted by changing the non-collinear structure of incident filaments and creates the structure similar as that of photonic-crystal fiber. The results can be used to guide the laser pulse with high peak intensity and makes the foundation for the creation of novel plasma waveguides.3. Based on the formation of interference-assisted self-guide channel, the periodical refractive index distribution is formed in the interaction region and fulfills the 1-and 2-Dimensional plasma dynamic gratings in air. Experimentally, the parameters of grating and variation of energy diffraction of second and third harmonics is measured by changing the relative polarization and intensity ratio of the incidence pulses. Based on the results, we find the relation between the formation of dynamic gratings and the parameters of laser pulse and make the foundation for the practical application of dynamic grating.
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