The Propagation Properties In Plasma Induced By High Intensity Laser Pulses

Recently, with the rapid development of the ultra-fast laser technique, the propagation of ultra-short laser pulses in nonlinear medium has attracted considerable attention. The propagation of femto-second pulses in plasma has become intriguing topic due to its abundant and complicated nonlinear phenomenon.In this thesis, we experimentally investigated the properties of the femto-second laser pulses propagation in the plasma induced by high intensity laser pulses in liquid, and their physical mechanisms are explicitly discussed and analyzed.Firstly, the development and property of the ultra-short laser pulse propagating in the plasma are reviewed.Secondly, conical emission and pulse self-compression of ultra-short laser pulses propagating in water are investigated. This conical emission arises from the constructive and destructive interference of the spatiotemporal gradient of the free-electron density at transverse wave-vector. Second harmonic generation frequency-resolved optical gating (SHG-FROG) trace shows that the pulse width of the output laser is compressed and its spectral width is broadened. In order to interpret the experimental observation, pulse self-compression of ultra-short laser pulses propagating in nonlinear medium is simulated based on Shorokhov's theory. Our experimental results indicate that intense laser pulse self-compression can also be realized in liquid medium, and this provides a new method to achieve pulse self-compression.Finally, the propagation of white light in plasma induced by high intensity laser pulses is studied. In experiment, Bessel beams generation of the white light propagating in plasma is observed. The long wavelength components of white light generate the zeoth-order Bessel beams, and short wavelength components generate the first-order Bessel beams. Fischer's theory is employed to interpret our experimental observation, and the simulation results are well consistent with the experimental data. So we reasonably believe that Bessel beams can be achieved in axicon plasma channel induced by high intensity laser pulses, this provides a feasible method to generate Bessel beams.