Tunneling In The Strong Field Ionization And High Harmonic Generation

In strong-field physics, nonlinear phenomena occupy an important position. To study the nonlinear phenomenon in strong-field, it gives us a deeper understanding of the nonlinear nature, and provides a field to use knowledge of nonlinear to home analyze and understand the particle movement in strong-field and most importantly, it is a chance to make better use of the law nature to service for human development.This article is divided into several sections, firstly, we give a general presentation about strong-fieldand then focus on two important nonlinear phenomenons of strong-field, ADK tunneling ionization and high-order harmonic generation in symmetrical diatomic molecule. We use the theory of ADK tunneling ionization to put forward a method that can indirectly measure the laser field strength, which has an important bearing on the experiment. Because of the continual development of laser technology, to measure the maximum field strength become the largest difficult for experiment.and even impossible to have a direct way to do so. but the ADK formula accurately reflects the ionization ratio of ionizing strong nonlinear changes, and the ionization ratio easier to be detected experiments, then we can use the experimental measurements of ionization ratio,which in turn used for the pilot estimated strong, and thus indirectly analysis the greatest intensity the laser pulse can reach. So our approach has important practical significance.Experiments have shown the interaction between powerful laser and gas can produce high-order harmonics. In theory, people use variety of models trying to explain the high-order harmonics generation. Theory could be divided into two types roughly : 1) The laser and plasma interactions produce high harmonics;2) laser and the atomic interactions produce high-order harmonics generation.We will be primarily through Schrcdinger eguation to study the high-order harmonics because of the nonlinear response when laser and atomic interaction. The ratio of the symmetrical diatomic molecule generates more than the atomic's because of charge resonance in theory. So research symmetrical diatomicmolecule have a significance. On the one hand, the high harmonics generated in laser applications have broad prospects;On the other hand, By studying symmetrical diatomic molecule, we examined the structure of harmonics , analyzed the phenomena in experimental, the accord in theory and numerical experiments prove the correctness of our model. Particularly, we analyze the changes of the width of harmonic bifurcations with field strength and the internuclear separation,which will contribute significantly to the research of molecule high-order harmonic generation.