THz Wave Emission From Argon In Two-color Laser Field

A terahertz(THz) wave which frequency usually was located between0.1THz-10THz(1THz=1012Hz) is a special electromagnetic wave. It is between microwave and infrared light in the whole electromagnetic wave spectrum and has many unique characteristics, for instance the lower-energy photons, broad bandwidth,strong penetrability, good instantaneity and coherence. Therefore, numerous applications of THz wave can be found in a widely area such as physics, chemistry,biology, materials, communication technology and security detection and so on.However, the perfect method of producing strong THz wave hasn’t determined, it is called “THz Gap”. In this thesis, we have investigated the coherent optical radiation process of atom in intense laser field with different laser frequencies and intensity to observe some laws and physics mechanism of THz wave spectra. The main research work is summarized as follows:We used the split-operator method to numerically compute the one-dimensional time-dependent Schr?dinger equation(TDSE) for studying the THz wave emission from a model argon atom in an intense combined field of 800 nm and 400 nm laser pulse. According to the projection method, we have made a distinction between bound state and continuous state during the atom stimulated process. And then, we report the THz wave rules which include both discontinuous and continuum ones and identify the discontinuous part of THz wave. Our analysis points out that the continuum part and the discontinuous part(sharp peak) of the THz wave respectively come from continuum-continuum and high-rydberg to high-rydberg state resonance transition of atomic energy levels, and we have found that the continuum THz spectra are matched with ones obtained from the total time-dependent wave function of the system.