The Theoretical Study On The CW And Quasi-CW THz Wave Generation By Optical Method

Due to the Terahertz frequency range, its major features, and its application prospect in spectrograph, materials science, biology, medicine, communication, and on national defense, he terahertz technology has been interested in. The Terahertz source is the base of Terahertz research range. At present, the research of THz source concentrate on the two fields, the THz radiation generated by the electronics technology, and the THz radiation generated by the optical method. The CW and quasi-CW THz source that is based on the nonlinear optical effect, can continuously tunable operate at room temperature. The two kinds of the THz sources are the THz source based on the DFG, and the THz parametric oscillation (TPO) based on the Raman Effect. The main content and innovative points in the dissertation can be summarized as follows:1. The features of THz radiation and the development of the THz technology are reviewed. The application prospect is introduced. Make a detailed summary of development, and application for the THz source, particularly the THz source based on the nonlinear effect.2. An analysis is made for the inorganic nonlinear crystals about their character in THz frequency range, the phase matching conditions, and the tunable conditions. Numerical simulations showed ZnTe crystal can achieve tunable operation between 0.4-2.7THz, correspondingly conversion efficiency between , with the dual-wavelength KTP-OPO operating near degeneracy as the difference frequency generation (DFG) pump source. 5×10?5 ~25×10?53. The theoretical study is made for the laser-induced phase transition. The character of phase-transition temperature in time domain is numerically stimulated by the finite element method and the Galerkin's method, and the threshold of the phase-transition is achieved.4. An analysis is made between the different theoretical models. Numerical stimulation is made for the space distribution of the THz radiation with the dual-wavelength KTP-OPO operating near degeneracy as the difference frequency generation (DFG) pump source.5. The theoretical study is made for operation of the LiNbO3-TPO, the phase-matching condition of the LiNbO3 crystal, the gains of the THz wave and the ideal wave. Numerical stimulation shows the operation of the TPO.