The Fundamental Research Of Frequency Tuning Technology Of Terahertz Wave Parametric Oscillator

Developing stable, efficient,compact-structured, high energy output and room temperature operated terahertz?THz? wave resource is the key of THz wave application technology. In this thesis, we systematically studied the frequency tuning technology of THz parametric oscillator ?TPO? based on stimulated polariton scattering. TPO has several outstanding advantages, such as wider frequency tuning width, compact experimental structure, lower cost and etc. Therefore it can be widely applied in the fields of spectral analysis, biomedical imaging, space communications and other THz applications. In order to tap its potential, researchers have paid closely attention to optimize frequency tuning range, THz-wave gain characteristics, output directivity of TPO.In this thesis, we use LiNbO₃?LN?, LiTaO₃?LT? and KTP crystal as the working medium, theoretically studying the operation characteristics of TPO with the angle tuning method ?ATM?, pump-wave tuning method ?PWTM? and electric-field tuning method ?EFTM? respectively. The results of three methods are compared as follows:Compared with LT-TPO, LN-TPO has wider frequency tuning width and higher gain characteristic with ATM. For KTP-TPO, it can intermittently tunes THz wave frequencies with ATM, and the generated THz wave which frequency is far from lattice vibration modes has higher gain characteristics. In addition, the output directivity of KTP-TPO is relatively stable on the whole.With PWTM, LN-TPO has wider frequency tuning width and higher gain coefficient, but less stable output direction than LT-TPO. PWTM intermittently tunes KTP-TPO THz wave frequency with PWTM, and the THz waves generated by different lattice vibration modes have different gain and output directivity.Due to electro optical properties of LN, the refractive indices of LN crystal can be changed by applying biased electric field at z axis of the crystal. It is a trial to explore the feasibility of LN-TPO with EFTM and analyze the gain characteristic.The calculation results of this thesis can provide necessary theoretical support and data references to improve the operation characteristics of TPO in the experiments.