中文摘要：

提出了一种周期极化铌酸锂（PPLN）晶体差频产生太赫兹（THz）波的新型结构。基于非线性晶体三波互作用理论模型，根据周期极化掺镁铌酸锂（PPMgLN）晶体的准相位匹配原理和掺铒光纤激光器（EDFL）双波长输出激光特性，并结合晶体折射率差公式，理论分析了工作温度及极化反转光栅周期对其输出THz波的影响，给出一定频率范围内其输出波长连续可调谐的实现方法。本文系统结构简单、成本低和调谐容易，激光器可室温运转。

英文摘要：

As research in the field of the photoelectron and electromagnetic waves continues, the development of terahertz wave has attracted more and more attention. This paper proposes a new and potential structure of the tunable and narrow-band terahertz wave （THz-wave） radiation via the nonlinear optical difference frequency generation on a periodically poled Mg-doped lithium niobate （PPMgLN） crystal. According to quasi-phase-matching （QPM） in the PPLN crystal based on the theoretical model of three wave interactions in a nonlinear medium and the output characteristics of dual-wavelength erbium-doped fiber laser,the experimental refractive index difference on the periodically poled Mg-doped lithium niobate crystal is given. Through analyzing the working temperature and the grating period on its output of the THz-wave in theory,the reliable method to generate the continuous-tunable output wave through the PPMgLN in a small frequency range is obtained. The DFG device structure is relatively simple, low cost, and the tuning is easy to implement. In addition,the laser can be operated at room temperature.