太赫兹（THz）波在通信、医疗、安检等领域具有重要的应用价值，但当前小型化自由电子THz辐射器件面临着频率难以提升的难题。相干史密斯-帕塞尔辐射（SPR）是周期群聚电子团飞过光栅表面产生的相干电磁辐射，基于相干SPR的高阶倍频辐射有望提升辐射频率。虽然在电子加速器中已经实现了高频THz相干SPR，但在小型化器件中实现1THz以上的相干SPR仍面临挑战。同时，自由电子THz频梳也是在大型储存环中产生，小型化自由电子THz频梳器件未见报道。 本论文理论和仿真研究了基于返波群聚电子的1.02THz相干SPR辐射产生。设计了返波群聚电子和辐射谐振增强的两级结构，仿真了光栅表面0.255THz返波群聚直流电子过程，形成的周期电子团产生了~1.8mW的1.02THz四倍频相干SPR辐射，同时辐射频率将随着电子枪电压的抖动而漂移，引起频谱线宽的展宽。 理论和实验研究了基于受激相干SPR的1.02THz小型化辐射器件。设计了泵浦波群聚直流电子的褶皱矩形波导，通过预群聚电子诱导的受激相干SPR实现低功率泵浦下的高密度电子群聚，并利用相干辐射结构获得高频THz输出。仿真结果表明，在10mW的0.34THz泵浦作用下，器件产生了~2mW的1.02THz三倍频相干SPR辐射，并且辐射频率不随电子能量改变。实验研制出1.02THz相干辐射器件，在60mW的0.3398THz泵浦输入下，观测到功率~6μW、线宽~35GHz的1.0193THz辐射。本论文首次在1.02THz频率附近实现了小型化相干SPR辐射器件，其尺寸比电子加速器缩小2-3个数量级。 提出并实现了基于非线性交调失真的THz频梳产生方法和小型化器件。理论研究了幅度调制后的泵浦波在受激相干SPR器件中的交调失真效应，通过调控电子群聚分布产生了等频率间隔的交调分量，在高阶倍频辐射中形成THz频梳。实验实现了0.3THz附近的小型化自由电子频梳器件，调制后的0.0972THz泵浦波输入器件中，获得了以泵浦波三倍频0.2916THz为中心、频谱覆盖10MHz、梳齿数量超过100的频梳。其精度可达1×10-9；重复频率降至100kHz，并可根据调制频率调谐；相比大型储存环，相干SPR辐射器件尺寸和成本大大降低。 本论文研究了基于相干SPR的高频THz辐射产生，研制出的1.02THz相干辐射器件和0.3THz附近频梳器件有助于小型化自由电子THz辐射器件的发展。

Terahertz (THz) wave plays an important role in the applications of communication, medical and security checking fields. However, it is difficult currently for the miniaturized free electron emission devices to increase the operation frequency. Coherent Smith-Purcell Radiation (SPR) is the coherent electromagnetic emission generated by periodically bunched electrons flying over the gratings. Radiation at high harmonics based on coherent SPR is expected to increase the emission frequency. Although coherent SPR at high harmonics has been realized in the accelerators, it is still a challenge to generate coherent SPR above 1 THz in the miniaturized devices. In addition, the free electron THz frequency comb is produced in the storage ring. THz frequency comb cannot be realized in the miniaturized free electron devices. In this dissertation, the generation of 1.02 THz coherent SPR based on electrons bunched by backwave is studied theoretically and numerically. The structures used for bunching electrons by backwave and enhancing THz emission are designed. The process of 0.255 THz backwave on the grating surface bunching direct current (DC) electrons is simulated. The fouth harmonics coherent SPR at 1.02 THz with power of ~1.8mW is generated by the periodically bunched electrons. Meanwhile, it is found that the radiation frequency drifts with the jitter of the electron gun voltage, which would cause the broadening of spectral linewidth. The 1.02 THz miniaturized emission device based on stimulated coherent SPR is studied theoretically and experimentally.The rectangular waveguide with gratings is designed for DC electrons bunching with pump wave. Bunched electrons with high density under low-power pump wave are achieved due to the effect of stimulated coherent SPR induced by pre-bunched electrons. And high-frequency THz emission is generated utilizing coherent radiation structure. The simulation results show that the device could generate third harmonics coherent SPR radiation at 1.02 THz with power of ~2 mW under the 0.34 THz pump wave of 10 mW. It is found that the emission frequency does not change with the electron energy. And the 1.02 THz coherent esmission device is fabricated and measured. Under the 0.3398 THz pump input of 60 mW, 1.0193 THz radiation of ~6 μW with linewidth of~35GHz is observed. Here, the miniaturized coherent SPR emission device at frequency of near 1.02 THz is realized for the first time. The size of this device is about 2-3 orders of magnitude smaller than the electron accelerator. The THz frequency comb generation method based on nonlinear intermodulation distortion is proposed and the miniaturized device is realized. The intermodulation distortion effect of amplitude modulated pump wave in the stimulated coherent SPR device is theoretically studied. The intermodulation frequency components with equal frequency interval are generated by adjusting the distribution of bunched electrons, and THz frequency comb is formed in the high harmonics radiation spectrum. A miniaturized free electron frequency comb device near 0.3 THz is realized in the experiment. With the input of modulated wave with carrier frequency at 0.0972 THz, the frequency comb with more than 100 comb teeth covering a frequency range of 10 MHz is obtained. The centered frequency is on the third harmonics of pump wave. The accuracy of frequency comb can reach 1×10-9, and the repetition frequency is reduced to 100kHz and can be tuned by changing the modulation frequency. Compared with the large storage ring, the size and cost of coherent SPR emission device are greatly reduced. In this dissertation, the generation of THz emission near 1THz based on coherent SPR is studied. The 1.02 THz coherent emission device and the frequency comb device near 0.3 THz are helpful of promoting the development of miniaturized free electron THz emission devices.