Investigation Of Coherent Terahertz Smith-Purcell Radiation Drived By Premodulated Electron Beam

Terahertz (THz) wave generally refers to the electromagnetic wave with thefrequency of100GHz~10THz.Beacause of the unique advantages in theelectro-magnetic spectrum, it has widely potential applications in many areas. A stableterahertz radiation source is one of the keys to develop the terahertz (THz) science andtechnology. The terahertz source based on vacuum electronics played a great role in thedevelopment of terahertz (THz) science and technology.A terahertz radiation sourcedevice based on the Smith-Purcell radiation principle has become a hotspot in theresearch of terahertz source in recent years because it can work on high harmonics withlower starting current.The coherent THz radiation generated by pre-modulated electron beam is studiedin this paper.The major works are as follows:1).The dispersion relation of two-asymmetric grating and sub-wavelength holearrays are achieved by mode-matching method. Numerical method is used to get thedispersion curves and growth rate. The influence of structural parameters is discussedthen.2).The structure of two-asymmetric grating combined sub-wavelength holes arrayis studied. Particle-in-cell(PIC) simulation is used to investigate the bunching propertyand radiation property. From the study, the conclusions can be achieved: Firstly, theelectron beam bunched well at the frequency of0.31THz because of the beam-waveinteraction. Secondly, the Smith-Purcell superradiation with the angle corresponding tothe2nd harmonics frequency component of the prebunched electron beams has beenclearly observed. Thirdly, the two electron beams can be coupled with each otherthrough the holes array so the intensity of the radiated field has been enhanced abouttwice larger than that excited by one electron beam.3). The structure of sub-wavelength holes array combined3-mirror quasi-opticalcavity is presented in this part. The quasi-optical cavity system has the characteristics ofhigh-Q value、tunable frequency and tunable angle, so it can work as the feedbacksystem and resonant system of the Smith-Purcell superradiation to increase the radiation intensity and efficiency.The results shows that this radiation source can work well onthe second harmonics mode.