Study Of Extended Interaction Oscillator In Terahertz Wave Regime

Terahertz (THz) wave, electromagnetic radiation between far infrared and millimeter wave, has very important academic and application value. One kind of THz radiation source, extended interaction oscillator (EIO), is presented in this dissertation. The theoretical, simulation and experimental studies have been carried out in detail.The main work includes as the following:1. A novel slow wave structure (SWS) of rectangular reentrance coupled-cavity suitable for THz wave has been proposed as the SWS of THz EIO.2. The cold cavity characteristic of the SWS has been theoretically studied in detail. The frequency and the circuit parameters of a rectangular reentrance resonant cavity have been studied by the unperturbed theory and the principle of the equivalent circuit of a ridged waveguide, respectively. The circuit model and the dispersion characteristic of the SWS have been studied by adopting the equivalent circuit method.3. The beam-wave interaction in THz wave EIO has been studied. With the electrons motion equation, the beam-wave interaction efficiency and the normalized electron conductance as well as the staring current have been calculated in detail. From the concept of large signal based on electron disk model, each electron disk operating equations in each gap and drift zone and the matching equation at the boundary between the gap and the drift zone have been obtained. These parameters in THz wave region have been calculated and discussed in detail by programming. The optimal period number has been calculated.4. With CST and MAGIC software, the filed distribution, and the dispersion characteristic of the operating mode of the SWSs obtained by theoretical study have been simulated. The coupled impedance and characteristic impedance of the SWSs have been computed. The dispersion characteristic of the SWSs obtained by theoretical study agrees well with that by the simulation study. The beam-wave interaction of THz EIOs has been carried out by PIC (particle in cell) code. Simulation results have shown that the EIO output peek power are 512W, 44W and 200W at 0.12THz and 0.225THz with round beam tunnel and at 0.215THz with rectangular beam tunne, respectively. The study shows that THz EIOs can operate in very wide voltage.5. Combined with the domestic machining technique, high frequency circuits of 0.11THz EIO and 0.22THz EIO have been fabricated. The experiment of the EIO at 8mm band with U-shaped folded waveguide SWS has being carried out. The 8mm EIO tube has been designed including the SWS, the transferring waveguide, the electronic gun and the magnet. The preliminary experiments have been carried out, including the performance of the cathod and the electronic gun and the measurement of the output power and the operating frequency.