折返结构太赫兹倍频放大器机理研究

Sources and amplifiers at terahertz frequency have remarkable advantages in fields as imaging, security or comunication, which become to be attractive research region. And the vacuum terahertz(THz) electronic device is to be hot spot research for its potential capacities to obtain high terahertz radiation power. However, there comes up a big difficult against to extend the traditional vacuum electronic device from microwave to THz. Because there has been a limitation between the microwave frequency, the tube structure and the output power in vacuum electronic devices. When the microwave frequency up to THz, the micro-fabrication should be introduced for the dimensions of the structure are much small, the beam current can not be bunched so long for the thin current which also can not supply large power, and the input signal is also lack at THz frequency.. A forward-backward wave interaction with beam in THz multiplier amplifier has been proposed and the mechanism is developed. The electromagnetic wave interacts with beam in an enfold way, which fundamental wave travelling in forward wave mode then inspire second harmonic wave return to backward wave, using a single beam and folding the interaction region. Two Schottky diodes have been utilized to translate the fundamental wave to second harmonic wave, which show a way of combing the solid circuit with the vacuum electronic device at THz.The double-corrugated waveguide (DCW) interaction structure is utilized as the slow wave structure, which can be easily realized by modern microfabrication techniques, and can be easily integrated to combine the power by multibeam. So the mechanism study on the forward-backward multiplier amplifier will be the significant work to fabricate the compact integrated THz device.

太赫兹技术因其在成像、检测、通信等领域具有无可比拟的优势而备受关注，基于真空电子学的太赫兹辐射源因其可望获得大功率太赫兹辐射成为研究热点。传统微波真空电子器件受限于几何尺寸和工作频率的共度性原理制约，到太赫兹频段，将出现器件几何尺寸变小、互作用效率下降、功率容量变低等问题，这已成为传统微波真空电子器件向太赫兹频段拓展时面临的巨大挑战。. 本项目提出一类新型折返结构太赫兹倍频放大器，在同一段电路中构建电磁波折返工作的高频结构，复用一束电子注，可有效缩短注波互作用长度。电路中前向波工作于基波频率，返波工作于倍频，并引入肖特基变容二极管加速倍频转化，探索真空固态复合太赫兹功率器件的可能性。同时采用周期排列金属方柱结构，易加工易多注集成，可突破功率制约。本项目通过对折返结构太赫兹倍频放大器机理与实验研究，为研制紧凑型易加工大功率输出的新型真空太赫兹辐射源奠定理论和技术基础。

该项目提出一种新型折返结构太赫兹倍频放大器，利用行波管的“功率洞”特性，构建前向波-返波折返式注波互作用回路，将返波变废为宝，由抑制倍频返波激励变为加速返波放大，产生群聚的倍频高频电流，最终实现倍频信号的稳定输出。具体描述如下：该放大器分为两段式电路，第一段采取折返结构，第二段采用倍频功率辐射电路。在第一段电路中前向波-返波互作用放大，尽可能激励携带二次谐波或者更高次谐波的电子注，最终产生有效群聚的倍频高频电流。该电流作为级联电路的输入源，在级联的第二段电路中再次激励放大携带某次高频信号的电磁波，从而实现倍频信号的输出。通过对折返结构太赫兹倍频放大器机理与实验研究，探索了半导体材料与真空器件倍频的可行性，建立了折返式倍频互作用非线性理论和返波级联非线性注波互作用理论，解决了行波-倍频返波共同作用下竞争平衡与倍频转化以及返波级联与离散电子注再同步的关键问题，为研制紧凑型易加工大功率输出的新型真空太赫兹辐射源奠定理论和技术基础。