利用循环移频环路产生的倍频因子可调谐太赫兹信号

Generation of THz signal based on recirculating frequency-shifting loop with tunable frequency multiplication factor

太赫兹(THz)波在电磁波频谱中占有很重要的地位,THz技术是国际科技界公认的一个非常重要的交叉前沿领域。因此,提出了一种以循环移频环路(RFSL)为基础产生THz信号的微波光子学系统。输入光信号经由RFSL多次移频后在高速光电探测器中拍频产生THz信号。在RFSL中,基于射频(RF)控制的单边带(SSB)调制器是光信号移频的主要器件,每经过一次SSB调制器,光信号将产生一个与RF信号频率相等的移频间隔。THz信号的倍频因子由光在环路中循环的圈数控制。THz信号的频率随着倍频因子的增加而增加,频率大小为倍频因子与移频间隔的乘积。实验上实现了THz信号的倍频因子从1～25可调谐,测量了拍频获得的5～20 GHz微波信号光谱和电谱,测量了20 GHz信号功率以及中心频率的稳定性,并最终实验获得了0.25 THz的信号。

Terahertz(THz)waves occupy a very important position in the electromagnetic spectrum.THz technology is recognized as a major cross-cutting frontier in the international scientific and technology community.Photonic generation of THz signal using a recirculating frequency-shifting loop(RFSL)was proposed and experimentally demonstrated.The frequency of optical source was shifted by the RFSL and beats with each other in a high-speed photodetector to generate a THz signal.In the RFSL,the single sideband(SSB)modulator driven by a radio frequency(RF)signal was a key component for frequency-shifting.The frequency multiplication factor(FMF)of the THz signal was controlled by the lap number circulating in the loop.The frequency of the THz signal increased with the improvement of FMF and equals to the frequency multiplication factor multiplied by the frequency of RF signal.Experimentally,tunable signals from 5 GHz to 20 GHz were generated and the FMF was successfully tuned from 1 to 25.The stability of the power and center frequency was detected when the frequency of the signal was20 GHz.0.25 THz signal was finally generated by this system.