【作者】 唐海涛；

【导师】 于源； 张新亮；

【作者基本信息】 华中科技大学 ， 光学工程， 2020， 博士

【摘要】 微波光子学是把传统的微波技术与光电子技术进行融合的一门交叉学科。与传统的微波技术相比,微波光子技术把微波信号的产生、传输与处理放在光域中来完成,不仅可以打破电子瓶颈,还可以兼顾光子技术的优势。光生微波信号就是其典型应用。通讯系统的发展离不开高质量的微波信号,而不同的系统对微波频段的需求也不一样。随着各国军事力量的发展,战场环境日趋复杂,为提高战场生存力,国家号召实现雷达、通信和电子战对抗等多系统融合。多系统的融合对高质量可调谐的微波信号提出了迫切需求。光电振荡环(Optoelectronic Oscillator,OEO)可以很好地满足需求。与传统微波振荡器不同,OEO利用光纤超低的传输损耗,让储能延时过程在光域中完成,基于光电混合正反馈环路,将光能直接转换为微波信号能量,克服了传统微波振荡器随振荡信号频率升高而相位噪声显著劣化的缺陷。但是目前报道的OEO很难同时具有低相位噪声、超大边模抑制比、超宽的可调范围等优点。本文将大范围可调的超窄宽带的微波光子带通滤波器(Microwave Photonic Bandpass Filter,MPBF)用于OEO中进行模式选择,可以满足OEO在保持低相位噪声的同时具有大边模抑制比且振荡频率大范围自由可调的优点。高质量宽带可调的OEO是一种非常理想的微波信号源,在无线通信、雷达、电子对抗、光学传感、电子测量等领域具有广泛的应用前景。本论文在保持OEO低相位噪声的前提条件下,围绕提升其频率调谐范围、抑制模式竞争、提升边模抑制比以及OEO的小型化与集成化等方面展开研究工作。本论文的主要贡献与创新点如下:(1)基于高非线性光纤(High Nonlinear Fiber,HNLF)中的受激布里渊散射效应(Stimulated Brillouin Scattering,SBS)构建了一个微波光子滤波器(Microwave Photonic Filter,MPF)。通过建立理论模型分析基于SBS的微波光子滤波器(SBS-MPF)的产生机理,优化SBS的泵浦功率、HNLF的长度以及泵浦光与信号光之间的偏振态,抑制了由SBS损耗特性产生的微波通带,打破了之前报道的SBS-MPF的调谐范围小于两倍布里渊频移频率的限制,并进行了实验验证。实验测得的单通带微波光子滤波器可以实现0到40 GHz范围可调谐,抑制比可以达到50 d B,滤波器的半高全宽(Full Width at Half Maximum,FWHM)带宽约为16 MHz。(2)基于级联微波光子滤波器实现宽带可调的超窄带通MPF。通过分析微波光子级联滤波器的实现条件与机理,将SBS-MPF与基于有源光纤环的无限冲激响应(Infinite Impulse Response,IIR)滤波器(IIR-MPF)进行级联。实验得到的单通带MPF的FWHM带宽仅为150 k Hz,据本人所知,这是目前报道的带宽最窄的单通带可调谐MPF。将此级联MPF用于OEO选模,顺利实现了OEO的单模起振。借助于SBS-MPF的大范围可调谐性,级联滤波器的频率调谐范围也达到40 GHz,实现了OEO同时具有低相位噪声、宽带可调谐性、大边模抑制比的优良特性。(3)基于高Q硅基微环构建了一种小型化OEO。本论文介绍了片上高Q器件的设计、制作与测试,在绝缘体上硅(Silicon on Insulator,SOI)平台上制备了高Q微环谐振器并得到了窄带宽的单通带MPF。在此基础上验证了基于微环的小型化OEO,为实现单片集成OEO奠定基础。更多还原

【Abstract】 Microwave photonics(MWP),which combines the worlds of microwave engineering and optoelectronics,is an interdisciplinary area.Compared with the traditional microwave engineering,MWP enables the generation,transmission and processing of microwave signals in the optical domain.In this way,MWP cannot only solve the problem of electronic bottleneck,but also takes the advantages of photonic technology.Optical generation of microwave signals is one key applications.The development of communication systems is inseparable from high-quality microwave signals,and different systems have different requirements for microwave frequency bands.With the development of military forces in various countries,the battlefield environments are becoming more and more complex.To improve battlefield survivability,the integration of multiple systems such as radar,communications,and electronic warfare,is significantly demanded.The fusion of multiple systems places an urgent need on high-quality tunable microwave signals.Optoelectronic oscillator(OEO)can meet the needs well.Different from the traditional microwave oscillators,OEO uses the ultra-low transmission loss of optical fibers to store energy in the optical domain.Based on the opto-electronic hybrid positive feedback loop,in OEOs the optical energy is directly converted to the microwave signal,which overcomes the disadvantage that the phase noise of traditional electronic oscillators is significantly deteriorated with the increase of the oscillating frequency.However,it is difficult for OEO to have the advantages of low phase noise,large side mode suppression ratio(SMSR)and ultra-wide tunable range at the same time.A widely tunable microwave photonics bandpass filter(MPBF)with an ultra-narrow passband is used in the OEO for mode selection,which can meet the free switching of the oscillating frequency in a wide spectral range while mataining low phase noise and large SMSR.Wideband tunable OEO is an ideal microwave signal generator,which can be widely applied to wireless communication,radar,electronic warfare,optical sensing,electronic measurement and clinical medicine,etc.This thesis focuses on improving the frequency tunability of OEO,improving phase noise performance,suppressing mode competition,improving the SMSR and miniaturization and integration of OEO.The main contributions and innovations of this thesis are as follows:(1)Based on the stimulated Brillouin scattering(SBS)in high nonlinear fiber(HNLF),a narrowband MPBF is proposed.We analyze the operation principle of SBS-based MPF(SBS-MPF)to optimize the performance of the SBS-MPF.By optimizing the pump power,the HNLF length and the polarization states of the pump and signal waves,the amplitude suppression ratio between the passbands generated by SBS gain and loss is increased.Therefore,the limitation that maximum tuning range of the previously reported SBS-MPFs is limited within two folds of the Brillouin frequency shift,is successfully broken.In the experiment,the central frequency of the single passband MPF can be tuned from 0 to 40 GHz,the rejection ratio can reach above 50 d B and the full width at half-maximum(FWHM)bandwidth is 16 MHz.(2)Based on cascaded MPFs,an ultra-narrow bandpass MPF with wideband tunability is proposed and experimentally demonstrated.By analyzing the operation principle and operation conditions of the cascaded filters,the ultra-narrow passband is realized by cascading the SBS-MPF and an infinite impulse response MPF(IIR-MPF)based on an active fiber recirculating delay loop.The measured FWHM bandwidth of the cascaded MPFs is 150 k Hz.To the best of my knowledge,this is the first time realizing such a narrow passband in single-passband MPF.Owing to the widely tunability of SBS-MPF,the frequency tunability of the cascade MPFs also reaches 40 GHz.Using the cascaded MPFs to replace the electronic bandpass filter in the OEO for mode selection,a widely tunable low phase noise OEO is achieved.The obtained OEO can maintain low phase noise,wideband tunability,and large SMSR simultaneously.(3)A miniaturized OEO is proposed based on high-Q silicon microring resonator(MRR).The design,fabrication and testing of on-chip high-Q microcavities are introduced.An MRR based on silicon-on-insulator is fabricated and a single passband MPF with narrow bandwidth is achieved.Then the miniaturized OEO is conducted and demonstrated,which lays the foundation for monolithically integrated OEO.更多还原