【作者】 张羽；

【导师】 张新亮；

【作者基本信息】 华中科技大学 ， 光学工程， 2010， 博士

【摘要】 微纳光纤是纳米光子学中的一个重要研究领域,它以其卓越的性能成为未来光器件微型化集成化的一种可供选择的基本单元。微纳光纤作为光波导具有以下独特的优点：具有极低的光纤到器件再到光纤的耦合损耗,粗糙度极低的波导表面,高折射率差的强限制光场,大百分比的倏逝场,极轻的质量及灵活的色散特性。所以对微纳光纤特性、微纳光纤光子器件及微纳光纤应用的研究正吸引越来越多研究者的注意。本论文针对微纳光纤还从未涉足的领域：光信号处理展开研究;除了提出并实验实现了一些基于微纳光纤的新型光子器件,还对微纳光纤在全光码型转换和微波光子学中的应用进行了深入研究,概括全文的研究成果和贡献,有如下几个方面：(1)建立了微纳光纤的物理模型,推导了微纳光纤的单模传输条件,分析了微纳光纤基模的电场分布和能量分布的特点,以及群速度和波导色散,采用FDTD法研究了微纳光纤相互之间的的模场耦合特性。(2)搭建了微纳光纤的拉制平台和基于微纳光纤的光子器件的装配测试平台,成功制作出了可满足实验需求的各种直径和长度的微纳光纤,并装配测试了多种微纳光纤光子器件,为后续的应用实验研究工作打下了坚实的基础。(3)提出了反射型微纳光纤环谐振器(RMRR)的概念,推导了该器件的反射传递函数,实验组装了RMRR,获得了一系列不同FSR的梳状反射谱。提出了微纳光纤布拉格光栅(MFBG)的概念,理论推导了多模传输的MFBG除了具有正向基模与反向基模耦合产生的反射峰,还有正向高阶模式与反向基模耦合所产生的反射峰；利用包层部分掺锗的特殊光纤拉制出微纳光纤,并通过相位掩模板在KrF准分子激光器的紫外曝光下,成功制作出不同直径的MFBG;并用其进行了折射率传感的实验,获得了较高的传感灵敏度。(4)提出了基于微纳光纤环谐振器(MRR)的RZ到NRZ的全光码型转换方案,理论模拟了利用MRR进行RZ到NRZ码型转换的原理,分析了MRR的失谐量、消光比及精细度对转换的NRZ信号的质量的影响；基于MRR的可调谐性实验实现了20Gb/s和40Gb/s等不同速率下的的RZ到NRZ码型转换；并且实验验证了多信道RZ码到NRZ码的码型转换的可行性。(5)提出了基于MRR的微波光子学滤波器实现方案,首先利用MRR构建了单纵模双波长激光器,然后利用色散介质引入延时差,实现了大FSR的微波光子学滤波器；理论分析了MRR特性参数对微波光子学滤波器滤波特性的影响,实验结果表明通过调节微纳光纤环的直径可以方便实现微波光子学滤波器的可调谐性。(6)提出了基于微纳光纤的毫米波超宽带信号的产生方案,理论推导了利用该方案产生正负monocycle和正负doublet的毫米波超宽带信号的原理,实验实现了24GHz的毫米波超宽带信号,通过调谐微纳光纤环谐振器的透射谱,可以获得正monocycle的和负monocycle自由切换的毫米波超宽带信号,所获得24GHz的毫米波超宽带信号的频谱完全符合FCC的要求。更多还原

【Abstract】 As an important research topic of Nano-photonics, microfiber will become an alternative fundamental building block of future miniaturized and integrated photonic devices or circuits thanks to its excellent performance. Microfibers have many particular characteristics such as very low fiber-to-fiber coupling loss, extremely small surface roughness, strongly confined field due to high refractive index difference, high fractional evanescent field, extremely light in mass, and flexible dispersion property. Therefore, there are more and more efforts devoted to the research of microfiber fabrication, photonic devices based on microfiber, and application of microfiber.In this thesis, some novel photonic devices based on microfiber are proposed and demonstrated. Optical format conversion and microwave photonics devices based on microfibers are researched. Several research achievements and contributions are summarized as followings:(1) Theoretical model of microfiber and single mode condition of microfiber are researched. We numerically simulate and analyze the distribution of electric-field and power, as well as the properties of waveguide dispersion and group velocity. FDTD simulation is used to research evanescent coupling between parallel microfibers.(2) We establish the fabrication setup of microfiber and assembling and measurement platform of photonic devices based on microfibers. A variety of microfibers with different diameters and lengths are fabricated successfully, which are utilized to assemble some photonic devices based on microfiber. All of these are substantial groundwork of the following experimental research.(3) Reflected microfiber ring resonator (RMRR) is proposed. The transfer function of RMRR is derived. Several RMRRs with different free spectral range are experimentally demonstrated. Novel microfiber Bragg grating (MFBG)is proposed. Simulation results show that the coupling between the forward-propagating fundamental mode and the backward-propagating fundamental mode produces the long-wavelength reflection, and the coupling between the counter propagating HE11 and HE12 modes generates the short-wavelength reflection. We demonstrate several MFBGs with different diameters using specially Ge doped microfiber through KrF excimer laser irradiation with a uniform phase mask. The diffractive index sensors based on these MFBGs are demonstrated,which have high sensitivity.(4) An all-optical return-to-zero (RZ) to nonreturn-to-zero (NRZ) format converter utilizing microfiber ring resonator is proposed. The operation principle is numerically simulated and analyzed. We analyze the Q factor of converted NRZ signal affected by detuning, extinction ratio, and finesse of MRR. We experimentally demonstrate the format conversion from RZ to NRZ at the different bit rates of 20 Gb/s and 40 Gb/s through adjusting the diameter of MRR. The multi-channel format conversions from RZ to NRZ are also successfully demonstrated(5) A novel tunable microwave photonic filter based on MRR is proposed and experimentally demonstrated. A fiber ring laser based on the microfiber ring resonator is employed to generate two singlelongitudinal-mode carriers, then the dispersive element introduces the delay between two modulated carriers. By adjusting the diameter of the microfiber ring resonator, the proposed microwave photonic notch filter with high free spectral range canbe continuously and widely tuned.(6) The photonic generation of millimeter-wave (MMW) ultra-wideband (UWB) signal using MRR is proposed, The operation principle of generating MMW-UWB with opposite polarities monocycle and doublet waveform is analyzed. We experimentally demonstrated the 24-GHz MMW-UWB signal. Through adjusting the transmission spectrum of MRR, the polarity of monocycle waveform can be switched. The generated 24-GHz MMW-UWB signal has power spectrum density complying with the Federal Communication Committee regulation.更多还原