【作者】 张帆；

【导师】 董建绩；

【作者基本信息】 华中科技大学 ， 光学工程， 2021， 硕士

【摘要】 微波光子学是利用光学器件和技术来产生、传输、处理和探测射频信号的学科。基于微波光子学的射频信号处理方法能对超宽带信号进行处理,可以根据需求灵活设计射频响应,处理后的信号还可以利用光纤进行低损耗传输。微波光子学兼具微波技术和光学技术的优势,是解决通信系统带宽瓶颈的重要技术手段之一。作为微波光子学的重要部件之一,光延时线在相控阵天线、微波光子滤波器等领域发挥着重要作用。但目前的集成光延时线存在带宽小、延时不能连续调节、特征尺寸过小等问题。针对这些问题,本文围绕啁啾布拉格光栅延时线开展理论和应用研究。主要内容如下:(1)详细介绍了目前主流的集成光学延时线方案,并对这些方案的优缺点做了分析。简要介绍了光波导的计算方法。使用耦合模理论分析了布拉格光栅的工作原理,推导了耦合系数等重要参数。(2)对反向耦合型啁啾光栅进行了详细的分析。在此基础上,提出并实验验证了四通道光学延时网络,测得的色散系数分别为10.35,4.00,-4.32和-14.38 ps/nm,可用带宽为7 nm。计算了相应的扫描角度,通过改变工作波长可实现从-33.9度到36.4度的角度扫描。(3)提出了一种基于多模波导的啁啾布拉格光栅。采用占空比渐变实现啁啾,非对准切趾抑制延时抖动。制备并实验测试了长度均为1.192 mm的正、负色散系数的两种啁啾光栅,验证了非对准切趾的有效性。对于正色散系数的啁啾光栅,实现了22.9 ps的延时,延时抖动幅度约为2.5 ps,单位延时损耗为0.17 d B/ps,延时相关损耗为0.052 d B/ps。对于负色散系数的啁啾光栅,实现了17.7 ps的延时,单位延时损耗为0.1 dB/ps,延时相关损耗为0.019 dB/ps。更多还原

【Abstract】 Microwave photonics is a discipline that uses optical devices and technologies to generate,transmit,process and detect radio frequency signals.The radio frequency signal processing method based on microwave photonics can process ultra-wideband signals,and flexibly tailor the radio frequency response according to requirements.The processed signals can also transmit in low loss optical fibers.Microwave photonics has the advantages of both microwave technology and optical technology,which is one of the important solutions to cope with the bandwidth bottleneck in communication systems.As one of the important components of microwave photonics,optical delay lines play an important role in the fields of phased array antenna,microwave photonic filter and so on.However,the current integrated optical delay lines have drawbacks such as small bandwidth,discrete delay adjustment and small feature size.To deal with these problems,this thesis focuses on the theory and application of chirped Bragg grating delay lines.The main contents are as follows:(1)The mainstream integrated optical delay line schemes are introduced in detail,the advantages and disadvantages of these schemes are analyzed.The calculation methods of optical waveguide are briefly introduced.The working principle of Bragg gratings are analyzed using coupled mode theory,and some important parameters such as coupling coefficient are derived.(2)The contradirectional coupling chirped Bragg grating is analyzed in detail.Based on the analysises,a four-channel optical delay network was proposed and demostrated,the measured dispersion coefficients were 10.35,4.00,-4.32 and-14.38 ps/nm with 7 nm available bandwidth.The corresponding scanning angle was calculated,from-33.9 degree to 36.4 degree by changing the operation wavelength.(3)Chirped Bragg gratings based on multimode waveguide were proposed,which uses gradual duty cycle to achieve chirp and mismatch apodization to suppress delay ripples.Two chirped Bragg gratings with a length of 1.192 mm with positive and negative dispersion coefficient are fabricated and measured,the effectiveness of mismatch apodization was verified.For the chirped grating with positive dispersion coefficient,a delay of 22.9 ps is achieved,the amplitude of delay ripples is about 2.5 ps,the unit delay loss is 0.17 d B/ps and the delay related loss is 0.052 d B/ps.For the chirped grating with negative dispersion coefficient,a delay of 17.7 ps is realized,the unit delay loss is 0.1 d B/ps and the delay related loss is 0.019 dB/ps.更多还原