新型离散傅里叶锁模光纤激光器理论与实验研究

项目名称： 新型离散傅里叶锁模光纤激光器理论与实验研究

项目编号： No.61475131

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 无线电电子学、电信技术

项目作者： 卫炳江

作者单位： 香港理工大学深圳研究院

项目金额： 82万元

中文摘要： 傅里叶锁模激光器是下一代扫频光学相干断层扫描(OCT)技术最具潜力的光源之一。新型离散傅里叶锁模激光器的研究将能极大地提高激光器的输出信号质量，提高OCT系统的灵敏度，信噪比和探测深度。 本项目将建立离散傅里叶锁模激光器的理论模型，对腔内脉冲形成机制进行深入的分析，研究影响信号稳定性、信噪比、相干性等指标的关键机理和参数，探索提高输出脉冲质量的方法；研究基于特种非线性光纤和光纤光栅的腔内脉冲压缩整形技术，探索降低离散子脉冲信号带宽脉宽积的方案以提高脉冲信号质量，并研制基于此方案的离散傅里叶锁模激光器；提出基于幅度调制器实现时域离散傅里叶锁模激光器的方案，采用时域调制的方法对扫频信号进行离散化，极大地提高系统灵活性；提出结合梳状滤波器和时域调制的时频域双锁模激光器方案，采用光纤马赫曾德滤波器进行频域离散化，并触发调制器对光信号进行斩波压缩，从而实现频域上均匀分布的高性能离散傅里叶锁模激光器。

中文关键词： 傅里叶锁模；光纤激光器；离散通道；扫频光源

英文摘要： We propose to develop a theoretical model for discrete Fourier domain mode locked (DFDML) fiber lasers. We will investigate the mechanism of pulse formation and shaping in the DFDML laser cavity. The principle and parameters that affect pulse quality, particularly stability, relative intensity noise (RIN), and coherence length will be systematically investigated. We will also explore the methods to improve pulse quality. We will theoretically investigate the pulse shaping and compression mechanism which are achieved by incorporating a segment special nonlinear fibers such as dispersion decreasing fiber or a nonlinear fiber Bragg grating in the DFDML laser cavity. Methods and laser configurations to reduce the time-bandwidth product of the discrete chirped sub-pulse in the cavity will be explored. Guided by the results of the theoretical investigation, DFDML fiber lasers with improved output pulse quality will be built experimentally. We propose two novel DFML fiber laser configurations. The first one is based on time domain intensity modulation. The scheme uses an intensity modulator to discretize the frequency sweep signal into multiple sub-pulses. The flexibility of the laser system is expected to be significantly improved without using a comb filter such as Fabry-Perot etalon in the cavity. The second one is based on a novel mode-locking technique we invented, called time-frequency mode locking (TFML), which can improve the linearity of the frequency sweeping in the output signal of DFDML fiber laser. A fiber based Mach-Zehnder interferometer is used to slice the spectrum and generate the corresponding clock signal in time domain. The clock signal is then used to trigger a series of ultra-short electrical pulses to drive an intensity modulator, which will then chop the frequency sweeping optical signal into short sub-pulses. A high-quality DFDML fiber laser output is expected using the proposed scheme.

英文关键词： Fourier domain mode locking;Fiber lasers;Discrete channel;Swept Source