We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at ∼1938.72 nm. The temporal pulse-to-pulse separation among the multiple solitons, 10 in a single-pulse bunch, increases from 0.89 ns to 1.85 ns per round trip. In addition, with the increasing pump power, the number of bunched solitons increases from 3 up to 24 linearly, while the average time separation in the soliton bunch varies irregularly between ∼0.80 and ∼1.52 ns. These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.

基于色散傅里叶变换技术研究了反常色散腔内传统孤子和正常色散腔内耗散孤子建立时的孤子动力学过程。为探究脉冲在光放大器中如何随放大功率演变, 实验和模拟研究了这两类孤子经放大器放大后的动态变化。结果表明, 这两类孤子的光谱在建立时会经历不同的振荡过程, 传统孤子光谱会由能量有剧烈振荡的调制拍频状态过渡至稳定, 耗散孤子光谱则会由无序调制状态平稳展宽至稳定。在放大器中, 随着放大器泵浦功率的上升, 传统孤子光谱中心能量将被转移而展宽, 耗散孤子光谱则在保持谱宽不变的情况下在边沿出现尖峰。这些锁模光纤激光器和光放大器中的动态孤子非线性现象在超快激光及其放大系统中有着潜在的应用价值。

报道了一种基于Figure-9光纤振荡器和单级单模光纤放大器的皮秒脉冲光纤前端。通过优化光纤振荡器腔内光纤长度, 获得了中心波长约为 1064 nm、重复频率10 MHz、脉冲能量0.4 nJ的自启动单脉冲锁模窄带耗散孤子皮秒脉冲；通过优化光纤放大器的增益光纤长度, 对光纤振荡器产生的21.07 ps脉冲进行单级单模光纤放大后, 脉冲能量达10 nJ时的脉冲光谱依然呈钟形结构, 3 dB谱宽和脉宽分别为0.31 nm和19.8 ps, 该皮秒脉冲光纤前端有望在精密加工等领域发挥重要作用。

采用半导体可饱和吸收镜的锁模光纤激光器是构建皮秒脉冲光纤放大器的热门候选种子光源之一。本文利用非线性薛定谔方程从理论上分析了单模传输光纤和单模增益光纤的模场半径、增益光纤的光纤长度、光纤布拉格光栅的反射率、半导体可饱和吸收镜的调制深度、非饱和损耗和饱和通量对输出脉冲特性的影响。对输出激光的脉冲和光谱特性也进行了理论研究。根据仿真结果，搭建了基于非保偏线型腔和SESAM的掺镱锁模光纤激光器系统。在没有任何腔内色散补偿和外部偏振控制的情况下，获得了中心波长为1.06 μm、脉冲宽度小于12.51 ps、光谱宽度为0.32 nm、重复频率为37 MHz、输出功率为2 mW的稳定锁模脉冲激光输出。在我们的实验中，激光脉冲的光谱边缘平滑，光谱分布非常接近高斯线型。最后，通过系统的仿真，近红外锁模光纤激光器的整体结构得到了优化。本文介绍的锁模光纤激光器具有紧凑的非保偏光纤结构、精简的腔内配置和较少的元器件、高质量的输出脉冲相关特性，有望为下一代皮秒脉冲光纤激光器提供性能优异的实用化种子光源。

We report a Yb-doped mode-locked fiber laser based on a nonlinear amplifying loop mirror (NALM), which is all-normal-dispersion (ANDi), and allows the output wavelength to be tunable. The laser can generate a stable femtosecond dissipative soliton with a maximum output power of 196 mW. Its repetition rate is 112.4 MHz, and the final pulse duration is 236 fs. By adjusting the angle of the reflective diffraction grating, the mode-locked fiber laser was realized to tune the output with a tuning range of 54 nm from 1011.8 nm to 1065.6 nm. To the best of our knowledge, this is the widest tuning range of an ANDi Yb-doped mode-locked fiber laser based on NALM.

本文提出了一种提高被动锁模光纤激光器计算效率的方法,该方法由对称分步傅立叶方法（SSFM）和全局误差局部能量（GELE）方法组成。该方法可将与全局误差相关的局部能量增量限制在一定范围内来控制步长。该方法具有自动步长调整机制。达到同程度的计算精度，本文方法的计算时间为255 s，而小的恒定步长SSFM方法需要3855 s。这表明本文方法可以将计算效率提高10余倍。本文方法还可以通过RK4IP、Adams、预测-校正等高阶算法进行扩展，以提高精度。

We report a compact, tunable, self-starting, all-fiber laser-based asynchronous optical sampling (ASOPS) system. Two Er-doped fiber oscillators were used as the pulsed-laser source, whose repetition rate could be set at 100 MHz with a tuning range of 1.25 MHz through a fiber delay line. By employing phase-locked and temperature control loops, the repetition rate offset of the two lasers was stabilized with 7.13 × 10^-11 fractional instability at an average time of 1 s. Its capabilities in the terahertz regime were demonstrated by terahertz time-domain spectroscopy, achieving a spectral bandwidth of 3 THz with a dynamic range of 30 dB. The large range of repetition rate adjustment in our ASOPS system has the potential to be a powerful tool in the terahertz regime.

Wavelength-tunable dissipative solitons and amplifier similaritons have been obtained by inserting all-fiber Mach–Zehnder interferometer (MZI) filters with different free spectral ranges (FSRs) in a Yb-doped mode-locked fiber laser. The MZI filter is fabricated by splicing one segment of seven-core fiber (SCF) between two segments of single-mode fibers. The bandwidth of the filter depends on the FSR of the modulated interference curve and consequently depends on the tapered fiber diameter. Inserting MZI filters with bandwidths in a fiber laser and applying a tensile strain on the tapered SCF, both wavelength-tunable dissipative solitons and amplifier similaritons have been obtained.

以锁模光纤激光器为研究平台，利用色散傅里叶变换技术，实时观察到调制频率成比例的三周期隐形孤子脉动现象。通过分析孤子的演化特性，笔者所在课题组认为孤子的调制不稳定性引起了色散波和孤子的参量耦合过程，导致了色散波和孤子的能量交换，从而产生了参量边带和隐形孤子脉动。部分能量在色散波和孤子间的交换使得孤子总能量几乎不变。因此这种孤子脉动难以通过时域脉冲序列分辨。此外，文中实验分析了隐形孤子脉动完整的演化路径，即仅通过增加泵浦功率使得脉动产生至消失的过程。与传统的可见脉动过程相比，这种隐形孤子脉动的调制周期随泵浦功率的变化较小。该工作不仅加强了对孤子脉动动力学现象的理解，还对锁模激光稳定性的提升具有重要意义。