We firstly report a 2-μm all-fiber nonlinear pulse compressor based on two pieces of normal dispersion fiber (NDF), which enables a high-power scaling ability of watt-level and a high pulse compression ratio of 13.7. With the NDF-based all-fiber nonlinear pulse compressor, the 450-fs laser pulses with a repetition rate of 101.4 MHz are compressed to 35.1 fs, corresponding to a 5.2 optical oscillation cycle at the 2-μm wavelength region. The output average power reaches 1.28 W, which is believed to be the highest value never achieved from the previous 2-μm all-fiber nonlinear pulse compressors with a high pulse repetition rate above 100 MHz. The dynamic evolution of the ultrafast pulse inside the all-fiber nonlinear pulse compressor is numerically analyzed, matching well with the experimental results.

Multimode nonlinear optics is used to overcome a long-standing limitation of fiber optics, tightly phase locking several spatial modes and enabling the coherent transport of a wave packet through a multimode fiber. A similar problem is encountered in the temporal compression of multimillijoule pulses to few-cycle duration in hollow gas-filled fibers. Scaling the fiber length to up to 6 m, hollow fibers have recently reached 1 TW of peak power. Despite the remarkable utility of the hollow fiber compressor and its widespread application, however, no analytical model exists to enable insight into the scaling behavior of maximum compressibility and peak power. Here we extend a recently introduced formalism for describing mode locking to the analog scenario of locking spatial fiber modes together. Our formalism unveils the coexistence of two soliton branches for anomalous modal dispersion and indicates the formation of stable spatiotemporal light bullets that would be unstable in free space, similar to the temporal cage solitons in mode-locking theory. Our model enables deeper understanding of the physical processes behind the formation of such light bullets and predicts the existence of multimode solitons in a much wider range of fiber types than previously considered possible.

建立了不同类型衍射元件对衍射效率的影响模型，比较了单层衍射元件、谐衍射元件和双层衍射元件之间衍射效率的差异，重点分析在红外双波段光学系统中应用双层衍射元件的突出优势，计算不同材料组合情况下双层元件的平均衍射效率，以此为基础设计一款适合于高空机载平台的折衍混合红外双波段双视场光学系统。大视场对应的地物分辨率为1.5 m@16 km，长焦、短焦分别为960 mm和480 mm，通过切换反射镜改变光路来实现变焦功能，保证变焦过程中系统的光轴稳定性。仿真结果表明在−40~60 ℃的大温差环境下，系统的MTF曲线平滑且接近衍射极限，RMS半径位于艾里斑半径以内，二元衍射面的最小特征尺寸为6.9 μm，设计结果满足工程使用要求。