Ultrashort laser pulse propagation through few-mode optical fibers is a complex spatiotemporal event: due to mode spatial structures and intermodal delays and dispersions, pulses in such fibers experience spatial patterns and temporal elongations, which are generally considered detrimental for beam quality and pulse shape. However, with careful control of the launched modal contents and their interactions, we demonstrate that, using a single-mode-few-mode (SFe) optical fiber device, ultrashort pulses with various desirable spatiotemporal properties can be achieved. In the SFe device, pulse transformations over space, time, and frequency are related by multimode interference, and in the far field, pulse profile can be obtained by calculating diffraction integrals. We show that, using two example cases (a Bessel-like pulse and an optical bottle pulse), our approach can generate spatiotemporally structured pulses potentially suitable for applications in material science and biological imaging.

中文翻译：

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使用单模少模光纤装置进行超短激光脉冲时空剖面控制

通过少模光纤的超短激光脉冲传播是一个复杂的时空事件：由于模式空间结构和模间延迟和色散，此类光纤中的脉冲会经历空间模式和时间伸长，这通常被认为对光束质量和脉冲形状有害。然而，通过仔细控制发射的模态内容及其相互作用，我们证明，使用单模少模（SFe）光纤装置，可以实现具有各种理想时空特性的超短脉冲。在 SFe 器件中，脉冲在空间、时间和频率上的变换与多模干涉有关，而在远场中，可以通过计算衍射积分来获得脉冲轮廓。我们表明，