We demonstrate a real-time transverse-mode switching of ultrafast pulse via a cascading mode conversion. The cascading all-fiber mode converter is comprised of a mode-selective coupler (MSC) and an acoustically induced fiber grating (AIFG), which functions as a broadband and controllable beam shaper, and offers a real-time mode switching between LP₁₁ and LP₂₁ modes with $\sim ~190~\mu \text{s}$ switching time. Such a transverse mode-switchable all-fiber laser presents a pulse duration of 1.4 ps and flexible transverse-mode switching. We believe that this compact and robust all-fiber laser source would find promising applications in the field of ultrafast optics and structured light microscope.

中文翻译：

---

超短脉冲实时横模切换的全光纤方法

我们通过级联模式转换演示了超快脉冲的实时横向模式切换。级联全光纤模式转换器由模式选择耦合器 (MSC) 和声诱导光纤光栅 (AIFG) 组成，用作宽带和可控光束整形器，并提供 LP ₁₁和LP ₂₁模式 $\sim ~190~\mu \text{s}$ 切换时间。这种可横向模式切换的全光纤激光器具有 1.4 ps 的脉冲持续时间和灵活的横向模式切换。我们相信这种紧凑而坚固的全光纤激光源将在超快光学和结构光显微镜领域找到有前景的应用。