Ding Yihang, Xiao Xiaosheng, Liu Kewei, Fan Shuzheng, Zhang Xiaoguang, Yang Changxi
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China.
State Key Laboratory of Information Photonics and Optical Communications, School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China.
Phys Rev Lett. 2021 Mar 5;126(9):093901. doi: 10.1103/PhysRevLett.126.093901.
Dissipative nonlinear wave dynamics have been investigated extensively in mode-locked lasers with single transverse mode, whereas there are few studies related to three-dimensional nonlinear dynamics within lasers. Recently, spatiotemporal mode locking (STML) was proposed in lasers with small modal (i.e., transverse-mode) dispersion, which has been considered to be critical for achieving STML in those cavities because the small dispersion can be easily balanced. Here, we demonstrate that STML can also be achieved in multimode lasers with much larger modal dispersion, where we find that the intracavity saturable absorber plays an important role for counteracting the large modal dispersion. Furthermore, we observe a new STML phenomenon of passive nonlinear autoselection of single-mode mode locking, resulting from the interaction between spatiotemporal saturable absorption and spatial gain competition. Our work significantly broadens the design possibilities for useful STML lasers thus making them much more accessible for applications, and extends the explorable parameter space of the novel dissipative spatiotemporal nonlinear dynamics that can be achieved in these lasers.
耗散非线性波动力学在单横模锁模激光器中已得到广泛研究，而关于激光器内部三维非线性动力学的研究却很少。最近，在具有小模式（即横模）色散的激光器中提出了时空锁模（STML），小色散被认为对于在这些腔中实现STML至关重要，因为小色散易于平衡。在此，我们证明在具有大得多的模式色散的多模激光器中也能实现STML，我们发现腔内可饱和吸收体在抵消大模式色散方面起着重要作用。此外，我们观察到一种新的STML现象，即单模锁模的被动非线性自选择，这是由时空可饱和吸收与空间增益竞争之间的相互作用导致的。我们的工作显著拓宽了实用STML激光器的设计可能性，从而使其在应用中更易于实现，并扩展了这些激光器中可实现的新型耗散时空非线性动力学的可探索参数空间。
