As a newly discovered type of structured light, a spatiotemporal optical vortex (STOV), which is remarkable for its space–time spiral phase and transverse orbital angular momentum (OAM), has garnered substantial interest. Most previous studies have focused on the generation, characterization, and propagation of STOVs, but their nonlinear frequency conversion remains largely unexplored. Here, we experimentally demonstrate the generation of green and ultraviolet (UV) STOVs by frequency upconversion of a STOV carried near-infrared (NIR) pulse emitted by a high repetition rate Yb-doped fiber laser amplifier system. First, we verify that the topological charge of spatiotemporal OAM (ST-OAM) is doubled along with the optical frequency in the second-harmonic generation (SHG) process, which is visualized by the diffraction patterns of the STOVs in the fundamental and second-harmonic field. Second, the space–time characteristic of NIR STOV is successfully mapped to UV STOV by sum-frequency mixing STOV at 1037 nm and Gaussian beams in the green band. Furthermore, we observe the topological charges of the ST-OAM could be degraded owing to strong space–time coupling and complex spatiotemporal astigmatism of such beams. Our results not only deepen our understanding of nonlinear manipulation of ST-OAM spectra and the generation of STOVs at a new shorter wavelength, but also may promote new applications in both classical and quantum optics.

Time-of-Flight （ToF）成像是利用光在目标和相机之间的飞行时间来获取场景的深度信息，具有体积小、成本低、实时成像等优势。在散射环境中，由于散射介质对光的散射作用，ToF成像受到多径干扰的影响，深度测量误差较大，限制了ToF相机在散射场景中的应用。ToF透散射介质成像技术是校正因散射光引起的多径干扰效应，从传感器接收到的混叠信号中分离出目标分量，实现散射场景中的深度信息恢复，其在雾天自动驾驶、水下勘测、生物医学等领域具有广阔的应用前景。依据ToF成像系统的不同，详细介绍了PL-ToF和CW-ToF成像的基本原理，阐述和分析了散射场景中ToF稳态成像和瞬态成像的机理和特点，分别回顾和总结了ToF稳态成像和瞬态成像的透散射介质成像研究现状，并介绍了ToF透散射介质成像的应用前景，最后依据现有ToF透散射介质成像技术的优缺点，对未来发展趋势进行了展望。

Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear systems. Here we introduce an orbital-angular-momentum (OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical vortices. By this means, long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are revealed. This simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures.