Today, it is well known that light possesses a linear momentum that is along the propagation direction. Besides, scientists also discovered that light can possess an angular momentum, a spin angular momentum (SAM) associated with circular polarization and an orbital angular momentum (OAM) owing to the azimuthally dependent phase. Even though such angular momenta are longitudinal in general, an SAM transverse to the propagation direction has opened up a variety of key applications¹. In contrast, investigations of the transverse OAM are rare due to its complex nature. Here, we demonstrate a three-dimensional wave packet that is a spatiotemporal (ST) optical vortex with a controllable purely transverse OAM. Contrary to the transverse SAM, the magnitude of the transverse OAM carried by the ST vortex is scalable to a larger value by simple adjustments. Since the ST vortex carries a controllable OAM uniquely in the transverse dimension, it has strong potential for novel applications that may not be possible otherwise. The scheme reported here can be readily adapted for other spectral regimes and different wave fields, opening opportunities for the study and applications of ST vortices in a wide range of areas.

今天，众所周知，光具有沿传播方向的线性动量。此外，科学家还发现由于归因于相位的相位，光可以具有角动量，与圆偏振有关的自旋角动量（SAM）和轨道角动量（OAM）。即使这样的角动量通常是纵向的，但横向于传播方向的SAM已经打开了各种关键应用¹。相比之下，由于横向OAM的复杂性，对其的研究很少。在这里，我们演示了三维波包，它是具有可控的纯横向OAM的时空（ST）光学涡旋。与横向SAM相反，ST涡流携带的横向OAM的大小可以通过简单的调整扩展到更大的值。由于ST涡流在横向方向上唯一地承载着可控制的OAM，因此它在新应用中具有强大的潜力，而在其他情况下则不可能。本文报道的方案可以很容易地适用于其他光谱范围和不同的波场，为在广泛区域内研究和应用ST旋涡提供了机会。