Abstract
<title>Abstract</title> <p>In this study, we investigate the transverse Orbital angular momentum (OAM) properties of twisted spatiotemporal optical vortex (STOV) beams which are partially coherent sources simultaneously carrying a twist phase and a vortex phase coupling their space and time dimensions. With the aid of the Huygens-Fresnel integral, the transverse linear momentum density and transverse OAM flux density per photon are formulated and numerically analyzed under free-space propagation. Our results reveal that the twist phase and vortex phase have a significant impact on the transverse OAM flux density distribution of the STOV beams during propagation, which in turn provides great flexibility in modulating the transverse OAM flux density through adjusting the twist factor and topological charge. In addition, the preservation of the total transverse OAM of the STOV beams upon propagation is demonstrated through numerical examples and the additional degree of freedom for modulating the total OAM is addressed.</p>