Creating Light Vortex in Spacetime: Creating Designer Beams in Spacetime. Artistic rendering of color conversion in spatiotemporal vortex of light. A second-harmonic spatiotemporal orbital angular momentum of an optical pulse (right, blue torus) is converted from a fundamental pulse (left, red torus). In addition to optical frequency doubling, the space-time topological charge (rainbow-colored phase structures in the reflection) is also doubled and conserved in the nonlinear process. Publication: G. Gui, N. Brooks, H. Kapteyn, M. Murnane, and C.-T. Liao. "Second-harmonic generation and the conservation of spatiotemporal orbital angular momentum of light," Nature Photonics 15, 608 (2021) / This work is supported by an AFOSR MURI grant (FA9550-16-1-0121) - Harnessing Strong-Field Mid-Infrared (IR) Lasers: Designer Beams of Relativistic Particles and THz- to-X-ray Light. Contributors: Chen-Ting Liao, Steven Burrows (art illustration), the Murnane and Kapteyn groups