Bright XUV pulses with spin-orbital angular momentum control via laser-plasma mirror interaction

Ultrafast extreme ultraviolet (XUV) sources with tailored spin and orbital angular momentum are expected to achieve higher sensitivity and information dimensionality in exploring material microstructures. However, generating bright sources with simultaneous and flexible control in a compact setup remains a challenge. Here, we numerically demonstrate a laser-plasma scheme to generate bright XUV pulses with controlled spin-orbital angular momentum. In this scheme, a circularly polarized vortex laser pulse is obliquely incident on a plasma mirror, and the reflected radiation contains topological-spectral-correlated XUV pulses. Particle-in-cell simulations reveal a linear topological-spectral relationship: the orbital angular momentum of the n^th harmonic scales as nm, where m is the topological charge of the driver, while its spin state is preserved. By synthesizing a selected harmonic band, spatiotemporal optical beams with programmable helical structures (e.g., single- or multiple-armed light springs) can be constructed. This scheme opens a promising route to generate bright attosecond XUV pulses with multidimensional control of photon angular momentum in a straightforward and efficient way.