Spatio-Temporal Couplings in Ultrashort Vortex Pulses Generated by Spiral Phase Plates

Ultrashort pulses are usually treated as a separated product of temporal and spatial factors. However, this separability falls for very short pulses as the temporal (or spectral) and spatial factors are interdependent. It translates into a series of various distortions known as spatio-temporal couplings (STCs) occurring when a pulse propagates through angularly dispersive media or due to misalignment of temporarily dispersive components as each frequency in the pulse propagates at a different angle and group velocity. Shorter pulses are more susceptible to STCs.