Coherent artifact study of two-dimensional spectral shearing interferometry

We study multi-shot intensity-and-phase measurements of unstable trains of ultrashort pulses using twodimensional spectral shearing interferometry (2DSI). We find that, like other interferometric ultrashort-laser pulse-measurement methods, it measures only the coherent artifact and so yields effectively only a lower bound to the pulse length. We also attempt to identify warning signs of pulse-shape instability in 2DSI and find that it responds to instability with reduced fringe visibility, although this effect is very small when using the small spectral shears appropriate for large temporal ranges. We conclude that 2DSI should be used with caution and largeshear measurements or alternative techniques should be used to verify the stability of the pulse train. © 2015