Effects of spatial beam profile on GRENOUILLE trace

In grading-eliminated no-nonsense observation of ultrafast incident laser light e-fields(GRENOUILLE) measurements of femtosecond laser pulse, a nonuniform spatial beam profile can largely distort the trace, which results in an inaccurate temporal measurement. The spatial beam profile effects on the GRENOUILLE trace are demonstrated both theoretically and numerically. Results from the numerical simulation show that due to the presence of feedback regarding the validity of the measurement data, the GRENOUILLE phase-retrieval algorithm is insensitive to trace distortion; hence a nonuniform spatial beam profile can hardly introduce any noticeable inaccuracy. Special attention should be paid to the situation where incident beam is too narrow to generate adequate delay between two replicas of the pulse, which leads to a clipped trace followed by a misleading temporal result.