Rapid amplitude-phase reconstruction of femtosecond pulses from intensity autocorrelation and spectrum

The retrieval of time-dependent intensity and phase of femtosecond laser pulses is a long standing problem. To date, frequency-resolved optical gating (FROG) is probably the most trustworthy pulse measurement method. However, it requires a substantial experimental and numerical involvement. This motivates the quest for other simpler high-fidelity pulse measuring techniques. We present a new method of deciphering the pulse structure from the intensity autocorrelation trace and the intensity spectrum. We show that such a set of data is sufficient to restore the intensity and phase of a femtosecond pulse except for the typical uncertainties concerning the time shift and direction. The main feature of the proposed method is its robustness and swift convergence. Unlike a two-step pulse reconstruction, our algorithm employs the time- and frequency-domain data simultaneously, which in general provides a much faster convergence