Phase measurements without interferometry: 2D transverse phase detection by numerical beam intensity analysis

A whole family of laser-plasma interaction experiments is based on the phase analysis of the laser pulse after the propagation in a plasma. Typically, this phase is obtained by means of interferometry. As pulsed interferometry is a much more difficult task than taking simple images of the beam, we developed a numerical code for extracting phase information from images. The technique, based on the algorithm of Gerchberg-Saxton, showed to be very effective in retrieving 2D phase distributions of simulated as well as real beams. The convergence of the algorithm is fast (some minutes on a personal computer). The electronic noise in real images is intrinsically discarded by the algorithm.