COMPLETE DIAGNOSTIC OF ULTRASHORT PULSES WITHOUT NONLINEAR PROCESS

We propose an ultrashort-pulse diagnostic scheme that avoids any nonlinear process and iterative calculation. The method is based on the fact that a pulse is completely determined by its spectral amplitude and relative phase in the Fourier space. As a feasibility test, we have produced stable interference patterns between different sections of the spectrum of an ultrashort-pulse train. Based on such an interference, we show that the relative phase between different frequency components of a pulse or a mode-locked pulse train can be measured by cross correlation in the Fourier space.