We show that the autocorrelation function of mode-locked laser pulses can be measured by interfering a pulse with its time-delayed replica in a conventional photoconductor to generate a pulsating grating that can be represented as a superposition of moving gratings. The resonance current peak resulting from matching the carrier drift velocity to the velocity of one of the grating components is proportional to the autocorrelation function. Unlike conventional autocorrelators, the proposed method uses no nonlinear effects and thus can be utilized for measuring weak pulses. ©1997 American Institute of Physics.