the invention features methods and systems for optical correlation of ultrashort optical waveforms , e . g ., pulses . the optical waveform passes through a diffractive optic , e . g ., a mask or grating , to generate multiple sub - beams corresponding to different diffractive orders . at least two of the sub - beams are then imaged onto the sample to produce a desired crossing pattern . to perform the correlation , the diffracted sub - beams are variably delayed relative to one another prior to overlapping on the sample . the sample generates a signal beam in response to the overlapping sub - beams , the signal beam providing a correlation between the sub - beams for each of the variable delays .