Study of gratings with variable periods

A theoretical study with sinusoidal amplitude diffraction gratings, elaborated with variable periods is shown. The diffraction pattern behavior and the symmetry degree of the gratings were observed. The grating period is increased, fringe to fringe, starting with a small period and ending with a big period that is; the grating edge, start with high spatial frequency and finish with low spatial frequency. This gratings modulation causes a widening in the diffracted orders.