Analysis of diffraction efficiency of phase gratings in dependence of grooves number

The analysis of dependence of diffraction efficiency on number of grooves of phase gratings with square and sine profiles was performed by means of diffraction modeling using angular spectrum method. Phase gratings with different number of grooves from 1 to 100 was modeled and diffraction efficiency was estimated from the obtained diffraction pattern. It was shown that the main dependence of diffraction efficiency on the number of grooves is regarding to the ratio of the reading beam diameter to the grating area. As this ratio increases the DE of non-zero orders decreases up to zero. Using the appropriate diameter of reading beam the maximum value of diffraction efficiency could reach the value of 40.5% and 33.9% for square and sine profile correspondingly. Obtained results make it possible to tune smoothly the diffraction efficiency changing the diameter of the reading beam.