The analysis of dependence of diffraction efficiency on duty cycle and modulation depth of phase gratings with rectangular and Gaussian profile was performed by means of specially designed program. An Angular Spectrum method applied for monochromatic light propagation in far field through phase grating was used for calculation of diffraction efficiency of gratings. Diffraction efficiency maps of 0-5^th diffraction orders were obtained for different grating profiles. It is shown that changing the duty cycle of grating makes it possible to tune smoothly the diffraction efficiency and to redirect the light intensity in required orders.