In this paper, we investigated the electromagnetically induced phase grating in a four-level quantum system with closed loop configuration via relative phase between applied fields. We found that the diffraction intensity can be adjusted via intensities and relative phase of applied lights. We also studied separately the diffraction patterns of amplitude and phase modulations of the probe light by controlling the intensity of cycling field. We found that the probe energy can transfer from zero order to high orders of diffraction when the phase modulation of the probe light becomes important. T...
