The electromagnetically induced grating(EIG)effect is theoretically studied under the cold atomic and room-temperature atomic systems,respectively.The study results show that the first-order diffraction efficiencies in the cold atomic system and the room-temperature atomic system can reach 32.5% and 30%,respectively.The two diffraction efficiencies are very close to the ideal diffraction efficiency of a sinusoidal grating.However,as far as the actual condition is concerned,the preparation of a cold atom sys...