The holographic gratings on photopolymer films are studied by three different thicknesses for samples A, B, and C. The photopolymer emulsion is prepared with potassium dichromate and nickel (II) chloride hexahydrate in polyvinyl alcohol matrix. The evolution of diffraction efficiency is evaluated during holographic recording with and without voltaje as a function of energy exposure by changing the thickness. The curves of diffraction efficiency reach a peak when the films are continuously exposed to energy for a period of time. Sample B obtains the highest diffraction efficiency ©2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3569623]