Methods, devices and systems for improved fabrication and measurement of holographic elements are described. One example method includes directing a reference and an object beam toward a holographic material for formation of a diffraction grating in the holographic material, and blocking one of the reference or the object beams to prevent the beam from reaching the holographic material for at least a portion of time during which the diffraction grating is being formed. During the blockage of the beam, a power level of a diffracted beam associated with the reference or the object beam that is not being blocked is measured. Based on the measured power level, it is then determined whether a particular diffraction grating efficiency is reached. The described techniques enable real-time measurement of diffraction grating efficiency as the grating is being formed and enable improved fabrication of holographic elements hat must meet precise diffraction grating efficiency requirements.