<p>A new analytical approach for determining the diffraction efficiency of a phase holographic grating and the relative intensity of an object wave during two-wave mixing in a cubic photorefractive crystal is proposed. It is based on the classical theory of light wave propagation in an optically active birefringent medium. The values of the output energy characteristics of the reflection hologram found using this approach are shown to be in good agreement with numerical data obtained by solving the coupled wave equations. The optimal conditions under which the greatest diffraction efficiency is achieved for a holographic experiment during reconstruction and amplification of the object wave can be established based on the described physical mechanism of diffraction and mixing of linearly polarized light waves by a volume phase hologram.</p>