Effect of diffraction of light on the signal-to-noise ratio in thin-film optical memory based on spectral hole burning

The effect of the light diffraction pattern in the vicinity of a focus on the signal-to-noise ratio (S/N) in the optical memory based on the binary data storage by spectral hole burning is considered. Dependences of the S/N on the storage density and the aperture angle are obtained for focusing systems with different laws of the transformation of the incident linearly polarized plane wave into a spherical wave and with different amplitude filters. It is shown that the diffraction pattern of a focused light beam substantially determines not only the maximum achievable optical storage density but can considerably affect the S/N in the case of a low storage density as well.