There are two known competitive arrangements for reflection-type coaxial holographic storage systems: the optical layout developed by OPTWARE, which is a so-called collinear or ''split-aperture system'', and the ''common-aperture system'' developed by the European consortium named ATHOS. We modeled the reference diffraction noise for both arrangements by the beam propagation method (BPM), and compared the results from the M number (M#) consumption point of view. We suggest the use of reference beam apodization for the split aperture system to reduce the diffraction noise caused by the reference beam at the object area.

When developing a compact holographic storage system it is beneficial to use a reflection-type arrangement, where the entire optical system is on the same side of the storage material. For reflection type holographic discs, it is important to use half-cone-shaped spherical reference beams to avoid the ghost images caused by phase conjugate readout. The goal of this paper is to look for appropriate engineering tools to model diffraction efficiency of finite volume holograms created by half-cone-shaped reference beams. Two numerical methods -volume integral and beam propagation -were applied to calculate the shift selectivity curves. Simulation results show significant discrepancies between the shift selectivity curves corresponding to the approximated analytical equation and the numerically calculated shift selectivity curves; there are no Bragg zeros and there are no selective and nonselective directions. Beside the shift selectivity curves, track, focus, tilt and wavelength tolerance values are shown for finite volume holograms.

Analytical shift selectivity equations assume an infinite hologram size. When developing a compact holographic storage system, one uses small holograms. From a practical viewpoint, it is better to use reflection type discs, in which the entire optical system, writing and reading objectives, among others, are on the same side of the disc. For reflection-type holographic discs, it is important to use half-cone-shaped reference beams to avoid generating ghost images caused by phase conjugate readout. Our calculations show significant discrepancy between the shift selectivity curves corresponding to the approximated analytic equation and the numerically calculated shift selectivity curves.