Comparison of recording densities in three-dimensional optical storage systems: multilayered bit recording versus angularly multiplexed holographic recording

We compare the geometrical limits of the recording density that can be attained in three-dimensional optical memory systems that employ the multilayered bit-recording method and the angularly multiplexed holographic recording method. Both recording methods have the potential to overcome the recording density limitations in current optical storage systems. Using the Ewald sphere construction, we analyze the lateral and longitudinal bandwidths for each recording method. The respective recording densities of the two methods are also derived directly in the space domain and compared with each other. With the bit-recording method we found that the memory density increases inversely with the f-number of the recording lens. On the other hand, the density that can be achieved using holographic recording first increases with the f-number values, attains a maximum, and then decreases at larger f-number values. This implies that the bit-recording method yields larger memory densities when lenses of smaller f-numbers are used in the optical system.