Experimental evaluation of incoherent/coherent volume holographic interconnection systems

Abstract

A previously described holographic interconnection system uses an array of self-coherent but mutually incoherent sources to generate a set of overlapping holograms in a photorefractive crystal.1,2 In the current work, we assess the performance of this interconnection system experimentally. A linear array of self-coherent but mutually incoherent sources at visible wavelengths is generated by using an acousto-optic (AO) cell (TeO2) and custom analog electronics. Mutual incoherence is obtained by super-imposing a set of diffraction gratings (one for each source) at different frequencies in the AO cell, so that each diffraction grating yields a frequency shift in the corresponding diffracted beam. We present experimental results in Fe:LiNbO3 at 514.5 nm on the fidelity of the photorefractive interconnection in terms of diffraction efficiency, cross talk, and accuracy, as a function of both the number of multiplexed volume holograms and the degree of spatial overlap of the holograms. Some of these experimental results are compared with results obtained from simulation. The measured fidelity of this incoherent/coherent inter connection system is also compared to that of a fully coherent interconnection system.