Substrate-mode holograms used in optical interconnects: design issues

We discuss a number of design issues that affect the performance tolerances of substrate-mode holograms used for optical interconnect systems. We examine the effects of emulsion uniformity, thickness variation, and index variation on the ability to determine the Bragg angle and the diffraction angle within the substrate accurately. The environmental stability with respect to temperature, laser irradiance, and humidity are considered. Experimental results are presented for substrate-mode holograms fabricated in spin-coated dichromated-gelatin emulsions. The coupling properties for a 1 × 2 multiplexed substrate-mode hologram with two superimposed gratings are also described.