Parametric down conversion permits the generation of entangled photon pairs. However, the production rate is unfortunately very low, typically with nine to ten orders of magnitude between input and output power. A combination of approaches is considered to significantly enhance the overall production rate. The use of large crystals simply improves the production rate by increasing the interaction length, as does the use of beam-folding optics. Since the produced entangled photon pairs have twice the wavelength of the pump beam, the use of "hot" and "cold" mirrors can be used to redirect unused pump power back into the crystal. Analysis of these approaches is used to indicate a potential improvement of six orders of magnitude. Practical design limitations such as the rejection of waste heat, currently available crystal dimensions, and differential walkoff of correlated photons due to birefringence are considered. Application to type I and type II parametric down conversion and walkoff compensation techniques are detailed. Application to an entangled optical communication link and its use over astronomical distances are outlined.
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