Mid-infrared entangled photon generation in optimised asymmetric semiconductor quantum wells

The optimal design of asymmetric quantum well structures for generation of entangled photons in the mid-infrared range by spontaneous parametric downconversion is considered, and the efficiency of this process is estimated. Calculations show that a reasonably good degree of entanglement can be obtained, and that the optical interaction length required for optimal conversion is very short, in the few μm range.