We continue the work carried out by Christian Mikkelsen and Dik Bouwmeester into down-conversion effiency with periodically poled lithium niobate material, in order to produce entangled photons.
Entangled photons play a crucial role in schemes for quantum cryptography and quantum communication.
Unfortunately, most pair photon sources currently used, such as type I and type II BBO crystals, have a very low efficiency which is a serious limitation for any commercial applications. A picture of experimental setup can be viewed here .