Photon Pair Entanglement in 2-Dimensional Periodically Poled Nonlinear Optical Superlattice

Recent progresses in quantum information processing scheme highlights the necessity for entangled two photon states [1]. Micro structure materials such as photonic crystals and periodically poled optical superlattices have been utilized as a source of entangled photon pairs in down-conversion process [2, 3]. Higher amount of photon pair entanglement with the high efficiency of the emerged photon pairs should be prepared using quasi-phase-matching [4] with the help of one and two-dimensional periodically poled nonlinear optical superlattice [5, 6 and 7]. In the present paper, we study the possibility of using two-dimensional periodically poled lithium niobate (PPLN) as an efficient source of entangled photon pairs via spontaneous parametric down conversion (SPDC) and the PPLN is defined with a periodic poling pattern along two dimensions. The amount of entanglement between photon pairs is investigated by using an appropriate measure such as the Von-Neumann entropy [7].