Lee KJ, Lee S, Shin H.
Appl Opt. 2016 Dec 1;55(34):9791-9796. doi: 10.1364/AO.55.009791.We report the extended phase-matching (EPM) properties of two kinds of periodically poled potassium niobate (KNbO<sub>3</sub> or KN) crystals (i.e., periodic 180°- and 90°-domain structures) that are highly useful for the generation of polarization-entangled photon pairs in the mid-infrared (IR) spectral region. Under the degenerate Type II spontaneous parametric downconversion process satisfying the EPM condition, an input single photon with a frequency of 2ω generates a pair of synchronized photons with identical frequencies of ω that are orthogonally polarized with respect to each other (i. Read More