Quasi-Phase-Matched Waveguide Devices for Generation of Postselection-Free Polarization-Entangled Twin Photons

Quasi-phase-matched (QPM) Ti : LiNbO
₃
waveguide devices for generation of postselection-free polarization-entangled twin photons are proposed. The devices consist of cascaded two sections of slightly different QPM parameters. Generation of the entangled photons in the telecommunication band in a fabricated device of 2 times 15 mm interaction length is demonstrated through photon coincidence counting and quantum interference experiments.