Type-I Quasi-Phase-Matched Waveguide Device for Polarization-Entangled Twin Photon Generation

Quantum-entangled twin photons are expected to play an important role in future quantum communications and information processing. We propose and demonstrate a Type-I quasi-phase-matched (QPM) nonlinear-optic (NLO) LiNbO
₃
waveguide device for high-efficiency polarization-entangled twin photon generation. The device consists of a Ti:LiNbO
₃
channel waveguide, a ferroelectric domain-inverted grating for Type-I QPM, and a thin-film half-wave plate for polarization conversion at the center of the NLO interaction region. Generation of polarization-entangled twin-photons is demonstrated through quantum interference experiment.