We demonstrate a cross-polarized twin photon generation device using a LiNbO3waveguide for the first time. Type II quasi-phase matching (TE→TE+TM) and nonlinear tensor element d24were used for twin photon generation in the 1.55μm band.
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) LiNbO3waveguide device for high-efficiency polarization-entangled twin photon generation. The device consists of a Ti:LiNbO3channel 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.