We report the observation of correlated photon pairs generated by spontaneous parametric downconversion of a 400-nm pump pulse in a quasi-phase-matched KTiOPO<sub>4</sub> nonlinear waveguide. The highest ratio of coincidence to single-photon count rates observed near 800 nm exceeds 18%. This suggests that nonlinear waveguides will be a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the downconverted photons produced in multimode waveguide structures.
© 2001 Optical Society of America
Konrad Banaszek, Alfred B. U’Ren, and Ian A. Walmsley, "Generation of correlated photons in controlled spatial modes by downconversion in nonlinear waveguides," Opt. Lett. 26, 1367-1369 (2001)