Compact energy–time entanglement source using cascaded nonlinear interactions
Pascal Lefebvre, Raju Valivarthi, Qiang Zhou, Lee C. Oesterling, Daniel Oblak, Wolfgang Tittel · Journal of the Optical Society of America B · 2021
Entangled photon pair sources are essential for applications such as quantum communication and metrology. Here we present a compact energy–time entangled photon pair source at telecom wavelengths realized through cascaded second harmonic generation and spontaneous parametric down conversion in a single periodically poled lithium niobate waveguide. We introduce and characterize methods to diminish the effects of Raman scattering, the principal being quasi-CW pumping. The quality of energy–time entanglement produced by the compact source is analyzed using two-photon interference and Franson interference, and visibilities as high as 93.9 % ± 0.4 % and 90.5 % ± 0.6 % are achieved, respectively.