2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/170052We report the observation of beatings of the coincidence event rate in a Hong-Ou-Mandel interference (HOMI) between signal and idler photons from a parametric downconversion (PDC) process inside a multi-mode KTP waveguide. As explanation we introduce bi-photonic states entangled in their broadband frequency modes generated by waveguide mode triples and propose a suitable entanglement detection scheme.7 pages, 3 figures; added 3 references; shortened and clarified in placesQuantum Physicstext