Hong-Ou-Mandel interference with absorption and dispersion from rare earth ions

The coherent interactions between photons and rare earth ion ensembles are crucial for quantum storage and quantum information processing. Hong-Ou-Mandel (HOM) interference, a well-known quantum interference phenomenon, has been widely used in precision measurement applications. However, there have been no reports to date on observing coherent interactions between light and ionic ensembles using HOM interferometry. In this study, we experimentally generated entangled photons from two 10-mm-long type-0 phase-matched PPKTP crystals. Then we constructed a HOM interferometer and achieved a HOM dip with a visibility of 82.4% and a width of 152.5 ± 0.2 fs. Finally, we inserted a N d³⁺ : Y V O₄ (rare earth ion) crystal into the optical path and successfully observed the splitting of the HOM dip. This experiment may provide valuable insights into light-matter interactions and could be beneficial for quantum storage applications.