Hong–Ou–Mandel interference: a spectral–temporal analysis

Hong–Ou–Mandel interference is most dramatic when the photons involved are perfectly indistinguishable. Departures from this ideal scenario, however, are also interesting and useful to consider. In this tutorial, we analyze scenarios where the degree of the photons’ distinguishability depends on their spectral and temporal “overlap”. We first consider photons that are both spectrally pure and spectrally separable. We then generalize this to include spectrally entangled (but still spectrally pure) photons and spectrally mixed (but still spectrally separable) photons. This tutorial equips researchers with tools for a deeper understanding of this interesting phenomenon and its various applications.