  The Hong-Ou-Mandel (HOM) effect ranks among the most notable quantum
interference phenomena, and is central to many applications in quantum
technologies. The fundamental effect appears when two independent and
indistinguishable photons are superimposed on a beam splitter, which achieves a
complete suppression of coincidences between the two output ports. Much less
studied, however, is when the fields share coherence (continuous-wave lasers)
or mode envelope properties (pulsed lasers). In this case, we expect the
existence of two distinct and concurrent HOM interference regimes: the
traditional HOM dip on the coherence length time scale, and a structured HOM
interference pattern on the pulse length scale. We develop a theoretical
framework that describes HOM interference for laser fields having arbitrary
temporal waveforms and only partial overlap in time. We observe structured HOM
interference from a continuous-wave laser via fast polarization modulation and
time-resolved single photon detection fast enough to resolve these structured
HOM dips.

Quantum Physics;Optics