  Recently, different experimental methods to investigate the entangled
two-photon absorption (ETPA) process in a variety of materials have been
reported. The present work reports on a different approach on which the ETPA
process is detected based on the changes induced on the Hong-Ou-Mandel (HOM)
interferogram of two photons produced by a spontaneous parametric down
conversion (SPDC) Type-II process. Using an organic solution of the laser dye
Rhodamine B as a model, it is demonstrated that ETPA at 800nm can be monitored
by the changes in the temporal-width and visibility of the HOM interferogram
produced by the photons at a beam splitter after interacting with the sample.
Additionally, we present a detail model in which the sample is modeled as a
filtering function which fullfills the energy conservation conditions required
by ETPA, allowing to explain the experimental observations with excellent
agreement. We believe that this work represents a new perspective to study the
ETPA process, by using an ultra-sensitive quantum interference technique and a
detailed mathematical model of the process.
