Spectral Considerations of Entangled Two-Photon Absorption Effects in Hong–Ou–Mandel Interference Experiments

Abstract

Recently, different experimental methods intended to detect the entangled two-photon absorption (ETPA) phenomenon in a variety of materials have been reported. The present work explores a different approach in which the ETPA process is studied based on the changes induced in the visibility of a Hong–Ou–Mandel (HOM) interferogram. By using an organic solution of Rhodamine B as a model of nonlinear material interacting with entangled photons at ∼800 nm region produced by spontaneous parametric down-conversion (SPDC) Type-II, the conditions that make possible to detect changes in the visibility of a HOM interferogram upon ETPA are investigated. We support the discussion of our results by presenting a model in which the sample is considered as a spectral filtering function which fulfills the energy conservation conditions required by ETPA, allowing us to explain the experimental observations with good agreement. We believe that this work represents a new perspective to studying the ETPA interaction, by using an ultrasensitive quantum interference technique and a detailed mathematical model of the process.

Entangled Two-Photon Absorption in Transmission-Based Experiments: Deleterious Effects from Linear Optical Losses

“…Indeed, the visibility is intrinsically related to the quantum state of the down-converted photons, 52,62 while the absorption of entangled photons should modify the quantum state. 51 These observations, and the fact that in the transmission vs P pump experiments there is no depletion of R TPA signal even for temporal delay longer than the entanglement time, support the conclusion that the calculated σ e values presented in Table 1 result from artifacts produced by the sample which emulate the ETPA activity.…”

“…In a previous paper from our group, 51 we proposed the application of the HOM interferometer as a sensing device for measuring the occurrence of ETPA in transmission-based experiments. As the theoretical model of the cited work shows the interaction of an absorptive nonlinear material with photon pairs, produced by an SPDC process with an engineered quantum state, results in modification of the JSI function of the two-photon state, directly altering the visibility of the corresponding HOM interferogram in a noticeable way.…”

“…51 In this work, we focus on the changes introduced in the visibility because, as will be shown below, linear losses do not affect V of the HOM dip, while it is expected that the nonlinear interaction is able to induce V changes. 51 The HOM dip visibility is defined by…”

“…In a previous work from our group, 51 we proposed a novel configuration to study the ETPA process by using a HOM interferometer as an ultrasensitive detection device. In the cited work, we presented a theoretical model and implemented the corresponding measurements of transmission vs two-photon temporal delay, which allowed us to understand the effects of a nonlinear sample rhodamine B (RhB), modeled as a notch-type two-photon spectral filter, over the asymmetric 52 quantum state of photon pairs produced by type-II SPDC, in the CW and pulsed excitation regimes.…”

“…It is shown that while the linear losses lead to overestimating σ e when the transmission is detected as a function of pump power, in the case of transmission vs temporal delay the losses only produce a reduction of the raw base level of coincidence counts (CCs) of a HOM interferogram but without changing the visibility of its dip. Notice that the visibility of a HOM dip changes upon modifications to the quantum state of the photon pairs, and changes in the quantum state are expected in the case of ETPA activity . Thus, the transmission versus time delay configuration not only is equivalent to the standard scheme used to study ETPA but also offers the remarkable advantage of discriminating the presence of deleterious linear optical losses over the HOM dip, becoming a good option for studying the elusive ETPA process.…”