Two photon absorption

Stephen V. Kershaw

Baihong Li, Holger Friedrich Hofmann

Two photon absorption processes are known to be sensitive to energy-time entanglement between the absorbed photons. It should therefore be possible to characterize the energy-time entanglement by observing the two photon absorption cross-sections in a known medium controlled by external conditions. In this paper, we analyze the correspondence between two photon absorption and projective measurements of the two photon wavefunction. It is shown that the two photon absorption process is described by a projection onto an energy-time entangled two photon state, indicating that the absorption cross-section can provide direct evidence of entanglement between the absorbed photon pairs.

Hans Kleinpoppen

Dmitry Tabakaev, Aleksa Djorović, Luca La Volpe +6 more

We experimentally study entangled two-photon absorption in rhodamine 6G as a function of the spatial properties of a high flux of broadband entangled photon pairs. We first demonstrate a key signature dependence of the entangled two-photon absorption rate on the type of entangled pair flux attenuation: linear, when the laser pump power is attenuated, and quadratic, when the pair flux itself experiences linear loss. We then perform a fluorescence-based Z-scan measurement to study the influence of beam waist size on the entangled two-photon absorption process and compare this to classical single- and two-photon absorption processes. We demonstrate that the entangled two-photon absorption shares a beam waist dependence similar to that of classical two-photon absorption. This result presents an additional argument for the wide range of contrasting values of quoted entangled two-photon absorption cross sections of dyes in literature.

Han Seb Moon, Heung‐Ryoul Noh

We report the physical origins of the on-resonant and off-resonant two-photon absorption (TPA) in an open-ladder-type atomic system of the 5S1/2(F=1)-5P3/2(F′=0,1,2)-5D5/2(F′′=1,2,3) transitions in Rb87 atoms. When the on-resonant TPA, including electromagnetically induced transparency (EIT), was transformed into the off-resonant TPA according to the coupling laser frequency detuning, we clarified the dynamics of the atomic coherences by decomposing into the two-photon coherence (TC) and the crossover coherence (CC) terms mixed between one-photon coherence (OC) and TC terms. The physical origins of the two TPAs were completely different; the cause of the on-resonant TPA was the CC term, and that of the off-resonant TPA was the TC term.

Salvatore Carusotto, A. Giulietti, Moreno Vaselli