Emission, Absorption, and Photons

Michael P. Keating

Alica R. Guzman, Michael R. Harpham, Özgün Süzer +2 more

Entangled photons generated by spontaneous parametric down-conversion (SPDC) have been used to investigate entangled two-photon absorption (ETPA) in multiannulene systems. The ETPA characteristics are shown to depend on the spatial orientation of the SPDC emission pattern. The expected dependence of the absorption rate on input flux is seen for emission patterns that exhibit spatial indistinguishability between the signal and idler photons, while no absorption is observed for a spatially distinguishable emission pattern. The amount of absorption of entangled photons is also seen to depend on the degree of overlap of the entangled photons for the indistinguishable conditions. Tunability of the entangled photon absorption can thus be achieved by utilizing the spatial characteristics of the entangled photon pairs.

K.J. Ebeling

Markus Pollnau

It is generally believed that absorption and stimulated emission are inverse processes, as both are driven by an external field, their strength is quantified by the same Einstein B coefficient, and they occur with a defined phase, opposite to each other, namely in phase and in anti-phase with the driving field, whereas spontaneous emission is a different process that occurs with an arbitrary phase with respect to a potential incident field. Recently, the phase relation in absorption and emission was shown to differ from this believe. Here it is verified via the amplitude–phase diagram and via the interference of sine waves that, precisely speaking, only the absorption process, in which a number φ + 1 of incident photons is decreased by one photon, and the emission process, in which a number φ of incident photons is increased by one photon, are truly inverse processes also in their phase. Particularly, this implies that absorption of a single incident photon and spontaneous emission of a photon into an empty mode are inverse processes in the amplitude–phase diagram.

Mitchel Weissbluth

Cheng Guo, Shanhui Fan

Unitary control changes the optical absorption and emission of an object by transforming the external modes. We answer two basic questions: Given an object, what absorptivity, emissivity, and their difference are attainable via unitary control? How to obtain given absorptivity, emissivity, and their difference? We show that both questions can be answered using the mathematics of majorization.