Modified dipole-dipole interactions on optically excited pair transitions (A)

H. H. Jen

Juan Francisco Lam, Stephen Colby Rand

The absorption of single photons by coupled pairs of ions in rare-earth solids was first observed by Varsanyi and Dieke.1 They noticed that weak absorption of light occurred in PrCl3 at frequencies close to the sum of transition frequencies of individual Pr ions, giving rise to rare-earth fluorescence. This effect was explained by the perturbation theory of Dexter.2 He showed that weak multipole or exchange interactions between rare-earth ions permitted the simultaneous promotion of two ions to excited states by the action of one absorbed photon in an electric dipole allowed transition. Similarly, two ions initially in excited states could emit one sum frequency photon in a cooperative manner.

Gavin K. Brennen

Guan‐Zhang Lu, Che-Sheng Chou, H Y Lin +3 more

A concept termed “stimulated dipole–dipole interaction” as a framework is proposed to describe coherence-enhanced light–matter interactions. Unlike conventional dipole–dipole interactions, excitation-induced dipoles, generated through external perturbations, coherently stimulate and couple with each other, leading to reinforced transition pathways and modified physical characteristics. Theoretically, the phenomenon of stimulated dipole–dipole interaction can be well understood and calculated based on the additional interference terms between transition dipole matrix elements of perturbed Hamiltonians in Fermi’s golden rule, where coherent coupling between excitation-induced and intrinsic dipoles alters the overall transition probability. This framework can be applied to many platforms, including wrinkled graphene, quantum dots, plasmonic dipoles, exciton–polaritons in stacked two-dimensional materials, and electric and magnetic dipoles in spin resonance, offering a versatile approach for engineering light–matter interactions. It is pointed out that the underlying mechanism of the originally proposed stimulated emission can also be understood well based on stimulated dipole–dipole interaction. Therefore, the proposed stimulated dipole–dipole interaction paves a milestone to advance the further exploration of not-yet realized quantum optics phenomena.

Thomas Unold, Kerstin Mueller, Christoph Lienau +2 more

We demonstrate coherent nonlinear-optical control of excitons in a pair of quantum dots (QDs) coupled via dipolar interaction. The single-exciton population in the first QD is controlled by resonant picosecond excitation, giving rise to Rabi oscillations. As a result, the exciton transition in the second QD is spectrally shifted and concomitant Rabi oscillations are observed. We identify coupling between permanent excitonic dipole moments as the dominant interaction mechanism, whereas quasiresonant (Förster) energy transfer is weak. Such control schemes based on dipolar interaction are a prerequisite for realizing scalable quantum logic gates.

F. Robicheaux