Remarkable Orientation Dependence of Plasmon-CoupledResonanceEnergy Transfer

We study the effect of chromophore orientation on the enhancement of plasmon-coupled resonance energy transfer (PC-RET) rates in three systems: a donor–acceptor pair above a bulk gold surface, on opposite sides of a spherical gold nanoparticle, and within a cylindrical waveguide. Employing theoretical and numerical methods, we evaluate RET rate enhancements relative to vacuum rates and derive analytical relationships between system parameters. Our results reveal, for shorter intermediate-range separations, a consistent and dramatic enhancement of RET when the donor–acceptor pair are oriented at approximately 60° with respect to their separation vector, across all three systems. Using quasi-static approximations, we uncover additional nontrivial regimes of enhancement related to chromophore orientation and separation distance. Notably, in the waveguide system, we observe mode-specific RET enhancements. These findings highlight the importance of chromophore orientation in PC-RET and provide insights for optimizing energy transfer near inhomogeneous, dispersive, and absorbing bodies, aiding the development of advanced light-harvesting technologies.