Laser-assisted resonance-energy transfer

The process of laser-assisted resonance-energy transfer (LARET) is described and analyzed within the framework of molecular quantum electrodynamics. LARET is a higher-order perturbative contribution to the familiar spontaneous dipole-dipole mechanism for resonance-energy transfer, in which an auxiliary laser field is applied specifically to stimulate the energy transfer. The frequency of the auxiliary beam is chosen to be off-resonant with any molecular transition frequencies in order to eliminate direct photoabsorption by the interacting molecules. Here consideration is given to the general case where the energy exchange takes place between two uncorrelated molecular species, as for example in a molecular fluid, or a system in which the molecules are randomly oriented. In the ensuing calculations it is necessary to implement phase-weighted averaging in tandem with standard isotropic averaging procedures. Results are discussed in terms of a laser intensity-dependent mechanism for energy transfer. Identifying the applied field regime where LARET should prove experimentally significant, transfer rate increases of up to 30% are predicted on reasonable estimates of the molecular parameters. Possible detection techniques are discussed and analyzed with reference to illustrative models.