Single and dual beam optical switching of resonance energy transfer

Through photonic mechanisms based on near-field coupling, laser radiation can engage with resonant energy transfer in a variety of suitably designed materials and molecular structures. Energy that has been acquired, through the initial absorption of resonant laser light, undergoes transfer between chromophores only on the throughput of off-resonant light, the process known as laser-assisted resonance energy transfer. The comprehensive results that are presented here extend and generalize the theory for both single and dual beam configurations, producing results that are applicable to media of various types including doped crystals, heterogeneous multichromophore solids, and solutions. The detailed principles, here explained in terms of both energetics and optical selection rule criteria, are specifically illustrated for a variety of materials. It is shown how general application of the theory can facilitate the elucidation of experiments, by clearly interpreting the effects of laser polarization manipulation. On further analysis of the photophysical mechanisms it is also demonstrated that such effects represent an entirely practicable basis for optical switching and logic gate operation. The additional polarization selectivity afforded by a two-beam setup proves to allow the most complete system control. With such a configuration, there is considerable promise for the realization of new optically driven logic and molecular devices.