Förster Resonance Energy Transfer and the Local Optical Density of States in Plasmonic Nanogaps

Forster resonance energy transfer (FRET) is a fundamental phenomenon in photosynthesis and of increasing importance for the development enhancement wide range optoelectronic devices, including color-tuning LEDs lasers, light harvesting, sensing systems, quantum computing. Despite its importance, questions remain unanswered on FRET rate dependency local density optical states (LDOS). In this work, we investigate directly, both theoretically experimentally, using 30 nm plasmonic nanogaps formed between silver nanoparticle an extended film, which LDOS can be controlled size nanoparticle. Experimentally, uranin-rhodamine 6G donor-acceptor pairs coupled to such yielded enhancements 3.6 times. This, combined with 5-fold emission acceptor, resulted overall 14-fold acceptor's intensity. By tuning size, also show that those systems linearly dependent LDOS, result directly supported by our finite difference time domain (FDTD) calculations. Our results provide simple but powerful method control via direct modification.