Fluorescence enhancing photonic devices

It is demonstrated that fluorescence enhancing nanostructures can be designed using a classical electromagnetics approach. A classical model of a molecule capable of absorbing and re-radiating one quantum of energy is presented and demonstrated to work in FDTD, the finite-difference in the time domain computational solution of Maxwell's Equations. Bohr's Correspondence Principle is satisfied by this model in the sense that the molecule's classical radiation decay lifetime behaves exactly as the quantum mechanical radiative transition rate in the presence of nearby dielectric boundaries. The so-called photonic mode density effect that enhances fluorescence in the presence of Surface Plasmon Resonant (SPR) boundaries has its direct analog in the modification of the classical molecule's radiation resistance. Fluorescence enhancement is then shown to be an impedance matching problem, where enhancing radiation from a molecule is equivalent to increasing its radiation resistance. A comparison is made between fluorescence enhancing nanostructures including metal nanorods, nanodisks and the metal symmetrical folded dipole using FDTD simulations that incorporate dispersive materials in its update equations. In order to demonstrate the radiation enhancement capabilities of the symmetric folded dipole, experimental measurement were performed by scaling a molecule and the symmetrical folded dipole to RF frequencies. Experimental results are then compared to computational results. The results indicate that the symmetrical folded dipole is a suitable candidate for the enhancement of fluorescence at optical frequencies.