On the determination of the temperature distribution within the color conversion elements of phosphor converted LEDs.

We present an iterative optical and thermal simulation procedure which enables the determination of the temperature distribution in the phosphor layer of a phosphor converted LED with good accuracy. Using the simulation both the highest phosphor temperatures, which are mostly relevant to material degradation as well as the temperatures of those phosphor particles which mainly contribute to converted light emission can be determined. We compare the simulations with experimental studies on the phosphor temperature.

Förster-type resonant energy transfer influenced by metal nanoparticles.

We show experimentally and numerically that Forster-type resonant energy transfer between molecules strongly depends on the interaction with plasmonic resonances in a nearby metallic nanoparticle (MNP). Acceptor luminescence emerges at the expense of donor luminescence when an acceptor molecule harvests the donor's near-field energy. By tuning the resonance of a close-by MNP across the transition energy bands of the molecules, we show how the molecular luminescence is affected and in part even strongly increased.

Observation of phase conjugation of light arising from enhanced backscattering in a random medium.

We measure the fundamental phase conjugation of a light field arising from enhanced backscattering in a multiple scattering medium. The measurements employ a two-window, time-resolved heterodyne method to suppress specularly reflected light and to determine the transverse Wigner function of the field, yielding joint amplitude and phase information. Using this method, a light field backscattered from an aqueous suspension of polystyrene spheres is found to reverse curvature relative to that of the incident field.