White light emission via cascade Förster energy transfer in (Ga, In)N quantum well/polymer blend hybrid structures

We have studied the room-temperature non-radiative energy transfer processes in hybrid structures composed of (Ga, In)N/GaN single quantum wells and semiconducting polymer blend films placed in nanometre-scale proximity. The blends consist of three polyfluorene materials with concentrations adjusted so that they emit white light. Power-dependent photoluminescence (PL) measurements are used to investigate the process of energy transfer from the quantum wells to the different components of the polymer blend. We show that energy distribution among the hybrid structures involves competition between nanoscale range non-radiative energy transfer processes from the inorganic well to the polymer components and within the blend itself.

Investigation of the laserlike behavior of polymeric scattering gain media under subpicosecond laser excitation

The narrowing effects of scatterers on the lifetime and the spectral width of the laser-induced fluorescence of organic dyes hosted in poly(methyl methacrylate) polymer sheets were studied. The excitation source was a distributed-feedback dye laser emitting 0.5-ps pulses at 496 nm. Spectral and temporal features were recorded simultaneously on a spectrograph-streak-camera detection system. The results were then compared with those obtained from dye solutions in methanol that were recorded in previous studies. The effects of the different host environments on the fluorescence characteristics of the dye were thus investigated. These effects are currently studied when the dye is inserted into human tissue in an attempt to boost tumor detection and photodynamic-therapy efficiency. Some initial results are presented.