The first objective is to study and optimize the light confinement induced by Bragg gratings such as Distributed Bragg Reflectors (DBR) and Distributed FeedBack structures, inserted in OLETs. Quantitative calculations will be done, using several existing numerical tools (Transfer Matrix Method, Finite Element Method, Fourier Methods), to simulate exciton emission in the 3D non-planar multilayer structures, and evaluate the lasing threshold. We will thoroughly study the effect of location and orientation of the excitons (dipole emitter), on the emitted light. Then, a large part of the Ph-D will be devoted to experimental characterization of the fabricated OLETs. First, the refractive index and layer thicknesses will be measured by ellipsometry. Then, the light emission spectrum, and its angular dependancy will be measured, as well as the localization of the emission zone. A Scanning Near Field Optical Microscope under development would permit the candidate to observe the exciton profile at the nanoscale.
The second objective is to study the exciton dynamics in the structure, using simple rate equations to describe the transition between the energy levels of the emitting molecule, coupled to the light propagation in the structured medium, and thereby evaluate the perfomance of the emitting layer.