The demonstration of an electrically pumped organic laser remains a major issue of organic optoelectronics for several decades. This goal requires an improved device configuration so as to reduce losses which are intrinsically higher under electrical excitation compared to optical pumping. Moreover a systematic investigation of the material properties is still missing and should lead to a reliable estimate of the lasing threshold under optical pumping, and then to a lower limit for electrical pumping. In this thesis we addressed the issue of gain and polarization properties of organic materials in the case of dye-doped polymer thin films. The originality of this work lies in the study of materials via the features of dielectric micro-lasers, allowing to investigate the issues of gain and mode coupling and the physics of open systems. We propose a quantitative description of amplification in organic materials. The "gain-loss-threshold" relation was developed and demonstrated for a Fabry-Perot type cavity, opening the way to study both amplification in organic materials and light out-coupling in dielectric micro-cavities via the lasing threshold. Within this context, different cavity shapes were studied, for instance squares, where light out-coupling takes place by diffraction at dielectric corners. We evidence that polarization properties of such lasing system originate from the intrinsic fluorescence anisotropy of dyes, which required to develop a specific anisotropic model going beyond the existing theory. We also investigated the role of the cavity geometry on the polarization states of the micro-lasers and proposed different ways to influence these features.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-01063044 |
| Date | 16 October 2012 |
| Creators | Gozhyk, Iryna |
| Publisher | École normale supérieure de Cachan - ENS Cachan |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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