Coh2Shape · Modeling of partially spatially coherent distributed sources: derivation of an extended reciprocity theorem, creation of a numerical tool and experimental validation.

Going up to infrared or optical frequencies, classical antenna technology fails due to the lack of efficient localized feeds. At such frequencies, emitters generally rely on distributed feeds. Each point of the extended source zone emits fields randomly, so that the total fields generated by the device are only partially spatially coherent. The partially spatially coherent aspect of the fields has received limited attention so far, especially in the engineering community. However, it is well known that the spatial coherence of the fields plays a key role in shaping and enhancing the radiation from thermal and electroluminescent sources. In this project, we propose a framework where the fields emitted by such sources are decomposed into an incoherent sum of fully coherent modes. During this project, we will develop a versatile open-source software that can simulate such devices using a full-wave integral equation method. This software can be used to study thermal or electroluminescent emitters of various geometries while rigorously accounting for the partial coherence of the fields. The software will be validated through experiments and shared with the community. Using the modal framework, an extended reciprocity theorem between the fields emitted by thermal or electroluminescent sources and the fields they absorb that includes the partially coherent aspect will be derived and validated through experiments. This project is expected to deeply impact the field since no such tool that can rigorously account for the partial coherence of the fields has been proposed so far. Moreover, the experimental characterization of emitters will be easier using the extended reciprocity. This project will be done in the University of Cambridge in collaboration with J.-J. Greffet (France) and C. Craeye (Belgium). Through this project, the researcher will develop skills in experimental research, which he is currently missing to reach an independent position.