Playing Ping Pong with Light: Directional Emission of White Light

Over the last decades, light-emitting diodes (LED) have replaced common light bulbs in almost every application, from flashlights in smartphones to automotive headlights. Illuminating nightly streets requires LEDs to emit a light spectrum that is perceived as pure white by the human eye. The power associated with such a white light spectrum is not only distributed over the contributing wavelengths but also over the angles of vision. For many applications, the usable light rays are required to exit the LED in forward direction, namely under small angles to the perpendicular. In this work, we demonstrate that a specifically designed multi-layer thin film on top of a white LED increases the power of pure white light emitted in forward direction. Therefore, the deduced multi-objective optimization problem is reformulated via a real-valued physics-guided objective function that represents the hierarchical structure of our engineering problem. Variants of Bayesian optimization are employed to maximize this non-deterministic objective function based on ray tracing simulations. Eventually, the investigation of optical properties of suitable multi-layer thin films allowed to identify the mechanism behind the increased directionality of white light: angle and wavelength selective filtering causes the multi-layer thin film to play ping pong with rays of light

Pulmonary vein isolation using a novel decapolar over-the-wire mapping and ablation catheter

Recently, a novel radiofrequency (RF) ablation system has been developed to perform pulmonary vein (PV) isolation. The system consists of a decapolar, steerable, over-the-wire mapping and ablation catheter combined with a multichannel RF generator that delivers energy in a temperature-controlled, power-limited fashion in both uni- and bi-polar modes. Using this technique, long continuous ablation lesions can be created within the left atrial antrum around the PV ostium. Electrical disconnection of PVs can be achieved in 93% of targeted PVs. Medium-term success is reported as 79.5% of patients with paroxysmal atrial fibrillation (no atrial fibrillation episodes detected during intensive holter monitoring). Ablation procedures using the novel technique are reported to be short (mean procedure duration: 84-201 min), including RF application duration of up to 40 min. Procedure-related complications are rare (1.8%) but the included total patient numbers are small and further studies on larger patient populations are neede

Photonik - Material und Technologien. Teilvorhaben: Verfahrensentwicklung zur flaechenselektiven MOMBE Abschlussbericht

Available from TIB Hannover: DtF QN1(72,59) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman