Enhancing brightness of Lambertian light sources with luminescent concentrators: the light extraction issue

• Published in: Optics express Vol. 27; no. 8; pp. 11830 - 11843
• Main Authors: Gallinelli, T, Barbet, A, Druon, F, Balembois, F, Georges, P, Billeton, T, Chenais, S, Forget, S
• Format: Journal Article
• Language: English
• Published: United States Optical Society of America - OSA Publishing 15.04.2019
• Subjects: Engineering Sciences; Optics; Photonic
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.27.011830

Luminescent concentrators (LC) enable breaking the limit of geometrical concentration imposed by the brightness theorem. They enable increasing the brightness of Lambertian light sources such as (organic) light-emitting diodes. However, for illumination applications, light emitted in the high-index material needs to be outcoupled to free space, raising important light extraction issues. Supported by an intuitive graphical representation, we propose a simple design for light extraction: a wedged output side facet, breaking the symmetry of the traditional rectangular slab design. Angular emission patterns as well as ray-tracing simulations are reported on Ce:YAG single crystal concentrators cut with different wedge angles, and are compared with devices having flat or roughened exit facets. The wedge output provides a simple and versatile way to simultaneously enhance the extracted power (up to a factor of 2) and the light directivity (radiant intensity increased by up to 2.2.).