Light Extraction and Brightness Enhancement of Luminescent Rectangular Slabs

Abstract

The extraction efficiency and the brightness are critical parameters to increase the performance of luminescent rectangular slabs such as scintillators, luminescent concentrators, or diamonds with NV centers. This work explains how an additional face breaking the rectangular symmetry can improve the extraction efficiency and brightness. The study is based on a fully analytical approach corroborated experimentally with cerium‐doped yttrium aluminum garnet (Ce:YAG) slabs. The model gives an analytical expression of the extraction efficiency and the brightness of the additional face as a function of the slab parameters (dimensions, refractive index, losses). Results highlight that the extraction efficiency by an additional face can be improved even if the area of the additional face is lower than the area of the smallest face of the slab, generally chosen as the output face in a standard configuration. Therefore, the output brightness can be easily improved and controlled by the dimension of the additional face. Balancing the extraction efficiency and the brightness, a 1 × 3 × 22 mm3 Ce:YAG slab with an optimized edge face and with mirrors on the lateral faces exhibits an efficiency 1.9 times better and a brightness 5.6 higher than a Ce:YAG in a standard configuration.

Keywords

• brightness
• light guide
• luminescent concentrator
• luminescent materials
• scintillators