Eutectic phosphor for high-power excitation

Abstract

High-power blue-emitting laser diodes have been used in projectors and lighting systems as excitation sources for yellow-emitting phosphors. These phosphors must be robust and should not exhibit thermal quenching. In this work, we developed a durable eutectic phosphor consisting of single-crystal Ce-doped yttrium aluminum garnet (Ce:YAG) phosphor and Al₂O₃ (sapphire), with a thermal conductivity greater than 20 W/(m·K). This eutectic phosphor is named EPOCH-Neo. EPOCH-Neo specimens were cut from a large crystal substrate prepared by an edge-defined film-fed growth method. We evaluated the optical properties of EPOCH-Neo specimens and the optical uniformity of an EPOCH-Neo substrate. In addition, to control the chromaticity, the Y-sites of Ce:YAG were doped with Gd at concentrations as high as 50% and the chromaticity and thermal characteristics of the resultant phosphors were evaluated. Moreover, the characteristics of a device composed of EPOCH-Neo on a heatsink under blue laser excitation were examined. The results showed that EPOCH-Neo is a durable phosphor suitable for use in high-power-excitation applications.