Core-cladding-like phosphor ceramic wafer: A path to ultrahigh luminance
Yifeng Lai, Jiaochun Zheng, Zhi‐Qi Zhang, Gang Zhong, Shuxing Li, Rong‐Jun Xie
Abstract
The utilization of blue lasers to excite phosphor materials holds great potential for the development of high-brightness laser-driven light sources. However, phosphor materials that can simultaneously constrain light spot expansion and enhance maximum luminous flux have been elusive, thereby limiting output luminance. Herein, optical fiber-inspired core-cladding phosphor ceramics (CCPC) of YAG:Ce@Al<sub>2</sub>O<sub>3</sub> wafers were engineered using a gel-casting technique to restrict the light spot expansion. The smaller refractive index of Al<sub>2</sub>O<sub>3</sub>, combined with the dense and sharp core-cladding interface of these CCPC, effectively confines the light spot area. The sample with a 1.0 mm core diameter exhibits a small spot size nearly identical to that of the incident blue laser beam. Furthermore, the high thermal conductivity of the non-luminescent Al<sub>2</sub>O<sub>3</sub> cladding endows the CCPC with an impressive luminance saturation threshold of 30 W·mm⁻<sup>2</sup> and a maximum luminous flux of 2100 lm for white light within a straightforward transmissive optical setup. The combination of a confined light spot area and an elevated luminous flux results in an ultra-high luminance of 3900 lm·mm⁻<sup>2</sup>, surpassing current reports. This research presents a pioneering approach to the design of phosphor materials, targeting the realization of light sources with unprecedented luminance for broad frontier applications.