Packaging for Laser-Based White Lighting: Status and Perspectives

Abstract

AbstractLight-emitting diodes (LEDs) have gained wide adoption in general illumination applications in the last decade. However, the efficiency drop of LEDs with increasing current density limits the luminous flux per wafer area. In contrast, laser diodes (LDs) can achieve higher efficiency at high current density. Likewise, the etendue of LDs is very low due to the small emitting area and divergent angle, facilitating the high-luminance. Hence, LDs may outperform LEDs in future high-luminance solid-state lighting (SSL). However, the rapid development of high-luminance white laser diode (WLD) is still facing some challenges. First, the heat flux of LD chip is extremely high, leading to a higher junction temperature. Second, the laser beam exhibits an elliptical and astigmatic pattern with Gaussian intensity distribution, which may deteriorate the lighting performances. Third, to achieve high-luminance lighting, the laser beam is usually focused onto the phosphor layer, which may easily increase the phosphor temperature to the thermal quenching region. A comprehensive understanding of these problems enables the advancements of packaging designs for WLDs. In this review, we summarized the recent progress in the packaging of WLDs. First, the advantages and applications of LDs were presented. Then, the state-of-the-art methods of generating white light using LDs were reviewed, in terms of packaging structures and performances. Finally, the challenges and corresponding progresses for the packaging of WLDs were overviewed. This review intends to contribute to the development of next-generation high-luminance laser-based white lighting.