Improving the luminous efficacy and resistance to blue laser irradiation of phosphor-in-glass based solid state laser lighting through employing dual-functional sapphire plate

Abstract

White lighting sources based on laser diodes (LDs) are strongly regarded as the next generation of high luminance lighting sources because the luminous efficiency of LDs increases linearly with operating current, which can resolve the “efficiency droop” of LEDs. To facilitate the advent of high brightness solid state lighting, searching for a light convertor with high thermal stability, high conversion efficiency, and irradiation stability is essential. Herein, we developed a robust light convertor, YAG:Ce³⁺ based on phosphor-in-glass (denoted as YAG-PiG), exhibiting a quantum efficiency of 70.1% and a high thermal conductivity of 0.89 W m⁻¹ K⁻¹. The microstructure and luminescent properties of YAG-PiG were also investigated in detail. Compared to YAG-PiS (phosphor-in-silicone), this YAG-PiG shows an overall increase in irradiation and thermal stability performances. A high power white LDs was constructed by coupling the YAG-PiG with a 445 nm blue laser and a sapphire plate modified by an antireflection layer and a blue-pass filter serving as the heat sink. The constructed PiG converted LDs@sapphire exhibits a luminous efficacy of 217 lm W⁻¹ and a CRI (color rendering index) of 57 at 3646 K under a driven power of 3 W. Compared to the conventional white LDs, the luminous efficacy and the resistance to laser irradiation of the white LDs@sapphire are obviously enhanced. Therefore, we predict that this white emitting PiG converted LDs@sapphire will become a promising candidate for future lighting sources and promote the use of sapphire plate as the heat sink.