Enhanced Color Quality of Phosphor-Converted White Laser Diodes Through Bicolor Phosphor-in-Glass

In this work, phosphor-converted white laser diodes (pc-WLDs) with high color quality were fabricated by combining blue lasers and bicolor phosphor-in-glass (PiG) converters. The bicolor PiGs were prepared by printing and sintering green/red phosphor glass films on sapphire substrates, and then applied in the transmission type of pc-WLDs. The PiG-based white laser diodes (WLDs) display broadband emission and their optical performances were adjusted by varying the PiG film thickness. When the film thickness increases from 80 to
$160~\mu \text{m}$
, the luminous flux and correlated color temperature (CCT) of PiG-based WLDs are gradually decreased, and they still have high color rendering index (CRI). At the film thickness of
$160~\mu \text{m}$
, the PiG-based WLD achieves high color quality with a CRI of
${R}_{a} = {88}$
,
${R}_{{9}} = {91}$
, and
${R}_{{13}} = {93}$
, a CCT of 4571 K, and a chromaticity coordinate of (0.3525, 0.3541) at a laser power of 2.4 W. Furthermore, the PiG-based WLD has stable color quality at high laser power and the luminous flux reaches to 553 lm at a laser power of 5 W. The results indicate that the bicolor PiG-based WLDs realize high-quality white light, which can promote the practical applications of laser lighting in high-quality fields.