Laser-pumped high-power compact near-infrared light sources based on phosphor-in-glass films

Abstract

Phosphor-in-glass (PiG) films are thought to be the best color converters for lighting of laser diodes (LDs) because of their better efficiency and outstanding thermal conductivity. Since laser-driven illumination can overcome the limitations of power density at higher incident optical power densities, in this paper, Cr³⁺-activated oxides were prepared as near-infrared emitters with thermally stable photoluminescence using a practical blade-coating approach. When pumped using a blue laser, the CaZrTaGa_0.2Ge_0.4Zn_0.4O₇:0.01Cr³⁺ PiG film presents a near infrared (NIR) emission band, with a peak at 812 nm and a full width at half maximum (FWHM) of 248.37 nm. Its internal quantum efficiency reaches 90.20% and the emission intensity at 423 K remains at 92.32% of that at room temperature (RT). In addition, when coupled with a blue laser diode (LD), the optical output power of the NIR LD reaches up to 2.07 W mm⁻² at an input power of 9 W mm⁻², which is significantly higher than the output power of the NIR phosphor-converted light-emitting diodes (pc-LEDs). Thus, this study advances the development of Cr³⁺ activated oxide-based PiG films with thermally stabilized luminescence properties and confirms their promising applications in laser-pumped dental monitoring and near-infrared high-power illumination.