Thermally stable laser-driven phosphor converted white light source using multilayer structured diffuser system

Abstract

We report the development of a thermally stable laser-driven phosphor-converted white light source using a multilayer structured diffuser system for general illumination. The developed extended diffuser system comprises an acrylic sheet, two glass plates, and a phosphor layer with the arrangement in a glass-acrylic-phosphor-glass combination. The high-power laser beam was gradually distributed inside the diffuser system for exciting the phosphor layer optimally without burning the resin and thermal quenching. The method is simple and efficient in which both the directionality and scattering properties of laser source are exploited using the transmission properties of diffusers. The high specular transmission of diffusers resulted in the optimum transfer of laser directional photons for exciting the middle section of phosphor layer, and the remaining laser photons were scattered from diffuser surfaces. The glass-acrylic combination results the refractive index inhomogeneity inside the system and helped to expand the scattered photons throughout the phosphor layer. The radiant power distribution of blue laser source inside the system resulted in synchronization between optimal absorption quantum efficiency and fluorescent conversion quantum efficiency of the phosphor layer. As a result, the thermal quenching effect on phosphor inside the white light system was minimized for efficient illumination. With this geometry, a bright and thermally stable white light source was realized due to the proper distribution of high-power laser throughout the system. The luminescence properties of the proposed laser-based white light system were examined and found thermally stable in terms of spectral changes, luminance, and correlated color temperature.