Laser-driven white light generation by mixing blue (BAM), green (GYAG), and red (nitride) phosphors

Abstract

In the present work, a purple laser diode of 405 nm is employed for the excitation of different types of phosphors for the purpose of building a white light source. Three different types of phosphor materials were synthesized – a blue phosphor (BAM), a green phosphor (GYAG) and a red phosphor based on nitride. These samples were synthesized in the form of silicone pellets, having different thicknesses and different concentrations in the silicone matrix. In this study, two different approaches were followed. First, the three different samples were stacked together in various combinations to study the colorimetric parameters of the emitted converted light, particularly the correlated color temperature (CCT) and the color rendering index (CRI). In the second approach, the three types of phosphors were merged in the same silicone pellet. Pellets with different thickness and ratio of the three phosphors were prepared, and their CCT and CRI parameters were measured under laser excitation. In the first case, a CCT of 2264 K and a CRI of 74 were achieved while with the second approach, an average temperature of 4500 K and a CRI of 85 were reached. While the difference between the CRI values for both cases is not big, the CCT value of the mixed samples is twice as high as the value of the stacked pellets, something attributed to simultaneous excitation of phosphors in mixed samples while, when stacked, each material is irradiated in a specific order.