In this work a simulation software is employed to study how the different shapes of the phosphor material may affect the white light production of the light source. In particular, while usually the phosphors that are being used in a laser driven configuration are flat plates, in this case we examine what happens when curvature is introduced. It is shown that curvature affects the way the produced white light is distributed and it can also increase the conversion of laser light to white light by the phosphor due to its curved shape. Sample phosphors of different curvature and geometry were studied and compared to the flat shaped ones.
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.
The phosphor excitation by blue laser diode and an influence of its irradiation on the material were investigated. Two types of materials were elaborated to perform these experiments—yellow phosphor (YAG) and green phosphor mixed with nitride phosphor (GYAG). These phosphors were packaged into silicone plates, having different thickness and concentration in silicon resin. The results from exciting the phosphor by blue laser present that emission of converted light increases when concentration and thickness increase. Also, the dependency of these two parameters on optical power shows certain behavior. Subsequently, the concentration and thickness were replaced by particle number in sample. It revealed that the dependency of the particle numbers on the optical power can replace the conventional parameters as thickness or concentration. Results show that correlated color temperature finds it dependency on number of particles also. In addition, it turned out, that for each of the material, there might exist an optimal particle number for the maximum luminous power. Finally, the influence of the irradiation of blue laser diode on the materials was investigated. After intensive irradiation for 30 min, we observed that the efficiency of light conversion decreases. It can be caused by damages made by laser on particles. Results show parts of nitride (650 nm) conversion decrease less than yellow or green phosphor. Less affection of irradiation can be explained by nitride being very covalent material, more resistant to modification. Also, we found that there is no fundamental modification of material structure because of no changing in spectrum shape of converted light.
The phosphor excitation by blue laser diode and an influence of its irradiation on the material were investigated. Two types of materials were elaborated to perform these experiments – yellow phosphor (YAG) and green phosphor mixed with nitride phosphor (GYAG). These phosphors were packaged into silicone plates, having different thickness and concentration in silicon resin. The results from exciting the phosphor by blue laser present that emission of converted light increases when concentration and thickness increases. Also the dependency of these two parameters on optical power shows certain behavior. Subsequently, the concentration and thickness was replaced by particle number in sample. It revealed that the dependency of the particle numbers on the optical power can replace the conventional parameters as thickness or concentration. Results show that correlated color temperature finds it dependency on number of particles also. In addition, it turned out, that for each of the material, there might exist an optimal particle number for the maximum luminous power. Finally, the influence of the irradiation of blue laser diode on the materials was investigated. After intensive irradiation for 30 minutes, we observed efficiency of light conversion decreases. It can be caused by damages made by laser on particles. Results show parts of nitride (650nm) conversion decrease less than yellow or green phosphor. Less affection of irradiation can be explained by nitride being very covalent material, more resistant to modification. Also, we found that there is no fundamental modification of material structure because of no changing in spectrum shape of converted light.
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