In this paper, we present our study in packaging efficiency for phosphor-converted white LED (pcW-LED). Then the
limit of luminous efficacy of a pcW-LED in different types of packaging is estimated. In the calculation, the EQE of the
blue die is assumed 81% and the Stokes loss is counted, we obtain the limit of luminous efficacy, which reaches 300
lm/W, when the color appearance is green-white and the corresponding CCT is between 4000K to 5000K. More
consideration for practical limit take consideration of phosphor quantum loss and geometry loss, and the limit of
luminous for CRI around 60 is around 240 lm/W, and for CRI larger than 80 is around 175 lm/W.
Based on Monte Carlo ray tracing we present a study of GaN die with a reflective layer coated on a p-GaN surface inside the light guide as a planar light source. We simulated the lights extracted from the GaN die implanting pyramid microstructure on the top surface of sapphire or on the top surface of p-GaN. Micro pyramid array with different slanted angle from 5<sup>0</sup> to 85<sup>0</sup> is shown to effectively improve the light extraction efficiency. In addition, the pattern sapphire substrate with slanted angle of ten degrees is found to be an effective way to increase the lateral directionality than the surface texture.
In this letter, we present a new design for a light-emitting diode- based bike headlamp. The optical design contains two horizontal reflectors and a light pipe with two horizontal parallel mirrors. The designed illumination pattern in our simulations performs a contrast of 250 in the K-mark regulation, and it was measured to be 21 in the experiment with a not well-finished prototype, which was operated at 1 W. The contrast is higher than 5 as requested in the regulation.
In this paper, we demonstrate a method to calculate the phosphor particle numbers and study the relationship among
phosphor particle numbers, light output and correlated color temperature (CCT) of LEDs under remote package type and
dispensing package type. We also discuss the influence of the thickness and concentration of phosphors on the
performance of LEDs. We compare the various thicknesses and concentrations to check the resultant CCT and the output
flux, where we can see that the lumen output is almost equal as the phosphor particle numbers is similar with the CCT at
6500±200 and 5000±100 K under the remote package type.