Laser-drilled microstructures for enhanced luminous efficiency and wide-angle emission in WLEDs

This study presents a hybrid approach to enhance the optical performance of phosphor-in-glass (PiG) structures for white light-emitting diodes (WLEDs) by integrating laser-fabricated microlens arrays (MLAs) onto the phosphor surface. The MLA structures were directly patterned using laser direct writing and drilling, offering precise photon redirection without compromising the thermal or mechanical stability of the PiG material. By varying the microlens spacing (100, 105, 120, and 135 μm), the effect of structural parameters on light extraction and angular emission was systematically investigated. Experimental results show that the sample with 120 μm spacing achieves optimal performance, increasing the emission angle from 80° to 120° and enhancing luminous efficacy by 12.5%. The scattering ratio improves from 51.4% to 80.3%, while the color conversion efficiency increases from 64.7% to 74.6%. Ray-tracing simulations based on geometric optics confirm the observed improvements and reveal the underlying mechanisms of enhanced light scattering and reduced internal reflection. The proposed fabrication method is scalable, maskless, and compatible with high-power LED packaging. These findings demonstrate a practical and effective strategy for improving both angular distribution and luminous efficiency in next-generation WLEDs, particularly for automotive and solid-state lighting applications.