Numerical evaluation of nano-scale structure for optical field adjustment in small micro LEDs

We numerically investigate TiO2 nanostructure arrays on a GaN substrate to reshape micro-LED-like emission across the visible spectrum. As pixel sizes approach the micrometer scale, the broad Lambertian-like radiation reduces forward photon density in compact optical engines. Beam shaping is evaluated from the axial intensity distribution above the emitter by locating the axial maximum and its distance from the metasurface. Parameter sweeps show consistent trends for red, green, and blue: increasing nanostructure diameter or height enhances forward concentration while shifting the axial maximum closer to the surface, indicating a reduced focal distance. We also examine the effect of excitation beam size and find that the source waist influences both the focal position and the degree of axial concentration. These results provide design guidelines for tuning nanostructure geometry and excitation conditions for visible-band micro-LED beam shaping.