Fabrication and simulation investigation of zig-zag nanorod-structured graded-index anti-reflection coatings for LED applications
Abstract
In this study, we report the fabrication, characterization, and modeling of a zigzag nanorod-structured graded-index antireflection coating fabricated by the oblique angle deposition (OAD) method. The optical properties of the reported coating were engineered by sculpting its composition and morphology using OAD, and the coating was designed to work with high-index, YAG:Ce ceramic phosphor plates. The coating enhances the normal-direction transmission of the phosphor plate over the broad visible-light spectrum. At 764 nm, the transmission is enhanced by 7.82%, compared to a potential maximum enhancement of 8.53%. For 633-nm light incident at 5°, the reported coating was measured to induce scattering loss of no greater than 1.27%. We developed a mathematical model that can use the OAD morphology information, developed from the film growth mechanism, as input parameters to simulate the optical properties of the nanostructured coatings. A finite-difference time-domain (FDTD) simulation was able to capture the polarization-dependent, antireflective performance of the coating, and the simulated transmission spectrum was in good agreement with both the measured spectrum and the spectrum calculated using the measured effective refractive indices in a transfer matrix formulation. In addition, the FDTD model was applied to predict the scattering losses. The simulation supports the experimental results and shows that the coating induces very weak scattering loss.
- Publication:
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Journal of Applied Physics
- Pub Date:
- May 2019
- DOI:
- 10.1063/1.5083582
- Bibcode:
- 2019JAP...125q3102L