Detailed analysis of experimentally observed far-field diffraction patterns from LEDs containing a buried photonic quasi-crystals (PQC) slab are presented for devices with PQC layer depths of 300 to 1300 nm and pitch 400 nm. Ewald constructions allowed identification of the features in experimental data to be correlated with identified waveguide modes from which light is extracted. Effective indices for the slab waveguide modes calculated by a modal expansion method are found to be in close agreement with values extracted from the experimental results, allowing validation of both an effective medium model for the PQC slabs and a design and analysis method for LED structures with diffractive buried photonic crystals.
Lewins, C. J., Allsopp, D. W. E., Shields, P. A., Gao, X., Humphreys, B., & Wang, W. N. (2013). Light extracting properties of buried photonic quasi-crystal slabs in InGaN/GaN LEDs. IEEE/OSA Journal of Display Technology, 9(5), 333-338. https://doi.org/10.1109/JDT.2012.2233194