Transmittance design of internal reflection triangular-groove grating at large dimension domain

We present that the internal reflective triangular-groove grating can be effectively analyzed and designed by the developed scalar diffraction theory and the effective medium theory at the certain feature size. This grating profile could be applied in enhancing significantly the light extraction efficiency of light-emitting diodes. The accuracy of these both uncomplicated methods is quantitatively evaluated by the comparison of diffraction efficiencies predicted from them to exact results calculated by the rigorous coupled wave analysis method. When the normalized period of a grating is more than fourfold wavelengths of emitted light, the developed scalar diffraction theory is accurate and useful to analyze the internal reflective triangle grating. As the higher order diffraction waves other than zero order wave is not to propagate, the effective medium theory can precisely evaluate the transmittance within the error of about 1.2%. Besides, the used limitation of these simple methods as a function of the normalized height is also quantitatively determined. Furthermore, the transmission characteristics of manufacturing deficiencies of an internal reflection grating as a function of the groove width are quantitatively calculated by using the rigorous coupled wave analysis.

► We investigate mainly the transmittance of triangular grating microstructure.
► The developed scalar diffraction theory is proposed to analyze the transmittivity.
► The effective medium theory is applied to design the microstructure transmittance.
► The accuracy of these both uncomplicated methods is quantitatively evaluated.