Comparison of simplified theories in the analysis of the diffraction efficiency in surface-relief gratings

Abstract

In this work a set of simplified theories for predicting diffraction efficiencies of diffraction phase and triangular gratings are considered. The simplified theories applied are the scalar diffraction and the effective medium theories. These theories are used in a wide range of the value Λ/λ and for different angles of incidence. However, when 1 ≤ Λ/λ ≤ 10, the behaviour of the diffraction light is difficult to understand intuitively and the simplified theories are not accurate. The accuracy of these formalisms is compared with both rigorous coupled wave theory and the finite-difference time domain method. Regarding the RCWT, the influence of the number of harmonics considered in the Fourier basis in the accuracy of the model is analyzed for different surface-relief gratings. In all cases the FDTD method is used for validating the results of the rest of theories. The FDTD method permits to visualize the interaction between the electromagnetic fields within the whole structure providing reliable information in real time. The drawbacks related with the spatial and time resolution of the finite-difference methods has been avoided by means of massive parallel implementation based on graphics processing units. Furthermore, analysis of the performance of the parallel method is shown obtaining a severe improvement respect to the classical version of the FDTD method.

Precise-Integration Time-Domain Formulation for Optical Periodic Media

“…The length h has been varied for obtaining the results shown in Figure 5a. PITD simulation is compared to SF-FDTD results [33], showing that PITD provides close values to SF-FDTD. Some minor deviations are in the curves that can be produced by the spatial average that must be carried on in time-domain simulations and differences between spatial and time resolutions in both methods.…”

“…More specifically, Figure 5a shows the diffraction efficiency of the 0thand 1st-orders as a function of the normalised pillar length. The scheme of a binary phase grating is shown in Figure 1c where the parameters are the same ones used in the analysis in [33]: ∆ = 2λ, n g = 1.5 and f = 50%. The length h has been varied for obtaining the results shown in Figure 5a.…”

Analysis of periodic anisotropic media by means of split-field FDTD method and GPU computing

“…This validation is done for both the isotropic and the anisotropic version. The systems simulated are based on the analysis performed in 3,19 . In all cases the software runs under a Unix based platform with an Intel Core i7-950 Processor with 8MB of cache, a clock speed of 3.06 GHz and 6 GB of global DDRAM3.…”

Further enhancement of light extraction efficiency from light emitting diode using triangular surface grating and thin interface layer

“…A number of research papers have been published, suggesting ways to improve the LEE or the external quantum efficiency in LEDs. Random surface texturing or roughening [3][4][5], periodic surface modification in the form of nanopyramids [6] or surface gratings [7], and exploiting photonic crystals (PCs) [8][9][10][11][12][13] or surface plasmon resonance [14,15] are some of the interesting approaches aimed at increasing the LEE of LEDs. Interesting reports [16] are also made on improving the efficiency by using top transmission gratings only.…”