This is consistent with the above observation.īoth the transmission and reflection show abrupt changes in the number of grating orders at 0.9 \(\mu m\), below which new grating orders kick in.įractional power into a specific diffraction order vs. This is because the index of the substrate (1.45) is larger than that of the air, meaning a shorter effective wavelength in the substrate. The reflection shows larger number grating order than the transmission. The grating supports a larger number of diffraction orders at a shorter wavelength. The following plot shows the number of transmitted/reflected orders the grating supports in terms of the wavelength. Alternatively, you can manually run the analysis (Right-click on the analysis group and select "Run analysis") and explore the results in the Results View window. The provided script collects some representative results from the two analysis groups ("grating_T" and "grating_R") and visualizes them. Open and run the script file (diffraction_grating_FDTD.lsf.) Open and run the simulation file (diffraction_grating_FDTD.fsp.) Instructions for running the model and discussion of key results The above results are returned as a function of wavelength and can be directly used in your grating design or further processed to yield the figure of merit of your interest. Grating efficiency into S- or P-polarized light for each grating orderĭirection cosine of each grating order (Equivalently, theta and phi values in the farfield half-sphere) Grating efficiency for each grating order The “grating order transmission” analysis group uses various grating-related commands and returns a comprehensive list of results useful for general characterization of grating: A broadband (0.85-1 \(\mu m\)) planewave is normally incident on the surface grating from the substrate, resulting in multiple diffraction orders in the transmission and the reflection regions. The diffraction grating in this example is a 2D array of half-ellipsoids on a planar surface. Understand the simulation workflow and key results The grating analysis group is also useful to obtain the fraction of power for a specific grating order. Lumerical provides a set of grating scripts as well as “grating order transmission” analysis group, making it easy to calculate common results such as number of grating orders, diffraction angles and grating efficiencies at different wavelengths. This example characterizes a diffraction grating in response to a broadband planewave at normal incidence.
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