Step Action
1 From the Simulation menu, select Simulate 2D Using 64-bit Simulator. The Simulation Parameters dialog box appears.
2 Type/select the following information:

Polarization:                         TM Unselect Auto for mesh

Mesh Delta X [µm]:              0.02

Mesh Delta Y [µm]:              0.02

3 Click the Advanced button to check the boundary condition settings. Default parameter is for most general simulations (except when the mesh size is smaller than 0.008 for metallic layout). For this simulation, we will use the default setting.
4 Click OK to close the advanced setting.
5 Set Time Step Size as Auto.

Note: Auto time step size followed CFL condition. Which guarantee the FDTD method stable.

6 Unselect Auto for Run for Time Steps. This auto value will keep the initial wave-front propagate through the whole wafer size. However for the resonant structure like this grating, the time domain iteration number should resonant structure like this grating, the time domain iteration number should be increased so that the resonant wave can be caught. Set this value as 9000.
7 Set Spectrum region.

•     Click DFT Spectrum Button

•     Uncheck the Auto checkbox.

•     Number of Samples:101

•     Start wavelength1.4

•     End wavelength1.9

•     Use Wavelength

•     Click OK

8 Select Simulate Using Sweep
9 Time domain Sampling Interval: 1

Note: The time domain step size in FDTD simulation is quite small. It is not necessary to use such a fine sampling data to do the Fourier transform (FT). We can just enlarger the sampling rate for the FT analysis. However, to get more accurate results, we can still use the original fine data if we set Time domain Sampling Interval as 1

10 Click OK to accept/finish the simulation parameter settings.

Note: Before running the simulation, save the project to a file.