From the two peaks in the spectrum we can find the size and location of the band gap, which correspond to the bandwidth and center wavelength of the Bragg grating. Once the simulation finishes running, the spectrum at k x = π/a is returned by the bandstructure analysis group, as shown below. Simulation Results Bandwidth and center wavelength For this simulation, we are interested in the spectrum at the band edge k x = π/a, which will give us the size and location of the band gap of the grating. ![]() A mode source is used as the excitation, and the bandstructure analysis group is used to calculate the spectrum. Bloch boundaries are used for the x min/max boundaries, which allows us to set the kx value for the infinitely periodic device. In Bragg_FDTD_unit_cell.fsp, the simulation region contains exactly one unit cell of the grating. Simulation Setupįor this example, we will use a 3D FDTD simulation of a single unit cell of the grating to find the center wavelength and bandwidth of the infinitely periodic device. ![]() These devices are often used as optical filters for achieving wavelength selective functions. ![]() BackgroundĪ waveguide Bragg grating is an example of a 1D photonic bandgap structure where periodic perturbations to the straight waveguide forms a wavelength specific dielectric mirror. In this example, we will use 3D FDTD simulations to access how the performance of the Bragg grating is affected by geometric parameters such as the corrugation depth and misalignment.
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