A square lattice of holes with radius = 130nm have been etched into the layer, with the lattice period ax = 500 nm. Here, the membrane structure has thickness 200nm and a refractive index value of 3.4. This example is similar to the Planar 3D example. We will also compare the results to that of 3D FDTD to show that the 2.5D FDTD method can give comparable results with a fraction of the memory and simulation time required by 3D FDTD. In this example, we use the 2.5D FDTD propagation method in MODE to calculate the bandstructure of a slab photonic crystal with a square and hexagonal lattice. This technique is very useful for most photonic crystal devices compatible with CMOS technology, where the geometry is planar, with a non-periodic 3rd dimension. One advantage of using the finite-difference time-domain (FDTD) method is that one can calculate slab photonic crystals without band-folding effects. In general, bandstructures can be calculated using a time domain method or using a plane wave expansion method. In this example, we will focus on how to use MODE' 2.5D FDTD propagation method to calculate the bandstructure of a slab photonic crystals device with a square and hexagonal lattice of holes.įor an introduction to calculating bandstructures using FDTD, see Rectangular Photonic Crystal Bandstructure. Accurate bandstructure calculations are important for the design and analysis of photonic crystal devices.
