Simulation box

Simulation box

The Maxwell simulation box is divided into mainly two regions, one inner region for the requested Maxwell propagation and an outer region to simulate the proper boundary conditions. Later in the input file, the simulation box sizes refer to the total simulation box which includes the boundary region. The inner simulation box is defined by the total box size minus the boundary width. In case of zero boundary condition, there is no boundary region. Boundaries in 2D

Boundaries in 2D

The boundary region can be set up by absorbing boundaries, incident plane waves or a combination of both. In the latter case, the absorbing boundary region is the inner boundary region, and the plane waves region is the outer boundary region. Again, the box sizes are determined by the total simulation box size and the corresponding boundary width. Plane Waves and PML

Plane Waves and PML

For a given size of the propagation region, the boundaries have to be added to the total box size. The boundary width is given by the derivative order (default is 4) times the spacing. The width of the absorbing boundary region is defined by the variable MaxwellABWidth.

The matter grid is in general located inside the Maxwell grid. There are several possible types of grids to describe a coupled Maxwell-matter system. The following figure illustrates some possible cases overlaying Maxwell and matter grids. In the Octopus code, currently only the types e), f), and g) are implemented. So the matter box sizes and Maxwell box sizes can be chosen independently, whereas the spacings of both grids have to be equal and the grid points have to lie on the top of each other. The only exception is type g), where the matter grid is much smaller than the Maxwell grid. In this case, the matter grid size has to be smaller than the Maxwell grid spacing. Multiscale