Local Linear Grating Approximation (LLGA)

The LLGA solver works in the spatial domain (x domain), locally, in a pointwise manner. The solver follows that

• the input field on the surface is treated as a composition of local plane waves (LPWs),
• the part of the surface seen by each LPW is considered a linear grating (locally), and,
• the interaction of the LPW with the local linear grating can be modeled by the FMM/RCWA, TEA, or the idealized grating function.

At an arbitrary location on the surface, an approximate local boundary condition is applied, which assumes the interaction of the LPW with the local linear grating. Thus, the FMM/RCWA, TEA, or the idealized grating function can respectively be used to connect input and output fields.