Efficient computation scheme of grating structure using RCWA and FDFD

Rigorous coupled-wave analysis, a classic approach for calculating grating structures, will be very slow in some cases, as involved lots of matrix's eigenvalue problems. The use of finite-difference frequency-domain can avoid eigenvalue problem by introduce a large number of difference calculations. Lots of matrix computations are involved in both methods. Matrix computation library accelerated by GPU (Graphic Processing Unit) was introduced to carry out the calculations more effectively. Because of that library isn't suitable for all size of matrix, the performance of some functions that used in the algorithms were tested. To calculate the structure of grating effectively, the differences of the quantity of calculations between the two approaches were compared in different diffracting orders and grating structures with different math libraries. Finally, the best approach was chosen by combination of these three factors.