Approaches to improve the calculating convergence of grating diffraction

From three respects such as mathematical principle,geometric stratification and numerical calculation,we have studied the convergence of rigorous coup led-wave approach (RCWA) in solving the grating diffraction problems. The a pproaches which can be applied to improve the convergence of RCWA are propo sed,It is found that,for different cases of grating,the major factors affec ting the convergence of RCWA are different. Therefore,the improving methods should be practically chosen for concrete case of grating.