The current study describes frequency conversion processes in a poly domain consisting of two phases of "grating" modulation of nonlinear susceptibility (i.e., from four con-secutively organized domains). As a result, the complex amplitudes of interaction waves at the outlet of each main serve as the entry values for the equivalent complex ampli-tudes in the subsequent domain. The factors that limit the effectiveness of frequency conversion have been investigated. In addition, the scenario of n domains has been considered. Furthermore, in this approximation, coherent length is found to be depend-ent on task characteristics such as basic radiation intensity and medium losses, as well as interaction wave mismatch. Constant-intensity approximation allows for a more rigorous analysis of nonlinear interaction of waves in regular domain structure (RDS) compared to constant-field approximation, which does not consider the given change. It has been found that selecting suitable pump intensity and phase ratio settings can greatly improve conversion efficiency when compared to the noncavity arrangement. The examination of η3(lj) indicates that as the main number increases, the steepness of dependence reduces. In other words, the process of frequency conversion has reached saturation. Using two domains increases conversion efficiency by 3.69, three domains by 1.97, four domains by 1.46, five domains by 1.22, and six domains by 1.02. As a re-sult, the transit through the layer domains from the right to the left efficiently transfers laser radiation energy to energy of the sum-frequency wave [η3(l6), practically, achieves 100%]. Under realistic experimental conditions, numerical estimates closely match pre-dicted efficiencies.The suggested theoretical method can be used to investigate para-metric intracavity frequency conversion.