Abstract The simulated annealing algorithm was applied for optimizing binary phase masks used in the conversion of optical modes through spatial light modulation in free space. The method changes the phase distribution to be displayed on a spatial light modulator, in such a way maximizes the correlation between de converted mode and the theoretical mode. The method allowed the optimal conversion of the linearly polarized modes through a diffractive process. The analysis of the correlations between obtained and theoretical modes showed the effectiveness of the method and its capability to generate optical modes similar to those in an optical fiber. The optimized phase masks could be applied in a dynamic and arbitrary mode converter.