Dependences of conversion efficiency of radiation energy of pump wave ( mcm) to energy of wave of second harmonic in AgGa_0.6In_0.4Se₂ crystal as a function of the pump intensity calculated in the constant-intensity approximation for  cm⁻¹,  cm⁻¹ [4], and  cm⁻¹ at crystal length of  cm [4] (curve 1), 0.75 cm (curve 2), and 0.65 cm (curve 3).