My understanding is that this effect has been considered by the spatial intensity distribution at incident interface between air and material.
What I did before is to solve the Maxwell equation for electric-magnetic wave propagation of laser in the material, which yields the overall reflectivity R or optical absorption coefficient alf from its complex refractive index for (single layer case), or laser intensity decay in multilayer structure and poynting vector to calculate the laser power density through the multilayer structure. Then you can cure-fit them into some polynomial functions into ANSYS for load function.