Yes, this is exactly what OptiBPM was designed to do. Place the input plane at Z = 0, make the wafer of length Z_max so that the end of the wafer is the plane Z = Z_max. Specify the Input Plane to determine the initial conditions at Z = 0. If you like, you can have the simulator output the field on the output plane by selecting the Complex Field (end of propagation) check box in the Additional Output Data dialog box. If you would rather see that result in the OptiBPM Analyzer, you can request a Z Cut for Z = Z_max instead.