It has been printed face down for no support use and to save time. Thats why the early layers with huge overhang is printed so bad. The correct way would have been so print it with support the way you have it in the picture. It would take twice as long to print but the end result would have been much better. It all depends on what you paid I guess.
Yeah, that is a pretty nasty print. Ideally you want it printed with the waveguide facing upwards, in ABS or ASA so that you can use acetone to smooth the top surface.