A system for controlling inclination and depth of ablation of a polymer planar waveguide or semiconductor wafer substrate utilizes a laser which directs the beam at the substrate to ablate portions of the surface thereof and a translatable stage for moving the substrate relative to the beam to create a path of ablated material from the surface. The velocity of the substrate is controlled relative to ablation rate of material from the surface or the dimension of the beam is controlled along the path of ablated material to create a desired inclination and depth of ablated material in the path. The depth of ablated material is a function of the beam width along the path of ablated material, workpiece velocity and ablation rate and is substantially controlled by the formula: D=R(W/V) where D is the depth of ablated material, R is ablation rate, W is beam dimension along the path of ablated material, and V is workpiece velocity.