The field distributions (for the device in Fig. 1), |φ| of a TE wave incident at normal (a) and grazing (θ = 89^o ) (b). Similarly for the TM case, |ψ| for normal (c) and grazing (θ = 89^o ) (d). At normal incidence, the absolute value of the field is not constant on the left, indicating there is reflection, whereas for grazing, the equal field amplitude on the two sides of the profile shows that there is no reflection.