Augment microlens array example to include conformal AR coating

[smartalecH]

It would be interesting (and probably difficult) to modify the microlens array example to include a conformal AR coating. This is particularly important when the index contrast is particularly high, and the injected fields have high spatial frequencies (they aren't described by a simple planewave). In these cases, significant energy is reflected back through the stack.

[smartalecH]

Note that there are two ways to discretize the lens (and coating):

1. (the current way) which has uniform steps in the R direction
2. an alternative way involving uniform steps in the Z direction