rugate

adj

1. Having alternate ridges and depressions; wrinkled.

   “Unifacial, superior surface transversely rugate, with minute oririmes at the bottom of the furrows”

2. Having a varying refractive index.

   “Rugate coatings typically consist of a single layer deposited onto a substrate where the refractive index of the layer continuously changes as a function of depth.”

   “Researchers have focused on various manufactured periodically nonhomogeneous dielectric materials, including rugate filters and periodically multilayered materials.”