Encapsulation materials for flat optical devices

A method, comprising:

• forming a first arrangement of a first plurality of pillars on a surface of a substrate, the first arrangement of the first plurality of pillars comprising:
• pillars having a height h and a lateral distance d;
• and
• a gap g corresponding to a distance between adjacent pillars of the first plurality of pillars, wherein an aspect ratio of the gap g to the height h is between about 1:1 and about 1:20;
• disposing a first adhesion-promoting material over the first arrangement of the first plurality of pillars;
• and
• disposing a gap-fill portion over the first adhesion-promoting material and comprising a first material having a first refractive index;
• and
• disposing a cap portion comprising a second material having a second refractive index disposed over the first plurality of pillars, wherein the first refractive index and the second refractive index are different, the gap-fill portion filling the gap g between adjacent pillars of the first plurality of pillars, and the gap-fill portion and the cap portion form a first encapsulation layer.

A device, comprising:

• a substrate having a first arrangement of a first plurality of pillars formed thereon, the first arrangement of the first plurality of pillars comprising:
• pillars having a first surface facing away from the substrate and one or more side surfaces facing adjacent pillars;
• and
• trenches formed between adjacent pillars;
• a first adhesion-promoting material disposed on the first surface and the one or more side surfaces of the pillars, the first adhesion-promoting material comprising a fluorosilane;
• a gap-fill portion disposed over the first adhesion-promoting material and comprising a first material having a first refractive index;
• and
• a cap portion comprising a second material having a second refractive index, wherein the first refractive index and the second refractive index are different, the gap-fill portion filling the trenches between adjacent pillars of the first plurality of pillars, and the gap-fill portion and the cap portion form a first encapsulation layer comprising an amorphous fluoropolymer.