Refractive sapphire microlenses fabricated by chlorine-based inductively coupled plasma etching

Appl Opt. 2001 Aug 1;40(22):3698-702. doi: 10.1364/ao.40.003698.

Abstract

We have fabricated refractive sapphire microlenses and characterized their properties for what we believe to be the first time. We use thermally reflown photoresist lenslet patterns as a mask for chlorine-based dry etch of sapphire. Pattern transfer to the mechanically hard and chemically inert sapphire substrate is made possible by an inductively coupled plasma etch system that supplies a high-density plasma gas. Processed sapphire microlenses exhibit properties close to the ideal and operate nearly in the diffraction limit.