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

We have fabricated refractive sapphire microlenses and characterized their properties for what we believe to be the first time. We use thermally reflo wn photoresist lenslet patterns as a mask for chlorine-based dry etch of sa pphire. Pattern transfer to the mechanically hard and chemically inert sapp hire substrate is made possible by an inductively coupled plasma etch syste m that supplies a high-density plasma gas. Processed sapphire microlenses e xhibit properties close to the ideal and operate nearly in the diffraction limit. (C) 2001 Optical Society of America.