Fabrication of refractive microlenses in semiconductors by mask shape transfer in reactive ion etching

Refractive microlenses are formed in semiconductor materials by transfer of a lens-like shape of reflowed erodable polyimide mask into the substrate by reactive ion etching. Simultaneous monitoring of the etch rates of the mask material and the semiconductor results in precise control of the lens radius of curvature. We demonstrate wafer-scale integration of GaAs microlenses with vertical-cavity laser diodes and InP microlenses with InGaAs photodetectors. These integrated components can be used directly in optical systems without additional external optics.