Improved surface quality of anisotropically etched silicon {111} planes for mm-scale optics

We have studied the surface quality of millimetre-scale optical mirrors produced by etching CZ and FZ silicon wafers in potassium hydroxide to expose the {111} planes. We find that the FZ surfaces have four times lower noise power at spatial frequencies up to 500 mm−1. We conclude that mirrors made using FZ wafers have higher optical quality.