Use of mass transport to reduce surface roughness in replicated gallium phosphide refractive microlenses

Mass-transport smoothing has been used to reduce the surface roughness of a gallium phosphide (GaP) microlens from 50.0 nm (rms) to 6.5 nm (rms) while preserving the original surface figure. The initial GaP surface was fabricated by dry-etch transfer of a polymer microlens into a GaP substrate. This result demonstrates that mass transport can significantly improve the performance of economically feasible high-refractive-index micro-optical elements having arbitrary surface profiles.