Large-numerical-aperture microlens fabrication by one-step etching and mass-transport smoothing

Precision f/1 microlenses have been fabricated in GaP by smoothing a multiple-mesa structure etched with a designed width and length variation. High-resolution lithography and ion-beam- assisted etching were used for mesa definition and resulted in accurate lens profiles after mass-transport smoothing at 900–1070 °C. This much simplified fabrication technique is highly promising for efficient, diffraction-limited micro-optical elements.