Single crystal diamond blazed diffraction gratings and Fresnel microlens arrays with improved optical performance by high-resolution 3D laser lithography and pattern transfer by dry etching

We present a method to fabricate high precision 3D micro-optical components in single crystal diamond, and we demonstrate and experimentally characterize Fresnel microlens arrays and blazed diffraction gratings. The fabrication process is based on high-resolution 3D dip-in laser lithography and pattern transfer by chlorine-based reactive ion etching with a low diamond:photoresist selectivity (1:15) to obtain smooth etched surfaces with Ra < 2 nm. The fabricated microlenses have a focal length that deviates by 4% from the target value, while the blazed diffraction gratings have a maximum relative efficiency of 66% in the first order.