Fabrication and characterization of diamond micro-optics

Owing to its hardness and chemical inertness, most of the previous studies to fabricate structures and devices on diamond have used the conventional Reactive Ion Etching (RIE). Recently, etching of diamond using Inductively Coupled Plasma (ICP) system was reported to have a higher etch rate than using RIE. In this work, ICP etching with Ar/O2 plasma has been employed to fabricate micro-optics on both natural diamond and high-pressure, high-temperature (HPHT) synthetic diamond. The diamond etch rate has been studied as a function of ICP platen power, coil power and gas pressure. The etch rate is shown to increase with increasing ICP platen and coil powers. Arrays of negative (concave) and positive (convex) diamond microlenses with diameters ranging from 10 to 100 μm were fabricated using hot-embossing and photoresist re-flow methods, respectively, followed by ICP etching. Surface morphology of these diamond micro-lenses was characterized by using both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). These measurements show that the natural diamond micro-lenses have root-mean-squared surface roughness of 1.2 nm. The optical properties of the convex diamond microlens arrays, such as focal length and spot size, were characterised by a laser scanning reflection/transmission confocal microscopy technique. The measured optical parameters are close to the calculated values, confirming that the fabricated diamond lenses have a high-quality surface profile.