Fabrication of natural diamond microlenses by plasma etching

Advantageous properties including optical transparency, high thermal conductivity, and high carrier mobility make natural diamond an attractive choice for a range of optical and electrical devices. However, its hardness and chemical inertness provide a significant challenge for device processing. We demonstrate the ability to etch natural type IIa diamond using inductively coupled plasma etching with a significant etch rate of 228 nm/min. The etched surfaces were characterized by atomic force microscopy and found to have a root-mean-square roughness of below 3 nm. Using the photoresist reflow technique, refractive microlens arrays, with diameters ranging from 10 to 100 µm, were fabricated on the same diamond substrates. The lenses were characterized by confocal microscopy, which showed that their focal lengths, ranging from 5 to 500 µm, were in excellent agreement with the predicted values, demonstrating the high fidelity of the fabrication process.