Large radius of curvature micro-lenses on single crystal diamond for application in monolithic diamond Raman lasers

The design and fabrication of large radii of curvature micro-lenses in single crystal chemical vapour deposition diamond is described. An optimised photoresist reflow process and low selectivity inductively coupled plasma etching are used to actualize a uniform array of micro-lenses with radii of curvature of 13 mm or more and a high quality surface of a root-mean-square roughness of 0.18 nm. The processes developed have the potential to achieve diamond micro-lenses with an even larger radius of curvature. These new diamond micro-lenses enable the pulse energy scalable monolithic diamond Raman laser where a large radius of curvature of the micro-lenses is critical.