Diffractive optical elements in single crystal diamond

We demonstrate the design, fabrication, and experimental characterization of near-field binary phase transmission diffractive optical elements (DOEs) in single crystal diamond. Top-hat and arbitrary pattern DOE beam shapers were numerically optimized using an iterative Fourier transform algorithm (IFTA). Commercially available single crystal diamond plates (3 mm x 3 mm x 0.3 mm) were patterned using hardmask deposition (alpha-Si), e-beam lithography, and O-2 plasma-based diamond reactive ion etching. The resulting binary phase relief patterns were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental characterization of the single crystal diamond DOES in transmission at lambda = 532 nm confirms excellent uniformity of the resulting top-hat beam profile as required in copper welding applications. (C) 2020 Optical Society of America