Fabricated hemispherical mirror. (a) Photograph of a fabricated hemispherical mirror. A euro coin is used for comparison. (b) Schematic showing a cross section of the mirror with its relevant dimensions. Note that the 3 mm diameter drilled holes provide laser access to the center of curvature (CoC) of the mirror where the ion will be located. Reproduced with permission from Higginbottom et al., “Fabrication of ultrahigh-precision hemispherical mirrors for quantum-optics applications,” Sci Rep 8, 221 (2018). Copyright 2018 licensed under a Creative Commons Attribution (CC BY) license.