  We present the design, fabrication, and measured performance of metamaterial
Anti-Reflection Cuttings (ARCs) for large-format alumina filters operating over
more than an octave of bandwidth to be deployed on the Simons Observatory (SO).
The ARC consists of sub-wavelength features diced into the optic's surface
using a custom dicing saw with near-micron accuracy. The designs achieve
percent-level control over reflections at angles of incidence up to 20$^\circ$.
The ARCs were demonstrated on four 42 cm diameter filters covering the 75-170
GHz band and a 50 mm diameter prototype covering the 200-300 GHz band. The
reflection and transmission of these samples were measured using a broadband
coherent source that covers frequencies from 20 GHz to 1.2 THz. These
measurements demonstrate percent-level control over reflectance across the
targeted pass-bands and a rapid reduction in transmission as the wavelength
approaches the length scale of the metamaterial structure where scattering
dominates the optical response. The latter behavior enables the use of the
metamaterial ARC as a scattering filter in this limit.
