Simons Observatory: broadband metamaterial antireflection cuttings for large-aperture alumina optics

Abstract

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 • . 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.

The Simons Observatory: Development and Optical Evaluation of Achromatic Half-Wave Plates

“…The MF-1 and UHF AHWPs use the two-layer AR coating described in Sakaguri et al [26]. The MF-2 AHWP uses the metamaterial AR described in Golec et al [27].…”

Integrated form-position measurement of large-aperture transparent elements based on stereoscopic phase measuring deflectometry

“…The continuous advancement of science and technology, particularly in aerospace, optical imaging, and defense industries, has led to the widespread applications of large and intricate transparent optical components [1,2]. Both surface form and position accuracy of these transparent optics significantly affect the reliability and performance of the opto-electronics systems.…”

“…Therefore, the actual pixel points are obtained using the bilinear interpolation. The correspondence screen points S 2 and S 2 1 are then identified according the retrieved phases associated ). The normal vector n 2 at M 3 in the view of camera 2 is calculated using equation (3).…”

The Simons Observatory: Development and Optical Evaluation of Achromatic Half-wave Plates

“…The MF-1 and UHF AHWPs use the 2-layer AR coating described in Sakaguri et al [16]. The MF-2 AHWP uses the metamaterial AR described in Golec et al [22].…”