CCAT: Silicon-Platelet Feedhorns for Submillimeter Wavelengths

TL;DR

This paper demonstrates silicon-platelet feedhorn arrays operating at submillimeter wavelengths, showing their advantages and matching performance with traditional metal feedhorns, marking a significant technological advancement.

Contribution

First demonstration of silicon-platelet feedhorns at submillimeter wavelengths with performance comparable to traditional metal feedhorns.

Findings

Feedhorns operate effectively at 850 GHz, a 3x increase in frequency.

Performance measurements align well with simulations.

Cryogenic efficiency measurements show promising results.

Abstract

Silicon-platelet feedhorn arrays are an established technology at millimeter wavelengths that, for some applications, can provide significant advantages over traditional direct-machined metal feedhorns. The Prime-Cam focal planes operating in the 350 GHz ($\sim$860 $\mathrm{\mu}$m) and 850 GHz ($\sim$350 $\mathrm{\mu}$m) bands are anticipated to carry the first silicon-platelet feedhorn arrays to operate fully at submillimeter wavelengths, representing a significant step forward in the application of this technology. In particular, the feedhorns designed for operation in the 850 GHz band represent a 3x increase in frequency compared to previously demonstrated and deployed devices of this type. Here we present a demonstration of silicon-platelet feedhorns at these submillimeter wavelengths, including in-lab performance characterization. We present fabrication metrology, room-temperature beammaps, and cryogenic optical efficiency measurements where the feedhorns are coupled to prototype CCAT Prime-Cam detectors. We show that feedhorn performance measurements are well matched to simulation and compare that performance directly to traditional, direct-machined metal feedhorns.