CCAT-prime: The Design and Characterization of the Silicon Mirrors for the Fabry-Perot Interferometer in the Epoch of Reionization Spectrometer

TL;DR

This paper details the design, fabrication, and testing of silicon mirrors with metamaterial coatings for a Fabry-Perot interferometer used in a spectrometer aimed at studying the Epoch of Reionization.

Contribution

It introduces a novel silicon mirror design with double-layer anti-reflection coatings and metal mesh reflectors for high-performance FPI in astrophysical spectroscopy.

Findings

Successful fabrication of silicon mirrors with tailored reflectance profiles.

Effective characterization demonstrating suitability for the FPI application.

Enhanced spectral resolution capabilities for the EoR-Spec instrument.

Abstract

The Epoch of Reionization Spectrometer (EoR-Spec) is one of the instrument modules to be installed in the Prime-Cam receiver of the Fred Young Submillimeter Telescope (FYST). This six-meter aperture telescope will be built on Cerro Chajnantor in the Atacama Desert in Chile. EoR-Spec is designed to probe early star-forming regions by measuring the [CII] fine-structure lines between redshift z = 3.5 and z = 8 using the line intensity mapping technique. The module is equipped with a scanning Fabry-Perot interferometer (FPI) to achieve the spectral resolving power of about RP = 100. The FPI consists of two parallel and identical, highly reflective mirrors with a clear aperture of 14 cm, forming a resonating cavity called etalon. The mirrors are silicon-based and patterned with double-layer metamaterial anti-reflection coatings (ARC) on one side and metal mesh reflectors on the other. The double-layer ARCs ensure a low reflectance at one substrate surface and help tailor the reflectance profile over the FPI bandwidth. Here we present the design, fabrication processes, test setup, and characterization of silicon mirrors for the FPI.