Large-area Reflective Infrared Filters for Millimeter/sub-mm Telescopes

TL;DR

This paper introduces laser etching as a scalable method for fabricating large-area reflective infrared filters, enabling sizes up to 700 mm for millimeter/sub-millimeter telescopes to better manage infrared loading.

Contribution

It presents a novel laser etching technique for creating large reflective infrared filters, overcoming photolithography size limitations.

Findings

Laser etching successfully produces 500 mm filters in lab tests.

Large-area filters up to 700 mm are feasible with current laser etching technology.

The method offers a scalable solution for infrared filtering in large telescopes.

Abstract

Ground-based millimeter and sub-millimeter telescopes are attempting to image the sky with ever-larger cryogenically-cooled bolometer arrays, but face challenges in mitigating the infrared loading accompanying large apertures. Absorptive infrared filters supported by mechanical coolers scale insufficiently with aperture size. Reflective metal-mesh filters placed behind the telescope window provide a scalable solution in principle, but have been limited by photolithography constraints to diameters under 300 mm. We present laser etching as an alternate technique to photolithography for fabrication of large-area reflective filters, and show results from lab tests of 500 mm-diameter filters. Filters with up to 700 mm diameter can be fabricated using laser etching with existing capability.