Metal Mesh IR Filter for wSMA

TL;DR

This paper presents the design, fabrication, and testing of metal mesh IR filters for the Submillimeter Array, demonstrating effective IR blocking and passband performance verified through measurements and simulations.

Contribution

It introduces a new metal mesh IR filter design fabricated on quartz wafers with anti-reflection coating, validated by experimental and simulation results.

Findings

Filters effectively block IR radiation reducing cryostat thermal load

Measured passband performance aligns with EM simulations

IR reflectivity around 70%, indicating high IR rejection

Abstract

Since the start of full science operations from 2004, the Submillimeter Array has been implementing plans to expand IF bandwidths and upgrade receivers and cryostats. Metal mesh low-pass filters were designed to block infrared (IR) radiation to reduce the thermal load on the cryostats. Filters were fabricated on a quartz wafer through photolithography and coated with anti-reflection (AR) material. The filters were tested from 200 to 400 GHz to verify their passband performances. The measurement results were found to be in good agreement with EM simulation results. They were tested in the far-infrared (FIR) frequency range to verify out-of-band rejection. The IR reflectivity was found to be approximately 70%, which corresponded to the percentage of the area blocked by metal.