Reflectance measurements of mm-wave absorbers using frequency-domain continuous wave THz spectroscopy

TL;DR

This paper presents a frequency-domain continuous wave THz spectroscopy testbed for measuring the reflection and transmission properties of mm-wave absorbers, aiding the development of components for CMB experiments.

Contribution

It introduces a novel optical testbed capable of simultaneous reflection and transmission measurements of mm-wave absorbers across a broad frequency range.

Findings

Measured reflection responses of five absorber materials from 100 to 500 GHz.

Analyzed both specular and scattered reflection responses for different polarizations and angles.

Demonstrated the testbed's effectiveness for characterizing absorber optical properties.

Abstract

Due to high dynamic range and ease of use, continuous wave terahertz spectroscopy is an increasingly popular method for optical characterization of components used in cosmic microwave background (CMB) experiments. In this work, we describe an optical testbed that enables simultaneous measurements of transmission and reflection properties of various radiation absorbing dielectric materials, essential components in the reduction of undesired optical loading. To demonstrate the performance of the testbed, we have measured the reflection response of five absorbers commonly used for such applications: TKRAM, carbon- and iron-loaded Stycast, HR10, AN72, and an in-house 3D printed absorber across a frequency range of 100 to 500 GHz, for both S- and P-polarization, with incident angles varying from 15 to 45 degrees. We present results on both the specular and scattered reflection response of these absorbers.