Return-Path Mueller Ellipsometry via Retroreflective Materials for Cryogenic Applications

Ellipsometry is a useful method for characterizing the complex dielectric properties of materials and has recently received attention for applications in cryogenic environments where the photonic (optical, infrared) and plasmonic properties are not entirely known, for example for samples such as coinage metals (Cu, Au, Ni, Co, etc.). Cryogenic ellipsometers do exist but are typically rigid in their construction and are thus limited in their application as they are typically set-up for a single sample or configuration of interest. In this work, we will report on our progress to develop a modular, multi-angle, return-path ellipsometer (RPE) using commercial off-the-shelf optical components and retroreflective materials. With this, determination of said optical properties for a range of samples spanning from bulk, non-homogenous materials to deposited thin films or materials stacks to intentionally-structured metamaterials can be realized at cryogenic temperatures. Knowledge of these properties is critical to the development of technologies and applications in areas including cryogenic quantum systems, neuromorphic computing, and space-travel.