A broadband silicon quarter-wave retarder for far-infrared spectroscopic circular dichroism

TL;DR

This paper introduces a broadband silicon quarter-wave retarder for far-infrared spectroscopy, enabling precise circular dichroism measurements by distinguishing electronic excitations of different handednesses in materials.

Contribution

The paper presents a novel in-line silicon retarder that operates over a broad spectral range, enhancing far-infrared circular dichroism spectroscopy capabilities.

Findings

Successfully distinguished electronic excitations of different handednesses in GaAs.

Demonstrated effective performance of the silicon retarder in magnetic field conditions.

Enabled potential new studies of circular dichroism in various materials.

Abstract

The high brightness, broad spectral coverage and pulsed characteristics of infrared synchrotron radiation enable time-resolved spectroscopy under throughput-limited optical systems, as can occur with the high-field magnet cryostat systems used to study electron dynamics and cyclotron resonance by far-infrared techniques. A natural extension for magnetospectroscopy is to sense circular dichroism, i.e. the difference in a material's optical response for left and right circularly polarized light. A key component for spectroscopic circular dichroism is an achromatic 1/4 wave retarder functioning over the spectral range of interest. We report here the development of an in-line retarder using total internal reflection in high-resistivity silicon. We demonstrate its performance by distinguishing electronic excitations of different handednesses for GaAs in a magnetic field. This 1/4 wave retarder is expected to be useful for far-infrared spectroscopy of circular dichroism in many materials.