Tunable cryogenic THz cavity for strong light-matter coupling in complex materials

TL;DR

This paper presents a tunable cryogenic THz cavity setup enabling the study of strong light-matter coupling in complex materials, demonstrated through vibrational coupling in CuGeO3 crystals at low temperatures.

Contribution

It introduces a novel experimental setup for studying light-matter interactions in cryogenic conditions with tunable cavity parameters.

Findings

Successful demonstration of vibrational strong coupling in CuGeO3

Versatile cavity setup for different quality factors and temperature tuning

Broadband THz spectroscopy characterization

Abstract

We report here the realization and commissioning of an experiment dedicated to the study of the optical properties of light matter hybrids constituted of crystalline samples embedded in an optical cavity. The experimental assembly developed offers the unique opportunity to study the weak and strong coupling regime between a tunable optical cavity in cryogenic environment and low energy degrees of freedom such as phonons, magnons or charge fluctuations. We describe here the setup developed which allows the positioning of crystalline samples in an optical cavity of different quality factor, the tuning of the cavity length at cryogenic temperatures and its optical characterization with a broadband time domain THz spectrometer (0.2-6 THz). We demonstrate the versatility of the setup by studying the vibrational strong coupling in CuGeO3 single crystal at cryogenic temperatures.