Free-space confocal magneto-optical spectroscopies at milliKelvin temperatures

TL;DR

This paper details a free-space confocal optical microscope integrated into a dilution refrigerator, enabling advanced spectroscopic measurements at milliKelvin temperatures with a versatile magnetic field setup.

Contribution

It introduces a novel microscope design that allows rapid sample exchange and multi-modal optical spectroscopy at ultra-low temperatures.

Findings

Successful operation of the microscope at milliKelvin temperatures

Implementation of a vector magnet for versatile magnetic field orientations

Capability to perform various spectroscopies including photoluminescence and Kerr effect

Abstract

We describe the operation of a free-space confocal optical microscope operated in a dilution refrigerator. The microscope is installed on a cold insertable probe to enable fast sample exchange while the refrigerator is held at low temperatures. A vector magnet provides a 6 T field normal to the sample and 1 T fields at arbitrary angles. A variety of optical microscopies and spectroscopies, including photoluminescence, Raman, magneto-optical Kerr effect, and spin relaxometry measurements are described, and some of the challenges associated with performing these measurements at milliKelvin temperatures are explored.