Highly sensitive frequency metrology for optical anisotropy measurements

TL;DR

This paper introduces a highly sensitive frequency metrology apparatus that measures tiny optical anisotropies and birefringences with unprecedented precision, surpassing traditional polarimetry methods, enabling detection of subtle magneto-electro-optical effects.

Contribution

The paper presents a novel frequency metrology setup using a high finesse resonant cavity for measuring small optical anisotropies, offering higher sensitivity than existing techniques.

Findings

Achieved sensitivity of dn ~ 2 x 10^-18

Demonstrated capability to detect magneto-electro-optical effects in gases

Frequency metrology surpasses state-of-the-art sensitivity for birefringence measurements

Abstract

In this paper we present a novel apparatus aimed at measuring very small birefringences and anisotropies, based on frequency metrology and not on polarimetry as usual. In our experiment, a very high finesse resonant cavity is used to convert the phase difference into a resonance frequency difference, which can then be measured with very high accuracy. We describe the set-up and present the results of experimental tests which exhibited a sensitivity dn ~ 2 x 10?18, allowing for the measurement of long-predicted magneto-electro-optical effects in gases. Since the shotnoise limited sensitivity of our apparatus lies well below the state-of-the-art sensitivity, frequency metrology appears as a promising technique for small birefringence measurements.